The Science of the Total Environment, 123/124 (1992) 29-37 Elsevier Science Publishers B.V., Amsterdam
29
Gas chromatographic determination of some modern pesticides in fruits A. Neicheva a, D. Karageorgiev b and T. Konstantinova c aHigher Institute of Food Industry, 26 Maritza BI., 4002 Plovdiv, Bulgaria bFruit Growing Research Institute, Plovdiv, Bulgaria CTechnological University of Sofia, 1756 Sofia, Bulgaria
ABSTRACT A method was developed for determination for residual amounts of some modern insecticides, acaricides and fungicides in fruits. The pesticides were extracted with methanol and partitioned into chloroform. The extract was purified by column chromatography on sodium sulphate/Florisil/Celite/charcoal. Analysis by gas liquid chromatography with 63Ni electron capture detection was completed successivelyon a column (150 cm x 4 mm) with 3% SE-30 and a column (150 cm x 2 mm with 3% OV-17 liquid phase. Recoveries of 17 pesticides from fortified samples of apples ranged from 83.3% to 98.4% for a level of 0.1 mg/kg. Key words: pesticides; analysis; residues; gas-liquid chromatography; fruits
INTRODUCTION The strict control o f pesticide residues in fruits is necessary for protecting the consumer from harmful impact. The quickest way to achieve this involving least expense is by means of applying methods for multicomponent gas chromatographic analysis [1-5]. The aim of our study was to develop a quick and economical method for determination of some m o d e m insecticides, acarieides and fungicides in fruits. The study includes pesticides not referred to in the literature, with respect to the conditions ensuring their simultaneous extraction and gas chromatographic determination. We have also studied preparations which are applied for treating fruit tree crops throughout their period in fruit, ineluding the time near the harvest in which way they can contaminate fruit production.
30
A. NEICHEVA ET AL.
EXPERIMENTAL
Materials Standard acetone solutions containing 0.001 mg/ml of each of the following pesticides: dimethoate, tetrachlorvinphos, diazinon, phosalone, fenitrithion, chlorpyriphos, cyhalothrin, triflumizole, fenarimol, vinclosolin, hexathiazox, flubenzimine and guazatin, as well as 0.005 mg/ml of pyrazophos, pyrimiphosmethyl iprodione and deltamethrin. As solvents acetonitrile, methanol, petroleum ether, diethyl ether and chloroform, were all used analytical grade. Chromatographic supports. Florisil, Celite and charcoal (Fluka). Apparatus. A Pye Unicam Model 304 gas chromatograph with 63Nielectron capture detector supplied with a Spectra Physics Model SP4270 Integrator.
Procedure A solution containing 10 ~g of each of the pesticides studied was mixed with 100 g of apple homogenate, free of pesticides. All pesticides were extracted with 130 ml methanol for 50 min on a shaking machine at a speed ensuring good blending of the whole material. After filtration the water/methanol mixture was added to 150 ml of 10% solution of NaCI in a separatory funnel. The pesticides were successively re-extracted for 1 min with 80 ml chloroform (for recovering the more polar pesticides - - diazinon, dimethoate, vinclosolin, tetrachlorvinphos, etc.) and with 80 ml of chloroform/petroleum ether (8:2) (for the more complete recovery of nonpolar pesticides - - deltametrin, cyhalothrin, flubenzimine, hexathiasox, etc.). The chloroform extracts were concentrated to 4-5 ml at 40°C and were passed down a chromatographic column (d = 1 cm), packed with 5 g of mixture of sodium sulphate/Florisil/Celite/charcoal (1:1:0.5:0.1). The elution of the pesticides from the column was carried out with 90 ml of CHC13/diethyl ether (95:5). The eluate was evaporated to dryness at 40°C and the dry residue was dissolved in 4 ml of acetone. Gas chromatography of 1 #1 of this solution was achieved on a column (150 cm × 4 mm) with 3% SE-30 on 100-120 mesh Chromosorb W with programmed change of temperature 150°C -- l°C/min -- 170°C -- 4°C/min -- 200°C, as well as on a column (150 cm x 2 mm) with 3% OV-17 on a 100-120 mesh Chromosorb W and change of temperature 170°C --, 2°C/min -- 210°C (12 min) --10°C/rain -. 230°C. The flow of the carrier gas (nitrogen) was 50-60 ml/min, the temperature of the injector and detector being 240°C and 280°C. The standard acetone solution of the pesticides (1 #1) was successively
GAS CHROMATOGRAPHIC DETERMINATION OF PESTICIDES IN FRUITS
31
chromatographed on both columns under the same conditions. The chromatogramms were processed according to the method of absolute calibration. RESULTS AND DISCUSSION
Finding effective conditions for extraction of 17 pesticides studied, which appear to be phosphorus-, chlorine-, sulfur and nitrogen-containing compounds, is the first stage in developing a method for their determination. In our experiments with some extracting agents that have become widespread in multicomponent pesticide analysis, we found that the change in the degree of pesticide recovery from the fruits is in the following order: CH3OH > acetonitrile > acetone. The choice of methanol as an extracting agent was determined not only by its higher extracting ability towards the pesticides studied (from 3% to 10% for the different representatives), but also because the methanol fruit extracts contain less co-extractives than the acetone or acetonitrile extracts (Fig. 1).
AI 4
o.g 0,8,
3 ~
0,7. 08
o..s
o,2 o,t o #,oo
2Jo
3o0
j~
nrn
Fig. 1. UV spectra of purified apple extract without pesticides, in different extracting agents: 1, acetone; 2, acetonitrile; 3, methanol/acetonitrile (hi); 4, methanol.
32
A. NEICHEVA ET AL.
8 * 9~'fO
#,~
(O)
"H
¢5
3
b _._..
o :,
~ ~
~s 2o ~;~ ,~8 e:e -;6 ,;o ~ ~8 ,;-,e ~8 ;o rain
Fig. 2. Gas Chromatogram of a standard mixture of 17 pesticides. (a) Column (15 cm x 4 mm) with 3% SE-30 at temperature programme: 150°C -- l°C/min -- 170°C -- 4°C/min -200°C. (b) Column (150 cm x 2 mm) with 3% OV-17 at temperature programme: 170°C 2°C/min - 210°C (12 rain) --10°C/min -- 230°C. Peaks and spike level (ng): l, dimethoate (1); 2, diazinon (l); 3, vunclosolin (1); 4, fenitrothion (1); 5, pyrimiphosmethyl (5); 6, chlorpyriphos (1); 7, quazatin (1); 8, tetrachlorvinphos (1); 9, triflumizole (1); 10, hexathiazox (1); 11, flubenzimine (1); 12, iprodione (5); 13, phosalone (1); 14, fenarimol (l); 15, pyrazophos (5); 16, cyhalothrin (1); 17, deltamethrin (5).
T h e c l e a n - u p o f fruit e x t r a c t s was c a r r i e d o u t b y m e a n s o f l i q u i d - l i q u i d s e p a r a t i o n o f the pesticides a n d c o - e x t r a c t i v e s a n d a s u b s e q u e n t c o l u m n c h r o m a t o g r a p h y [6]. T h e n e x t i m p o r t a n t stage in the s i m u l t a n e o u s d e t e r m i n a t i o n o f the c o m b i n a t i o n o f 17 pesticides s t u d i e d was the c h o i c e o f a n a d e q u a t e s t a t i o n a r y
33
GAS CHROMATOGRAPHIC DETERMINATION OF PESTICIDES IN FRUITS
(bJ
,pf
I #6
47
8
mi,"l
Fig. 2 (Continued).
phase. For this purpose we studied comparatively the ability of 4 different polar phases (3% SE-30, 3% OV-17, 3% OV-225 and 1.5% OV-17 + 1.95% QF-1) for quick separation and determination of the pesticides, the standard mixture of the studied compounds being chromatographed on each one of them in columns of equal length (150 cm) at adequately chosen temperature conditions. An electron capture detector (ECD) was used being an effective detecting system for chemically different halogenated pesticide residues. From the chromatograms we got it turned out that the most suitable for pesticide determination were columns with phases 3% SE-30 and 3% OV-17, which is why we give data only for the separation performed on them (Fig. 2).
34
A. NEICHEVA ET A L
8+ g + "IO
42
fa)
3 ¢3
H
6 45+ IG
!
(0)
Fig. 3. Gas chromatogram analysing apples. (a) Column (150 cm x 4 mm) with 3% SE-30 at temperature programme: 150°C -- l°C/min -- 170°C -- 4°C/rain -- 200°C. (b) Column (150 cm x 2 mm) with 3% OV-17 at temparature programme: 170°C -- 2°C/min -- 210°C (12 min) -- 10°C/min - 230°C. Untreated apples fortified with (0.1 mg/kg), a, b: 1, dimethoate; 2, diazinon; 3, vinclosolin; 4, fenitrothion; 5, pyrimiphosmethyl; 6, chlorpyriphos; 7, quazatin; 8, tetrachlorvinphos; 9, triflumizole; 10, hexathiazox; 11, flubenzimine; 12, iprodione; 13, phosalone; 14, fenarimol; 15, pyrasophos; 16, cyhalothrin; 17, deltamethrin; Untreated apples: a ' , b'.
35
GAS CHROMATOGRAPHIC DETERMINATION OF PESTICIDES 1N FRUITS
~h
/b)
46
~4 ~2
I
(b)
\ b
2~
8
¢2
¢6
20 24 2a
32
38 40
44
48
S~ ,~8
Fig. 3 (Continued).
The chromatographic studies made up show that the simultaneous determination of the pesticides under study is possible with one ECD-detector when they are chromatographed successively under temperature conditions chosen, on a column with 3% SE-30 (ensuring analysis of dimethoate,
36
A. NEICHEVAEl"AL.
TABLE 1
Gas chromatographic determination of pesticides in apples using the method of standard addition No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Pesticide
Diazinon Dimethoate Pyrimiphosmethyl Chlorpyriphos Tetrachlorvinphos Phosalone Fenitrothion Pyrasophos Deltametrin Cyhalothrin Fenarimol Vinclosolin Triflumizole Iprodione Guazatin Flubenzimine Hexathiazox
Standard addition (mg kg -l)
0.1 0.1 0.1 0.1 0. I 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Analytical recovery
Relative standard
(%) (n = 12)
(%) (n = 12)
86.2 91.5 93.8 91.2 91.8 98.4 92.6 96.4 87.2 84.0 95.5 98.0 85.8 94.0 90.2 83.3 87.5
6.2 5.4 2.8 3.6 4.1 2.8 7.4 5.6 5.2 4.2 3.3 2.2 6.7 4.5 7.5 5.6 6.5
Minimum determination limits (mg kg -1) 0.004 0.008 0.040 0.004 0.002 0.004 0.008 0.020 0.020 0.004 0.008 0.008 0.004 0.020 0.040 0.002 0.020
diazinon, vinclosolin, fenitrothion, pyrimiphosmethyl, chlorpyriphos, guazatine, flubenzimine, iprodione, phosalone and fenarimol) and on a column with 3% OV-17 (for analysis of deltamethrin, tetrachlorvinphos, triflumizole, hexathiazox, pyrasophos and cyhalotrin, which are not separated on the non-polar phase SE-30). On the basis of the chosen optimum conditions for the extraction, clean-up and gas chromatographic determination of the 17 pesticides studied we have offered a method for analysis of products contaminated with residual pesticide amounts. The chromatograms analysing apples are show shown in Fig. 3 with addition of pesticides 0.1 mg/kg (a, b) and without (a', b'). The recovery and reproducibility of the analytical procedure were ascertained using the method of standard addition (Table 1).The results show that the relative error for the different pesticide varies from 1.6% to 16.7% while the reproducibility varies from 2.2% to 7.5%. Besides, the minimum determination limits ascertained are low (0.002-0.04 mg/kg).
GAS CHROMATOGRAPHIC DETERMINATION OF PESTICIDES IN FRUITS
37
The m e t h o d has been successively applied in analysing other fruit species: apricots, peaches, grapes, etc. The results o f these gas c h r o m a t o g r a p h i c studies show t h a t this m e t h o d is suitable for control o f residual a m o u n t s o f the pesticides in fruit products. REFERENCES 1 A. Ambrus, E. Visi, F. Zakar, E. Hargital, L. Szabo and A. Papa, General method for determination of pesticides residues in samples of plant origin, soil and water. III. Gas chromatographic analysis and confirmation. J. Assoc. Off. Anal. Chem., 64 (1981) 749-768. 2 P.T. Holland and T.K. McGhie, Multiresidue method for determination of pesticides in kiwifruit, apples and berryfruits. J. Assoc. Off. Anal. Chem., 66 (1983) 1003-1008. 3 S.M. Prinsloo and P.R. De Beer, Gas chromatographic relative retention data for pesticides on nine packed columns; I organophosphorous pesticides, using flame photometric detection. J. Assoc. Off. Anal. Chem., 68 (1985) 110-1109. 4 M.A. Luke, J.E. Froberg, G.M. Doose and H.T. Masumoto, Improved multiresidue gas chromatographic determination of organophosphorous, organonitrogen and organohalogen pesticides in produce, using flame photometric and electrolytic conductivity detectors. J. Assoc. Off. Anal. Chem., 64 (1981) 1187-1195. 5 E. Bolygo and F. Zakar, Gas-liquid chromatographic screening for six synthetic pyrethroid insecticides. J. Assoc. Off. Anal. Chem., 66 (1983) 1013-1017. 6 A. Neicheva, E. Kovacheva and D. Karageorgiev, Simultaneous determination of insecticides, acaricides and fungicides by thin-layer chromatography. J. Chromatogr., 509 (1990) 263-269.
29
Gas chromatographic determination of some modern pesticides in fruits A. Neicheva a, D. Karageorgiev b and T. Konstantinova c aHigher Institute of Food Industry, 26 Maritza BI., 4002 Plovdiv, Bulgaria bFruit Growing Research Institute, Plovdiv, Bulgaria CTechnological University of Sofia, 1756 Sofia, Bulgaria
ABSTRACT A method was developed for determination for residual amounts of some modern insecticides, acaricides and fungicides in fruits. The pesticides were extracted with methanol and partitioned into chloroform. The extract was purified by column chromatography on sodium sulphate/Florisil/Celite/charcoal. Analysis by gas liquid chromatography with 63Ni electron capture detection was completed successivelyon a column (150 cm x 4 mm) with 3% SE-30 and a column (150 cm x 2 mm with 3% OV-17 liquid phase. Recoveries of 17 pesticides from fortified samples of apples ranged from 83.3% to 98.4% for a level of 0.1 mg/kg. Key words: pesticides; analysis; residues; gas-liquid chromatography; fruits
INTRODUCTION The strict control o f pesticide residues in fruits is necessary for protecting the consumer from harmful impact. The quickest way to achieve this involving least expense is by means of applying methods for multicomponent gas chromatographic analysis [1-5]. The aim of our study was to develop a quick and economical method for determination of some m o d e m insecticides, acarieides and fungicides in fruits. The study includes pesticides not referred to in the literature, with respect to the conditions ensuring their simultaneous extraction and gas chromatographic determination. We have also studied preparations which are applied for treating fruit tree crops throughout their period in fruit, ineluding the time near the harvest in which way they can contaminate fruit production.
30
A. NEICHEVA ET AL.
EXPERIMENTAL
Materials Standard acetone solutions containing 0.001 mg/ml of each of the following pesticides: dimethoate, tetrachlorvinphos, diazinon, phosalone, fenitrithion, chlorpyriphos, cyhalothrin, triflumizole, fenarimol, vinclosolin, hexathiazox, flubenzimine and guazatin, as well as 0.005 mg/ml of pyrazophos, pyrimiphosmethyl iprodione and deltamethrin. As solvents acetonitrile, methanol, petroleum ether, diethyl ether and chloroform, were all used analytical grade. Chromatographic supports. Florisil, Celite and charcoal (Fluka). Apparatus. A Pye Unicam Model 304 gas chromatograph with 63Nielectron capture detector supplied with a Spectra Physics Model SP4270 Integrator.
Procedure A solution containing 10 ~g of each of the pesticides studied was mixed with 100 g of apple homogenate, free of pesticides. All pesticides were extracted with 130 ml methanol for 50 min on a shaking machine at a speed ensuring good blending of the whole material. After filtration the water/methanol mixture was added to 150 ml of 10% solution of NaCI in a separatory funnel. The pesticides were successively re-extracted for 1 min with 80 ml chloroform (for recovering the more polar pesticides - - diazinon, dimethoate, vinclosolin, tetrachlorvinphos, etc.) and with 80 ml of chloroform/petroleum ether (8:2) (for the more complete recovery of nonpolar pesticides - - deltametrin, cyhalothrin, flubenzimine, hexathiasox, etc.). The chloroform extracts were concentrated to 4-5 ml at 40°C and were passed down a chromatographic column (d = 1 cm), packed with 5 g of mixture of sodium sulphate/Florisil/Celite/charcoal (1:1:0.5:0.1). The elution of the pesticides from the column was carried out with 90 ml of CHC13/diethyl ether (95:5). The eluate was evaporated to dryness at 40°C and the dry residue was dissolved in 4 ml of acetone. Gas chromatography of 1 #1 of this solution was achieved on a column (150 cm × 4 mm) with 3% SE-30 on 100-120 mesh Chromosorb W with programmed change of temperature 150°C -- l°C/min -- 170°C -- 4°C/min -- 200°C, as well as on a column (150 cm x 2 mm) with 3% OV-17 on a 100-120 mesh Chromosorb W and change of temperature 170°C --, 2°C/min -- 210°C (12 min) --10°C/rain -. 230°C. The flow of the carrier gas (nitrogen) was 50-60 ml/min, the temperature of the injector and detector being 240°C and 280°C. The standard acetone solution of the pesticides (1 #1) was successively
GAS CHROMATOGRAPHIC DETERMINATION OF PESTICIDES IN FRUITS
31
chromatographed on both columns under the same conditions. The chromatogramms were processed according to the method of absolute calibration. RESULTS AND DISCUSSION
Finding effective conditions for extraction of 17 pesticides studied, which appear to be phosphorus-, chlorine-, sulfur and nitrogen-containing compounds, is the first stage in developing a method for their determination. In our experiments with some extracting agents that have become widespread in multicomponent pesticide analysis, we found that the change in the degree of pesticide recovery from the fruits is in the following order: CH3OH > acetonitrile > acetone. The choice of methanol as an extracting agent was determined not only by its higher extracting ability towards the pesticides studied (from 3% to 10% for the different representatives), but also because the methanol fruit extracts contain less co-extractives than the acetone or acetonitrile extracts (Fig. 1).
AI 4
o.g 0,8,
3 ~
0,7. 08
o..s
o,2 o,t o #,oo
2Jo
3o0
j~
nrn
Fig. 1. UV spectra of purified apple extract without pesticides, in different extracting agents: 1, acetone; 2, acetonitrile; 3, methanol/acetonitrile (hi); 4, methanol.
32
A. NEICHEVA ET AL.
8 * 9~'fO
#,~
(O)
"H
¢5
3
b _._..
o :,
~ ~
~s 2o ~;~ ,~8 e:e -;6 ,;o ~ ~8 ,;-,e ~8 ;o rain
Fig. 2. Gas Chromatogram of a standard mixture of 17 pesticides. (a) Column (15 cm x 4 mm) with 3% SE-30 at temperature programme: 150°C -- l°C/min -- 170°C -- 4°C/min -200°C. (b) Column (150 cm x 2 mm) with 3% OV-17 at temperature programme: 170°C 2°C/min - 210°C (12 rain) --10°C/min -- 230°C. Peaks and spike level (ng): l, dimethoate (1); 2, diazinon (l); 3, vunclosolin (1); 4, fenitrothion (1); 5, pyrimiphosmethyl (5); 6, chlorpyriphos (1); 7, quazatin (1); 8, tetrachlorvinphos (1); 9, triflumizole (1); 10, hexathiazox (1); 11, flubenzimine (1); 12, iprodione (5); 13, phosalone (1); 14, fenarimol (l); 15, pyrazophos (5); 16, cyhalothrin (1); 17, deltamethrin (5).
T h e c l e a n - u p o f fruit e x t r a c t s was c a r r i e d o u t b y m e a n s o f l i q u i d - l i q u i d s e p a r a t i o n o f the pesticides a n d c o - e x t r a c t i v e s a n d a s u b s e q u e n t c o l u m n c h r o m a t o g r a p h y [6]. T h e n e x t i m p o r t a n t stage in the s i m u l t a n e o u s d e t e r m i n a t i o n o f the c o m b i n a t i o n o f 17 pesticides s t u d i e d was the c h o i c e o f a n a d e q u a t e s t a t i o n a r y
33
GAS CHROMATOGRAPHIC DETERMINATION OF PESTICIDES IN FRUITS
(bJ
,pf
I #6
47
8
mi,"l
Fig. 2 (Continued).
phase. For this purpose we studied comparatively the ability of 4 different polar phases (3% SE-30, 3% OV-17, 3% OV-225 and 1.5% OV-17 + 1.95% QF-1) for quick separation and determination of the pesticides, the standard mixture of the studied compounds being chromatographed on each one of them in columns of equal length (150 cm) at adequately chosen temperature conditions. An electron capture detector (ECD) was used being an effective detecting system for chemically different halogenated pesticide residues. From the chromatograms we got it turned out that the most suitable for pesticide determination were columns with phases 3% SE-30 and 3% OV-17, which is why we give data only for the separation performed on them (Fig. 2).
34
A. NEICHEVA ET A L
8+ g + "IO
42
fa)
3 ¢3
H
6 45+ IG
!
(0)
Fig. 3. Gas chromatogram analysing apples. (a) Column (150 cm x 4 mm) with 3% SE-30 at temperature programme: 150°C -- l°C/min -- 170°C -- 4°C/rain -- 200°C. (b) Column (150 cm x 2 mm) with 3% OV-17 at temparature programme: 170°C -- 2°C/min -- 210°C (12 min) -- 10°C/min - 230°C. Untreated apples fortified with (0.1 mg/kg), a, b: 1, dimethoate; 2, diazinon; 3, vinclosolin; 4, fenitrothion; 5, pyrimiphosmethyl; 6, chlorpyriphos; 7, quazatin; 8, tetrachlorvinphos; 9, triflumizole; 10, hexathiazox; 11, flubenzimine; 12, iprodione; 13, phosalone; 14, fenarimol; 15, pyrasophos; 16, cyhalothrin; 17, deltamethrin; Untreated apples: a ' , b'.
35
GAS CHROMATOGRAPHIC DETERMINATION OF PESTICIDES 1N FRUITS
~h
/b)
46
~4 ~2
I
(b)
\ b
2~
8
¢2
¢6
20 24 2a
32
38 40
44
48
S~ ,~8
Fig. 3 (Continued).
The chromatographic studies made up show that the simultaneous determination of the pesticides under study is possible with one ECD-detector when they are chromatographed successively under temperature conditions chosen, on a column with 3% SE-30 (ensuring analysis of dimethoate,
36
A. NEICHEVAEl"AL.
TABLE 1
Gas chromatographic determination of pesticides in apples using the method of standard addition No.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Pesticide
Diazinon Dimethoate Pyrimiphosmethyl Chlorpyriphos Tetrachlorvinphos Phosalone Fenitrothion Pyrasophos Deltametrin Cyhalothrin Fenarimol Vinclosolin Triflumizole Iprodione Guazatin Flubenzimine Hexathiazox
Standard addition (mg kg -l)
0.1 0.1 0.1 0.1 0. I 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
Analytical recovery
Relative standard
(%) (n = 12)
(%) (n = 12)
86.2 91.5 93.8 91.2 91.8 98.4 92.6 96.4 87.2 84.0 95.5 98.0 85.8 94.0 90.2 83.3 87.5
6.2 5.4 2.8 3.6 4.1 2.8 7.4 5.6 5.2 4.2 3.3 2.2 6.7 4.5 7.5 5.6 6.5
Minimum determination limits (mg kg -1) 0.004 0.008 0.040 0.004 0.002 0.004 0.008 0.020 0.020 0.004 0.008 0.008 0.004 0.020 0.040 0.002 0.020
diazinon, vinclosolin, fenitrothion, pyrimiphosmethyl, chlorpyriphos, guazatine, flubenzimine, iprodione, phosalone and fenarimol) and on a column with 3% OV-17 (for analysis of deltamethrin, tetrachlorvinphos, triflumizole, hexathiazox, pyrasophos and cyhalotrin, which are not separated on the non-polar phase SE-30). On the basis of the chosen optimum conditions for the extraction, clean-up and gas chromatographic determination of the 17 pesticides studied we have offered a method for analysis of products contaminated with residual pesticide amounts. The chromatograms analysing apples are show shown in Fig. 3 with addition of pesticides 0.1 mg/kg (a, b) and without (a', b'). The recovery and reproducibility of the analytical procedure were ascertained using the method of standard addition (Table 1).The results show that the relative error for the different pesticide varies from 1.6% to 16.7% while the reproducibility varies from 2.2% to 7.5%. Besides, the minimum determination limits ascertained are low (0.002-0.04 mg/kg).
GAS CHROMATOGRAPHIC DETERMINATION OF PESTICIDES IN FRUITS
37
The m e t h o d has been successively applied in analysing other fruit species: apricots, peaches, grapes, etc. The results o f these gas c h r o m a t o g r a p h i c studies show t h a t this m e t h o d is suitable for control o f residual a m o u n t s o f the pesticides in fruit products. REFERENCES 1 A. Ambrus, E. Visi, F. Zakar, E. Hargital, L. Szabo and A. Papa, General method for determination of pesticides residues in samples of plant origin, soil and water. III. Gas chromatographic analysis and confirmation. J. Assoc. Off. Anal. Chem., 64 (1981) 749-768. 2 P.T. Holland and T.K. McGhie, Multiresidue method for determination of pesticides in kiwifruit, apples and berryfruits. J. Assoc. Off. Anal. Chem., 66 (1983) 1003-1008. 3 S.M. Prinsloo and P.R. De Beer, Gas chromatographic relative retention data for pesticides on nine packed columns; I organophosphorous pesticides, using flame photometric detection. J. Assoc. Off. Anal. Chem., 68 (1985) 110-1109. 4 M.A. Luke, J.E. Froberg, G.M. Doose and H.T. Masumoto, Improved multiresidue gas chromatographic determination of organophosphorous, organonitrogen and organohalogen pesticides in produce, using flame photometric and electrolytic conductivity detectors. J. Assoc. Off. Anal. Chem., 64 (1981) 1187-1195. 5 E. Bolygo and F. Zakar, Gas-liquid chromatographic screening for six synthetic pyrethroid insecticides. J. Assoc. Off. Anal. Chem., 66 (1983) 1013-1017. 6 A. Neicheva, E. Kovacheva and D. Karageorgiev, Simultaneous determination of insecticides, acaricides and fungicides by thin-layer chromatography. J. Chromatogr., 509 (1990) 263-269.
