Accepted Manuscript Title: Magnetic ionic liquid-based dispersive liquid-liquid microextraction for the determination of triazine herbicides in vegetable oils by liquid chromatography Author: Yuanpeng Wang Ying Sun Bo Xu Xinpei Li Rui Jin Hanqi Zhang Daqian Song PII: DOI: Reference:
S0021-9673(14)01749-X http://dx.doi.org/doi:10.1016/j.chroma.2014.11.009 CHROMA 355995
To appear in:
Journal of Chromatography A
Received date: Revised date: Accepted date:
28-6-2014 4-11-2014 5-11-2014
Please cite this article as: Y. Wang, Y. Sun, B. Xu, X. Li, R. Jin, H. Zhang, D. Song, Magnetic ionic liquid-based dispersive liquid-liquid microextraction for the determination of triazine herbicides in vegetable oils by liquid chromatography, Journal of Chromatography A (2014), http://dx.doi.org/10.1016/j.chroma.2014.11.009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
• DLLME was used for preconcentration of triazine herbicides from
2
vegetable oils.
3
• Magnetic ionic liquid was select as a novel microextraction solvent of
4
DLLME.
5
• Magnetic separation of the ionic liquid met the requirement of rapid
6
analysis.
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• The performances were acceptable in comparison to existing methods.
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Magnetic ionic liquid-based dispersive liquid-liquid microextraction
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for the determination of triazine herbicides in vegetable oils by liquid
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chromatography
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cr
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Yuanpeng Wang, Ying Sun, Bo Xu, Xinpei Li, Rui Jin, Hanqi Zhang,
15
Daqian Song*
an
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College of Chemistry, Jilin University, Qianjin Street 2699,
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Changchun 130012,
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PR China
*Corresponding author: Daqian Song Tel.: +86-431-85168399
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Fax: +86-431-85168399
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E-mail address: [email protected]
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Abstract
31
Magnetic ionic liquid-based dispersive liquid-liquid microextraction
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(MIL-based DLLME) was developed for extracting triazine herbicides
33
from
34
tetrachloroferrate ([C6mim] [FeCl4]), was used as the microextraction
35
solvent. The magnetic separation time was shortened by simply mixing
36
carbonyl iron powder with the MIL in the sample after DLLME. The
37
effects of several important experimental parameters, including the
38
amount of MIL, the time of ultrasonic extraction, the type
39
volume of cleanup solvent were investigated. The MIL-based DLLME
40
coupled with liquid chromatography gave the limits of detection of
41
1.31-1.49 ng mL-1 and limits of quantification of 4.33-4.91 ng mL-1 for
42
triazine herbicides. When the present method was applied to the analysis
43
of vegetable oil samples, the obtained recoveries were in the range of
45 46 47
MIL,
1-hexyl-3-methylimidazolium
ip t
The
and the
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oils.
Ac ce p
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vegetable
81.8 -114.2% and the relative standard deviations were lower than 7.7%. Compared with existing methods, the performances achieved by the present method were acceptable.
48
Magnetic
ionic
liquids;
Dispersive
49
Keywords:
50
microextraction; Vegetable oil; Triazine herbicides
51
1. Introduction
liquid-liquid
3
Page 3 of 40
Triazine herbicides are a class of pre- and post-emergent broadleaf
53
herbicides with similar chemical structure that inhibit the growth of
54
weeds through disruption of photosynthesis pathways [1]. These
55
herbicides, such as atrazine, cyanazine, and desmetryn, are used widely
56
for maize, sorghum, citrus orchards, and grapes [2]. Because of the
57
prolonged and widespread use, the residues of the herbicides have been
58
found in a lot of agriculture products [3, 4]. The study has indicated that
59
some triazine herbicides are suspected to cause cancers, birth defects, and
60
interruption of hormone functions [5]. Consequently, there is a growing
61
need to monitor triazine herbicides in agriculture products.
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52
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Vegetable oils which are mainly composed of triglycerides, are
64
commonly extracted from plant seeds, i.e., the oilseeds, such as the
65
seeds of soybean, maize, and sunflower. Pesticide residues in these seeds
67 68 69
te
Ac ce p
66
d
63
may be
transfered to vegetable oils during the oil extraction process.
Maximum residue limits (MRLs) in the range of 0.05-0.1 mg kg-1 for the residues of some triazine herbicides in oilseeds are established by the European Union (Commission Directive 2008/149/EC),
while the
70
MRLs for triazine herbicide residues in vegetable oils have not been
71
established. Therefore, a sensitive and accurate method for determination
72
of triazine herbicides in vegetable oils is particularly important to
73
guarantee public health and safety. To the best of our knowledge, the 4
Page 4 of 40
74
available literatures on determination of triazine herbicides in vegetable
75
oils are very limited [6, 7]. Extraction and cleanup are the most challenging parts for
77
determination of pesticide residues in food stuffs, especially in vegetable
78
oils with inherent complex fatty matrices [8]. Additionally, the low
79
concentrations of pesticide residues in oil samples also make the direct
80
determining of them difficult by chromatographic methods, such as liquid
81
chromatography (LC) or gas chromatography (GC) [9]. Therefore, there
82
is a need to employ exhaustive sample preparation technique for the
83
extraction and preconcentration of the residues from oil samples before
84
determination.
85
liquid-liquid extraction (LLE) [6-8, 10-11] and low-temperature fat
86
precipitation (LTFP) [12, 13], have been widely applied to the extraction
87
and preconcentration of target analytes from fatty samples. However,
89 90 91
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sample
preparation
techniques,
such
as
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Various
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76
traditional LLE need time-consuming operating procedure and large amount of organic solvents, and LTFP usually takes a long time to precipitate fats in samples. Other preparation techniques, including solid-phase extraction (SPE) [8, 10, 13], matrix solid-phase dispersion
92
(MSPD) [7, 9], and dispersive solid-phase extraction (dSPE) [11] were
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commonly coupled with the above-mentioned techniques and applied for
94
the clean-up. In recent years, research efforts on sample preparation
95
techniques have been directed towards simplifying the extraction 5
Page 5 of 40
procedure, saving operating time and reducing the consumption of
97
organic solvents.
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Since dispersive liquid-liquid microextraction (DLLME) was proposed
99
by Assadi and coworkers [14], this method has attracted much attention
100
owning to its significant advantages including small solvent usage of
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microliter volumes, rapidity and high enrichment factor. DLLME is a
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promising alternative to the classic LLE and has been widely appliedto
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the extraction of target analytes in water-soluble samples [15-17], while
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there are only a couple of reports about the application of DLLME in the
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sample preparation of fat-soluble vegetable oils [18, 19].
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Ionic liquids (ILs) are a class of organic salts with low melting
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points [20]. The unique properties of ILs, including negligible vapor
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pressure, good chemical and thermal stability, excellent solubility for both
109
organic and inorganic compounds, and environmental friendliness [21,
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d
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22], make them promising extraction solvents used in separation [16, 17, 23]. The combinations of different organic cations with various organic or inorganic anions leads to a large amount of ILs with numerous possible applications, and ILs with special properties can also be designed through proper chemical modifications [24].
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Nowadays, developments and applications of magnetizable ILs
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become a new field and a hotspot of research in sample preparation
117
techniques [25-28]. Generally, ILs were bonded or immobilized on the 6
Page 6 of 40
surface of magnetic supports to form solid materials and used as magnetic
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adsorbents in magnetic solid-phase extraction [25-27], while only few
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publications reported on the metal-containing ILs, which incorporated the
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metal in the ILs to introduce magnetic property [28]. Recently, a novel
122
class of magnetic ionic liquids (MILs) with single-component was
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discovered, of which the magnetic property is no longer introduced as
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external magnetic supports, but provided by complex ions of metals [26,
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29-30]. The first example of MILs is 1-butyl-3-methylimidazolium
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tetrachloroferrate ([C4mim] [FeCl4]). Although the compound has been
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known for some time [31], its magnetic behavior was not described until
128
2004 [32]. These MILs are basically based on the anions containing
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high-spin d5 iron (Ⅲ), which were in the forms of tetrachloro- or
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tetrabromoferrate (III), with varieties of counter cations. Because of their
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high single-ion magnetic moments, MILs show a good response to an
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external magnetic field [28], and are very interesting to be employed as novel extraction solvents to take the place of routine nonmagnetic ILs of DLLME. The MILs can be uniformly dispersed in sample solutions through ultrasound irradiation and can be isolated from the solutions by
136
means of an external magnetic field. However, to our knowledge, there is
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only one report about the application of MILs on separation of target
138
analytes, in which the MIL was used for solvent extraction of phenolic
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compounds from aqueous solution [33]. Because MILs contain polar 7
Page 7 of 40
functional groups, such as protonated primary amines and esters, as well
141
as the hydrophilic tetrachloroferrate (III) anions, most MILs are miscible
142
with water or other polar solvents after vigorous shaking, which restrict
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their applications of separation and concentration of analytes dissolved in
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water. In contrast, they are immiscible with hydrophobic solvents such as
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carbon tetrachloride and n-hexane [26]. Herein, MILs are promising
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microextraction solvents of DLLME for vegetable oils.
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In
this
study,
an
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1-hexyl-3-methylimidazolium
tetrachloroferrate
([C6mim] [FeCl4]) was selected as the microextraction solvent of the
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MIL-based DLLME for extracting triazine herbicides from vegetable oils,
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including two soybean oils, three maize oils and two sunflower seed oils.
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In addition, carbonyl iron powder (CIP) was added to shorten magnetic
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separation time after DLLME, which can be magnetically attracted by the
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d
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M
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MIL to form a combination of CIP and MIL (CIP-MIL). Several important experimental parameters, such as the amount of MIL, the time of ultrasound extraction, the type and the volume of cleanup solvent, were optimized. Under the optimized conditions, the present method was successfully applied to the analysis of real vegetable oil samples
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2. Experimental
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2.1. Chemicals and reagents Chromatographic grade acetonitrile was purchased from Fisher
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Scientific Company (UK). [C6mim] [FeCl4] (> 99%) was purchased from
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Chengjie Chemical Co. LTD (Shanghai, China). CIP with average particle
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size less than 4.30 μm (Purity > 97.8%) was purchased from Jilin Jien
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Nickel Industry (Panshi, China). Padding materials of primary secondary
168
amine (PSA, 50 μm), C18 (50 μm) and graphitized carbon black (GCB)
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were purchased from Bonna-Agela Technologies. All other reagents were
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of analytical grade and purchased from Beijing Chemical Factory
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(Beijing, China).
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Standards
of
d
system (Millipore, New York, USA). cyanazine,
te
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Deionized water was obtained with a Milli-Q water purification
desmetryn,
secbumeton,
terbutryn,
dimethametryn and dipropetryn were obtained from National Institute for
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the Control of Pharmaceutical and Biological Products (Beijing, China). The chemical structures of these herbicides are shown in Fig. 1. Stock solutions were prepared by dissolving each substance in chromatographic grade acetonitrile at a concentration of 400 μg mL-1 and stored at 4 ℃ in
180
darkness. Mixed working solutions at desirable concentrations were
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prepared by mixing the stock solutions followed by diluting with
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chromatographic grade acetonitrile.
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2.2. Instruments LC analyses) were performed using a LC-20ADXR liquid
186
chromatograph (Shimadzu, Japan) with two pumps (LC-20AD), an
187
autosampler (SIL-20A), a column oven (CTO-20A) and a UV-vis detector
188
(SPD-20A). Chromatographic separation of the analytes were carried out
189
using a shim-pack VP-ODS column (150 mm × 4.6 mm, 4.6 μm particle
190
size). Relevant data acquisition and processing were accomplished with
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Shimadzu LC solution software.
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The KQ-100 ultrasonic cleaner was purchased from Kunshan
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Ultrasonic Instrument Co., Ltd. (Kunshan, China). The frequency and
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output power of the ultrasonic cleaner are 40 kHz and 100 W,
196
respectively.
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2.3. Samples
The vegetable oil samples were purchased from local supermarkets.
Seven vegetable oil samples, including 2 soybean oil (sample 1, 2), 3 maize oils (sample 3-5) and 2 sunflower seed oil (sample 6, 7) were
202
analyzed. The samples used for recovery and precision studies were
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previously analyzed. The experimental results showed that there wasno
204
peak at the retention positions of the analytes in the chromatograms
205
obtained with the sample extracts. The target pesticides in the samples 10
Page 10 of 40
were undetectable. Spiked samples containing triazine herbicides were
207
prepared by spiking the mixed working standard solutions into samples.
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After being well mixed, the samples were equilibrated for 1 h in the dark
209
at room temperature. All the experiments were carried out with sample 1
210
except for those mentioned in Section 3.2.4 in which all samples
211
(sample1-7) were used.
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2.4. Extraction procedure
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2.4.1. DLLME
an
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1 mL of vegetable oil sample was diluted with 7 mL of n-hexane in
216
10 mL centrifuge tube and mixed for 2 min. Subsequently, 90 μL of
217
[C6mim] [FeCl4] was added into the tube and ultrasonicated for 7 min to
218
extract the analytes from samples. Then 400 mg of CIP was added, and
219
the mixture was vigorously shaken for 30 s to form the CIP-MIL. Then,
221 222 223
d
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M
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the CIP-MIL was subsequently collected with a strong magnet placed out the wall of the tube, and the supernatant was decanted. The CIP-MIL was washed with 500 μL of n-hexane for three times. Then, 1.5 mL of deionized water was added into the tube to dissolve the MIL, and then 1.5
224
mL of ethyl acetate was added to extract the target analytes. The resulting
225
mixture was shaken for 4 min, then the upper layer of ethyl acetate was
226
sucked into a glass tube and evaporated under a gentle nitrogen stream at
227
40℃. Finally, the residuewas redissolved in 100 μL of acetonitrile and 11
Page 11 of 40
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filtered through a 0.22 μm nylon membrane, followed by LC analysis.
229
Illustration of the whole extraction procedure is shown in Fig. 2.
230
2.4.2. QuEChERS The quick, easy, cheap, effective, robust and safe (QuEChERS)
232
procedure was performed according to a previousliterature [34]. 1 mL of
233
vegetable oil sample and 2.5 mL of water were added into 10 mL
234
centrifuge tube. Then, 3.5 mL of acetonitrile was added, along with 1.4 g
235
of anhydrous magnesium sulphate and 0.35 g of sodium chloride. The
236
tube was vigorously shaken for 1 min. The mixture was centrifuged (4000
237
rpm) for 1 min. The tube was horizontally stored in freezer at -20 ℃ for 2
238
h. Then, the supernatant was transferred into a PTFE centrifuge tube
239
containing 450 mg of anhydrous magnesium sulphate, 150 mg of PSA,
240
150 mg of C18 and 150 mg of GCB. After shaken for 30 s, the mixture
241
was centrifuged (4000 rpm) for 1 min. The supernatant was evaporated to
243 244 245 246
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d
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dryness under a gentle nitrogen stream at 40℃. Finally, the residues were redissolved in 100 μL of acetonitrile and filtered through a 0.22 μm nylon membrane, followed by LC analysis.
2.5. LC analysis
247
The LC analysis was conducted in gradient mode. The gradient has
248
been optimized in advance. Mobile phases A and B are acetonitrile and
249
water, respectively. The gradient program is as follows: 0-10 min, 12
Page 12 of 40
80-70% B; 10-18 min, 70-40% B; 18-25 min, 40-35% B; 25-30 min,
251
35-80% B. The flow rate of mobile phase was kept at 1.0 mL min-1.
252
Injection volume of analytical solution was 10 μL. The monitoring
253
wavelength was 220 nm for all the target compounds [35].
3. Results and discussion
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3.1. Optimization of MIL-based DLLME conditions
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In order to obtain high extraction efficiency, the effects of several
259
experimental parameters, such as the amount of [C6mim] [FeCl4], the
260
ultrasound extraction time, the type and the volume of cleanup solvent
261
were investigated. All the experiments were performed in triplicate.
264 265 266 267
d
te
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3.1.1. Effect of amount of [C6mim] [FeCl4]
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The triazine herbicides were hardly extracted with CIP in the
absence of [C6mim] [FeCl4], indicating that the [C6mim] [FeCl4] played a key role in the extraction of target analytes. The effect of the amounts of [C6mim] [FeCl4] ranging from 30 μL to 110 μL were investigated. As can
268
be concluded from Fig. 3, the extraction efficiency increases rapidly
269
when the amount of [C6mim] [FeCl4] increases from 30 μL to 90 μL,
270
indicating the remarkable enrichment ability of [C6mim] [FeCl4]. No
271
obvious change is observed when the amount of [C6mim] [FeCl4] 13
Page 13 of 40
increases from 90 μL to 110 μL, indicating that excessive MIL without
273
combination to CIP can not be collected by magnetic separation.
274
Therefore, 90 μL was employed as the amount of [C6mim] [FeCl4] in the
275
following experiments.
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3.1.2. Effect of ultrasound extraction time
The effect of ultrasound extraction time was investigated by
279
increasing the time from 2 to 15 min. The profiles of extraction time and
280
extraction efficiency for the analytes are shown in Fig. 4. The recoveries
281
of triazine herbicides increase with the increase of extraction time from 2
282
to 5 min, and remain stable with a further increase of extraction time from
283
5 to 10 min. To ensure the complete extraction of analytes, the extraction
284
time was selected as 7 min.
286 287 288 289
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3.1.4. Effect of cleanup solvent type The cleanup solvent can significantly affect the extraction of the
target analytes and cleanup capability within one step in this experiment. In order to improve the cleanup efficiency and reduce the extraction loss,
290
a selection of cleanup solvent is indispensable. The cleanup solvent
291
should have low solubility in water, high dissolving ability for triazine
292
herbicides and low dissolving ability for interference constituents. Based
293
on these considerations, four kinds of organic solvents, including 14
Page 14 of 40
petroleum ether, diethyl ether, ethyl acetate and dichloromethane, were
295
considered as the cleanup solvent. The extraction capabilities of the above
296
solvents are compared in Fig. 5. Under the same extraction conditions,
297
ethyl acetate provided the highest extraction efficiency due to its
298
strongest dissolving ability for triazine herbicides, and the clean
299
chromatogram with low baseline level and signal noise was also obtained
300
with ethyl acetate. Therefore, ethyl acetate was used as the cleanup
301
solvent in the following experiments
an
302
3.1.5. Effect of the volume of cleanup solvent
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The volume of ethyl acetate ranging from 0.5 mL to 2.5 mL was
305
investigated. As can be seen from Fig. 6, an increase in volume of ethyl
306
acetateranging from 0.5 to 1.5 mL results in an increase in the recoveries
307
of triazine herbicides, and no obvious change is observed when the
309 310 311 312
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d
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volume of ethyl acetate is larger than 1.5 mL. Therefore, 1.5 mL of ethyl acetate was selected for extraction of triazine herbicides in the following experiments.
3.2. Evaluation of the method
313
After the important conditions of extracting these herbicides were
314
validated, a new analytical method was developed for quantitative
315
determination of the six triazine herbicides in vegetable oils. In order to 15
Page 15 of 40
evaluate the performances of the present method, the working curves,
317
linear range, correlation coefficient (r), limit of detection (LOD) and
318
quantification (LOQ), and reproducibility were studied. The spiked
319
samples were analyzed by the present method.
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3.2.1. Linearity
The working curves were constructed by plotting the corresponding
323
peak areas measured versus the concentrations of triazine herbicides in a
324
series of spiked samples. As listed in Table 1, the present method exhibits
325
satisfactory linearity in the concentration range of 5.00-1000.00 ng mL-1
326
with good correlation coefficients (r) higher than 0.9992.
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330 331 332 333
te
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3.2.2. Limit of detection and quantification The LODs and LOQs were determined based on the signal-to-noise
Ac ce p
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d
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ratio of 3 and 10, respectively. The results obtained are given in Table 1. The LODs and LOQs are in the range of 1.31-1.49 ng mL-1 and 4.33-4.91 ng mL-1, respectively. Because of the interferences of complex fatty matrices in vegetable oils, the LODs obtained by the present method are
334
somewhat higher than that obtained by several previous methods [36, 37],
335
which were applied to the determination of triazine herbicides in aqueous
336
samples.
337
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Page 16 of 40
338
3.2.3. Precision and recovery The intra- and inter-day precision of the present method were
340
obtained by analyzing the spiked sample at concentrations of 25.00, 50.00
341
and 100.00 ng mL-1. The intra-day RSDs were obtained by analyzing the
342
sample five times a day, and the inter-day RSDs were obtained by
343
analyzing samples which were independently prepared for consecutive
344
five days. The RSDs obtained are listed in Table 2. The intra- and
345
inter-day RSDs were in the range of 1.9-5.7% and 2.5-7.5%, respectively,
346
indicating the acceptable precision.
348
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3.2.4. Analysis of real vegetable oil samples The developed MIL-based DLLME method coupled with LC was
350
applied to the determination of the six triazine herbicides in vegetable oil
351
samples. The real samples were pretreated under the optimized conditions
353 354 355
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d
349
and no herbicides were detectable. Seven kinds of spiked samples at analyte concentrations of 50.00 and 100.00 ng mL-1 were analyzed. The typical chromatograms of the blank and spiked sample are shown in Fig. 7, and the analytical results are listed in Table 3. As can be seen, the
356
present method provides good recoveries ranging from 81.8-114.2% and
357
acceptable precision lower than 7.7%.
358 359
3.2.5. Comparison with QuEChERS 17
Page 17 of 40
In order to further evaluate the present method, the present method
361
was compared with QuEChERS [35]. The recoveries and RSDs of the six
362
triazine herbicides obtained by QuEChERS at concentrations of 50.00
363
and 100.00 ng mL-1 range from 80.3 to 121.7% and 2.3 to 9.2%,
364
respectively. By comparation, the recoveries and RSDs of the same
365
spiked samples obtained by the present method range from 94.1-110.7%
366
and 1.4 to 7.4%. The LODs of QuEChERS are in the range of 4.32-5.12
367
ng mL-1, which are higher than these of the present method. These results
368
indicates that the precision and the sensitivity of the present method are
369
both better than that of QuEChERS. In addition, the consumption of
370
extraction solvent in the present method is low and the extraction time
371
(7min) is much shorter than that (122 min) of QuEChERS. Moreover, the
372
magnetic separation
373
eliminates the routine centrifugation procedure.
375 376 377
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d
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simplifies the sample preparement process and
Ac ce p
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3.2.6. Comparison with other reported methods The present method was further compared with the reported methods
for the determination of target analytes in fatty matrices [6, 7, 10, 11, 18]. The results are shown in Table 4. It can be seen that the consumption of
378
extraction solvent in the present method is lower than that in other
379
methods. Compared with acetonitrile and dichloromethane used in some
380
methods, n-hexane and ethyl acetate used in the present method have
381
lower toxicity. The LODs and RSDs obtained by the present method are 18
Page 18 of 40
similar to or lower than these obtained by the reported methods.
383
Therefore, it can be concluded that the present method is suitable for
384
the determination of triazine herbicides in vegetable oils.
ip t
382
385
4. Conclusion
cr
386
In summary, a rapid, easy and low-solvent-consumption extraction
388
method, MIL-based DLLME was successfully developed and applied for
389
the extraction of triazine herbicides from vegetable oils. It is the first time
390
to use MIL as the microextraction solvent for fat-soluble samples, and
391
magnetic separation was selected to simplify separation procedure. The
392
present method overcame the drawback of MILs being miscible with
393
water and the limitation unsuitable for fat-soluble samples. It could be
394
considered that this method is very promising for the extraction of
395
analytes from complex fat-soluble samples by varying extraction
397 398 399
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M
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Ac ce p
396
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387
parameters. Since the present method is pretty straightforward and easy to perform. The extraction step could be combined withLC for online determination of the herbicides. [38]
400 401
Acknowledgments
402
This work was supported by National Natural Science Foundation of
403
China (No. 20727003, 21075049, and 21105037), Program for New 19
Page 19 of 40
Century
Talents
in
University
(No.
405
Special-funded Programme on National Key Scientific Instruments and
406
Equipment Development (No. 2012YQ090194) and Science and
407
Technology Developing Foundation of Jilin Province (No. 20100356 and
408
20110162).
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411 412
References
M
413
NECT-10-0443),
cr
Excellent
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404
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[1] M. Graymore, F. Stagnitti, G. Allinson, Impacts of atrazine in aquatic
416
ecosystems, Environ. Int. 26 (2001) 483-495.
417
[2] A. Cabrera, L. Cox, W.C. Koskinen, M. J. Sadowsky, Availability of
419 420 421
te
Ac ce p
418
d
415
triazine herbicides in aged soils amended with olive oil mill waste, J. Agric. Food Chem. 56 (2008) 4112-4119. [3] K. Zhang, J.W. Wong, P. Yang, K. Tech, A.L. Dibenedetto, N.S. Lee, D.G. Hayward, C.M. Makovi, A.J. Krynitsky, K. Banerjee, L. Jao, S.
422
Dasgupta, M.S. Smoker, R. Simonds, A. Schreiber, Multiresidue pesticide
423
analysis of agricultural commodities using acetonitrile salt-out extraction,
424
dispersive solid-phase sample clean-up, and high-performance liquid
425
chromatography-tandem mass spectrometry, J. Agric. Food Chem. 59 20
Page 20 of 40
(2011) 7636-7646.
427
[4] O. Núñez, H. Gallart-Ayala, I. Ferrer, E. Moyano, M.T. Galceran,
428
Strategies for the multi-residue analysis of 100 pesticides by liquid
429
chromatography-triple quadrupole mass spectrometry, J. Chromatogr. A
430
1249 (2012) 164-180.
431
[5] P. Norouzi, B. Larijani, M.R. Ganjali, F. Faridbod, Admittometric
432
electrochemical
433
immune-biosensor using FFT-Square wave voltammetry, Int.
434
Electrochem. Sci. 7 (2012) 10414-10426.
435
[6] J.F. Garcia-Reyes, C. Ferrer, E.M. Thurman, A.R. Fernandez-Alba, I.
436
Ferrer, Analysis of herbicides in olive oil by liquid chromatography
437
time-of-flight mass spectrometry, J. Agric. Food Chem. 54 (2006)
438
6493-6500.
439
[7] C. Ferrer, M.J. Gómez, J.F. García-Reyes, I. Ferrer, E.M. Thurman,
441 442 443
cr
atrazine
by
nano-composite
us
of
J.
te
d
M
an
determination
Ac ce p
440
ip t
426
A.R. Fernández-Alba, Determination of pesticide residues in olives and olive
oil
by
matrix
solid-phase
dispersion
followed
by
gas
chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry, J. Chromatogr. A 1069 (2005) 183-194.
444
[8] A.L. Capriotti, C. Cavaliere, C. Crescenzi, P. Foglia, R. Nescatelli, R.
445
Samperi, A. Laganà, Comparison of extraction methods for the
446
identification and quantification of polyphenols in virgin olive oil by
447
ultra-HPLC-QToF mass spectrometry, Food Chem. 158 (2014) 392-400. 21
Page 21 of 40
448
[9] B. Gilbert-López, J.F. García-Reyes, A. Molina-Díaz, Sample
449
treatment and determination of pesticide residues in fatty vegetable
450
matrices: A review, Talanta 79 (2009) 109-128.
451
[10]
452
microwave-assisted extraction coupled with solid-phase extraction for
453
organophosphorus pesticide determination in olive oil, J. Chromatogr. A
454
1207 (2008) 38-45.
455
[11] M.Q. Cai, X.H. Chen, X.Q. Wei, S.D. Pan, Y.G. Zhao, M.C. Jin,
456
Dispersive solid-phase extraction followed by high-performance liquid
457
chromatography/tandem mass spectrometry for the determination of
458
ricinine in cooking oilFood Chem. 158 (2014) 459-465.
459
[12] C. Anagnostopoulos, G.E. Miliadis, Development and validation of
460
an easy multiresidue method for the determination of multiclass pesticide
461
residues using GC-MS/MS and LC-MS/MS in olive oil and olives,
463 464 465
Báez,
A.
Quiñones,
Suitability
of
ip t
M.E.
te
d
M
an
us
cr
Fuentes,
Ac ce p
462
E.
Talanta 112 (2013) 1-10.
[13] Ch. Lentza-Rizosa, E.J. Avramides, E. Visi, Determination of residues of endosulfan and five pyrethroid insecticides in virgin olive oil using gas chromatography with electron-capture detection, J. Chromatogr.
466
A 921 (2001) 297-304.
467
[14] M. Rezaee, Y. Assadi, M.R. Milani, E. Aghaee, F. Ahmadi, S.
468
Berijani, Determination of organic compounds in water using dispersive
469
liquid-liquid microextraction, J. Chromatogr. A 1116 (2006) 1-9. 22
Page 22 of 40
[15] L.H. Liu, L.J. He, X.M. Jiang, W.J. Zhao, G.Q. Xiang, J.L. Anderson,
471
Macrocyclic polyamine-functionalized silica as a solid-phase extraction
472
material coupled with ionic liquid dispersive liquid-liquid extraction for
473
the enrichment of polycyclic aromatic hydrocarbons, J. Sep. Sci. 37 (2014)
474
1004-1011.
475
[16] X.W. Chen, A. Sakurazawa, K. Sato, K-I. Tsunoda, J.H. Wang, A
476
solid-cladding/liquid-core/liquid-cladding sandwich optical waveguide
477
for the study of dynamic extraction of dye by ionic liquid BmimPF6, Appl.
478
Spectrosc. 66 (2012) 798-802.
479
[17] C. Yao, T.H. Li, P. Twu, W.R. Pitner, J.L. Anderson, Selective
480
extraction of emerging contaminants from water samples by dispersive
481
liquid-liquid microextraction using functionalized ionic liquids, J.
482
Chromatogr. A 1218 (2011) 1556-1566.
483
[18] W.X. Wang, T.J. Yang, Z.G. Li, T.T. Jong, M.R. Lee, A novel method
485 486 487
cr
us
an
M
d
te
Ac ce p
484
ip t
470
of ultrasound-assisted dispersive liquid-liquid microextraction coupled to liquid chromatography-mass spectrometry for the determination of trace organoarsenic compounds in edible oil, Anal. Chim. Acta 690 (2011) 221-227.
488
[19] M.P. Godoy-Caballero, M.I. Acedo-Valenzuela, T. Galeano-Díaz,
489
New reversed phase dispersive liquid-liquid microextraction method for
490
the determination of phenolic compounds in virgin olive oil by rapid
491
resolution liquid chromathography with ultraviolet-visible and mass 23
Page 23 of 40
spectrometry detection, J. Chromatogr. A 1313 (2013) 291-301.
493
[20] Y.T. Daia, J.V. Spronsen, G.J. Witkamp, R. Verpoorte, Y.H. Choi,
494
Natural deep eutectic solvents as new potential media for green
495
technology, Anal. Chim. Acta 766 (2013) 61-68.
496
[21] S. Pandey, Analytical applications of room-temperature ionic liquids:
497
A review of recent efforts, Anal. Chim. Acta 556 (2006) 38-45.
498
[22] C.F. Poole, S.K. Poole, Extraction of organic compounds with room
499
temperature ionic liquids, J. Chromatogr. A 1217 (2010) 2268-2286.
500
[23] P. Berton, R.G. Wuilloud, Highly selective ionic liquid-based
501
microextraction method for sensitive trace cobalt determination in
502
environmental and biological samples, Anal. Chim. Acta 662 (2010)
503
155-162.
504
[24] M. Li, S.L.D. Rooy, D.K. Bwambok, B. El-Zahab, J.F. DiTusa, I.M.
505
Warner, Magnetic chiral ionic liquids derived from amino acids, Chem.
507 508 509
cr
us
an
M
d
te
Ac ce p
506
ip t
492
Commun. 45 (2009) 6922-6924. [25] H.D. Qiu, M. Takafuji, X. Liu, S.X. Jiang, H. Ihara, Investigation of π-π and ion-dipole interactions on 1-allyl-3-butylimidazolium ionic liquid-modified silica stationary phase in reversed-phase liquid
510
chromatography, J. Chromatogr. A 1217 (2010) 5190-5196.
511
[26] M. Li, J.H. Zhang, Y.B. Li, B. Peng, W.F. Zhou, H.X. Gao, Ionic
512
liquid-linked dual magnetic microextraction: A novel and facile procedure
513
for the determination of pyrethroids in honey samples, Talanta 107 (2013) 24
Page 24 of 40
81-87.
515
[27] E. Yilmaz, M. Soylak, Ionic liquid-linked dual magnetic
516
microextraction of lead(II) from environmental samples prior to its
517
micro-sampling flame atomic absorption spectrometric determination,
518
Talanta 116 (2013) 882-886.
519
[28] B. Mallick, B. Balke, C. Felser, A.V. Mudring, Dysprosium
520
room-temperature ionic liquids with strong luminescence and response to
521
magnetic fields, Angew. Chem. Int. Ed. 47 (2008) 7635-7638.
522
[29] R.E. Del Sesto, T.M. McCleskey, A.K. Burrell, G.A. Baker, J.D.
523
Thompson, B.L. Scott, J.S. Wilkes, P. Williams, Structure and magnetic
524
behavior of transition metal based ionic liquids, Chem. Commun. 4 (2008)
525
447-449.
526
[30] T. Peppel, M. Kockerling, M. Geppert-Rybczynska, R. V. Ralys, J.K.
527
Lehmann, S.P. Verevkin, A. Heintz, Low-viscosity paramagnetic ionic
529 530 531
cr
us
an
M
d
te
Ac ce p
528
ip t
514
liquids with doubly charged [Co(NCS)4]2- Ions, Angew. Chem., Int. Ed. 49 (2010) 7116-7119.
[31] M.S. Sitze, E.R. Schreiter, E.V. Patterson, R.G. Freeman, Ionic liquids based on FeCl3 and FeCl2. Raman scattering and ab initio
532
calculations, Inorg. Chem. 40 (2001) 2298-2304.
533
[32] S. Hayashi, H. Hamaguchi, Discovery of a magnetic ionic liquid
534
[bmim]FeCl4, Chem. Lett. 33 (2004) 1590-1591.
535
[33] N. Deng M. Li, L.J. Zhao, C.F. Lu, S.L. de Rooy, I.M. Warner, 25
Page 25 of 40
Highly efficient extraction of phenolic compounds by use of magnetic
537
room temperature ionic liquids for environmental remediation, J. Hazard.
538
Mater. 192 (2011) 1350-1357.
539
[34] E. Sobhanzadeh, N.K. Abu Bakar, M.R. Bin Abas, K.Nemati, A
540
simple and efficient multi-residue method based on QuEChERS for
541
pesticides determination in palm oil by liquid chromatography
542
time-of-flight mass spectrometry, Environ. Monit. Assess. 184 (2012)
543
5821-5828.
544
[35] M. Battista, A. Di Corcia, M. Marchetti, Extraction and isolation of
545
triazine herbicides from water and vegetables by a double trap tandem
546
system, Anal. Chem. 61(1989) 935-939.
547
[36] D. Nagaraju, S.D. Huang, Determination of triazine herbicides in
548
aqueous samples by dispersive liquid–liquid microextraction with gas
549
chromatography-ion trap mass spectrometry, J. Chromatogr. A 1161
551 552 553
cr
us
an
M
d
te
Ac ce p
550
ip t
536
(2007) 89-97.
[37] Y.L. Hu, Y.Y. Wang, Y.F. Hu, G.K. Li, Liquid-liquid-solid microextraction based on membrane-protected molecularly imprinted polymer fiber for trace analysis of triazines in complex aqueous samples,
554
J. Chromatogr. A 1216 (2009) 8304-8311.
555
[38] B. Bjarnason, L. Chimuka, O. Ramström, On-line solid-phase
556
extraction of triazine herbicides using a molecularly imprinted polymer
557
for selective sample enrichment, Anal. Chem. 71 (1999) 2152-2156. 26
Page 26 of 40
558 559
ip t
560 561
cr
562
us
563 564
an
565 566
Figure Captions
M
567 568
d
Fig. 1. Chemical structures of the triazine herbicides.
te
569 570
572 573 574 575 576
Fig. 2. Schematic diagram of the extraction procedure.
Ac ce p
571
Fig. 3. Effect of the amount of [C6mim] [FeCl4] on the recoveries of the triazine herbicides.
Ultrasound extraction time, 7 min; cleanup solvent, ethyl acetate; volume of cleanup solvent, 1.5 mL; spiked concentration, 100 ng mL-1.
577 578
Fig. 4. Effect of the ultrasound extraction time on the recoveries of the
579
triazine herbicides. 27
Page 27 of 40
Amount of [C6mim] [FeCl4], 90 μL; cleanup solvent type, ethyl acetate;
581
the volume of cleanup solvent, 1.5 mL; spiked concentration, 100 ng
582
mL-1.
ip t
580
583
Fig. 5. Effect of cleanup solvent type on the recoveries of the triazine
585
herbicides.
586
The amount of [C6mim] [FeCl4], 90 μL; Ultrasound extraction time, 7
587
min; volume of cleanup solvent, 1.5 mL; spiked concentration, 100 ng
588
mL-1.
an
us
cr
584
M
589
Fig. 6. Effect of the volume of cleanup solvent on the recoveries of the
591
triazine herbicides.
592
Amount of [C6mim] [FeCl4], 90 μL; Ultrasound extraction time, 7 min;
593
cleanup solvent, ethyl acetate; spiked concentration, 100 ng mL-1.
595 596 597
te
Ac ce p
594
d
590
Fig. 7. Chromatograms of sample 1 (A) and spiked sample 1 (B). 1, Cyanazine; 2, desmetryn; 3, secbumeton; 4, terbutryn; 5, dimethametryn; 6, dipropetryn. Spiked concentration, 100 ng mL-1.
598 599
Tables
600 601
Table 1. Analytical performances of the present method 28
Page 28 of 40
602
Table 2. Inter- and intra-day precisions of the present method (n=5)
604
Table 3. Analytical results of real vegetable oil samples
ip t
603
605
Table 4. Comparison of the present method with other reported methods
cr
606
Ac ce p
te
d
M
an
us
607
29
Page 29 of 40
668
Table 1. Analytical performances of the present method
Analyte
Linear range
Regression equation
(ng mL-1)
Correlation
LOD
LOQ
coefficient (r)
(ng mL-1)
(ng mL-1)
5.00-1000.00
A=194.61c-118.41
0.9996
1.34
4.42
Desmetryn
5.00-1000.00
A=419.31c-515.13
0.9999
1.49
4.91
Secbumeton
5.00-1000.00
A=456.64c+3683.2
0.9994
1.31
4.33
Terbutryn
5.00-1000.00
A=339.25c+910.18
0.9994
1.40
4.61
Dimethametryn
5.00-1000.00
A=325.69c+908.44
0.9995
1.49
4.91
Dipropetryn
5.00-1000.00
A=314.07c+1700.2
0.9992
1.41
4.67
cr
669 670
ip t
Cyanazine
Ac ce p
te
d
M
an
us
671
32
Page 30 of 40
Table 2. Inter- and intra-day precisions of the present method (n=5) Concentration
Intra-day
-1
Terbutryn
Dimethametryn
Dipropetryn
RSD (%)
Recovery (%)
RSD (%)
25.00
98.3
4.4
101.7
5.7
50.00
103.8
3.2
101.9
5.3
100.00
105.1
3.5
103.0
4.1
25.00
93.7
3.4
100.7
50.00
104.9
5.7
103.1
100.00
95.2
2.1
96.3
25.00
99.1
4.7
102.8
50.00
102.0
3.3
95.9
5.8
100.00
98.8
4.5
97.8
6.0
25.00
100.7
2.6
50.00
108.1
5.7
100.00
96.2
2.5 2.8
25.00
102.2
50.00
103.8
100.00
100.5
25.00
96.0
50.00
103.4
100.00
103.6
2.5 6.3
105.2
7.4
101.1
6.7
95.0
2.8
109.4
7.5
3.3
99.3
7.4
2.5
100.3
5.1
5.5
91.1
6.5
1.9
106.5
7.3
3.2
101.6
4.6
te Ac ce p
609
5.8
d
608
7.4
ip t
Secbumeton
Recovery (%)
cr
Desmetryn
(ng mL )
us
Cyanazine
Inter-day
an
Analyte
M
607
30
Page 31 of 40
674
Table 3. Analytical results of real vegetable oils samples
675 676
Cyanazi
ple
ed
ne
n
eton
n
metryn
(ng
Reco R
Reco R
Reco R
Reco R
Reco R
mL-1
very S
very S
very S
very S
very S
)
(%)
(%)
(%)
(%)
(%)
D
Desmetry
Secbum
D
D
Terbutry
D
(
(
(
%
%
%
%
)
)
)
50.0
10
2.
98.
7.
10
4.
11
ple 1
0
5.7
6
2
4
2.0
6
0.7
100.
10
4.
94.
1.
99.
an
)
Sam
4.5
9
1
7
7
50.0
99.
2.
10
5.
99.
ple 2
0
4
6
5.9
7
4
100.
10
1.
95.
2.
00
0.0
2
9
9
Sam
50.0
95.
7.
99.
3.
ple 3
0
9
7
6
8
100.
10
1.
91.
7.
00
0.5
4
1
Sam
50.0
89.
5.
ple 4
0
3
5
100.
10
4.
95.
ryn
Reco R very S
D
(%)
D
(
(
%
%
)
)
6.
10
1.
10
2.
4
4.5
4
3.4
6
10
2.
10
3.
3.
5
8
3
0.9
1
2.4
7
4.
10
4.
10
4.
99.
5.
4
1.5
5
2.6
4
8
9
95.
6.
95.
3.
99.
3.
99.
4.
9
4
5
0
5
0
0
2
10
3.
10
3.
86.
7.
81.
7.
4.7
2
1.0
4
9
4
8
6
98.
5.
10
1.
10
4.
10
4.
4
1
4
1.1
1
3.7
5
1.6
1
10
7.
10
5.
10
6.
10
2.
10
6.
5.3
4
6.2
8
3.6
6
1.5
7
5.3
7
88.
3.
91.
5.
94.
6.
10
4.
87.
6.
Ac ce p
te
d
M
00 Sam
4.
Dipropet
us
(
Dimetha
ip t
Spik
cr
Sam
00
2.2
3
2
6
6
5
3
0
3.6
6
9
4
Sam
50.0
11
3.
10
6.
10
4.
94.
3.
94.
4.
92.
5.
ple 5
0
4.2
4
0.6
3
2.7
8
9
9
8
2
8
6
100.
10
7.
97.
3.
10
3.
97.
1.
10
3.
10
6.
00
5.7
4
3
6
1.8
5
6
7
0.9
2
5.3
8
Sam
50.0
11
4.
10
1.
10
6.
91.
1.
99.
7.
10
4.
ple 6
0
3.6
4
1.5
4
9.3
8
6
3
7
7
2.5
8
100.
10
4.
10
7.
10
4.
97.
4.
10
2.
93.
6.
00
6.5
5
2.6
1
2.3
3
5
0
4.8
9
6
9
Sam
50.0
10
7.
97.
5.
10
4.
96.
6.
86.
4.
85.
3.
ple 7
0
6.2
3
5
0
0.3
7
7
7
2
7
7
9
100.
10
5.
10
2.
92.
6.
98.
3.
10
7.
10
7.
00
2.7
7
0.1
6
9
3
8
7
0.3
6
1.5
2
677 678 34
Page 32 of 40
Analytes
Extraction (time)
Vegetable oil
Triazine herbicides
90 μL [C6mim] [FeCl4] (7 min)
Olive oil and olives
Multiclass pesticides
35 mL acetonitrile (6 min)
Olive oil and olives
Multiclass pesticides
35 mL acetonitrile (6 min)
Organoarsenic compounds
1.25 mL hexane containing 0.05 mL ammonium formate buffer solution (pH=7) (4 min)
Cooking oil
Ricinine
5 mL ethanol/water (20:80, v/v) (6 min)
Olive oil
Triazine herbicides
35 mL acetonitrile (7 min)
Olive oil
Organophosphorus
5 mL acetonitrile/ dichloromethane (90:10, v/v) (10 min)
an
1.5 mL deionized water + 1.5 mL ethyl acetate
d
M
MSPD: 2 g aminopropyl-bonded silica + 2 g florisil MSPD: 2 g aminopropyl-bonded silica + 2 g florisil
ep te
Ac c
Edible oil
Cleanup procedure
Detection
Recovery (%)
RSD (%)
LOD
LOQ
References
LC-UV
81.8 -110.7
1.1-7.7
1.31-1.49 ng mL-1
4.33-4.91 ng mL-1
This work
GC-MS
73.2-129.
3-15
3-80 ng g-1
-
7
LC-MS
81-108
5-10
0.2-4 ng g-1
-
7
LC-MS
89.9-94.7
2.9-9.6
1.0-5.8 ng g-1
-
18
LC-MS/MS
86.0-98.3
2.6–7.0
-
0.5 ng g-1
11
LC/TOF-MS
81-111
2-4
1-5 ng g-1
-
6
GC-FPD
64-104
1-10
-
7-20 ng g-1
10
us
Matrix
cr
Table 4. Comparison of the present method with other reported methods
ip t
Table 4
-
dSPE: 200 mg anhydrous sodium sulfate + 30 mg PSA + 30 mg C18 MSPD: 2 g aminopropyl-bonded silica + 2 g florisil SPE: 500 mg ENVI-Carb cartridge
Page 33 of 40
Ac
ce
pt
ed
M
an
us
cr
i
Figure 1
Page 34 of 40
Ac
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pt
ed
M
an
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cr
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Figure 2
Page 35 of 40
Ac
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pt
ed
M
an
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cr
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Figure 3
Page 36 of 40
Ac
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pt
ed
M
an
us
cr
i
Figure 4
Page 37 of 40
Ac
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pt
ed
M
an
us
cr
i
Figure 5
Page 38 of 40
Ac
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pt
ed
M
an
us
cr
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Figure 6
Page 39 of 40
Ac
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pt
ed
M
an
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cr
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Figure 7
Page 40 of 40
S0021-9673(14)01749-X http://dx.doi.org/doi:10.1016/j.chroma.2014.11.009 CHROMA 355995
To appear in:
Journal of Chromatography A
Received date: Revised date: Accepted date:
28-6-2014 4-11-2014 5-11-2014
Please cite this article as: Y. Wang, Y. Sun, B. Xu, X. Li, R. Jin, H. Zhang, D. Song, Magnetic ionic liquid-based dispersive liquid-liquid microextraction for the determination of triazine herbicides in vegetable oils by liquid chromatography, Journal of Chromatography A (2014), http://dx.doi.org/10.1016/j.chroma.2014.11.009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
• DLLME was used for preconcentration of triazine herbicides from
2
vegetable oils.
3
• Magnetic ionic liquid was select as a novel microextraction solvent of
4
DLLME.
5
• Magnetic separation of the ionic liquid met the requirement of rapid
6
analysis.
7
• The performances were acceptable in comparison to existing methods.
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Page 1 of 40
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Magnetic ionic liquid-based dispersive liquid-liquid microextraction
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for the determination of triazine herbicides in vegetable oils by liquid
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chromatography
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cr
12
us
13
Yuanpeng Wang, Ying Sun, Bo Xu, Xinpei Li, Rui Jin, Hanqi Zhang,
15
Daqian Song*
an
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M
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College of Chemistry, Jilin University, Qianjin Street 2699,
20
Changchun 130012,
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d
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PR China
*Corresponding author: Daqian Song Tel.: +86-431-85168399
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Fax: +86-431-85168399
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E-mail address: [email protected]
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Page 2 of 40
30
Abstract
31
Magnetic ionic liquid-based dispersive liquid-liquid microextraction
32
(MIL-based DLLME) was developed for extracting triazine herbicides
33
from
34
tetrachloroferrate ([C6mim] [FeCl4]), was used as the microextraction
35
solvent. The magnetic separation time was shortened by simply mixing
36
carbonyl iron powder with the MIL in the sample after DLLME. The
37
effects of several important experimental parameters, including the
38
amount of MIL, the time of ultrasonic extraction, the type
39
volume of cleanup solvent were investigated. The MIL-based DLLME
40
coupled with liquid chromatography gave the limits of detection of
41
1.31-1.49 ng mL-1 and limits of quantification of 4.33-4.91 ng mL-1 for
42
triazine herbicides. When the present method was applied to the analysis
43
of vegetable oil samples, the obtained recoveries were in the range of
45 46 47
MIL,
1-hexyl-3-methylimidazolium
ip t
The
and the
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d
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an
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cr
oils.
Ac ce p
44
vegetable
81.8 -114.2% and the relative standard deviations were lower than 7.7%. Compared with existing methods, the performances achieved by the present method were acceptable.
48
Magnetic
ionic
liquids;
Dispersive
49
Keywords:
50
microextraction; Vegetable oil; Triazine herbicides
51
1. Introduction
liquid-liquid
3
Page 3 of 40
Triazine herbicides are a class of pre- and post-emergent broadleaf
53
herbicides with similar chemical structure that inhibit the growth of
54
weeds through disruption of photosynthesis pathways [1]. These
55
herbicides, such as atrazine, cyanazine, and desmetryn, are used widely
56
for maize, sorghum, citrus orchards, and grapes [2]. Because of the
57
prolonged and widespread use, the residues of the herbicides have been
58
found in a lot of agriculture products [3, 4]. The study has indicated that
59
some triazine herbicides are suspected to cause cancers, birth defects, and
60
interruption of hormone functions [5]. Consequently, there is a growing
61
need to monitor triazine herbicides in agriculture products.
M
an
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52
62
Vegetable oils which are mainly composed of triglycerides, are
64
commonly extracted from plant seeds, i.e., the oilseeds, such as the
65
seeds of soybean, maize, and sunflower. Pesticide residues in these seeds
67 68 69
te
Ac ce p
66
d
63
may be
transfered to vegetable oils during the oil extraction process.
Maximum residue limits (MRLs) in the range of 0.05-0.1 mg kg-1 for the residues of some triazine herbicides in oilseeds are established by the European Union (Commission Directive 2008/149/EC),
while the
70
MRLs for triazine herbicide residues in vegetable oils have not been
71
established. Therefore, a sensitive and accurate method for determination
72
of triazine herbicides in vegetable oils is particularly important to
73
guarantee public health and safety. To the best of our knowledge, the 4
Page 4 of 40
74
available literatures on determination of triazine herbicides in vegetable
75
oils are very limited [6, 7]. Extraction and cleanup are the most challenging parts for
77
determination of pesticide residues in food stuffs, especially in vegetable
78
oils with inherent complex fatty matrices [8]. Additionally, the low
79
concentrations of pesticide residues in oil samples also make the direct
80
determining of them difficult by chromatographic methods, such as liquid
81
chromatography (LC) or gas chromatography (GC) [9]. Therefore, there
82
is a need to employ exhaustive sample preparation technique for the
83
extraction and preconcentration of the residues from oil samples before
84
determination.
85
liquid-liquid extraction (LLE) [6-8, 10-11] and low-temperature fat
86
precipitation (LTFP) [12, 13], have been widely applied to the extraction
87
and preconcentration of target analytes from fatty samples. However,
89 90 91
cr
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sample
preparation
techniques,
such
as
te
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Various
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76
traditional LLE need time-consuming operating procedure and large amount of organic solvents, and LTFP usually takes a long time to precipitate fats in samples. Other preparation techniques, including solid-phase extraction (SPE) [8, 10, 13], matrix solid-phase dispersion
92
(MSPD) [7, 9], and dispersive solid-phase extraction (dSPE) [11] were
93
commonly coupled with the above-mentioned techniques and applied for
94
the clean-up. In recent years, research efforts on sample preparation
95
techniques have been directed towards simplifying the extraction 5
Page 5 of 40
procedure, saving operating time and reducing the consumption of
97
organic solvents.
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Since dispersive liquid-liquid microextraction (DLLME) was proposed
99
by Assadi and coworkers [14], this method has attracted much attention
100
owning to its significant advantages including small solvent usage of
101
microliter volumes, rapidity and high enrichment factor. DLLME is a
102
promising alternative to the classic LLE and has been widely appliedto
103
the extraction of target analytes in water-soluble samples [15-17], while
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there are only a couple of reports about the application of DLLME in the
105
sample preparation of fat-soluble vegetable oils [18, 19].
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Ionic liquids (ILs) are a class of organic salts with low melting
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points [20]. The unique properties of ILs, including negligible vapor
108
pressure, good chemical and thermal stability, excellent solubility for both
109
organic and inorganic compounds, and environmental friendliness [21,
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d
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22], make them promising extraction solvents used in separation [16, 17, 23]. The combinations of different organic cations with various organic or inorganic anions leads to a large amount of ILs with numerous possible applications, and ILs with special properties can also be designed through proper chemical modifications [24].
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Nowadays, developments and applications of magnetizable ILs
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become a new field and a hotspot of research in sample preparation
117
techniques [25-28]. Generally, ILs were bonded or immobilized on the 6
Page 6 of 40
surface of magnetic supports to form solid materials and used as magnetic
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adsorbents in magnetic solid-phase extraction [25-27], while only few
120
publications reported on the metal-containing ILs, which incorporated the
121
metal in the ILs to introduce magnetic property [28]. Recently, a novel
122
class of magnetic ionic liquids (MILs) with single-component was
123
discovered, of which the magnetic property is no longer introduced as
124
external magnetic supports, but provided by complex ions of metals [26,
125
29-30]. The first example of MILs is 1-butyl-3-methylimidazolium
126
tetrachloroferrate ([C4mim] [FeCl4]). Although the compound has been
127
known for some time [31], its magnetic behavior was not described until
128
2004 [32]. These MILs are basically based on the anions containing
129
high-spin d5 iron (Ⅲ), which were in the forms of tetrachloro- or
130
tetrabromoferrate (III), with varieties of counter cations. Because of their
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high single-ion magnetic moments, MILs show a good response to an
133 134 135
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external magnetic field [28], and are very interesting to be employed as novel extraction solvents to take the place of routine nonmagnetic ILs of DLLME. The MILs can be uniformly dispersed in sample solutions through ultrasound irradiation and can be isolated from the solutions by
136
means of an external magnetic field. However, to our knowledge, there is
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only one report about the application of MILs on separation of target
138
analytes, in which the MIL was used for solvent extraction of phenolic
139
compounds from aqueous solution [33]. Because MILs contain polar 7
Page 7 of 40
functional groups, such as protonated primary amines and esters, as well
141
as the hydrophilic tetrachloroferrate (III) anions, most MILs are miscible
142
with water or other polar solvents after vigorous shaking, which restrict
143
their applications of separation and concentration of analytes dissolved in
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water. In contrast, they are immiscible with hydrophobic solvents such as
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carbon tetrachloride and n-hexane [26]. Herein, MILs are promising
146
microextraction solvents of DLLME for vegetable oils.
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In
this
study,
an
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1-hexyl-3-methylimidazolium
tetrachloroferrate
([C6mim] [FeCl4]) was selected as the microextraction solvent of the
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MIL-based DLLME for extracting triazine herbicides from vegetable oils,
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including two soybean oils, three maize oils and two sunflower seed oils.
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In addition, carbonyl iron powder (CIP) was added to shorten magnetic
153
separation time after DLLME, which can be magnetically attracted by the
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d
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M
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MIL to form a combination of CIP and MIL (CIP-MIL). Several important experimental parameters, such as the amount of MIL, the time of ultrasound extraction, the type and the volume of cleanup solvent, were optimized. Under the optimized conditions, the present method was successfully applied to the analysis of real vegetable oil samples
159 160
2. Experimental
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Page 8 of 40
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2.1. Chemicals and reagents Chromatographic grade acetonitrile was purchased from Fisher
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Scientific Company (UK). [C6mim] [FeCl4] (> 99%) was purchased from
165
Chengjie Chemical Co. LTD (Shanghai, China). CIP with average particle
166
size less than 4.30 μm (Purity > 97.8%) was purchased from Jilin Jien
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Nickel Industry (Panshi, China). Padding materials of primary secondary
168
amine (PSA, 50 μm), C18 (50 μm) and graphitized carbon black (GCB)
169
were purchased from Bonna-Agela Technologies. All other reagents were
170
of analytical grade and purchased from Beijing Chemical Factory
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(Beijing, China).
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Standards
of
d
system (Millipore, New York, USA). cyanazine,
te
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Deionized water was obtained with a Milli-Q water purification
desmetryn,
secbumeton,
terbutryn,
dimethametryn and dipropetryn were obtained from National Institute for
Ac ce p
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the Control of Pharmaceutical and Biological Products (Beijing, China). The chemical structures of these herbicides are shown in Fig. 1. Stock solutions were prepared by dissolving each substance in chromatographic grade acetonitrile at a concentration of 400 μg mL-1 and stored at 4 ℃ in
180
darkness. Mixed working solutions at desirable concentrations were
181
prepared by mixing the stock solutions followed by diluting with
182
chromatographic grade acetonitrile.
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Page 9 of 40
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2.2. Instruments LC analyses) were performed using a LC-20ADXR liquid
186
chromatograph (Shimadzu, Japan) with two pumps (LC-20AD), an
187
autosampler (SIL-20A), a column oven (CTO-20A) and a UV-vis detector
188
(SPD-20A). Chromatographic separation of the analytes were carried out
189
using a shim-pack VP-ODS column (150 mm × 4.6 mm, 4.6 μm particle
190
size). Relevant data acquisition and processing were accomplished with
191
Shimadzu LC solution software.
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The KQ-100 ultrasonic cleaner was purchased from Kunshan
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Ultrasonic Instrument Co., Ltd. (Kunshan, China). The frequency and
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output power of the ultrasonic cleaner are 40 kHz and 100 W,
196
respectively.
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2.3. Samples
The vegetable oil samples were purchased from local supermarkets.
Seven vegetable oil samples, including 2 soybean oil (sample 1, 2), 3 maize oils (sample 3-5) and 2 sunflower seed oil (sample 6, 7) were
202
analyzed. The samples used for recovery and precision studies were
203
previously analyzed. The experimental results showed that there wasno
204
peak at the retention positions of the analytes in the chromatograms
205
obtained with the sample extracts. The target pesticides in the samples 10
Page 10 of 40
were undetectable. Spiked samples containing triazine herbicides were
207
prepared by spiking the mixed working standard solutions into samples.
208
After being well mixed, the samples were equilibrated for 1 h in the dark
209
at room temperature. All the experiments were carried out with sample 1
210
except for those mentioned in Section 3.2.4 in which all samples
211
(sample1-7) were used.
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212
2.4. Extraction procedure
214
2.4.1. DLLME
an
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1 mL of vegetable oil sample was diluted with 7 mL of n-hexane in
216
10 mL centrifuge tube and mixed for 2 min. Subsequently, 90 μL of
217
[C6mim] [FeCl4] was added into the tube and ultrasonicated for 7 min to
218
extract the analytes from samples. Then 400 mg of CIP was added, and
219
the mixture was vigorously shaken for 30 s to form the CIP-MIL. Then,
221 222 223
d
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M
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the CIP-MIL was subsequently collected with a strong magnet placed out the wall of the tube, and the supernatant was decanted. The CIP-MIL was washed with 500 μL of n-hexane for three times. Then, 1.5 mL of deionized water was added into the tube to dissolve the MIL, and then 1.5
224
mL of ethyl acetate was added to extract the target analytes. The resulting
225
mixture was shaken for 4 min, then the upper layer of ethyl acetate was
226
sucked into a glass tube and evaporated under a gentle nitrogen stream at
227
40℃. Finally, the residuewas redissolved in 100 μL of acetonitrile and 11
Page 11 of 40
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filtered through a 0.22 μm nylon membrane, followed by LC analysis.
229
Illustration of the whole extraction procedure is shown in Fig. 2.
230
2.4.2. QuEChERS The quick, easy, cheap, effective, robust and safe (QuEChERS)
232
procedure was performed according to a previousliterature [34]. 1 mL of
233
vegetable oil sample and 2.5 mL of water were added into 10 mL
234
centrifuge tube. Then, 3.5 mL of acetonitrile was added, along with 1.4 g
235
of anhydrous magnesium sulphate and 0.35 g of sodium chloride. The
236
tube was vigorously shaken for 1 min. The mixture was centrifuged (4000
237
rpm) for 1 min. The tube was horizontally stored in freezer at -20 ℃ for 2
238
h. Then, the supernatant was transferred into a PTFE centrifuge tube
239
containing 450 mg of anhydrous magnesium sulphate, 150 mg of PSA,
240
150 mg of C18 and 150 mg of GCB. After shaken for 30 s, the mixture
241
was centrifuged (4000 rpm) for 1 min. The supernatant was evaporated to
243 244 245 246
cr
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d
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242
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dryness under a gentle nitrogen stream at 40℃. Finally, the residues were redissolved in 100 μL of acetonitrile and filtered through a 0.22 μm nylon membrane, followed by LC analysis.
2.5. LC analysis
247
The LC analysis was conducted in gradient mode. The gradient has
248
been optimized in advance. Mobile phases A and B are acetonitrile and
249
water, respectively. The gradient program is as follows: 0-10 min, 12
Page 12 of 40
80-70% B; 10-18 min, 70-40% B; 18-25 min, 40-35% B; 25-30 min,
251
35-80% B. The flow rate of mobile phase was kept at 1.0 mL min-1.
252
Injection volume of analytical solution was 10 μL. The monitoring
253
wavelength was 220 nm for all the target compounds [35].
3. Results and discussion
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3.1. Optimization of MIL-based DLLME conditions
an
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In order to obtain high extraction efficiency, the effects of several
259
experimental parameters, such as the amount of [C6mim] [FeCl4], the
260
ultrasound extraction time, the type and the volume of cleanup solvent
261
were investigated. All the experiments were performed in triplicate.
264 265 266 267
d
te
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3.1.1. Effect of amount of [C6mim] [FeCl4]
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The triazine herbicides were hardly extracted with CIP in the
absence of [C6mim] [FeCl4], indicating that the [C6mim] [FeCl4] played a key role in the extraction of target analytes. The effect of the amounts of [C6mim] [FeCl4] ranging from 30 μL to 110 μL were investigated. As can
268
be concluded from Fig. 3, the extraction efficiency increases rapidly
269
when the amount of [C6mim] [FeCl4] increases from 30 μL to 90 μL,
270
indicating the remarkable enrichment ability of [C6mim] [FeCl4]. No
271
obvious change is observed when the amount of [C6mim] [FeCl4] 13
Page 13 of 40
increases from 90 μL to 110 μL, indicating that excessive MIL without
273
combination to CIP can not be collected by magnetic separation.
274
Therefore, 90 μL was employed as the amount of [C6mim] [FeCl4] in the
275
following experiments.
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3.1.2. Effect of ultrasound extraction time
The effect of ultrasound extraction time was investigated by
279
increasing the time from 2 to 15 min. The profiles of extraction time and
280
extraction efficiency for the analytes are shown in Fig. 4. The recoveries
281
of triazine herbicides increase with the increase of extraction time from 2
282
to 5 min, and remain stable with a further increase of extraction time from
283
5 to 10 min. To ensure the complete extraction of analytes, the extraction
284
time was selected as 7 min.
286 287 288 289
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3.1.4. Effect of cleanup solvent type The cleanup solvent can significantly affect the extraction of the
target analytes and cleanup capability within one step in this experiment. In order to improve the cleanup efficiency and reduce the extraction loss,
290
a selection of cleanup solvent is indispensable. The cleanup solvent
291
should have low solubility in water, high dissolving ability for triazine
292
herbicides and low dissolving ability for interference constituents. Based
293
on these considerations, four kinds of organic solvents, including 14
Page 14 of 40
petroleum ether, diethyl ether, ethyl acetate and dichloromethane, were
295
considered as the cleanup solvent. The extraction capabilities of the above
296
solvents are compared in Fig. 5. Under the same extraction conditions,
297
ethyl acetate provided the highest extraction efficiency due to its
298
strongest dissolving ability for triazine herbicides, and the clean
299
chromatogram with low baseline level and signal noise was also obtained
300
with ethyl acetate. Therefore, ethyl acetate was used as the cleanup
301
solvent in the following experiments
an
302
3.1.5. Effect of the volume of cleanup solvent
M
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294
The volume of ethyl acetate ranging from 0.5 mL to 2.5 mL was
305
investigated. As can be seen from Fig. 6, an increase in volume of ethyl
306
acetateranging from 0.5 to 1.5 mL results in an increase in the recoveries
307
of triazine herbicides, and no obvious change is observed when the
309 310 311 312
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d
304
volume of ethyl acetate is larger than 1.5 mL. Therefore, 1.5 mL of ethyl acetate was selected for extraction of triazine herbicides in the following experiments.
3.2. Evaluation of the method
313
After the important conditions of extracting these herbicides were
314
validated, a new analytical method was developed for quantitative
315
determination of the six triazine herbicides in vegetable oils. In order to 15
Page 15 of 40
evaluate the performances of the present method, the working curves,
317
linear range, correlation coefficient (r), limit of detection (LOD) and
318
quantification (LOQ), and reproducibility were studied. The spiked
319
samples were analyzed by the present method.
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cr
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3.2.1. Linearity
The working curves were constructed by plotting the corresponding
323
peak areas measured versus the concentrations of triazine herbicides in a
324
series of spiked samples. As listed in Table 1, the present method exhibits
325
satisfactory linearity in the concentration range of 5.00-1000.00 ng mL-1
326
with good correlation coefficients (r) higher than 0.9992.
M
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322
330 331 332 333
te
329
3.2.2. Limit of detection and quantification The LODs and LOQs were determined based on the signal-to-noise
Ac ce p
328
d
327
ratio of 3 and 10, respectively. The results obtained are given in Table 1. The LODs and LOQs are in the range of 1.31-1.49 ng mL-1 and 4.33-4.91 ng mL-1, respectively. Because of the interferences of complex fatty matrices in vegetable oils, the LODs obtained by the present method are
334
somewhat higher than that obtained by several previous methods [36, 37],
335
which were applied to the determination of triazine herbicides in aqueous
336
samples.
337
16
Page 16 of 40
338
3.2.3. Precision and recovery The intra- and inter-day precision of the present method were
340
obtained by analyzing the spiked sample at concentrations of 25.00, 50.00
341
and 100.00 ng mL-1. The intra-day RSDs were obtained by analyzing the
342
sample five times a day, and the inter-day RSDs were obtained by
343
analyzing samples which were independently prepared for consecutive
344
five days. The RSDs obtained are listed in Table 2. The intra- and
345
inter-day RSDs were in the range of 1.9-5.7% and 2.5-7.5%, respectively,
346
indicating the acceptable precision.
348
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347
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339
3.2.4. Analysis of real vegetable oil samples The developed MIL-based DLLME method coupled with LC was
350
applied to the determination of the six triazine herbicides in vegetable oil
351
samples. The real samples were pretreated under the optimized conditions
353 354 355
te
Ac ce p
352
d
349
and no herbicides were detectable. Seven kinds of spiked samples at analyte concentrations of 50.00 and 100.00 ng mL-1 were analyzed. The typical chromatograms of the blank and spiked sample are shown in Fig. 7, and the analytical results are listed in Table 3. As can be seen, the
356
present method provides good recoveries ranging from 81.8-114.2% and
357
acceptable precision lower than 7.7%.
358 359
3.2.5. Comparison with QuEChERS 17
Page 17 of 40
In order to further evaluate the present method, the present method
361
was compared with QuEChERS [35]. The recoveries and RSDs of the six
362
triazine herbicides obtained by QuEChERS at concentrations of 50.00
363
and 100.00 ng mL-1 range from 80.3 to 121.7% and 2.3 to 9.2%,
364
respectively. By comparation, the recoveries and RSDs of the same
365
spiked samples obtained by the present method range from 94.1-110.7%
366
and 1.4 to 7.4%. The LODs of QuEChERS are in the range of 4.32-5.12
367
ng mL-1, which are higher than these of the present method. These results
368
indicates that the precision and the sensitivity of the present method are
369
both better than that of QuEChERS. In addition, the consumption of
370
extraction solvent in the present method is low and the extraction time
371
(7min) is much shorter than that (122 min) of QuEChERS. Moreover, the
372
magnetic separation
373
eliminates the routine centrifugation procedure.
375 376 377
cr
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d
te
simplifies the sample preparement process and
Ac ce p
374
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360
3.2.6. Comparison with other reported methods The present method was further compared with the reported methods
for the determination of target analytes in fatty matrices [6, 7, 10, 11, 18]. The results are shown in Table 4. It can be seen that the consumption of
378
extraction solvent in the present method is lower than that in other
379
methods. Compared with acetonitrile and dichloromethane used in some
380
methods, n-hexane and ethyl acetate used in the present method have
381
lower toxicity. The LODs and RSDs obtained by the present method are 18
Page 18 of 40
similar to or lower than these obtained by the reported methods.
383
Therefore, it can be concluded that the present method is suitable for
384
the determination of triazine herbicides in vegetable oils.
ip t
382
385
4. Conclusion
cr
386
In summary, a rapid, easy and low-solvent-consumption extraction
388
method, MIL-based DLLME was successfully developed and applied for
389
the extraction of triazine herbicides from vegetable oils. It is the first time
390
to use MIL as the microextraction solvent for fat-soluble samples, and
391
magnetic separation was selected to simplify separation procedure. The
392
present method overcame the drawback of MILs being miscible with
393
water and the limitation unsuitable for fat-soluble samples. It could be
394
considered that this method is very promising for the extraction of
395
analytes from complex fat-soluble samples by varying extraction
397 398 399
an
M
d
te
Ac ce p
396
us
387
parameters. Since the present method is pretty straightforward and easy to perform. The extraction step could be combined withLC for online determination of the herbicides. [38]
400 401
Acknowledgments
402
This work was supported by National Natural Science Foundation of
403
China (No. 20727003, 21075049, and 21105037), Program for New 19
Page 19 of 40
Century
Talents
in
University
(No.
405
Special-funded Programme on National Key Scientific Instruments and
406
Equipment Development (No. 2012YQ090194) and Science and
407
Technology Developing Foundation of Jilin Province (No. 20100356 and
408
20110162).
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an
411 412
References
M
413
NECT-10-0443),
cr
Excellent
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404
414
[1] M. Graymore, F. Stagnitti, G. Allinson, Impacts of atrazine in aquatic
416
ecosystems, Environ. Int. 26 (2001) 483-495.
417
[2] A. Cabrera, L. Cox, W.C. Koskinen, M. J. Sadowsky, Availability of
419 420 421
te
Ac ce p
418
d
415
triazine herbicides in aged soils amended with olive oil mill waste, J. Agric. Food Chem. 56 (2008) 4112-4119. [3] K. Zhang, J.W. Wong, P. Yang, K. Tech, A.L. Dibenedetto, N.S. Lee, D.G. Hayward, C.M. Makovi, A.J. Krynitsky, K. Banerjee, L. Jao, S.
422
Dasgupta, M.S. Smoker, R. Simonds, A. Schreiber, Multiresidue pesticide
423
analysis of agricultural commodities using acetonitrile salt-out extraction,
424
dispersive solid-phase sample clean-up, and high-performance liquid
425
chromatography-tandem mass spectrometry, J. Agric. Food Chem. 59 20
Page 20 of 40
(2011) 7636-7646.
427
[4] O. Núñez, H. Gallart-Ayala, I. Ferrer, E. Moyano, M.T. Galceran,
428
Strategies for the multi-residue analysis of 100 pesticides by liquid
429
chromatography-triple quadrupole mass spectrometry, J. Chromatogr. A
430
1249 (2012) 164-180.
431
[5] P. Norouzi, B. Larijani, M.R. Ganjali, F. Faridbod, Admittometric
432
electrochemical
433
immune-biosensor using FFT-Square wave voltammetry, Int.
434
Electrochem. Sci. 7 (2012) 10414-10426.
435
[6] J.F. Garcia-Reyes, C. Ferrer, E.M. Thurman, A.R. Fernandez-Alba, I.
436
Ferrer, Analysis of herbicides in olive oil by liquid chromatography
437
time-of-flight mass spectrometry, J. Agric. Food Chem. 54 (2006)
438
6493-6500.
439
[7] C. Ferrer, M.J. Gómez, J.F. García-Reyes, I. Ferrer, E.M. Thurman,
441 442 443
cr
atrazine
by
nano-composite
us
of
J.
te
d
M
an
determination
Ac ce p
440
ip t
426
A.R. Fernández-Alba, Determination of pesticide residues in olives and olive
oil
by
matrix
solid-phase
dispersion
followed
by
gas
chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry, J. Chromatogr. A 1069 (2005) 183-194.
444
[8] A.L. Capriotti, C. Cavaliere, C. Crescenzi, P. Foglia, R. Nescatelli, R.
445
Samperi, A. Laganà, Comparison of extraction methods for the
446
identification and quantification of polyphenols in virgin olive oil by
447
ultra-HPLC-QToF mass spectrometry, Food Chem. 158 (2014) 392-400. 21
Page 21 of 40
448
[9] B. Gilbert-López, J.F. García-Reyes, A. Molina-Díaz, Sample
449
treatment and determination of pesticide residues in fatty vegetable
450
matrices: A review, Talanta 79 (2009) 109-128.
451
[10]
452
microwave-assisted extraction coupled with solid-phase extraction for
453
organophosphorus pesticide determination in olive oil, J. Chromatogr. A
454
1207 (2008) 38-45.
455
[11] M.Q. Cai, X.H. Chen, X.Q. Wei, S.D. Pan, Y.G. Zhao, M.C. Jin,
456
Dispersive solid-phase extraction followed by high-performance liquid
457
chromatography/tandem mass spectrometry for the determination of
458
ricinine in cooking oilFood Chem. 158 (2014) 459-465.
459
[12] C. Anagnostopoulos, G.E. Miliadis, Development and validation of
460
an easy multiresidue method for the determination of multiclass pesticide
461
residues using GC-MS/MS and LC-MS/MS in olive oil and olives,
463 464 465
Báez,
A.
Quiñones,
Suitability
of
ip t
M.E.
te
d
M
an
us
cr
Fuentes,
Ac ce p
462
E.
Talanta 112 (2013) 1-10.
[13] Ch. Lentza-Rizosa, E.J. Avramides, E. Visi, Determination of residues of endosulfan and five pyrethroid insecticides in virgin olive oil using gas chromatography with electron-capture detection, J. Chromatogr.
466
A 921 (2001) 297-304.
467
[14] M. Rezaee, Y. Assadi, M.R. Milani, E. Aghaee, F. Ahmadi, S.
468
Berijani, Determination of organic compounds in water using dispersive
469
liquid-liquid microextraction, J. Chromatogr. A 1116 (2006) 1-9. 22
Page 22 of 40
[15] L.H. Liu, L.J. He, X.M. Jiang, W.J. Zhao, G.Q. Xiang, J.L. Anderson,
471
Macrocyclic polyamine-functionalized silica as a solid-phase extraction
472
material coupled with ionic liquid dispersive liquid-liquid extraction for
473
the enrichment of polycyclic aromatic hydrocarbons, J. Sep. Sci. 37 (2014)
474
1004-1011.
475
[16] X.W. Chen, A. Sakurazawa, K. Sato, K-I. Tsunoda, J.H. Wang, A
476
solid-cladding/liquid-core/liquid-cladding sandwich optical waveguide
477
for the study of dynamic extraction of dye by ionic liquid BmimPF6, Appl.
478
Spectrosc. 66 (2012) 798-802.
479
[17] C. Yao, T.H. Li, P. Twu, W.R. Pitner, J.L. Anderson, Selective
480
extraction of emerging contaminants from water samples by dispersive
481
liquid-liquid microextraction using functionalized ionic liquids, J.
482
Chromatogr. A 1218 (2011) 1556-1566.
483
[18] W.X. Wang, T.J. Yang, Z.G. Li, T.T. Jong, M.R. Lee, A novel method
485 486 487
cr
us
an
M
d
te
Ac ce p
484
ip t
470
of ultrasound-assisted dispersive liquid-liquid microextraction coupled to liquid chromatography-mass spectrometry for the determination of trace organoarsenic compounds in edible oil, Anal. Chim. Acta 690 (2011) 221-227.
488
[19] M.P. Godoy-Caballero, M.I. Acedo-Valenzuela, T. Galeano-Díaz,
489
New reversed phase dispersive liquid-liquid microextraction method for
490
the determination of phenolic compounds in virgin olive oil by rapid
491
resolution liquid chromathography with ultraviolet-visible and mass 23
Page 23 of 40
spectrometry detection, J. Chromatogr. A 1313 (2013) 291-301.
493
[20] Y.T. Daia, J.V. Spronsen, G.J. Witkamp, R. Verpoorte, Y.H. Choi,
494
Natural deep eutectic solvents as new potential media for green
495
technology, Anal. Chim. Acta 766 (2013) 61-68.
496
[21] S. Pandey, Analytical applications of room-temperature ionic liquids:
497
A review of recent efforts, Anal. Chim. Acta 556 (2006) 38-45.
498
[22] C.F. Poole, S.K. Poole, Extraction of organic compounds with room
499
temperature ionic liquids, J. Chromatogr. A 1217 (2010) 2268-2286.
500
[23] P. Berton, R.G. Wuilloud, Highly selective ionic liquid-based
501
microextraction method for sensitive trace cobalt determination in
502
environmental and biological samples, Anal. Chim. Acta 662 (2010)
503
155-162.
504
[24] M. Li, S.L.D. Rooy, D.K. Bwambok, B. El-Zahab, J.F. DiTusa, I.M.
505
Warner, Magnetic chiral ionic liquids derived from amino acids, Chem.
507 508 509
cr
us
an
M
d
te
Ac ce p
506
ip t
492
Commun. 45 (2009) 6922-6924. [25] H.D. Qiu, M. Takafuji, X. Liu, S.X. Jiang, H. Ihara, Investigation of π-π and ion-dipole interactions on 1-allyl-3-butylimidazolium ionic liquid-modified silica stationary phase in reversed-phase liquid
510
chromatography, J. Chromatogr. A 1217 (2010) 5190-5196.
511
[26] M. Li, J.H. Zhang, Y.B. Li, B. Peng, W.F. Zhou, H.X. Gao, Ionic
512
liquid-linked dual magnetic microextraction: A novel and facile procedure
513
for the determination of pyrethroids in honey samples, Talanta 107 (2013) 24
Page 24 of 40
81-87.
515
[27] E. Yilmaz, M. Soylak, Ionic liquid-linked dual magnetic
516
microextraction of lead(II) from environmental samples prior to its
517
micro-sampling flame atomic absorption spectrometric determination,
518
Talanta 116 (2013) 882-886.
519
[28] B. Mallick, B. Balke, C. Felser, A.V. Mudring, Dysprosium
520
room-temperature ionic liquids with strong luminescence and response to
521
magnetic fields, Angew. Chem. Int. Ed. 47 (2008) 7635-7638.
522
[29] R.E. Del Sesto, T.M. McCleskey, A.K. Burrell, G.A. Baker, J.D.
523
Thompson, B.L. Scott, J.S. Wilkes, P. Williams, Structure and magnetic
524
behavior of transition metal based ionic liquids, Chem. Commun. 4 (2008)
525
447-449.
526
[30] T. Peppel, M. Kockerling, M. Geppert-Rybczynska, R. V. Ralys, J.K.
527
Lehmann, S.P. Verevkin, A. Heintz, Low-viscosity paramagnetic ionic
529 530 531
cr
us
an
M
d
te
Ac ce p
528
ip t
514
liquids with doubly charged [Co(NCS)4]2- Ions, Angew. Chem., Int. Ed. 49 (2010) 7116-7119.
[31] M.S. Sitze, E.R. Schreiter, E.V. Patterson, R.G. Freeman, Ionic liquids based on FeCl3 and FeCl2. Raman scattering and ab initio
532
calculations, Inorg. Chem. 40 (2001) 2298-2304.
533
[32] S. Hayashi, H. Hamaguchi, Discovery of a magnetic ionic liquid
534
[bmim]FeCl4, Chem. Lett. 33 (2004) 1590-1591.
535
[33] N. Deng M. Li, L.J. Zhao, C.F. Lu, S.L. de Rooy, I.M. Warner, 25
Page 25 of 40
Highly efficient extraction of phenolic compounds by use of magnetic
537
room temperature ionic liquids for environmental remediation, J. Hazard.
538
Mater. 192 (2011) 1350-1357.
539
[34] E. Sobhanzadeh, N.K. Abu Bakar, M.R. Bin Abas, K.Nemati, A
540
simple and efficient multi-residue method based on QuEChERS for
541
pesticides determination in palm oil by liquid chromatography
542
time-of-flight mass spectrometry, Environ. Monit. Assess. 184 (2012)
543
5821-5828.
544
[35] M. Battista, A. Di Corcia, M. Marchetti, Extraction and isolation of
545
triazine herbicides from water and vegetables by a double trap tandem
546
system, Anal. Chem. 61(1989) 935-939.
547
[36] D. Nagaraju, S.D. Huang, Determination of triazine herbicides in
548
aqueous samples by dispersive liquid–liquid microextraction with gas
549
chromatography-ion trap mass spectrometry, J. Chromatogr. A 1161
551 552 553
cr
us
an
M
d
te
Ac ce p
550
ip t
536
(2007) 89-97.
[37] Y.L. Hu, Y.Y. Wang, Y.F. Hu, G.K. Li, Liquid-liquid-solid microextraction based on membrane-protected molecularly imprinted polymer fiber for trace analysis of triazines in complex aqueous samples,
554
J. Chromatogr. A 1216 (2009) 8304-8311.
555
[38] B. Bjarnason, L. Chimuka, O. Ramström, On-line solid-phase
556
extraction of triazine herbicides using a molecularly imprinted polymer
557
for selective sample enrichment, Anal. Chem. 71 (1999) 2152-2156. 26
Page 26 of 40
558 559
ip t
560 561
cr
562
us
563 564
an
565 566
Figure Captions
M
567 568
d
Fig. 1. Chemical structures of the triazine herbicides.
te
569 570
572 573 574 575 576
Fig. 2. Schematic diagram of the extraction procedure.
Ac ce p
571
Fig. 3. Effect of the amount of [C6mim] [FeCl4] on the recoveries of the triazine herbicides.
Ultrasound extraction time, 7 min; cleanup solvent, ethyl acetate; volume of cleanup solvent, 1.5 mL; spiked concentration, 100 ng mL-1.
577 578
Fig. 4. Effect of the ultrasound extraction time on the recoveries of the
579
triazine herbicides. 27
Page 27 of 40
Amount of [C6mim] [FeCl4], 90 μL; cleanup solvent type, ethyl acetate;
581
the volume of cleanup solvent, 1.5 mL; spiked concentration, 100 ng
582
mL-1.
ip t
580
583
Fig. 5. Effect of cleanup solvent type on the recoveries of the triazine
585
herbicides.
586
The amount of [C6mim] [FeCl4], 90 μL; Ultrasound extraction time, 7
587
min; volume of cleanup solvent, 1.5 mL; spiked concentration, 100 ng
588
mL-1.
an
us
cr
584
M
589
Fig. 6. Effect of the volume of cleanup solvent on the recoveries of the
591
triazine herbicides.
592
Amount of [C6mim] [FeCl4], 90 μL; Ultrasound extraction time, 7 min;
593
cleanup solvent, ethyl acetate; spiked concentration, 100 ng mL-1.
595 596 597
te
Ac ce p
594
d
590
Fig. 7. Chromatograms of sample 1 (A) and spiked sample 1 (B). 1, Cyanazine; 2, desmetryn; 3, secbumeton; 4, terbutryn; 5, dimethametryn; 6, dipropetryn. Spiked concentration, 100 ng mL-1.
598 599
Tables
600 601
Table 1. Analytical performances of the present method 28
Page 28 of 40
602
Table 2. Inter- and intra-day precisions of the present method (n=5)
604
Table 3. Analytical results of real vegetable oil samples
ip t
603
605
Table 4. Comparison of the present method with other reported methods
cr
606
Ac ce p
te
d
M
an
us
607
29
Page 29 of 40
668
Table 1. Analytical performances of the present method
Analyte
Linear range
Regression equation
(ng mL-1)
Correlation
LOD
LOQ
coefficient (r)
(ng mL-1)
(ng mL-1)
5.00-1000.00
A=194.61c-118.41
0.9996
1.34
4.42
Desmetryn
5.00-1000.00
A=419.31c-515.13
0.9999
1.49
4.91
Secbumeton
5.00-1000.00
A=456.64c+3683.2
0.9994
1.31
4.33
Terbutryn
5.00-1000.00
A=339.25c+910.18
0.9994
1.40
4.61
Dimethametryn
5.00-1000.00
A=325.69c+908.44
0.9995
1.49
4.91
Dipropetryn
5.00-1000.00
A=314.07c+1700.2
0.9992
1.41
4.67
cr
669 670
ip t
Cyanazine
Ac ce p
te
d
M
an
us
671
32
Page 30 of 40
Table 2. Inter- and intra-day precisions of the present method (n=5) Concentration
Intra-day
-1
Terbutryn
Dimethametryn
Dipropetryn
RSD (%)
Recovery (%)
RSD (%)
25.00
98.3
4.4
101.7
5.7
50.00
103.8
3.2
101.9
5.3
100.00
105.1
3.5
103.0
4.1
25.00
93.7
3.4
100.7
50.00
104.9
5.7
103.1
100.00
95.2
2.1
96.3
25.00
99.1
4.7
102.8
50.00
102.0
3.3
95.9
5.8
100.00
98.8
4.5
97.8
6.0
25.00
100.7
2.6
50.00
108.1
5.7
100.00
96.2
2.5 2.8
25.00
102.2
50.00
103.8
100.00
100.5
25.00
96.0
50.00
103.4
100.00
103.6
2.5 6.3
105.2
7.4
101.1
6.7
95.0
2.8
109.4
7.5
3.3
99.3
7.4
2.5
100.3
5.1
5.5
91.1
6.5
1.9
106.5
7.3
3.2
101.6
4.6
te Ac ce p
609
5.8
d
608
7.4
ip t
Secbumeton
Recovery (%)
cr
Desmetryn
(ng mL )
us
Cyanazine
Inter-day
an
Analyte
M
607
30
Page 31 of 40
674
Table 3. Analytical results of real vegetable oils samples
675 676
Cyanazi
ple
ed
ne
n
eton
n
metryn
(ng
Reco R
Reco R
Reco R
Reco R
Reco R
mL-1
very S
very S
very S
very S
very S
)
(%)
(%)
(%)
(%)
(%)
D
Desmetry
Secbum
D
D
Terbutry
D
(
(
(
%
%
%
%
)
)
)
50.0
10
2.
98.
7.
10
4.
11
ple 1
0
5.7
6
2
4
2.0
6
0.7
100.
10
4.
94.
1.
99.
an
)
Sam
4.5
9
1
7
7
50.0
99.
2.
10
5.
99.
ple 2
0
4
6
5.9
7
4
100.
10
1.
95.
2.
00
0.0
2
9
9
Sam
50.0
95.
7.
99.
3.
ple 3
0
9
7
6
8
100.
10
1.
91.
7.
00
0.5
4
1
Sam
50.0
89.
5.
ple 4
0
3
5
100.
10
4.
95.
ryn
Reco R very S
D
(%)
D
(
(
%
%
)
)
6.
10
1.
10
2.
4
4.5
4
3.4
6
10
2.
10
3.
3.
5
8
3
0.9
1
2.4
7
4.
10
4.
10
4.
99.
5.
4
1.5
5
2.6
4
8
9
95.
6.
95.
3.
99.
3.
99.
4.
9
4
5
0
5
0
0
2
10
3.
10
3.
86.
7.
81.
7.
4.7
2
1.0
4
9
4
8
6
98.
5.
10
1.
10
4.
10
4.
4
1
4
1.1
1
3.7
5
1.6
1
10
7.
10
5.
10
6.
10
2.
10
6.
5.3
4
6.2
8
3.6
6
1.5
7
5.3
7
88.
3.
91.
5.
94.
6.
10
4.
87.
6.
Ac ce p
te
d
M
00 Sam
4.
Dipropet
us
(
Dimetha
ip t
Spik
cr
Sam
00
2.2
3
2
6
6
5
3
0
3.6
6
9
4
Sam
50.0
11
3.
10
6.
10
4.
94.
3.
94.
4.
92.
5.
ple 5
0
4.2
4
0.6
3
2.7
8
9
9
8
2
8
6
100.
10
7.
97.
3.
10
3.
97.
1.
10
3.
10
6.
00
5.7
4
3
6
1.8
5
6
7
0.9
2
5.3
8
Sam
50.0
11
4.
10
1.
10
6.
91.
1.
99.
7.
10
4.
ple 6
0
3.6
4
1.5
4
9.3
8
6
3
7
7
2.5
8
100.
10
4.
10
7.
10
4.
97.
4.
10
2.
93.
6.
00
6.5
5
2.6
1
2.3
3
5
0
4.8
9
6
9
Sam
50.0
10
7.
97.
5.
10
4.
96.
6.
86.
4.
85.
3.
ple 7
0
6.2
3
5
0
0.3
7
7
7
2
7
7
9
100.
10
5.
10
2.
92.
6.
98.
3.
10
7.
10
7.
00
2.7
7
0.1
6
9
3
8
7
0.3
6
1.5
2
677 678 34
Page 32 of 40
Analytes
Extraction (time)
Vegetable oil
Triazine herbicides
90 μL [C6mim] [FeCl4] (7 min)
Olive oil and olives
Multiclass pesticides
35 mL acetonitrile (6 min)
Olive oil and olives
Multiclass pesticides
35 mL acetonitrile (6 min)
Organoarsenic compounds
1.25 mL hexane containing 0.05 mL ammonium formate buffer solution (pH=7) (4 min)
Cooking oil
Ricinine
5 mL ethanol/water (20:80, v/v) (6 min)
Olive oil
Triazine herbicides
35 mL acetonitrile (7 min)
Olive oil
Organophosphorus
5 mL acetonitrile/ dichloromethane (90:10, v/v) (10 min)
an
1.5 mL deionized water + 1.5 mL ethyl acetate
d
M
MSPD: 2 g aminopropyl-bonded silica + 2 g florisil MSPD: 2 g aminopropyl-bonded silica + 2 g florisil
ep te
Ac c
Edible oil
Cleanup procedure
Detection
Recovery (%)
RSD (%)
LOD
LOQ
References
LC-UV
81.8 -110.7
1.1-7.7
1.31-1.49 ng mL-1
4.33-4.91 ng mL-1
This work
GC-MS
73.2-129.
3-15
3-80 ng g-1
-
7
LC-MS
81-108
5-10
0.2-4 ng g-1
-
7
LC-MS
89.9-94.7
2.9-9.6
1.0-5.8 ng g-1
-
18
LC-MS/MS
86.0-98.3
2.6–7.0
-
0.5 ng g-1
11
LC/TOF-MS
81-111
2-4
1-5 ng g-1
-
6
GC-FPD
64-104
1-10
-
7-20 ng g-1
10
us
Matrix
cr
Table 4. Comparison of the present method with other reported methods
ip t
Table 4
-
dSPE: 200 mg anhydrous sodium sulfate + 30 mg PSA + 30 mg C18 MSPD: 2 g aminopropyl-bonded silica + 2 g florisil SPE: 500 mg ENVI-Carb cartridge
Page 33 of 40
Ac
ce
pt
ed
M
an
us
cr
i
Figure 1
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pt
ed
M
an
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cr
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Figure 2
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pt
ed
M
an
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cr
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Figure 3
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ce
pt
ed
M
an
us
cr
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Figure 4
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ce
pt
ed
M
an
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cr
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Figure 5
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Ac
ce
pt
ed
M
an
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cr
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Figure 6
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Ac
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pt
ed
M
an
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Figure 7
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