Chemometric study and optimization of extraction parameters in single-drop microextraction for the determination of multiclass pesticide residues in grapes and apples by gas chromatography mass spectrometry

A simple and rapid single-drop microextraction method coupled with gas chromatography and mass spectrometry (SDME-GC/MS) for the determination of 20 pesticides with different physicochemical properties in grapes and apples was optimized by the use of a multivariate strategy. Emphasis on the optimization study was given to the role of ionic strength, sugar concentration and pH of the donor sample solution prepared from the fruit samples. Since all three variables were found to affect negatively SDME (a lower extraction efficiency was observed as the values of variables were increased for most of the pesticides studied), donor sample solution was optimized using a central composite design to evaluate the optimum pH value and the optimum dilution of the sample extract. With some exceptions (chlorpyrifos ethyl, alpha-endosulfan, beta-endosulfan, pyriproxyfen, gamma-cyhalothrin and bifenthrin), the optimum method included the dilution of the analytical sample by 12.5-fold with a buffered acetone/water solution at pH = 4 and exhibited good analytical characteristics for the majority of target analytes (pyrimethanil, pirimicarb, metribuzin, vinclozolin, fosthiazate, procymidone, fludioxonil, kresoxim methyl, endosulfan sulfate, fenhexamid, iprodione, phosalone, indoxacarb and azoxystrobin) by providing high enrichment factors (14-328), low limits of detection (0.0003-0.007 mu g/g), and good precision (relative standard deviations below 15%). (C) 2009 Elsevier B.V. All rights reserved

Application of single-drop microextraction coupled with gas chromatography for the determination of multiclass pesticides in vegetables with nitrogen phosphorus and electron capture detection

In the present work the single-drop microextraction (SDME) technique coupled with GC-NPD and GC-ECD was evaluated for the determination of multi-class pesticides in vegetables. The donor sample solution preparation was optimized by testing different mixtures of solvents and dilutions with water. The SDME procedure was optimized by controlling drop organic solvent, drop volume, agitation, and exposure time. The optimum sample preparation was achieved with the use of a mixture of acetone/H(2)O (10/90, v/v) in donor sample Solution preparation and the consequent SDME using a toluene drop under mild stirring for 25 min. The efficiency of the extraction process was studied in fortified tomato and courgette samples and matrix effects were further estimated. The proposed method showed good linearity, limits of detection at the sub-mu g kg(-1) level and high precision (RSD <15%) and was applied with success in real vegetable samples showing that SDME can be a promising way for sample preparation in pesticide residue analysis. (C) 2008 Elsevier B.V. All rights reserved

Determination of Pesticide Residues in Honey by Single-Drop Microextraction and Gas Chromatography

A novel, simple, and rapid single-drop microextraction (SOME) procedure combined with GC has been developed, validated, and applied for the determination of multiclass pesticide residues in honey samples. The SDME was optimized using a Plackett-Burman screening design considering all parameters that may influence an SOME procedure and a consequent central composite design to control the parameters that were found to significantly influence the pesticide determination. The developed analytical method required minimal volumes of organic solvents and exhibited good analytical characteristics with enrichment factors ranging from 3 for alpha-endosulfan to 10 for lindane, procymidone, and captan and method quantification limits ranging from 0.03 mu g/kg for phosalone to 10.6 mu g/kg for diazinon. The relative recoveries obtained ranged from 70.8% for captan to 120% for fenarimol, and the precision (RSD) ranged from 3 to 15%. The proposed SDME procedure followed by GC with an electron capture detector for quantification and GC/MS for identification was applied with success to the analysis of 17 honey samples. Monitoring results indicated a low level of honey contamination by diazinon, chlorpyrifosethyl, procymidone, bromopropylate, and endosulfan (alpha-, beta-, and endosulfan sulfate) residues that were far below the maximum residue limit values specified by the European Union for endosulfan (10 mu g/kg) and bromopropylate (100 mu g/kg) in honey samples

Determination of diphenylamine in contaminated air of agricultural buildings using active sampling on solid sorbents

This paper reports the results of a study carried out with solid sorbents in order to establish the optimum procedure for sampling and determination of diphenylamine (DPA), the most widely used post-harvest chemical in apples, in the indoor air of apple storage buildings. Different sorbents (Amberlite XAD-2, Amberlite XAD-4, Supelpak 2, Florisil, and the octadecyl silica bonded sorbent, C-18) were evaluated for their capacity to efficiently retain DPA under different air sampling and storage conditions, whereas a desorption study of all sorbents tested was also performed to optimise a simple extraction procedure using low volumes of organic solvents. In general all sorbents produced acceptable results for DPA air sampling whereas DPA was recovered easily by the use of low volumes of both ethyl acetate and acetone from all sorbents studied thus making DPA a suitable analyte to be used in methods of indoor air analysis for multi-organic pollutants. However, the best results (analytical features, recovery results, and stability results during storage) were obtained by the use of Supelpak 2 as a sorbent for DPA active sampling. Limits of Quantification (LOQs) for the GC-NPD system ranged from 1.0 to 2.0 mu g m(-3) for 120 and 60 L air sampled, respectively. The developed air sampling procedure and analytical methodology was applied with success in the field to measure DPA residues in indoor air of two apple storage plants in Greece and results were further used to calculate the occupational inhalation exposure to DPA and consequently risk characterisation. Since DPA was detected in indoor air (at concentrations ranged from 1.6 to 580 mu g m(-3)), there is no zero occupational risk for workers. However, the inhalation exposure of workers to DPA estimated in this study is far below the Acceptable Operator Exposure Level recently reviewed by the European Union and far below the critical exposure level for haematotoxicity systemic effect observed in carcinogenicity studies in rats for long-term inhalation exposure to DPA

Headspace single-drop microextraction of common pesticide contaminants in honey-method development and comparison with other extraction methods

In the present study the main factors that may influence the headspace single-drop microextraction (HS-SDME) of common pesticide contaminants (diazinon, lindane, chlorpyrifos ethyl, p,p'-DDE, and endosulfan) that may occur in honey were determined and an analytical protocol was further developed by the use of a multivariate optimization. The HS-SDME analytical method developed and two more analytical protocols for the determination of pesticides in honey: (i) by direct SDME (D-SDME), and (ii) by liquid-liquid extraction (LLE), were further validated for the determination of target analytes. The three methods were also applied in the same real honey samples and results were further discussed. By D-SDME, LODs ranged from 0.04 mu g kg(-1) for beta-endosulfan to 2.40 mg mu g kg(-1) for diazinon and repeatability expressed as %RSD from 3 for lindane to 15 for diazinon and chlorpyrifos methyl; by HS-SDME, LODs ranged from 0.07 mu g kg(-1) for p,p'-DDE to 12.54 mu g kg(-1) for chlorpyrifos methyl and repeatability expressed as % RSD from 11 for chlorpyrifos methyl to 19 for p,p'-DDE; by LLE, LODs ranged from 0.09 mu g kg(-1) for beta-endosulfan to 19.31 mu g kg(-1) for diazinon and repeatability expressed as % RSD from 6 for p,p'-DDE to 11 for lindane. For all target pesticides but p,p'-DDE that could not be recovered by D-SDME method tested. The proposed HS-SDME optimized in this study was shown to be the method of choice for the determination of diazinon in honey whereas the most favourable analytical characteristics from the comparative study performed were achieved by D-SDME

Pesticide enrichment factors and matrix effects on the determination of multiclass pesticides in tomato samples by single-drop microextraction (SDME) coupled with gas chromatography and comparison study between SDME and acetone-partition extraction procedure

In this study a single-drop microextraction (SDME) method was extended for the determination of multiclass pesticides (metribuzin, vinclozolin, fosthiazate, procymidone, fludioxonil, kresoxim-methyl, fenhexamid, iprodione, bifenthrin, lambda-cyhalothrin, indoxacarb and azoxystrobin) in tomatoes and validated in comparison with a robust solvent extraction method in order to estimate the feasibility of SDME in more complicated determinations in terms of extraction efficiency, pesticides chromatographic stability and chromatographic induced matrix effects in pesticide residue analysis in food samples. Both sample preparation methods: (i) a single-drop microextraction method (SDME) developed recently in our laboratory, and (ii) a modified acetone-partition extraction procedure (APE) method that is being applied today for routine analysis of fruits and vegetables in many laboratories of pesticide residues analysis, were validated under ISO 17025 norms and SANCO Guide recommendations. For all pesticides studied, with the exception of pyrethroids, SDME exhibited good analytical characteristics by reporting from similar to 138 times lower LODs as compared with APE. The enrichment factors of the SDME procedure applied in tomato extracts ranged from 0.7 for bifenthrin to 812 for fenhexamid whereas, the concentration factors for the whole SDME studied ranged from <0.1 for bifenthrin and lambda-cyhalothrin to 52 for fenhexamid. Relative recoveries ranged from 67 to 90% for SDME and from 90 to 120% for APE. Matrix effects assessment performed for both methods studied indicated that matrix matched standards should be used for quantitation purposes. However, the estimation of the gas chromatographic matrix effects by SDME indicated that SDME is a more selective sample preparation method than APE