Multiresidue determination of pesticides in drinking and related waters by solid-phase extraction and liquid chromatography with ultraviolet detection: interlaboratory study

As part of a project funded by the European Commission (EC) for the development and evaluation of multiresidue methods for analysis of drinking and related waters, 17 European laboratories evaluated a method using styrene-divinylbenzene copolymer solid-phase extraction followed by liquid chromatography with diode array detection. The main aim of the study was to evaluate whether the method meets the requirements of EC Drinking Water Directive 98/83 in terms of accuracy, precision, and detection limit for 21 pesticides according to the following requirements: limit of detection, < or =0.025 microg/L; accuracy expressed as recovery, between 75 and 125%; and precision expressed as repeatability relative standard deviation of the method, <12.5%, and as reproducibility relative standard deviation of the method, <25%. Analyses for unknown concentrations were performed with commercial bottled and tap waters. All laboratories were able to achieve detection limits of 0.01 microg/L for all pesticides except pirimicarb (0.02 microg/L). The criteria for repeatability were met for all compounds. Terbutryn in bottled water and carbendazim in tap water did not meet the criteria for reproducibility. In terms of accuracy, the method met the requirements for all pesticides in both matrixes, except for metamitron. However, several compounds (linuron, terbutryn, propazine, metobromuron, and isoproturon) showed recoveries slightly below 75%.     

Multiresidue determination of pesticides in sediment by ultrasonically assisted extraction and gas chromatography/mass spectrometry

A gas chromatographic/mass spectrometric (GS/MS) method was developed for the multiple determination of pesticides in sediment. The investigated pesticides included 85 compounds, i.e., 13 fungicides, 43 herbicides, and 29 insecticides. The pesticides were extracted from sediment samples by an ultrasonically assisted procedure. The extract was cleaned up by using reversed-phase column chromatography followed by normal-phase column chromatography. A styrene-divinylbenzene copolymer cartridge and a silica gel cartridge were used as the reversed-phase column and the normal-phase column, respectively. The compounds were determined by GC/MS with 2 internal standard compounds. The overall recoveries were 70-105%, and the relative standard deviations ranged from 1.5 to 18%. The minimum detectable concentrations were 2-10 microg/kg. This method was successfully applied to sediment samples from the Shin River in Niigata, Japan. Twenty-five pesticides (6 fungicides, 11 herbicides, and 8 insecticides) were detected in the sediment samples. The concentrations of the detected pesticides ranged from 3 to 69 microg/kg. Herbicides were found May through July; insecticides and fungicides were found July through August, and during July through September, respectively. The presence of pesticides in the river sediment was correlated with the time of pesticide application in the Shin River basin.     

Multiresidue determination of pesticides in juice by solid-phase extraction and gas chromatography-mass spectrometry

A multiresidue method based on solid-phase extraction was developed for the simultaneous determination of 50 pesticides in commercial juices. The extraction procedure was carried out in C₁₈ columns preconditioned with acetonitrile and water. The subsequent elution of pesticides was performed with a mixture of hexane-ethyl acetate (1:1, v/v) prior to the determination by gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC-MS-SIM), using one target and two qualifier ions. Standards were prepared spiking blank juice samples to counteract the observed matrix effect. Average recoveries for all the pesticides studied were higher than 91% with relative standard deviations lower than 9% in the concentration range of 0.02-0.1 μg/mL and the detection limits achieved ranged from 0.1 to 4.6 μg/L. The proposed method was applied to the analysis of these compounds in commercial juices and diazinon, ethion and procymidone were the pesticides encountered, although the levels found were very low.     

Multiresidue determination of pesticides in fruit and vegetables by gas chromatography/tandem mass spectrometry

Pesticide residues in fruit and vegetables were determined by gas chromatography/tandem mass spectrometry (GC/MS/MS). Electron impact (EI)/MS/MS and chemical ionization (CI)/MS/MS were developed for 80 compounds, including organochlorine, organophosphorus, organonitrogen, and pyrethroids, providing unambiguous spectral confirmation for these complex matrixes. Residues were extracted from samples with acetone followed by a mixture of dichloromethane-petroleum ether. Two injections per sample were required for analysis of the entire pesticide list by EI/MS/MS and CI/MS/MS. Initial steps involving cleanup and concentration of extracts were eliminated. The excellent selectivity and good linearity allowed quantification and identification of low levels of pesticides in the most difficult matrixes. The method has been used for routine analysis of many vegetables.     

Rapid gas chromatography/mass spectrometry quinine determination in plasma after automated solid-phase extraction

The combined use of an automatic solid-phase extraction (SPE) apparatus with Oasis MCX cartridges and gas chromatography/mass spectrometry (GC/MS) to rapidly quantify quinine in biological samples with cyproheptadine as the internal standard is described. The selected ion monitoring mode, with the quantification ions m/z 136 and 287 (qualifier ions: m/z 261, 381 and 215, 96), allows the estimation of quinine levels, respectively. Separation was completed within 12.7 min. Excellent linearity was found up to 10 000 microg/L of plasma. The limit of detection (LOD) was 12.2 microg/L and the limit of quantification (LOQ) was 40.6 microg/L. High reproducibility (intra-assay CV range 1.9-4.3%, inter-assay CV range 2.2-11.3%) and accuracy values (intra-assay range 83.2-103.7%, inter-assay range 86.8-103.7%) were obtained. Recoveries were concentration-independent (97.2% and 89.8% for 4000 and 10 000 microg/L, respectively). This sensitive, simple assay for quinine in various matrices meets the current requirements for bioanalytical assays and may be used to monitor quinine levels in patients developing severe malaria with acute renal failure during hemofiltration. The optimal quinine dose in this situation is not really established and to improve clinical care, quinine concentrations might be explored to improve efficacy and minimise potential toxicity.     

New monitoring system for ninety pesticides and related compounds in river water by solid-phase extraction with determination by gas chromatography/mass spectrometry

A new monitoring system was established for the determination of 90 pesticides and 10 pesticide degradation products in river water. The pesticides consisted of 18 fungicides, 30 insecticides, and 42 herbicides. The pesticides were extracted with a solid-phase, styrene-divinylbenzene copolymer, eluted with acetone, hexane, and ethyl acetate, and determined by gas chromatography/mass spectrometry. Overall recoveries ranged from 72 to 118%. The limits of detection were 0.01-0.1 microgram/L. This system determines most of the pesticides used in Japan and was successfully applied to practical monitoring of water polluted with pesticides and related compounds.     

Multiresidue determination of pesticides in agricultural products by gas chromatography/mass spectrometry with large volume injection

A method is described for the rapid determination of pesticide residues in agricultural products. Pesticides were extracted from samples with acetonitrile. To remove pigments and fatty acids, an aliquot of the extract was cleaned up by a minicolumn that was packed both with graphitized carbon black and primary secondary amine. Analysis was performed by gas chromatography/ mass spectrometry with programmable temperature vaporizer-based large volume injection using a liner packed with phenylmethylsilicone chemically bonded silica. The method was evaluated for 114 pesticides by spiking into tomato, spinach, Japanese pear, grape, and brown rice at various concentrations of each pesticide (0.02-0.4 microg/g). The method, which gave good recovery (>60%) for 108 pesticides, is characterized by high cleanup efficiency and short cleanup time, and is useful as a rapid screening analysis.     

Continuous solid-phase extraction and gas chromatographic determination of organophosphorus pesticides in natural and drinking waters

A simple, rapid continuous-flow solid-phase extraction method with gas chromatographic detection for the determination of organophosphorus pesticides is proposed. The continuous system consists of an adsorbent column where pesticides are preconcentrated and subsequently eluted with ethyl acetate. Various sorbent materials were assayed of which RP-C18 was found to provide the best results, with a sorption efficiency close to 100%. A comparative study of the determination of pesticides in aqueous samples was conducted using gas chromatography with nitrogen-phosphorus (NPD) and flame ionization (FID) detection. The detection limits of the method for 10 ml of sample were between 50-130 ng/l and 4.5-1 1.7 microg/l with NPD and FID detection, respectively. The method was used to determine organophosphorus pesticides in river, pond, well and tap waters, all with good precision (2.9-4.3%) and recoveries ranging from 93.8 to 104.5%.     

Multiresidue determination of organochlorine pesticides and polychlorinated biphenyls in milk by gas chromatography with electron-capture detection after extraction by matrix solid-phase dispersion

A multiresidue analytical method based on matrix solid-phase dispersion was developed to analyze liquid milk for 22 organochlorine pesticides (OCPs) and 6 polychlorinated biphenyls (PCBs). Initial extraction is performed by loading 3 mL milk onto a 2.0 g octadecyl (C18)-bonded silica cartridge with n-hexane as the eluant. Neutral alumina column chromatography with sodium sulfate as the drying agent is used for further cleanup. The eluate is concentrated to 0.5 mL, and target analytes are determined by capillary gas chromatography with electron-capture detection. The optimized method was validated by determining accuracy (recovery percentages), precision (repeatability and reproducibility), and sensitivity (detection and quantitation limits) from analyses of milk samples fortified at 10 and 1 microg/L levels. Average recoveries were between 74 and 106% for all residues except beta-HCH, beta-endosulfan, and endosulfan sulfate. Both repeatability and reproducibility relative standard deviation values were < 22% for all residues. Detection limits ranged from 0.02 to 0.12 microg/L and quantitation limits were between 0.02 and 0.62 microg/L. The proposed analytical method may be used as a fast and simple procedure in routine determinations of OCPs and PCBs in milk.     

Multiresidue method for the gas chromatographic determination of pesticides in honey after solid-phase extraction cleanup

A new multiresidue method is described for the determination of pesticides in honey. The method involves dissolution of the honey in a methanol-water mixture, followed by solid-phase extraction cleanup and gas chromatographic determination. Twenty-six pesticides used on flowering field crops, on flowering fruit and vegetables, or as acaricides to control Varroa jacobsoni in beehives are determined by the method. Recoveries from honey, spiked at 0.02-1.6 mg/kg, ranged from 85 to 127% with a relative standard deviation (RSD) of 2-16%, except for the RSD of 27% for captan at 0.05 mg/kg.     

溶剂转移-气相色谱-质谱法和选择洗脱-气相色谱法测定大蒜中289种农药多残留

以溶剂转移净化为核心步骤,建立了一种适用于大蒜样品中农药多残留分析的前处理方法(方法I),配以一个辅助方法(方法II),构成大蒜中常见289种农药多残留的分析体系(方法I283种,方法II6种)。方法I中,样品用乙腈-水溶液提取,盐析分配,溶剂转移和固相萃取(SPE)净化后进行气相色谱-质谱(GC-MS)分析;方法II中,样品用无水Na2SO4配合乙酸乙酯均质研磨,超声波辅助提取,提取液经Primary Secondary Amine (PSA)粉末分散固相萃取和LC-Si柱选择洗脱净化后进行GC分析。GC-MS采用选择离子监测(SIM)方式,GC采用火焰光度检测器(FPD)检测,外标法定量。方法简便、快速,通过优化前处理和上机条件,在最优条件下进行测试,方法的定量限(S/N≥10)为0.01～0.05 mg/kg。方法I中,在加标水平为0.02、0.20 mg/kg时,回收率为52%～163%,其中回收率在70%～120%之间的占88%,相对标准偏差为2.4%～18%;方法II中,在加标水平为0.01、0.02、0.10、0.20 mg/kg时,回收率为70%～111%,相对标准偏差为3.2%～9.3%。详细描述了实验模型的构建,并对GC-MS灵敏度的提高提出了新的见解。该方法准确、灵敏、快速,可满足大蒜中多种农药残留的检测要求。     

Multiresidue determination of zeranol and related compounds in bovine muscle by gas chromatography/mass spectrometry with immunoaffinity cleanup

A gas chromatography/mass spectrometry (GC/MS) method with immunoaffinity cleanup was developed for the determination of zeranol and related compounds, taleranol, zearalanone, and alpha-zearalenol in bovine muscle. Muscle samples were extracted with methanol and cleaned up with immunoaffinity chromatography (IAC) columns containing monoclonal antibodies raised against zeranol coupled to CNBr-activated Sepharose 4B. After derivatization, the compounds were analyzed by GC/MS. The dynamic column capacities for zeranol, taleranol, zearalanone, and alpha-zearalenol were 2639.7, 2840.3, 2731.5, and 2736.3 ng/mL Sepharose gel, respectively. The limits of detection and quantification were 0.5 and 1.0 ng/g, respectively, for all 4 compounds. Mean recoveries were 79.6-110.7% with coefficients of variation of 3.2-11.4% at spiked levels of 1.0-5.0 ng/g. This IAC-GC/MS method may be used for the determination of zeranol, taleranol, zearalanone, and alpha-zearalenol residues in bovine muscle, and possibly other tissues.     

Multiresidue determination of pesticides in honey by matrix solid-phase dispersion and gas chromatography with electron-capture detection

A multiresidue method was developed for the determination of 15 pesticides (organochlorines, organophosphorus compounds, pyrethroids, and other acaricides) in various commercial honeys (eucalyptus, lavender, orange, rosemary, and multifloral). The analytical procedure is based on the matrix solid-phase dispersion of honey in a mixture of Florisil and anhydrous sodium sulfate; the mixture is placed in small plastic columns and extracted with hexane-ethyl acetate (90 + 10, v/v). The pesticide residues are determined by capillary gas chromatography with electron-capture detection. Recoveries with the method at concentrations between 0.15 and 1.5 microg/g ranged from 80 to 113%, and relative standard deviations were <10% for all the pesticides studied. The pesticide detection limits were within the range 0.5-5 microg/kg for organochlorines, around 3 microg/kg for the chlorinated organophosphorus pesticides studied, near 15 microg/kg for fluvalinate, and about 3 microg/kg for the other pyrethroids.     

Multiresidue method for determination of 90 pesticides in fresh fruits and vegetables using solid-phase extraction and gas chromatography-mass spectrometry

A multiresidue method for analysis of 90 pesticides with different physico-chemical properties in fruits and vegetables was developed. The method involves a rapid and small-scale extraction procedure with acetone using vortex mixing. Solid-phase extraction (SPE) on a highly cross-linked polystyrene divinylbenzene column (LiChrolut EN) was used for clean-up and pre-concentration of the pesticides from the water-diluted acetone extracts. For most fruit and vegetable samples this partial clean-up was sufficient, but some of them with more co-extracting substances need further clean-up (cereals, spinach, carrots, etc.). Diethylaminopropyl (DEA) modified silica was used for efficient removal of interferences caused by various organic acids, sugars, etc. The pesticide residues were determined by gas chromatography with a mass selective detector (GC-MS). The majority of pesticide recoveries for various fruits and vegetables were >80% in the concentration range from 0.01 to 0.50 mg/kg, except for the most polar pesticides (methamidophos, acephate, omethoate) which cannot be determined by this method. The limit of quantitation for most of the pesticides was 0.01 mg/kg with majority of relative standard deviations (R.S.D.s) below 10%.     

Multiresidue determination of 160 pesticides in wines employing mixed-mode dispersive-solid phase extraction and gas chromatography-tandem mass spectrometry

A new multiresidue method for the efficient screening, identification and quantification of over 160 pesticides belonging to different chemical classes in red, rose and white wines have been developed. The analysis was based on gas chromatographic-tandem quadrupole mass spectrometric determination (GC-QqQ-MS/MS). An optimization strategy involved the selection of buffering conditions and sorbents for dispersive-solid phase extraction (dispersive-SPE) in order to achieve acceptably high recoveries and reduce co-extractives in the final extracts. As a result, the optimized procedure allowed us to obtain consistent recoveries of the target pesticides including problematic ones such as captan, chlorothalonil, dichlofluanid, folpet and tolylfluanid. The attained recoveries were typically between 80 and 110% (89% on average) with RSD values typically lower than 10% (8% on average) at three spiking levels of 0.01, 0.05 and 0.2 mg kg⁻¹. Linearity was studied in the range between 0.005 and 0.2 mg kg⁻¹ using pesticide standards prepared both in pure solvent and in the presence of matrix, showing coefficients of determination (R²) higher than 0.99 for all the pesticides except for desmedipham, thiabendazole and thiamethoxam in pure solvent. The study of the ratio of the slopes obtained in solvent and in matrix provided information about the matrix effects, which was <10%, 10-20% and >20% for 33, 36 and 31% of the studied pesticides, respectively. To improve accuracy, matrix matched standards were always used for calculation of the quantification results. The expanded uncertainties were estimated by using a “top-down” approach as being 17% on average (coverage factor k = 2, confidence level 95%). Finally, the method was used with success to detect and quantify pesticide residues in commercial wines.     

Multiresidue analysis of pesticides in vegetables and fruits by gas chromatography/mass spectrometry after gel permeation chromatography and graphitized carbon column cleanup

A multiresidue method for pesticides that enables quantitative, sequential analysis of a large number of vegetable and fruit samples by gas chromatography/mass spectrometry has been developed. First, 89 important target compounds were selected for monitoring, and then the appropriate internal standards for these pesticides, 14 stable isotopically labeled pesticides (surrogates), were used. The sample was extracted with acetonitrile, and the extract was cleaned up by a salting-out step followed by redissolution in ethyl acetate. Coextractives were removed automatically by gel permeation chromatography with a graphitized carbon column, and then by use of a tandem silica-gel/PSA cartridge column. Recoveries of 82 of the 89 pesticides from fortified spinach, tomato, apple, and strawberry were within a range from 70 to 120%, and the relative standard deviation values of 80 of the 89 pesticides were <5%. The method was applied to 188 commercial vegetable and fruit samples to demonstrate its use in routine analysis.     

固相萃取-气相色谱-质谱联用法测定水中的硝基苯类有机污染物的分析方法研究

建立了固相萃取、毛细柱气相色谱-质谱、内标标准曲线法使用选择离子(SIM)监测采集数据定量分析水中硝基苯类有机化合物的分析方法.通过对固相萃取柱的选择、固相萃取条件(样品溶液的pH、上样速率、上样体积、洗脱液选择及配比)的优化,得出了最佳实验条件.始漏体积达1.5 L.回收率大于80%.检出限为0.015～0.045 μg/L.RSD在1.1%～5.9%之间.     

Multiresidue determination of 77 pesticides in textiles by gas chromatography-mass spectrometry

A simple and efficient method for multiple determination of 77 pesticides, including one organonitrogen, eight carbamate, 12 pyrethroid, 26 organochloride, 30 organophosphorous compounds, in textiles is developed. Six representative textiles are chosen as test samples. Extraction using hexane-ethyl acetate (1:1) assisted by ultrasonic processor is carried out twice, followed by clean-up using solid-phase extraction on a florisil column. The final solution is analyzed using gas chromatography-mass spectrometry, and 77 pesticides are determined. This method is highly sensitive, selective, and reproducible, with a broad linear range and reliable accuracy. Six blank samples are spiked with 0.50 and 2.00 mg/kg of the 77 pesticides, and the corresponding recoveries are between 64.5% and 99.1%; the precisions range from 4.04% to 14.78%; and the minimum detection limits of this method are 0.02-0.20 mg/kg.     

Multiresidue analytical method using dispersive solid-phase extraction and gas chromatography/ion trap mass spectrometry to determine pharmaceuticals in whole blood

A convenient analytical method for the simultaneous determination of more than 40 pharmaceuticals belonging to various therapeutic categories in whole blood has been developed. Exemplarily, the method was fully validated for eight different pharmaceuticals. The procedure entails addition of acetonitrile, magnesium sulfate and sodium chloride to a small amount of blood, then the mixture is shaken intensively and centrifuged for phase separation. An aliquot of the organic layer is cleaned up by dispersive solid-phase extraction employing bulk sorbents as well as magnesium sulfate for the removal of residual water. This method was based on the QuEChERS approach developed for pesticide residue analysis in food. Gas chromatography/ion trap mass spectrometry (GC/MS) with electron (EI) and chemical (CI) ionisation was then used for qualitative and quantitative determination of the pharmaceuticals. The dispersive SPE with PSA (sorbent functionalized with primary and secondary amines) was found more suitable than aminopropyl and a styrene-divinylbenzene sorbent for sample clean-up before drug level determination in whole blood and plasma, as it was found that most of endogenous matrix components were removed and the analytes were isolated from spiked samples with recoveries above 80%. Variation coefficients of the repeatability typically smaller than 10% have been achieved for a wide range of the investigated substances. The used analytical conditions allowed to separate successively a variety of drugs and poisons with the typical limit of detection at <20 ng mL(-1) levels using 1 microL injection of equivalent blood sample in whole blood. The method is simple, rapid, cheap and very effective for therapeutic drug monitoring and forensic chemistry.