Multi-residue analysis of 206 pesticides in grass forage by the one-step quick,easy, cheap,effective, rugged,and safe method combined with ultrahigh-performance liquid chromatography quadrupole orbitrap mass spectrometry

A novel method for detecting pesticide multi-residue in grass forage (alfalfa and oat) was established based on the one-step automatic extraction and purification technology of quick, easy, cheap, effective, rugged, and safe combined with ultrahigh-performance liquid chromatography quadrupole Orbitrap high-resolution mass spectrometry. The crushed sample was extracted with acetonitrile with 1% acetate, followed by a cleanup step with a primary-secondary amine, octadecylsilane, and graphitized carbon black. The extraction and purification were carried out using the one-step automatic pretreatment equipment. The target pesticides were acquired in positive ion electrospray ionization mode and full scan/data dependent secondary scan mode. The calibration curve shows good linearity over the corresponding concentration range, with the coefficient of determination greater than 0.99. The screening detection limits were 0.5–50 μg/kg, and the limit of quantification for the 206 pesticides was set at 1–50 μg/kg. At the spiking levels of one, two, and 10 times of limit of quantification, more than 95% of pesticides had recovery between 70–120%, with a relative standard deviation ≤20%. The method was proved to be simple, rapid, high-sensitivity, and could be routinely used for the high throughput screening and quantitative analysis of pesticide residues in alfalfa and oat.     

Simultaneous determination of 109 pesticides in unpolished rice by a combination of gel permeation chromatography and Florisil column purification, and gas chromatography/mass spectrometry

A multi-residue method is described for the simultaneous analysis of 109 pesticides with different properties in unpolished rice. The range covers organophosphorus, organochlorine, carbamate, and synthetic pyrethroid pesticides. The pesticides were extracted from the sample using ethyl acetate. Most higher molecular weight components such as lipids in the co-extractives were removed by gel permeation chromatography (GPC) with a Bio-bead SX-3 column. A Florisil column with ethyl acetate/hexane as the eluting solvents was used for further cleanup. The pesticides were finally simultaneously determined by gas chromatography/mass spectrometry (GC/MS) in selective ion monitoring (SIM) mode. The average recoveries for most pesticides (spiked level 0.02, 0.1 and 1 microg/g) ranged from 70% to 110%, the relative standard deviation (RSD) was below 20% in every case, and the limit of detection (LOD) varied from 1 to 20 ng/g.     

Multi-residue determination of pesticides in tropical fruits using liquid chromatography/tandem mass spectrometry

Monitoring pesticide residues in tropical fruits is of great interest for many countries, e.g., from South America, that base an important part of their economy on the exportation of these products. In this work, a LC-MS/MS multi-residue method using a triple quadrupole analyzer has been developed for around 30 pesticides in seven Colombian tropical fruits of high commercial value for domestic and international markets (uchuva, tamarillo, granadilla, gulupa, maracuya, papaya, and pithaya). After sample extraction with acetonitrile, an aliquot of the extract was diluted with water and directly injected into the HPLC-MS/MS system (electrospray interface) without any cleanup step. The formation of sodium adducts—of poor fragmentation—was minimized using 0.1% formic acid in the mobile phase, which favored the formation of the protonated molecule. However, the addition of ammonium acetate made the formation of the ammonium adducts in some particular cases possible, avoiding the presence of the sodium adducts. The highest sensitivity was observed in positive electrospray ionization for the wide majority of pesticides, with a few exceptions for acidic compounds that gave better response in the negative mode (e.g., 2,4-D, fluazinan). Thus, simultaneous acquisition on the positive/negative mode was applied. Two MS/MS transitions were acquired for each compound to ensure a reliable quantification and identification of the compounds detected in samples, although for malathion a third transition was acquired due to the presence of interfering isobaric compounds in the sample extracts. A detailed study of matrix effects was made by a comparison of standards in solvent and in matrix. Both ionization suppression and ionization enhancement were observed depending on the analyte/matrix combination tested. Correction of matrix effects was made by the application of calibration in matrix. Three matrices were selected (uchuva, maracuya, gulupa) to perform matrix calibration in the analysis of all seven fruit varieties studied. The method was validated by recovery experiments in samples spiked at two levels (0.05 and 0.5 mg/kg). The data were satisfactory for the wide majority of analyte/matrix combinations, with most recoveries between 70% and 110% and the RSD below 15%. Several samples collected from the market were finally analyzed. Positive findings were confirmed by evaluating the experimental Q/q ratios and retention times, and comparing them with those of reference standards.     

Displaced dual‐mode imaging with desorption electrospray ionization for simultaneous mass spectrometry imaging in both polarities and with several scan modes

Displaced dual‐mode imaging (DDI) is introduced as a method for simultaneous imaging in positive and negative‐ion mode on the same sample with desorption electrospray ionization imaging, as well as a method for simultaneous imaging in full‐scan and tandem mass spectrometry (MS/MS) mode. DDI is performed by using a smaller row distance in the y‐direction than the desired image resolution and recording for example every second row in positive‐ion mode and the other half of the rows in negative‐ion mode, thus resulting in two separate images. This causes some degree of oversampling, which is thus utilized to obtain complementary mass spectrometric of the sample. Imaging with both polarities is exemplified on an imprint of a Hypericum perforatum leaf containing secondary metabolites which ionize in both polarites and a mouse kidney containing phospholipids which ionize in positive or negative mode only. Simultaneous full‐scan and MS/MS imaging was demonstrated on the same mouse kidney, as the mouse had been given a relatively low dose of the antidepressive drug amitriptyline. While the full‐scan data allowed imaging of the endogenous phospholipids, the drug and its metabolites were only visible in the MS/MS images. The latter approach is useful, for example in whole‐body imaging experiments where the full‐scan data gives an overview of the tissue, and the MS/MS mode provides the sensitivity to image trace amounts of drugs and metabolites. Copyright © 2013 John Wiley & Sons, Ltd.     

Screening Method for the Determination at Parts Per Trillion Levels of Pesticide Residues in Vegetables Combining Solid‐Phase Microextraction and Gas Chromatography‐Tandem Mass Spectrometry

Abstract

A new analytical method is proposed for determining residues of 70 pesticides of different chemical families at parts per trillion levels in fresh vegetables. For that, only 4 g of the vegetable samples were quickly extracted with 10 ml of ethyl acetate. The method is based on a vanguard/rearguard strategy that reduces the average time required per sample when the method is applied to a high number of vegetable samples in a quality control laboratory. At the beginning, an aliquot of the extract is evaporated and re‐dissolved in a mixture water:acetone (9∶1 v/v). For screening purposes, the pesticides were extracted for only 10 min by direct immersion of a solid‐phase microextraction (SPME) fiber (65 µm polydimethylsiloxane‐divinylbenzene, PDMS‐DVB). The SPME device was automated and on‐line coupled to a gas chromatograph with an ion trap mass spectrometer (GC‐MS) operated in full scan mode for screening in less than 18 min those samples that potentially contain pesticides above 0.01 mg kg^?1 (cut off value). After that, only those potentially non‐negative samples were reanalyzed by a sensitive quantifying/confirming method that re‐extract by SPME the pesticides in 55 min of absorption and determine them by GC with tandem MS (MS/MS). The method has been validated following EU guidelines and compared with a conventional extraction method based on the use of higher amounts of organic solvents. The limits of detection (LOD), confirmation (LOC) and quantitation (LOQ) as well as the calibration curves obtained allowed the determination of the target pesticides at concentrations clearly below the maximum residue levels (MRL) stated by EU being possible the determination of parts per trillion of the pesticides in ecological (green) vegetables. The method has been applied to the analysis of real samples and the results compared with those obtained by a conventional extraction method accredited by ENAC (Spanish Accreditation Body). The proposed method was also evaluated participating in a proficiency test with adequate results (z‐score among±2).     

Multi‐mycotoxin analysis in complex biological matrices using LC‐ESI/MS: Experimental study using triple stage quadrupole and LTQ‐Orbitrap

In the present study, we report the application of LC‐MS based on two different LC‐MS systems to mycotoxin analysis. The mycotoxins were extracted with an ACN/water/acetic acid mixture and directly injected into a LC‐MS/MS system without any dilution procedure. First, a sensitive and reliable HPLC‐ESI‐MS/MS method using selected reaction monitoring on a triple quadrupole mass spectrometer (TSQ Quantum Ultra AM) has been developed for determining 32 mycotoxins in crude extracts of wheat and maize. This method was operated both in positive and in negative ionization modes in two separate chromatographic runs. The method was validated by studies of spiked recoveries, linearity, matrix effect, intra‐assay precision and sensitivity. Further, we have developed and evaluated a method based on accurate mass measurements of extracted target ions in full scan mode using micro‐LC‐LTQ‐Orbitrap as a tool for fast quantitative analysis. Both instruments exhibited very high sensitivity and repeatability in positive ionization mode. Coupling of micro‐LC to Orbitrap technology was not applicable to the negatively ionizable compounds. The LC triple quadrupole MS method has proved to be stable in quantitation, as it is with respect to the matrix effects of grain samples.     

Determination of multi-class pesticides in wines by solid-phase extraction and liquid chromatography-tandem mass spectrometry

This work reports a new sensitive multi-residue liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for detection, confirmation and quantification of forty-six pesticides and transformation products belonging to different chemical classes in wines. The proposed method makes use of a solid-phase extraction (SPE) procedure with Oasis HLB cartridges that combines isolation of the pesticides and sample clean-up in a single step. Analysis is performed by liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-MS/MS) operated in the selected reaction monitoring (SRM) mode, acquiring two specific precursor-product ion transitions per target compound. An investigation of matrix effects has been performed during method validation showing medium to low effects for the majority of the compounds. Limits of detection (LODs) were in the range 0.0003–0.003 mg L⁻¹ and limits of quantification (LOQs) were in the range 0.001–0.01 mg L⁻¹. The average recoveries, measured at two concentration levels (0.010 and 0.050 mg L⁻¹), were in the range 70–110% for most of the compounds tested with % relative standard deviations below 20%, while a value of 0.010 mg L⁻¹ has been established as the method limit of quantification (MLOQ) for all target species. Expanded uncertainty values were in the range 10–40% while the Horrat ratios were below 1. The method has been successfully applied to the analysis of 60 wine samples in the course of an annual monitoring study with carbendazim-benomyl, thiophanate-methyl and carbaryl being the most frequently determined pesticides.     

Optimization of a multi-residue screening method for the determination of 85 pesticides in selected food matrices by stir bar sorptive extraction and thermal desorption GC-MS

A multi-residue method to determine 85 pesticides, including organochlorine pesticides, carbamates, organophosphorus pesticides, and pyrethroids, in vegetables, fruit, and green tea, has been developed. The method is based on stir bar sorptive extraction (SBSE) coupled to thermal desorption (TD) and retention time locked (RTL) GC-MS operating in the scan mode. Samples are extracted with methanol and diluted with water prior to SBSE. Dilution of the methanol extract before SBSE was optimized to obtain high sensitivity and to minimize adsorption onto the glass wall of the extraction vessel as well as to minimize sample matrix effects (particularly for the pesticides with high log K(o,w) values). The optimized method consists of a dual SBSE extraction performed simultaneously on respectively a twofold and a fivefold diluted methanol extract. After extraction, the two stir bars are placed in a single glass thermal desorption liner and are simultaneously desorbed. The method showed good linearity (r2 > 0.9900) and high sensitivity (limit of detection: < 5 microg kg(-1)) for most of the target pesticides. The method was applied to the determination of pesticides at low microg kg(-1) in tomato, cucumber, green soybeans, spinach, grapes, and green tea.     

Multi-residue screening of pesticides in vegetables,fruits and baby food by stir bar sorptive extraction-thermal desorption-capillary gas chromatography-mass spectrometry

The performance of stir bar sorptive extraction (SBSE) for the enrichment of pesticides from vegetables, fruits and baby food samples is discussed. After extraction with methanol, an aliquot is diluted with water and SBSE is performed for 60 min. By applying a new thermal desorption unit (TDU), fully automated and unattended desorption of 98 stir bars is feasible, making SBSE very cost-effective. The presence of pesticide residues is elucidated with the retention time locked gas chromatography–mass spectroscopy method (RTL-capillary GC–MS). With SBSE–RTL-capillary GC–MS operated in the scan mode, more than 300 pesticides can be monitored in vegetables, fruits and baby food. The multi-residue method (MRM) described provides detectabilities from the mg/kg (ppm) to the sub-μg/kg (ppb) level, thereby complying with the maximum residue levels (MRLs) set by regulatory organizations for pesticides in different matrices. Several examples, i.e. pesticide residues in lettuce, pears, grapes and baby food, illustrate the potential of SBSE–RTL-capillary GC–MS.     

Multi-residue determination of 130 multiclass pesticides in fruits and vegetables by gas chromatography coupled to triple quadrupole tandem mass spectrometry

A multi-residue method has been developed and validated for the simultaneous quantification and confirmation of around 130 multiclass pesticides in orange, nectarine and spinach samples by GC-MS/MS with a triple quadrupole analyzer. Compounds have been selected from different chemical families including insecticides, herbicides, fungicides and acaricides. Three isotopically labeled standards have been used as surrogates in order to improve accurate quantitation. Samples were extracted by using accelerated solvent extraction (ASE) with ethyl acetate. In the case of spinach, an additional clean-up step by gel permeation chromatography was applied. Determination was performed by GC-MS/MS in electron ionization mode acquiring two MS/MS transitions for each analyte. The intensity ratio between quantitation transition (Q) and identification transition (q) was used as confirmatory parameter (Q/q ratio). Accuracy and precision were evaluated by means of recovery experiments in orange, nectarine, and spinach samples spiked at two concentration levels (0.01 and 0.05 mg/kg). Recoveries were, in most cases, between 70% and 120% and RSD were below 20%. The limits of quantification objective for which the method was satisfactorily validated in the three samples matrices were for most pesticides 0.01 mg/kg. Matrix effects over the GC-MS/MS determination were tested by comparison of reference standards in pure solvent with matrix-matched standards of each matrix. Data obtained showed enhancement of signal for the majority of analytes in the three matrices investigated. Consequently, in order to reduce the systematic error due to this effect, quantification was performed using matrix-matched standard calibration curves. The matrix effect study was extended to other food matrices such as raisin, paprika, cabbage, pear, rice, legume, and gherkin, showing in all cases a similar signal enhancement effect.     

Sample treatment and determination of pesticide residues in fatty vegetable matrices: A review

A demanding task in pesticide residue analysis is yet the development of multi-residue methods for the determination of pesticides in vegetables with relatively high fat content (i.e. edible oils and fatty vegetables). The separation of pesticides and other chemical contaminants from high-fat food samples prior to subsequent steps in the analytical process is yet a challenging issue to which much effort in method development has being applied. This review addresses the main sample treatment methodologies for pesticide residue analysis in fatty vegetable matrices. Even with the advent of advanced hyphenated techniques based on mass spectrometry these complex fatty matrices usually require extensive sample extraction and purification. Current methods involve the use of one or the combination of some of the following techniques for both the sample extraction and clean-up steps: liquid-liquid partitioning, solid-phase extraction (SPE), gel-permeation chromatography (GPC), matrix solid-phase dispersion (MSPD), etc. An overview of methods developed for these contaminants in fatty vegetables matrices is presented. Sample extraction and purification techniques are discussed and their most recent applications are highlighted. This review emphasizes that sample preparation is a critical step, but also the determination method is, and cannot be treated separately from sample treatment. In recent years, the appearance and use of new, more polar pesticides has fostered the development of liquid chromatography/mass spectrometry (LC-MS) besides gas chromatography. The main features of LC-MS for the analysis of multi-class pesticides in fatty vegetable samples will be also underlined, with an emphasis on the multi-class, multi-residue strategy and the difficulties associated.     

超高效液相色谱-串联质谱法对比11种净化方式对当归中50种农药残留检测的影响

采用超高效液相色谱-串联质谱仪(UPLC-MS/MS)同时测定当归药材中50种农药残留,对比了11种净化方式对检测结果的影响,筛选出最有效的基质净化方法。 以回收率为考察指标,评估了不同基质净化方法对当归中多农残的提取净化效果,最终确定样品经乙腈提取,NaCl净化,在电喷雾正负离子扫描、依赖保留时间的动态多反应监测模式(dMRM)下,以基质匹配内标法定量。 结果表明,50种农药在NaCl净化法下回收率最高,在各自的浓度范围内线性关系良好(R²>0.99);3个添加水平(10、50、100 μg/kg)下,大多数农药的回收率为70.1%~117.7%,相对标准偏差(RSD,n=6)不大于 20.0%,50种农药的定量限为1.0~20.0 μg/kg。 该方法为当归中准确、高效、经济的检测目标物提供了可靠依据。     

程序升温大体积进样和解卷积气相色谱-质谱法测定蔬菜水果中32种农药残留量

建立了蔬菜、水果中有机磷、有机氯、拟除虫菊酯和氨基甲酸酯等32种农药的气相色谱-质谱(GC-MS)检测方法。样品经乙腈提取,石墨碳黑串联丙氨基固相萃取柱净化,采用程序升温大体积进样,GC-MS全扫描模式采集,结合解卷积技术定性分析,内标法定量。分别对程序升温和大体积进样等条件进行了研究,并考察了方法选择性和耐用性。在最优条件下,32种农药的响应值与浓度呈良好的线性关系(r>0.995),各农药的方法检出限为2.0~5.0 μg/kg,以菠菜、四季豆和黄瓜为代表基质,进行3个水平(0.010~0.50 mg/kg)的加标回收试验(n=6),回收率为65.2%~120.3%,相对标准偏差(RSD)为4.1%~22.3%。该方法快速、灵敏、可靠、耐用,能满足蔬菜、水果中多类多残留痕量分析的要求。     

Injector-internal thermal desorption from edible oils performed by programmed temperature vaporizing (PTV) injection

Injector-internal thermal desorption is a promising technique for the analysis of a wide range of food components (e.g., flavors) or food contaminants (e.g., solvent residues, pesticides, or migrants from packaging materials) in edible oils and fats or fatty food extracts. Separation from the fatty matrix occurs during injection. Using programmed temperature vaporizing (PTV) injection, the oily sample or sample extract was deposited on a small pack of glass wool from which the components of interest were evaporated and transferred into the column in splitless mode, leaving behind the bulk of the matrix. Towards the end of the analysis, the oil was removed by heating out the injector and backflushing the precolumn. The optimization dealt with the gas supply configuration enabling backflush, the injector temperature program (sample deposition, desorption, and heating out), separation of the sample liquid from the syringe needle and positioning it on a support, deactivation of the support surface, holding the plug of fused silica wool by a steel wire, and the analytical sequence maintaining adsorptivity at the desorption site low. It was performed for a mixture of poly(vinyl chloride) (PVC) plasticizers in oil or fatty food. Using MS in SIM, the detection limit was below 0.1 mg/kg for plasticizers forming single peaks and 1 mg/kg for mixtures like diisodecyl phthalate. For plasticizers, RSDs of the concentrations were below 10%; for the slip agents, oleamide and erucamide, it was 12%. The method of incorporating PTV injection was used for about one year for determining the migration from the gaskets of lids for glass jars into oily foods.     

Development of a Straightforward and Cheap Ethyl Acetate Based Method for the Simultaneous Determination of Pesticides and Veterinary Drugs Residues in Bovine Liver and Muscle

The optimization and validation study of a qualitative and quantitative multiclass, ethyl acetate (EtOAc) multi-residue method to straightforward monitor 48 compounds in liver (6 veterinary drugs and 42 pesticides) and 54 in muscle (5 veterinary drugs and 49 pesticides) followed by high performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) and gas chromatography mass-spectrometry determination (GC–MS) is presented. Several clean-up sorbents were evaluated looking for the best strategy for the removal of the matrix co-extractives. A combination of aluminium oxide, (Al₂O₃), C-18 and magnesium sulphate (MgSO₄) yielded the best analytical results in terms of precision and accuracy. The method was validated at three fortification levels: 10, 100 and 250 µg kg⁻¹. The percentages of recovery were between 70 and 114 % for bovine muscle and 70–118 % for liver. Repeatability and intermediate precision percentages were below 20 % for both matrices. Most of the compounds under study presented good linearity and quantification limits below their corresponding European Union (EU) and Codex Alimentarius maximum residue levels (MRLs). Twenty-two randomly taken real samples were analyzed with the validated methodology, trying to prove its effectiveness and suitability for routine analysis. The validated methodology represents a fast and cheap alternative for the simultaneous analysis of pesticides and veterinary drugs which can be easily extend to other compounds and matrices.

     

Planar solid phase extraction--a new clean-up concept in multi-residue analysis of pesticides by liquid chromatography-mass spectrometry

Efficient clean-up is indispensable for preventing matrix effects in multi-residue analysis of pesticides in food by liquid and gas chromatography coupled to mass spectrometry. As a completely new approach, highly automated planar chromatographic tools were applied for powerful clean-up, called high-throughput planar solid phase extraction (HTpSPE). Thin-layer chromatography (TLC) was used to completely separate pesticides from matrix compounds and to focus them into a sharp zone, followed by extraction of the target zone by the TLC-MS interface. HTpSPE resulted in extracts nearly free of interference and free of matrix effects, as shown for seven chemically representative pesticides in four different matrices (apples, cucumbers, red grapes, tomatoes). Regarding the clean-up step, quantification by LC-MS provided mean recovery (against solvent standards) of 90-104% with relative standard deviations of 0.3-4.1% (n=5) for two spiking levels of 0.1 and 0.5 mg/kg. Clean-up of one sample was completed in a manner of minutes, while running numerous samples in parallel at reduced costs, with very low sample and solvent volumes.     

Selection of SPE cartridge for automated solid-phase extraction of pesticides from water followed by liquid chromatography-tandem mass spectrometry

In environmental analyses there is an ever-increasing need to develop simple and sensitive multi-residue methods. In many agricultural regions, there is particular concern of the potential for pesticides to enter rivers and other waterways. This study reports on the development and validation of a multi-residue method of analysis for 30 pesticides in water samples using solid-phase extraction (SPE) followed by LC-MS/MS. The electrospray and MS/MS parameters were optimised for each pesticide, including capillary voltage, collision-induced dissociation voltage, and selection of a precursor ion and two product ions. A variety of SPE sorbents were tested for sample pre-concentration, including numerous polymeric based phases. Bond Elut PPL and Oasis HLB were the only phases capable of retaining the majority of the target analyte classes in a single method. An off-line pre-concentration method using a Gilson Aspec system was optimised using the Bond Elut PPL cartridges, with a concentration factor of 25 producing limits of quantitation in the order of 6–100 ng/L. Excellent linearity (r ² > 0.9), precision (<20%) and recovery (>60%) was obtained for nearly all of the analytes, covering a wide variety of chemical and physical properties. This is the first study to fully validate Bond Elut PPL cartridges for use in multi-residue pesticide analysis.     

Study of automated mass spectral deconvolution and identification system (AMDIS) in pesticide residue analysis

The effects of overlapping levels and concentration ratios of overlapping components, and of scan rates of the mass spectrometer, on the capability of the automated mass spectral deconvolution and identification system (AMDIS) in pesticide residue analysis were studied. To investigate the capability of AMDIS in removing interferences from the overlapping peaks, this system was applied to data files obtained from the gas chromatography/mass spectrometry (GC/MS) analysis of two overlapping (co-eluting) pesticides (beta-HCH and PCNB) in full scan mode. Differences in overlap levels, the concentration ratios of the two overlapping components and the scan rates of the instrument were studied. When the difference in scan number of overlapping compounds was equal to 1 scan, AMDIS incompletely extracted 'purified' mass spectra but as the difference increased to 3 or more scans, complete correct spectra could be extracted. The results also show that when the scan rate was in the range of 0.4-0.90 s/scan and the concentration ratios of the target compound/interference were above 1/5, there were ideal deconvolution results for this approach. To further study the application of AMDIS to pesticide residue analysis, AMDIS was applied to the identification of pesticides spiked in real samples (cabbage and rice). Typical pesticides being evaluated were identified using AMDIS at concentrations >50 ng/g in the extracts.     

Solid-phase micro-extraction-gas chromatography-(tandem) mass spectrometry as a tool for pesticide residue analysis in water samples at high sensitivity and selectivity with confirmation capabilities

Gas chromatography-mass spectrometry (GC-MS) has been widely applied for pesticide monitoring because of its high sensitivity and specificity and for the potential of multi-residue and multi-class analysis. An analytical procedure was developed for the determination of pesticide multi-residues in water samples combining solid-phase micro-extraction (SPME) and gas chromatography-ion trap mass spectrometry. For SPME extraction a poly(dimethylsiloxane)-divinylbenzene coated fibre was selected whereas the mass spectrometer was operated under full scan, selected ion storage (SIS), microSIS (SIM) and MS-MS and the figures of merit compared. Quantitative and qualitative (confirmatory) capabilities of each operation mode are discussed. Using MS-MS, precision was typically below 10% and limits of detection (LODs) were improved by 1.3 to 20 times (to low- or sub-ppt levels) compared to microSIS, with the advantage of maintaining identification capabilities. The combination of selective extraction by SPME and highly selective determination by GC-MS-MS made possible ultra-selective and essentially error-free determination of pesticides in complex environmental samples. This aspect will be highlighted in the paper.     

QuEChERS-液相色谱-串联质谱法测定蔬菜中105种农药残留

通过优化QuEChERS前处理方法并结合液相色谱-串联质谱（LC-MS/MS）技术建立了蔬菜中105种典型杀虫剂、杀菌剂、除草剂、植物生长调节剂的多残留测定方法。目标化合物使用乙腈提取,以150 mg乙二胺-N-丙基硅烷（PSA）、150 mg封端十八烷基键合硅胶吸附剂（EC-C₁₈）、30 mg石墨化炭黑（GCB）作为基质提取液净化剂。实验结果表明,在0.010~0.200 mg/L范围内,105种目标化合物的线性相关系数（r）>0.99,方法定量限为0.010 mg/kg;3个添加水平的回收率范围为68.2%~108%,相对标准偏差（RSD）为1.02%~11.8%。该方法快速简便,净化效果好,可用于蔬菜中日常农药残留的测定。