Multiresidue method for determination of 35 pesticides in virgin olive oil by using liquid-liquid extraction techniques coupled with solid-phase extraction clean up and gas chromatography with nitrogen phosphorus detection and electron capture detection

A method for the multiresidue determination of 35 pesticides (30 insecticides and five herbicides) in olive oil by gas chromatography (GC) is described. Three liquid-liquid extraction (LLE) procedures based on (i) partition of pesticides between acetonitrile (ACN) and oil solution in n-hexane, (ii) partition of pesticides between saturated ACN with n-hexane and oil solution in n-hexane saturated with ACN, and (iii) partition of pesticides between ACN and oil were tested for the optimization of the highest pesticide recoveries with the lowest oil residue in the final extracts. Experimental tests were preformed in order to study the efficiency of different clean up procedures with N-Alumina, Florisil, C18, and ENVI-Carb solid-phase extraction (SPE) cartridges for the compounds analyzed by GC-nitrogen phosphorus detection. A second step of clean up was also performed for the compounds analyzed by GC-electron capture detection (ECD), by using phenyl-bonded silica (Ph), diol-bonded silica (Diol), cyanopropyl-bonded silica (CN), and amino propyl-bonded silica (NH2) SPE cartridges. LLE of the oil solution in hexane with ACN followed by an ENVI-Carb SPE clean up of the extract gave the best results for all target compounds. The ACN extract was additionally cleaned through a Diol-SPE cartridge for the determination of pesticides analyzed mainly by GC-ECD. Pesticide recoveries form virgin olive oil spiked with 20, 100, and 500 microg/kg concentrations of pesticides ranged from 70.9 to 107.4%. The proposed method featured good sensitivity, pesticide quantification limits were low enough, and the precision, expressed as relative standard deviation, ranged from 2.4 to 12.0%. The proposed method was applied successfully for the residue determination of the selected pesticides in commercial olive oil samples.     

Multiresidue screening of pesticides in fruits using an automatic solid-phase extraction system

About 20 pesticides were determined in lyophilized fruits using a semiautomatic multiresidue method, based on solid-phase extraction (SPE) with a silica column. The lyophilization of the sample, besides the SPE procedure selected, provided clean extracts despite the complexity of the matrixes studied. In addition, the lyophilization process allows sample preservation for at least three months without changes in the concentrations of the pesticides. Determination and quantitation of organochlorine and pyrethroid residues was carried out using a gas chromatograph equipped with an electron capture detector (GC-ECD), and a mass spectrometric detector (GC-MS) was used for confirmation purposes. Organochlorine pesticides provided average recoveries (spiked at three concentration levels in eight different fruits) near 93 +/- 4%, being lower (89 +/- 8%) for pyrethroids as a consequence of their higher degradation and interaction with the sample matrix. On the other hand, the detection limits achieved for all pesticides (0.5-8 ng per g of lyophilized fruit) allow their determination at the MRLs established by the European Union, with good precision ( approximately 5%). Finally, from the 100 different fruits screened, only 10 positive responses were obtained, which were further confirmed by GC-MS.     

Advanced solid phase extraction using molecularly imprinted polymers for the determination of quercetin in red wine

Solid phase extraction (SPE) based on molecularly imprinted polymers (MIPs) is a novel approach for sample preparation and preconcentration, gaining increased interest in the fields of environmental, clinical, and food analysis. The first application combining MIPs with SPE for advanced beverage analysis is reported. MIPs for the flavonoid quercetin have been generated, using quercetin as a template molecule in a self-assembly approach and yielding imprinting of 1% of the used template. The MIP achieved a capacity of 0.4 g quercetin per gram polymer and a recovery rate of 98.2%. The application of these synthetic receptors as SPE material for the selective extraction and preconcentration of quercetin from synthetic and red wine samples was investigated. Red wine samples from a French Merlot were directly applied onto the SPE cartridge. The collected fractions were analyzed by high-pressure liquid chromatography. For verification of the obtained results, a similarly prepared nonimprinted polymer and a classical octadecyl silane reversed-phase cartridge were applied as the SPE matrix during control experiments. The MIP enabled the selective extraction of quercetin from a complex matrix, such as red wine, spiked with 8.8 mg per liter quercetin, demonstrating the potential of molecularly imprinted solid phase extraction for rapid, selective, and cost-effective sample pretreatment.     

Multiresidue screen for organophosphorus insecticides using gel permeation chromatography--silica gel cleanup.

A multiresidue screen for quantitative determination of 43 organophosphorus insecticides in 5 g of plant and animal tissues is described. The organophosphorus insecticides are extracted with methanol-dichloromethane (10 + 90, v/v) and cleaned up using automated gel permeation chromatography with hexane-ethyl acetate (60 + 40) eluant and in-line silica gel minicolumns. Concentrated extracts are analyzed by gas chromatography with flame photometric detection. The method recovers 43 organophosphorus insecticides in the range of 72 to 115%. Analysis of fortified bovine liver (n = 5) shows an average 95.9 +/- 4.8% recovery at the 0.05 micrograms/g level and 93 +/- 3.8% at the 0.5 micrograms/g level. Analysis of fortified bovine rumen content (n = 5) shows an average 98 +/- 4.2% recovery at the 0.1 micrograms/g level and 98.7 +/- 2.8% at the 1 micrograms/g level. Method detection limits ranged from 0.01 to 0.05 micrograms/g for the compounds studied using a nominal 5 gram sample.     

Determination of organochlorine and organophosphorus pesticide residues in eggs using a solid phase extraction cleanup

A multiresidue solid phase extraction (SPE) method for the isolation and subsequent gas chromatographic determination of nonpolar organochlorine and polar organophosphorus pesticide residues in eggs is described. The method uses an acetonitrile extraction followed by an SPE cleanup using graphitized carbon black and aminopropyl SPE columns. Organophosphorus pesticides are determined by gas chromatography with flame photometric detection. After further cleanup of the extract using Florisil SPE columns, organochlorine pesticides are determined by gas chromatography with electron capture detection. Studies were performed using eggs containing both fortified and incurred pesticide residues. The average recoveries were 86-108% for 8 fortified organochlorine pesticide residues and 61-149% for 28 fortified organophosphorus pesticide residues.     

Determination of seven glycidyl esters in edible oils by gel permeation chromatography extraction and liquid chromatography coupled to mass spectrometry detection

A method based on a gel permeation chromatography (GPC) extraction procedure combined with an additional cleanup by solid-phase extraction (SPE) on silica gel and liquid chromatography-mass spectrometry (LC-MS) detection has been validated for the analysis of seven glycidyl esters (GEs) including glycidyl laurate, myristate, palmitate, stearate, oleate, linoleate, and linolenate in various edible oils. This method was conjointly developed and validated by two different laboratories, using two different detection systems, a LC time of flight MS (LC-ToF-MS) and a LC triple-quadrupole MS (LC-MS/MS). The extraction procedure allowed targeting low contamination levels due to a highly efficient matrix removal from the 400 mg oil sample loaded on the GPC column and is suitable for routine analysis as 24 samples can be extracted in an automated and reproducible way every 12 h. GPC extraction combined with SPE cleanup and LC-MS/MS detection leads to a limit of quantification in oil samples between 50 and 100 μg/kg depending on the type of glycidyl ester. Recoveries ranged from 68 to 111% (average = 93%). Quantification was performed by automated standard addition on extracts to compensate matrix effects artifacts. To control recoveries of each sample four isotopically labeled GEs ((13)C(3) or (13)C(4)) were included in the method.     

Matrix effects in analysis of β-agonists with LC-MS/MS: influence of analyte concentration, sample source, and SPE type

The synergistic influences of analyte concentration, sample source, and solid-phase extraction (SPE) type on matrix effects in the multiresidue analyses of eight β-agonists with LC-ESI-MS/MS were evaluated. Porcine muscle and liver extracts and urine from diverse sources were purified by strong or mixed-mode cation exchange and molecularly imprinted polymer SPE cartridges, respectively. Three spiked concentrations (2, 10, and 20 ng/mL) of eight β-agonists in the purified matrices and the different sample sources were analyzed. The results show that for most β-agonists there are significant differences in matrix effects between analyte concentrations or sample sources (P < 0.05), whereas there is no significant difference in matrix effects between different SPE cartridges (P > 0.05). Results from main effects testing indicated that analyte concentration was the main effector.     

土壤、沉积物和植物样品中多环芳烃（PAHs）不同提取与净化方法比较

系统分析和比较了土壤、沉积物和植物样品中多环芳烃（PAHs）的提取与净化方法,阐述和对比了索氏提取法、超声波提取法、超临界流提取法、固相提取与固相微提取法、固液提取法、微波辅助提取法、快速溶剂提取法等提取方法以及定量浓缩净化法、硅胶柱层析净化法、费罗里土柱层析净化法、氧化铝净化法、固相萃取（SPE）净化法等净化方法。旨在通过比较目前的提取和净化方法,展望将来提取与净化方法发展的新方向。     

Matrix solid phase dispersion (MSPD) extraction and gas chromatographic screening of nine chlorinated pesticides in beef fat

A multiresidue technique is presented for the extraction and quantitative gas chromatographic screening of 9 insecticides (lindane, heptachlor, aldrin, heptachlor epoxide, p,p'-DDE, dieldrin, endrin, p,p'-TDE, and p,p'-DDT) as residues in beef fat. Beef fat was fortified by adding the 9 insecticides, plus dibutyl chlorendate as internal standard, to 0.5 g portions of beef fat and blending with 2 g C18 (octadecylsilyl)-derivatized silica. The C18/fat matrix blend was fashioned into a column by adding the blend to a 10 mL syringe barrel containing 2 g activated Florisil. The insecticides were then eluted from the column with 8 mL acetonitrile, and a 2 microL portion of the acetonitrile eluate was then directly analyzed by gas chromatography with electron capture detection. Unfortified blank controls were treated similarly. The acetonitrile eluate contained all of the pesticide analytes (31.25-500 ng/g) and was free of interfering co-extractants. Correlation coefficients for the 9 extracted pesticide standard curves (linear regression analysis, n = 5) ranged from 0.9969 (+/- 0.0021) to 0.9999 (+/- 0.0001). Average relative percentage recoveries (85 +/- 3.4% to 102 +/- 5.0%, n = 25 for each insecticide), inter-assay variability (6.0 +/- 1.0% to 14.0 +/- 6.7%, n = 25 for each insecticide), and intra-assay variability (2.5-5.1% n = 5 for each insecticide) indicated that the methodology is acceptable for the extraction, determination, and screening of these residues in beef fat.     

Multiresidue determination of pesticides in soil by gas chromatography-mass spectrometry detection

An analytical multiresidue method for the simultaneous determination of various classes of pesticides in soil was developed. Pesticides were extracted from soil with ethyl acetate. Soil samples were placed in small columns, and the extraction was carried out assisted by sonication. Pesticides were determined by gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. Pesticides were confirmed by their retention times, their qualifier and target ions, and their qualifier/target abundance ratios. Recovery studies were performed at 0.2, 0.1, and 0.05 microg/g fortification levels of each pesticide, and the recoveries obtained ranged from 87.0 to 106.2% with a relative standard deviation between 2.4 and 10.6%. Good resolution of the pesticide mixture was achieved in approximately 41 min. The detection limits of the method ranged from 0.02 to 1.6 microg/kg for the different pesticides studied. The developed method is linear over the range assayed, 25-1000 microg/L, with determination coefficients >0.999. The proposed method was used to determine pesticide levels in real soil samples, taken from different agricultural areas of Spain, where several herbicides and insecticides were found.     

Development of multiclass methods for drug residues in eggs: hydrophilic solid-phase extraction cleanup and liquid chromatography/tandem mass spectrometry analysis of tetracycline, fluoroquinolone, sulfonamide, and beta-lactam residues

A method was developed for detection of a variety of polar drug residues in eggs via liquid chromatography/tandem mass spectrometry (LC/MS/MS) with electrospray ionization (ESI). A total of twenty-nine target analytes from four drug classes-sulfonamides, tetracyclines, fluoroquinolones, and beta-lactams-were extracted from eggs using a hydrophilic-lipophilic balance polymer solid-phase extraction (SPE) cartridge. The extraction technique was developed for use at a target concentration of 100 ng/mL (ppb), and it was applied to eggs containing incurred residues from dosed laying hens. The ESI source was tuned using a single, generic set of tuning parameters, and analytes were separated with a phenyl-bonded silica cartridge column using an LC gradient. In a related study, residues of beta-lactam drugs were not found by LC/MS/MS in eggs from hens dosed orally with beta-lactam drugs. LC/MS/MS performance was evaluated on two generations of ion trap mass spectrometers, and key operational parameters were identified for each instrument. The ion trap acquisition methods could be set up for screening (a single product ion) or confirmation (multiple product ions). The lower limit of detection for screening purposes was 10-50 ppb (sulfonamides), 10-20 ppb (fluoroquinolones), and 10-50 ppb (tetracyclines), depending on the drug, instrument, and acquisition method. Development of this method demonstrates the feasibility of generic SPE, LC, and MS conditions for multiclass LC/MS residue screening.     

Determination and confirmation of 5-hydroxyflunixin in raw bovine milk using liquid chromatography tandem mass spectrometry

A method was developed and validated to determine 5-hydroxyflunixin in raw bovine milk using liquid chromatography tandem mass spectrometry (LC/MS/MS). The mean recovery and percentage coefficient of variation (%CV) of 35 determinations for 5-hydroxyflunixin was 101% (5% CV). The theoretical limit of detection was 0.2 ppb with a validated lower limit of quantitation of 1 ppb and an upper limit of 150 ppb. Accuracy, precision, linearity, specificity, ruggedness, and storage stability were demonstrated. A LC/MS/MS confirmatory method using the extraction steps of the determinative method was developed and validated for 5-hydroxyflunixin in milk from cattle. Briefly, the determinative and confirmatory methods were based on an initial solvent (acetone/ethyl acetate) precipitation/extraction of acidified whole milk. The solvent precipitation/extraction effectively removed incurred ((14)C) residues from milk samples. The organic extract was then purified by solid phase extraction (SPE) using a strong cation exchange cartridge (sulfonic acid). The final SPE-purified sample was analyzed using LC/MS/MS. The methods are rapid, sensitive, and selective and provide for the determination and confirmation of 5-hydroxyflunixin at the 1 and 2 ppb levels, respectively.     

Analysis of coffee for the presence of acrylamide by LC-MS/MS

A variety of popular instant, ground, and brewed coffees were analyzed using a modified liquid chromatography-tandem mass spectrometry (LC-MS/MS) method specifically developed for the determination of acrylamide in foods. Coffee test portions were spiked with 13C3-labeled acrylamide as an internal standard prior to their extraction and cleanup. Ground coffees (1 g) and instant coffees (0.5 g) were extracted by shaking with 9 mL of water for 20 min. Brewed coffee test portions (9 mL) were taken through the cleanup procedure without further dilution with extraction solvent. Coffee test portions were cleaned up by passing 1.5 mL first through an Oasis HLB (hydrophilic/lipophilic copolymer sorbent) solid phase extraction (SPE) cartridge and then a Bond Elut-Accucat (cation and anion exchange sorbent) SPE cartridge. The cleaned up extracts were analyzed by positive ion electrospray LC-MS/MS. The MS/MS data was used to detect, confirm, and quantitate acrylamide. The limit of quantitation of the method was 10 ng/g for ground and instant coffees and 1.0 ng/mL for brewed coffee. The levels of acrylamide ranged from 45 to 374 ng/g in unbrewed coffee grounds, from 172 to 539 ng/g in instant coffee crystals, and from 6 to 16 ng/mL in brewed coffee.     

Multiclass pesticide determination in olives and their processing factors in olive oil: comparison of different olive oil extraction systems

The processing factors (pesticide concentration found in olive oil/pesticide concentration found in olives) of azinphos methyl, chlorpyrifos, lambda-cyhalothrin, deltamethrin, diazinon, dimethoate, endosulfan, and fenthion were determined in olive oil production process in various laboratory-scale olive oil extractions based on three- or two-phase centrifugation systems in comparison with samples collected during olive oil extractions in conventional olive mills located at different olive oil production areas in Greece. Pesticide analyses were performed using a multiresidue method developed in our laboratory for the determination of different insecticides and herbicides in olive oil by solid-phase extraction techniques coupled to gas chromatography detection (electron capture detection and nitrogen phosphorus detection), optimized, and validated for olive fruits sample preparation. Processing factors were found to vary among the different pesticides studied. Water addition in the oil extraction procedure (as in a three-phase centrifugation system) was found to decrease the processing factors of dimethoate, alpha-endosulfan, diazinon, and chlorpyrifos, whereas those of fenthion, azinphos methyl, beta-endosulfan, lambda-cyhalothrin, and deltamethrin residues were not affected. The water content of olives processed was found to proportionally affect pesticide processing factors. Fenthion sulfoxide and endosulfan sulfate were the major metabolites of fenthion and endosulfan, respectively, that were detected in laboratory-produced olive oils, but only the concentration of fenthion sulfoxide was found to increase with the increase of water addition in the olive oil extraction process.     

Investigation of sample treatment steps for the analysis of polycyclic aromatic hydrocarbons in ground coffee

Sample treatment procedures were tested for the determination of polycyclic aromatic hydrocarbons (PAHs) in ground coffee. Pressurized liquid extraction (PLE), under different conditions, was combined with several cleanup methods, namely in situ purification, C18-silica solid-phase extraction (SPE), silica SPE, acid digestion, and alkaline saponification. Soxhlet extraction and direct alkaline saponification were also tested. Best results were obtained using PLE with hexane/acetone 50:50 (v/v) under 150 degrees C. Alkaline saponification followed by cyclohexane extraction and silica SPE was required to eliminate interferent compounds. Finally, 11 PAHs could be quantified in ground coffee with limits of detection in the range of 0.11-0.18 microg kg(-1). Application to ground Arabica coffee lots from Colombia revealed the presence of several PAHs, giving an overall toxicity equivalence in the range of 0.16-0.87 microg kg(-1). PAH identification was performed using both high-performance liquid chromatography-diode array detection and gas chromatography coupled to mass spectrometry.     

固相萃取-高效液相色谱法测定有机肥中四环素类抗生素药物残留

建立了固相萃取-高效液相色谱(SPE-HPLC)法测定有机肥中土霉素(OTC)、四环素(TC)和金霉素(CTC)3种四环素类抗生素残留的方法。肥料样品采用甲醇、EDTA和McIlvaine缓冲液的混合液(pH=7.2)为提取液,用强阴离子交换柱(SAX)-亲水亲脂萃取柱(HLB)串联进行纯化和富集。采用甲醇-乙腈-0.01mol/L草酸溶液为流动相,进行HPLC分析。3种抗生素的线性范围为0.10～20 mg/L,OTC、TC和CTC的检测限分别为0.03、0.03和0.05 mg/L。不同添加水平的样品加标回收率为64%～86%,RSD在4.14%～8.16%之间。该方法测定了上海市场上40种肥料,发现部分样品有四环素类抗生素的残留物。     

Fast extraction and dilution flow injection mass spectrometry method for quantitative chemical residue screening in food

A prototype multiresidue method based on fast extraction and dilution of samples followed by flow injection mass spectrometric analysis is proposed here for high-throughput chemical screening in complex matrices. The method was tested for sulfonylurea herbicides (triflusulfuron methyl, azimsulfuron, chlorimuron ethyl, sulfometuron methyl, chlorsulfuron, and flupyrsulfuron methyl), carbamate insecticides (oxamyl and methomyl), pyrimidine carboxylic acid herbicides (aminocyclopyrachlor and aminocyclopyrachlor methyl), and anthranilic diamide insecticides (chlorantraniliprole and cyantraniliprole). Lemon and pecan were used as representative high-water and low-water content matrices, respectively, and a sample extraction procedure was designed for each commodity type. Matrix-matched external standards were used for calibration, yielding linear responses with correlation coefficients (r) consistently >0.99. The limits of detection (LOD) were estimated to be between 0.01 and 0.03 mg/kg for all analytes, allowing execution of recovery tests with samples fortified at ≥0.05 mg/kg. Average analyte recoveries obtained during method validation for lemon and pecan ranged from 75 to 118% with standard deviations between 3 and 21%. Representative food processed fractions were also tested, that is, soybean oil and corn meal, yielding individual analyte average recoveries ranging from 62 to 114% with standard deviations between 4 and 18%. An intralaboratory blind test was also performed; the method excelled with 0 false positives and 0 false negatives in 240 residue measurements (20 samples × 12 analytes). The daily throughput of the fast extraction and dilution (FED) procedure is estimated at 72 samples/chemist, whereas the flow injection mass spectrometry (FI-MS) throughput could be as high as 4.3 sample injections/min, making very efficient use of mass spectrometers with negligible instrumental analysis time compared to the sample homogenization, preparation, and data processing steps.     

Molecularly imprinted polymer online solid-phase extraction coupled with high-performance liquid chromatography-UV for the determination of three sulfonamides in pork and chicken

A selective imprinted amino-functionalized silica gel sorbent was prepared by combining a surface molecular imprinting technique with a sol-gel process for online solid-phase extraction-HPLC determination of three trace sulfonamides in pork and chicken muscle. The imprinted functionalized silica gel sorbent exhibited selectivity and fast kinetics for the adsorption and desorption of sulfonamides. With a sample loading flow rate of 4 mL min (-1) for 12.5 min, enhancement factors and detection limits for three sulfonamides ( S/ N = 3) were achieved. The precision (RSD) for nine replicate online sorbent extractions of 5 microg L (-1) sulfonamides was less than 4.5%. The sorbent also offered good linearity ( r (2) > 0.99) for online solid-phase extraction of trace levels of sulfonamides. The method was applied to the determination of sulfonamides in pork and chicken muscle samples. The prepared polymer sorbent shows promise for online solid-phase extraction for HPLC determination of trace levels of sulfonamides in pork and chicken samples.     

Multi-residue analysis of PAH, PCB, and OCP optimized for organic matter of forest soil

Purpose

Analyzing organic pollutants in forest soil is challenging because they are strongly physical and chemical bound to soil organic matter (SOM). Within the framework of a forest soil inventory, an analytical protocol for the determination of polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), and organochlorine pesticides (OCP) should be established and validated using one and the same extraction and cleanup procedure. The protocol should be applicable for reliable analysis of a high number of samples in a short timeframe.

Materials and methods

Two different soil samples representative for the humic layer from a typical mixed and coniferous forest soil had been used for the analysis. Three solvents of different polarity, namely cyclohexane (CH), ethylacetate (EA)/CH (1/1, v/v), and acetone (AC)/CH (2/1, v/v), and the six standard extraction techniques (pressurized liquid extraction (PLE), soxhlet extraction, fluidized bed extraction, sonication, shaking, and one-step extraction recommended for analyzing agricultural soil in Germany (VDLUFA 2008)) were compared concerning their extraction efficiency. For additional matrix separation, two different cleanup procedures (gel permeation chromatography (GPC) and solid-phase extraction (SPE) with different sorbents) were tested. Quantification was carried out using gas chromatography combined with mass spectrometry (GC–MS) and two different injection systems (split/splitless injection and programmable temperature vaporizer (PTV) injection). Labeled internal standards, added prior to extraction, were used for method evaluation.

Results and discussion

For the simultaneous extraction of PAH, PCB, and OCP from organic forest soil PLE with acetone/cyclohexane (2/1, v/v) provided the highest extraction efficiency. A two-step cleanup procedure consisting of GPC followed by SPE with silica gel was entirely sufficient for the separation of humic substances without discrimination of analytes. Recovery rates for the different extraction and cleanup steps ranged between 89% and 106%. For quantification, a GC–MS method was developed using two different injection systems and two capillary columns of different selectivity.

Conclusions

By comparing six standard extraction techniques for PAH, PCB, and OCP from forest soil, we obtained the highest extraction efficiency when using PLE with AC/CH (2/1). For sample injection, we achieved best results using an optimized PTV injection system as it highly reduced the breakdown of thermolabile pesticides. Using this combination of technical equipment, it is possible to determine a concentration of the analytes in the trace level range of 1–2 μg kg^?1 in humic soil.     

Rapid and simple analysis of pesticides persisting on green pepper surfaces swabbing with solvent-moistened cotton

A rapid and simple nondestructive extraction (NDE) method that includes wiping off of systemic neonicotinoid insecticides has been developed to streamline sample pretreatment procedures conducted before chromatographic determination. Pesticide residues were extracted from green pepper surfaces by swabbing them with absorbent cotton moistened with acetone or acetonitrile. After spraying of pesticides, the extraction rate decreased gradually, except for thiacloprid. Presumably, extraction rates depend on the physicochemical properties of pesticides, especially water solubility. It was thought that the applicability of the proposed method greatly depended on the systemic speed of each pesticide, and water solubility was placed as the index that was important to making certain. Direct analysis of some insecticides persisting on sample surfaces has been possible only by extraction before chromatographic determination. These findings indicate strongly that the proposed NDE method has collateral conditions, but it appears promising for on-site pretreatment for pesticide residue analysis.