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Modification and re-validation of the ethyl acetate-based multi-residue method for pesticides in produce.

Mol HG, Rooseboom A, van Dam R, Roding M, Arondeus K, Sunarto S - Anal Bioanal Chem (2007)

Bottom Line: The principle of the extraction procedure (solvent, salt) was not changed, to avoid the possibility invalidating data acquired over past decades.The modified method enables processing (from homogenization until final extracts for both GC and LC) of 30 samples per eight hours per person.Validation data for 341 pesticides and degradation products are presented.

View Article: PubMed Central - PubMed

Affiliation: Rikilt Institute of Food Safety, Pesticides and Contaminants, P.O. Box 230, 6700 AE, Wageningen, The Netherlands. hans.mol@wur.nl

ABSTRACT
The ethyl acetate-based multi-residue method for determination of pesticide residues in produce has been modified for gas chromatographic (GC) analysis by implementation of dispersive solid-phase extraction (using primary-secondary amine and graphitized carbon black) and large-volume (20 muL) injection. The same extract, before clean-up and after a change of solvent, was also analyzed by liquid chromatography with tandem mass spectrometry (LC-MS-MS). All aspects related to sample preparation were re-assessed with regard to ease and speed of the analysis. The principle of the extraction procedure (solvent, salt) was not changed, to avoid the possibility invalidating data acquired over past decades. The modifications were made with techniques currently commonly applied in routine laboratories, GC-MS and LC-MS-MS, in mind. The modified method enables processing (from homogenization until final extracts for both GC and LC) of 30 samples per eight hours per person. Limits of quantification (LOQs) of 0.01 mg kg(-1) were achieved with both GC-MS (full-scan acquisition, 10 mg matrix equivalent injected) and LC-MS-MS (2 mg injected) for most of the pesticides. Validation data for 341 pesticides and degradation products are presented. A compilation of analytical quality-control data for pesticides routinely analyzed by GC-MS (135 compounds) and LC-MS-MS (136 compounds) in over 100 different matrices, obtained over a period of 15 months, are also presented and discussed. At the 0.05 mg kg(-1) level acceptable recoveries were obtained for 93% (GC-MS) and 92% (LC-MS-MS) of pesticide-matrix combinations.

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Comparison of toluene and xylene as additives for preventing adsorption of planar pesticides by GCB in dispersive SPE
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Fig2: Comparison of toluene and xylene as additives for preventing adsorption of planar pesticides by GCB in dispersive SPE

Mentions: As is apparent from Fig. 1, even 10% toluene dramatically improved recovery. With 20% toluene recovery of all pesticides was higher than 65%. It should be noted that this experiment with standard solutions is the worst case. For real samples chlorophyll and carotenoids will also affect the distribution in favor of the pesticides in solution. Use of 30% of toluene further improved recovery only slightly. Twenty percent was regarded as optimum with regard to distribution and ease of solvent elimination in large-volume injection (see below). In addition to toluene, two alternative analogues, benzene and xylene, were also considered. Benzene, was not tested because it could not be used in routine practice because of its carcinogenic properties (although it would have been favorable with regard to solvent elimination). Xylene was tested in a similar way as toluene. Results obtained for hexachlorobenzene and chlorothalonil by use of the two solvents are compared in Fig. 2. Slight but consistently better recovery was obtained with xylene—>70% recovery could now be obtained for all pesticides. Because of its greater volatility, however, toluene was finally selected.Fig. 1


Modification and re-validation of the ethyl acetate-based multi-residue method for pesticides in produce.

Mol HG, Rooseboom A, van Dam R, Roding M, Arondeus K, Sunarto S - Anal Bioanal Chem (2007)

Comparison of toluene and xylene as additives for preventing adsorption of planar pesticides by GCB in dispersive SPE
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2117333&req=5

Fig2: Comparison of toluene and xylene as additives for preventing adsorption of planar pesticides by GCB in dispersive SPE
Mentions: As is apparent from Fig. 1, even 10% toluene dramatically improved recovery. With 20% toluene recovery of all pesticides was higher than 65%. It should be noted that this experiment with standard solutions is the worst case. For real samples chlorophyll and carotenoids will also affect the distribution in favor of the pesticides in solution. Use of 30% of toluene further improved recovery only slightly. Twenty percent was regarded as optimum with regard to distribution and ease of solvent elimination in large-volume injection (see below). In addition to toluene, two alternative analogues, benzene and xylene, were also considered. Benzene, was not tested because it could not be used in routine practice because of its carcinogenic properties (although it would have been favorable with regard to solvent elimination). Xylene was tested in a similar way as toluene. Results obtained for hexachlorobenzene and chlorothalonil by use of the two solvents are compared in Fig. 2. Slight but consistently better recovery was obtained with xylene—>70% recovery could now be obtained for all pesticides. Because of its greater volatility, however, toluene was finally selected.Fig. 1

Bottom Line: The principle of the extraction procedure (solvent, salt) was not changed, to avoid the possibility invalidating data acquired over past decades.The modified method enables processing (from homogenization until final extracts for both GC and LC) of 30 samples per eight hours per person.Validation data for 341 pesticides and degradation products are presented.

View Article: PubMed Central - PubMed

Affiliation: Rikilt Institute of Food Safety, Pesticides and Contaminants, P.O. Box 230, 6700 AE, Wageningen, The Netherlands. hans.mol@wur.nl

ABSTRACT
The ethyl acetate-based multi-residue method for determination of pesticide residues in produce has been modified for gas chromatographic (GC) analysis by implementation of dispersive solid-phase extraction (using primary-secondary amine and graphitized carbon black) and large-volume (20 muL) injection. The same extract, before clean-up and after a change of solvent, was also analyzed by liquid chromatography with tandem mass spectrometry (LC-MS-MS). All aspects related to sample preparation were re-assessed with regard to ease and speed of the analysis. The principle of the extraction procedure (solvent, salt) was not changed, to avoid the possibility invalidating data acquired over past decades. The modifications were made with techniques currently commonly applied in routine laboratories, GC-MS and LC-MS-MS, in mind. The modified method enables processing (from homogenization until final extracts for both GC and LC) of 30 samples per eight hours per person. Limits of quantification (LOQs) of 0.01 mg kg(-1) were achieved with both GC-MS (full-scan acquisition, 10 mg matrix equivalent injected) and LC-MS-MS (2 mg injected) for most of the pesticides. Validation data for 341 pesticides and degradation products are presented. A compilation of analytical quality-control data for pesticides routinely analyzed by GC-MS (135 compounds) and LC-MS-MS (136 compounds) in over 100 different matrices, obtained over a period of 15 months, are also presented and discussed. At the 0.05 mg kg(-1) level acceptable recoveries were obtained for 93% (GC-MS) and 92% (LC-MS-MS) of pesticide-matrix combinations.

Show MeSH