Different methods to select the best extraction system for solid-phase extraction.

www.jss-journal.com

Page 1

Journal of Separation Science

DIFFERENT METHODS TO SELECT THE BEST EXTRACTION SYSTEM FOR SOLID-PHASE EXTRACTION

Katarzyna Bielicka-Daszkiewicz* Institute of Technology and Chemical Engineering, Poznań University of Technology pl. M. Skłodowskiej-Curie 5, 60-965 Poznań, Poland

Keywords: breakthrough volume , Hansen solubility parameter, optimization methods, Solid-phase extraction,

* Corresponding author: K. Bielicka-Daszkiewicz D.Sc., Poznań University of Technology, Institute of Technology and Chemical Engineering, Berdychowo 4, 60-965 Poznań, Poland, phone: +4861 6653722, fax: +4861 6653717, e-mail: [email protected]

Received: 01-Oct-2014; Revised: 12-Nov-2014; Accepted: 12-Nov-2014 This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/jssc.201401083. This article is protected by copyright. All rights reserved.

www.jss-journal.com

Page 2


Abstract The optimization methods for planning a solid-phase extraction experiment are presented. These methods are based on a study of interactions between different parts of an extraction system. Determination of the type and strength of interaction depends on the physicochemical properties of the individual components of the system. The main parameters that determine the extraction properties are described in this work: The influence of sorbents’ and solvents’ polarity on extraction efficiency, Hansen solubility parameters and breakthrough volume determination on sorption and desorption extraction step.

1. Introduction The sample preparation step is one of the most important stages of the analysis which affects the accuracy of the final result of the analytical process. The SPE method is one of the most popular separation techniques used on the sample preparation step, before chromatographic analysis. It is suitable for isolation of organic and inorganic compounds from different matrices: there are water samples, gaseous samples, biological, medical and environmental samples. The analysis of water samples, using chromatographic techniques (especially GC), requires the isolation of analytes, transfer of analytes to the organic solvent and concentration the solution. Extraction techniques, especially SPE, are very useful for achieving this purpose. In the planning of the extraction experiment, the appropriate choice of sorbents and solvents is very important for ensuring the highest efficiency of the extraction process. Till now, the selection of sorbents and solvents has only been based on the polarity of analyte, sorbent and solvent. In practice, the sorbent and solvent selection, very often require many experiments in different analyte/sorbent/solvent systems. Based on these experiments, the system which achieved the best extraction recovery could be chosen. In the planning of the extraction experiment, described in Refs. [1–7] at least several sorbents and solvents must be examined. For example, Peček at al. [6], have optimized the SPE–GC–MS method for the determination of 20 pesticides in water. They examined 16 different sorbents, 6 solvents in 5 volumes, for 4 volumes of water samples. Of course, it is very tedious and time-consuming work. Reviewing the literature, we can see there is a need to develop the appropriate method for fast and accurate optimization of the extraction technique. Some statistical methods were applied for the optimization of the SPE analysis or This article is protected by copyright. All rights reserved.

www.jss-journal.com

Page 3


other analytical methods, for example, the Taguchi optimization method was used at the planning stage of the experiment [8–14]. In this article, some methods for characterization of the extraction system, without long experiment or calculation procedures are presented. These new methods can be very useful for accurate and fast selection of the best extraction system.

2. The main assumptions The aim of this work is the presentation of the optimization methods for planning the SPE experiment. These methods were developed, based on the study of the interactions between different parts of the extraction system, determination of the type and strength of interaction depending on the physicochemical properties of individual components of the system. The knowledge and expeditious estimation of these parameters can be used for developing a fast and accurate method for selecting the sorbents and solvents to obtain possible highest extraction recovery. To achieve the aim given above, the following problems were formulated and described in this work: –the relationship between properties of sorbent, analyte and solvents and the extraction efficiency expressed as the percentage of extraction recovery; –hydrodynamic characteristic of extraction systems, estimation of breakthrough volume and sorption capacity of the extraction bed; –preparation of fast and accurate method for choosing the extraction system on the basis of the relationship given above and the sorbents’ physicochemical characteristics.

2.1. The influence of polarity of sorbent, solvent and analyte on extraction recovery The efficiency of the extraction method is highly influenced by the physicochemical properties of sorbents as well as analytes and solvents. In Ref. [4], the relationship between the extraction recovery and the following parameters is presented: -

polarity of sorbents and solvents;

-

sorbent surface area, pore diameter, pore volume, pore size;

-

specific volume of solvent particles.

The research was carried out for phenol and hydroquinone acetic derivatives; polymeric sorbents were used: two commercial sorbents: styrene-divinylbenzene (ST-DVB) and styrene-divinybenzene modified with butyrolactame (StrataX) and four new porous polymers were examined, it was divinylbenzene copolymerized with the follow monomers: -

di(methacryloyloxymethyl)naphtalene (DMN-DVB);

This article is protected by copyright. All rights reserved.

www.jss-journal.com

Page 4


-

p,p'-dihydroxydiphenylmethane diglycidyl methacrylic ester (MEMDE-DVB);

-

p,p'-dihydroxydiphenylpropane diglycidyl methacrylic ester (MEDDE-DVB);

-

4,4'-bis(maleimido)diphenylmethane (BM-DVB).

The analysis of the relationship shows that for tested compounds the extraction recovery decreases with the increasing polarity of the sorbents. The higher recovery was achieved on sorbent characterized by smaller particle size and pore size and higher pore volume. Other comparison show that stronger influence on the extraction recovery have pore volume, surface area and porosity of sorbent than particle size and pore size. These studies have also shown that extraction recovery does not depend on polarity of solvents but rather on its specific volume (size of a solvent’s molecule). Based on the study and discussion of the results it can be concluded that SPE recovery is connected with the molecular geometry of the sorbent, eluent and analytes. Experimental results obtained for the studied extraction systems were used to verify the effectiveness of the extraction process according to physicochemical characteristics of the parts of the extraction system. These results were used for prediction of sorbents’ usefulness for the isolation of analytes from complex water samples [4].

2.2. The use of the Hansen solubility parameter for determination of the individual interactions between respective parts of the extraction device For determining the interdependence and interaction between sorbent, analytes and solvents the solubility parameter has been applied. This parameter describes the different types of intermolecular interactions. In the article [15], the application of the solubility parameter for the description of the interactions in the extraction systems is extensively presented. Such comparisons are an important element in the planning of the experiment and the selection of the individual parts of the extraction system. The total solubility parameter was introduced by Hildebrand in 1970 [16], it is defined as the square root of the cohesive energy density attributed to the unit of compound molar volume. Cohesive energy is defined as the potential energy of a liquid. It indicates the energy associated with the forces that keep the molecules close together in a condensed state. This definition was modified by Hansen. The cohesive energy might be divided into three parts corresponding to: dispersive, polar and hydrogen bonding interactions. Based on this assumption, the total solubility parameter δT (known as the corrected solubility parameter) can be defined as the sum of three components corresponding to the


www.jss-journal.com

Page 5


three types of molecular interactions mentioned above: dispersive δd, polar δp and hydrogen bonding δh. Ecoh= Ed + Ep + Eh δT2

2

2

= δd + δp + δh

(1) 2

(2)

Parameters δd, δp and δh are called the Hansen Solubility Parameters (HSP). In the SPE technique, the HSP has been used for the selection of the best analyte/sorbent/solvent system. Interactions between individual parts of the extraction system on the sorption step (introducing the sample onto the sorbent) and desorption step (elution of analytes) were taken into account. As the measure of the interaction, the square of the difference of the total solubility parameter has been taken for the following parts of extraction system: sorbent/analyte, sorbent/sample matrix, sorbent/eluent, analyte/sample matrix and analyte/eluent. (δT(A) – δT(B))2 (3) Designated parameters allowed for the description and comparison of interaction on the adsorption and desorption extraction steps. When the square of the difference given with the equation (3) is small, then the interactions are strong, and when this square of difference is high, then the interactions are weak. The Hansen solubility parameters were determined for two analytes: phenol and pbenzoquinone, for four solvents: methanol, dichloromethane, acetonitrile and ethyl acetate and for eight polymeric sorbents [15]: -

StrataX

–

styrene-divinylbenzene

copolymer

modified

with

butyrolactame,

interaction: RP; -

StrataX-C – StrataX sorbent modified with sulfonic groups, interaction: SCX and RP;

-

StrataX-CW –StrataX sorbent modified with carboxylic groups, interaction: WCX and RP;

-

StrataX-AW –StrataX sorbent modified with diamine, interaction: WAX and RP.

and divinylbenzene copolymers: DMN-DVB, MEMDE-DVB, MEDDE-DVB, BMDVB. For all steps mentioned above, the interaction between all components of the system are important. For example, in the sorption step the interaction between sorbent and analyte must be stronger than analyte/sample matrix and solvent/sorbent interaction. However, the analyte/sorbent interaction cannot be too strong because of desorption possibility. In the desorption step the interaction should be parallel: the strongest between analyte and solvent This article is protected by copyright. All rights reserved.

www.jss-journal.com

Page 6


(eluent), while the weakest should be analyte/sorbent and sorbent/eluent interaction. Determined values allow us to predict the elution sequence in the desorption step.

2.2.1. Chemometric analysis Calculation of the Hansen solubility parameters in different systems, gives us a large amount of data. These results can be grouped using chemometric methods. These methods allow for comparison, and grouping relevant extraction systems. In the previous research, some chemometric methods were used: principal component analysis (PCA); comparison of ranks by random numbers (CRRN); multiple linear regression (MLR) and partial least squares (PLS) [15]. Figure 1 shows a result of plots obtained with the use of the PCA chemometric method. The points plotted on graphs, are the values of the square of the differences of solubility parameters for different sorbent/eluent systems. Results given in Figure 1a and 1c illustrate the role of solvents on different extraction steps. Figure 1b gives the role of the sorbent. The applied method allows for grouping of the solvents and sorbents with similar properties. The presented plots show that the points can be divided into two separate groups. Points represented in systems with ethanol and acetonitrile, are clearly separated from those where methylene chloride and ethyl acetate are used as solvent (Fig. 1a). Similarly, the sorbents’ properties can be analyzed (Fig. 1b). The model proposed in this research enables the selection of optimal extraction systems for different compounds, taking into account the sorption and desorption step. For example: for phenol as analyte, suitable systems are StrataX-C and StrataX-CW sorbent and dichloromethane as eluent.

3. Determination of the sorption properties of the sorbents The next important element in the planning of the extraction process is designation of sorbent capacity. To solve this problem, breakthrough volume of solid sorbent were determined. In article [17], the determination of breakthrough volume for different sorbents has been discussed in detail. The determination of breakthrough volume is important, because we can estimate the sample volume that can be introduced into the sorbent bed without losing the analytes, and additionally, we can determine the sorbent efficiency with the number of theoretical plates. Breakthrough volume can be determined experimentally in several ways. The most widely known and used method for determination of breakthrough volume, is frontal analysis (frontal chromatography). It can be used in on-line and off-line mode [18– 20]. In this method, the effluent from the sorbent bed is analyzed during the sorption step and This article is protected by copyright. All rights reserved.

www.jss-journal.com

Page 7


the concentration of the analyte in the effluent is measured by UV detector in on-line mode or using HPLC in off-line mode. The breakthrough curve is determined in this way (Fig. 2). The breakthrough curve can be defined as: the dependence between the concentration of the analyte in the effluent and volume of the sample passed through the sorbent. Using this curve, the sorbent efficiency can be determined with number of theoretical plates and hold-up volume. This method is very time-consuming and relatively less accurate, because some parameters are determined from the breakthrough curve, graphically. A calculating method for quick and accurate estimation of the breakthrough volume of sorbent, without long and arduous experiment has been developed [17]. For calculation, the breakthrough volume of the relationship (4) proposed by Lövkvist and Jönsson is suitable [21]. 1 a1 a2  2  VB  VR  a0   2  N N  

(4)

From these equation the breakthrough time tB (5) and extraction time te (6) can be calculated.

L1  k   a a  tB   a0  1  22  u  N N 

1

2

L 1  k  te  u where:

(5)

(6)

VB – breakthrough volume VR – retention volume a0, a1, a2 – function of breakthrough level N – number of theoretical plates k – retention factor L – sorbent length u – linear velocity of solvent passed through the sorbent bed A detailed calculation method is presented in Ref. [17]. The experiment was only necessary for determination of the capacity factor (k) for individual analytes. A very significant aspect of this research is the determination of extraction efficiency of sorbents. The new calculation method allows us to determine the number of theoretical plates based on the following sorbent and solvent properties: surface area, pore volume, particle size This article is protected by copyright. All rights reserved.

www.jss-journal.com

Page 8


for sorbent and solvent flow rate, linear solvent velocity, diffusion coefficient for analyte. The number of theoretical plates was determined without the experiment. In many scientific papers, the number of theoretical plates is determined by using the HPLC technique. This method is effective but not always possible to execute, especially when we have small amount of sorbent. The method of determination of the breakthrough volume and other parameters was described for phenol, hydroquinone and benzoquinone, isolated from water samples, using some polymeric sorbents mentioned in Section 2. The results achieved using calculation method, were comparable with the results obtained by using frontal analysis. A comparison of these two procedures, demonstrate that the calculation method is more advantageous because it does not require a long experiment, is easy to use and is more accurate than frontal analysis. Determining the breakthrough volume of an extraction system, we can estimate the sorbent mass, length and the sample volume. Breakthrough volume determination can be useful for the description of the sorption and desorption extraction step, too. On the adsorption step, the breakthrough volume should be as large as possible (for sample matrix) to avoid the loss of analyte, resulting from elution analytes by sample matrix. On desorption (elution), the determined breakthrough volume describes the volume of eluent sufficient for removing the analyte from the SPE bed, this breakthrough volume should be as small as possible. The calculation method was used in the determination of steroids in biological samples [22]. In such analysis, calculation method is very important due to the fact that the standards of steroids are available in a very small amount and are very expensive. Calculation was done for nine steroids, including key estrogens and progestagens. The experiment was necessary for the determination of retention factor for examined sorbent. The breakthrough volume was determined for elution step. Retention factors were derived from a micro-TLC experiment, conducted on the same sorbent as in SPE experiment. The calculation was done for methanol/water mixture used as eluent. On the elution step, analytes should be eluted with the minimum volume of solvent. If we want to describe elution process, using breakthrough volume, adsorbed analytes should be eluted with the smallest volume of eluent, then the breakthrough volume determined for analytes in the eluent should be the smallest. In the research [22], three different methods for the description of the elution process were compared. One of them was determination of the elution profile (frontal analysis) – concentration of analytes was determined with UV spectroscopy in each eluent aliquot. Breakthrough volume was determined as volume of the whole elution peak. In the second This article is protected by copyright. All rights reserved.

www.jss-journal.com

Page 9


method, the breakthrough volume was determined as the center of elution peak gravity. In the final method, the breakthrough volume was calculated by using the procedure described above. In all these methods, breakthrough volume was determined for SPE silica sorbent C18. The comparison of these methods allowed for a detailed description of elution process. This way of calculation allows us to estimate the beginning of the steroid peak, when the analyte appears in the mobile phase flowing from the sorbent. Frontal analysis, involved at the end of the peak, allows us to determine the value of eluent that is necessary for the elution of the whole amount of analyte, while frontal analysis involving peak gravity criterion allows us to point the volume of solvent for elution near 80% of analyte.

4. Conclusion Experience obtained in the use of SPE for different analytical systems, isolation of compounds with different physicochemical properties, and the study of interaction of extraction system elements, allows us to propose the way of extraction system selection. All extraction steps are important. The study shows that the selection of individual elements of the extraction system is essential, both on the sorption and desorption (elution) step. First, physicochemical properties of analytes, sorbent and solvents, should be completed: physical state, solubility, boiling/melting point, reactivity, polarity, diffusion coefficient in different solvents for analytes, sorbent diameter, sorbent length, sorbent mass, pore diameter, pore volume, surface area, the hold-up volume, polarity, ionic properties for sorbent, and density, boiling point, flow rate for solvents. Following that, the determination of parameters is very important which allows the description of interaction between individual elements of the extraction system. After which, the Hansen solubility parameters can be determined between particular extraction elements: analyte/sorbent/solvent (eluent, sample matrix). This is useful for choosing the best extraction system. What would be more desirable is an extraction system in which analyte/sorbent interactions are bigger than the analyte/sample matrix and sorbent/sample matrix interaction. A system in which the desorption step analyte/eluent interactions are bigger than analyte/sorbent interaction and eluent/sorbent interactions are not too big is preferable. The use of a chemometric method will indicate which extraction systems are similar. Then, the breakthrough volume should be determined for the description of sorbent capacity and efficiency, and indirectly, extraction time or breakthrough time. It allows us to estimate sample volume and volume of eluent in extraction experiment.


www.jss-journal.com

Page 10


Assessing the suitability of the extraction system, we must base it not only on determination of the extraction recovery (this is necessary and obvious in the planning of the experiment), but also a more complete characterization of the extraction system can be done when we determine the sorbent capacity (capacity factor), breakthrough volume, extraction time and breakthrough time. The proposed method of selection for the best extraction system, which does not require an experiment (or requires a very short experiment), allows us to estimate the efficiency of extraction system and accurately plan the experiment with optimal condition. Acknowledgement This work was supported by DS PB 32-440/2014

References [1]. Mutavdžić Pavlović, D., Ašperger, D., Tolić, D., Babić, S., J. Sep. Sci., 2013, 36, 3042– 3049. [2]. Bielicka, K., Kaczorek, E., Olszanowski, A., Voelkel, A., Pol. J. Environ. Stud. 2002, 11/1, 11–16. [3]. Bielicka-Daszkiewicz, K., Dębicka, M., Voelkel, A., J. Chromatogr. A, 2004, 1052, 233– 236. [4]. Bielicka-Daszkiewicz, K., Voelkel, A., Szejner, M., Osypiuk, J., Chemosphere 2006, 62, 890–898. [5]. Bielicka-Daszkiewicz, K., Hadzicka, M., Voelkel, A., ISRN Chromatography (Open access journal), vol. 2012, article ID 680929, DOI: 10.5402/2012/680929. [6]. Peček, G., Mutavdžić Pavlović, D., Babić, S., Intern. J. Environ. Anal. Chem., 2013, 93/12, 1311–1317. [7]. Jordan, T.B., Nicholas, D.S., Kerr, N.I. Anal. Bioanal. Chem. 2009, 394, 2257–2267. [8]. Anbia, M., Ghasemian, M.B., Shariat, S., Zolfaghari, G., Anal. Methods, 2012, 4, 4220– 4229. [9]. Wang, T-Y., Huang, C-Y., Eur. J. Oper. Res., 2007, 176, 1052–1065. [10]. Ghambarian, M., Yamini, Y., Saleh, A., Shariati, S., Yazdanfar, N., Talanta, 2009, 78, 970–976. [11]. Musharraf, S.G., Mazhar, S., Siddiqui, A.J., Choudhary, M.I., Atta-ur-Rahman, Anal. Chim. Acta, 2013, 804, 180–189. [12]. Tarley, C.R.T., Silveira, G., das Santos, W.N.L., Matos, G.D., da Silva, E.G.P., Bezerra, M.A., Miró, M., Ferreira, S.L.C., Microchem. J., 2009, 92, 58–67. This article is protected by copyright. All rights reserved.

www.jss-journal.com

Page 11


[13]. Liu, L., Wen, Y-B., Liu, K-N., Sun, L, Wu, M., Han, G-F., Lu, Y-X., Wang, Q-M., Yin, Z., J. Chromatogr. B, 2013, 923–924, 8–15. [14]. Metafa, M., Economou, A., J. Chromatogr. A, 2013, 1305, 244–258. [15]. Bielicka-Daszkiewicz, K., Voelkel, A., Pietrzyńska, M., Héberger, K., J. Chromatogr. A, 2010, 1217, 5564–5570. [16]. Hildebrand, J.H., Prausnitz, J.M., Scott, R.L., Regular and Related Solutions, Van Nostrand-Reinhold, New York 1970. [17]. Bielicka-Daszkiewicz, K., Voelkel, A., Talanta, 2009, 80, 614–621. [18] Poole C. F., Poole S. K., Seibert D. S., Chapman Ch. M., J. Chromatogr. B, 1997, 698, 245. [19] Seibert D. S., Poole C. F., J. High Resolut. Chromatogr., 1998, 21(9), 481. [20] Poole C. F., Gunatilleka A. D., Sethuraman R., J. Chromatogr. A, 2000, 885, 17–39. [21]. Lövkvist, P., Jönsson, J.Å., Anal. Chem. 1987, 59, 818–821. [22]. Bielicka-Daszkiewicz, K., Voelkel, A., Rusińska-Roszak, D., Zarzycki, P., J. Sep. Sci. 2013, 36, 1104–1111.


www.jss-journal.com

Figure 1. PCA score plots


Page 12


www.jss-journal.com


Page 13


www.jss-journal.com

Page 14


Figure 2. Breakthrough curves determined for 2,4-dichlorophenol isolated from water sample on polymeric sorbents


Comparison of six different pretreatment methods for blood RNA extraction.

Finding best practices for fossil fuel extraction.

Comparison of different extraction methods of Alternaria allergens.

Influence of different cell extraction methods on cytometric features.

Methods for extraction and quantification of receptors.

The best option: Umbilical LESS radical nephrectomy with vaginal extraction.

Comparative evaluation of different extraction and quantification methods for forensic RNA analysis.

Four different methods comparison for extraction of astaxanthin from green alga Haematococcus pluvialis.

Comparison of different serum sample extraction methods and their suitability for mass spectrometry analysis.

Validation of a new extraction device for measuring faecal calprotectin in inflammatory bowel disease, and comparison to established extraction methods.

Electronic Nose Feature Extraction Methods: A Review.

Chemical Compounds and Extraction Methods of "Maollahm".

Generalized framework for context-specific metabolic model extraction methods.

Methods for selective extraction of chromosomal nonhistone proteins.

Alternative and efficient extraction methods for marine-derived compounds.

Extraction for metabolomics: access to the metabolome.

Mechanomyographic parameter extraction methods: an appraisal for clinical applications.

Modified Lipid Extraction Methods for Deep Subsurface Shale.

Supercritical fluid extraction of polychlorinated biphenyls and pesticides from soil. Comparison with other extraction methods.

Extraction of nucleic acids from agarose gel--a quantitative and qualitative comparison of four different methods.

Comparative Analysis of the Bufonis Venenum by Using TLC, HPLC, and LC-MS for Different Extraction Methods.

Study to find the best extraction solvent for use with guava leaves (Psidium guajava L.) for high antioxidant efficacy.

Plant Growth Biostimulants Based on Different Methods of Seaweed Extraction with Water.

[How can we nowadays select the best embryo to transfer?].