Comparison of tandem-in-space and tandem-in-time mass spectrometry in gas chromatography determination of pesticides: application to simple and complex food samples

Gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) is one of the most powerful techniques in pesticide residue analysis. MS/MS can be conceived in two ways: tandem in space (e.g. triple quadrupole, QqQ) or in time (e.g. ion trap, IT). QqQ and IT are commonly interfaced to GC; however, there has not been any direct comparison between them in pesticide residue analysis so far. In the present work, the performance of GC coupled to these two analyzers (GC-QqQ-MS/MS and GC-IT-MS/MS) was studied and compared for pesticide residue analysis as well as its application in food analysis. The large volume injection (LVI) technique together with programmed-temperature vaporization (PTV) was applied. For this purpose, 19 pesticides, including organochlorine and organophophorus pesticides and pyrethroids, were analyzed in both systems. Mass spectrometric data, performance characteristics (linearity, intra-day and inter-day precision) and the influence of the matrix nature on the analysis of low concentrations were compared. The target compounds were analyzed in solvent and in two representative food matrices such as cucumber (high water content) and egg (high fat content). MS data and intra-day precision were similar in QqQ and IT, whereas inter-day precision was significantly worse in QqQ. Linearity (expressed as determination coefficient, R(2)) in the range 10-150mugL(-1) was adequate in both systems; however, better R(2) values were obtained with the QqQ analyzer in high and low concentration ranges (1-50 and 1-750mugL(-1), respectively). The influence of the matrix nature on the analysis of low concentrations of each analyzer was also evaluated. The QqQ and IT performance was similar in cucumber and solvent. However, QqQ provided better sensitivity in egg working in selected reaction monitoring (SRM).     

Multiresidue pesticide analysis in ginseng and spinach by nontargeted and targeted screening procedures

Five different mass spectrometers interfaced to GC or LC were evaluated for their application to targeted and nontargeted screening of pesticides in two foods, spinach and ginseng. The five MS systems were capillary GC/MS/MS, GC-high resolution time-of-flight (GC/HR-TOF)-MS, TOF-MS interfaced with a comprehensive multidimensional GC (GCxGC/TOF-MS), an MS/MS ion trap hybrid mass (qTrap) system interfaced with an ultra-performance liquid chromatograph (UPLC-qTrap), and UPLC interfaced to an orbital trap high resolution mass spectrometer (UPLC/Orbitrap HR-MS). Each MS system was tested with spinach and ginseng extracts prepared through a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure. Each matrix was fortified at 10 and 50 ng/g for spinach or 25 and 100 ng/g for ginseng with subsets of 486 pesticides, isomers, and metabolites representing most pesticide classes. HR-TOF-MS was effective in a targeted search for characteristic accurate mass ions and identified 97% of 170 pesticides in ginseng at 25 ng/g. A targeted screen of either ginseng or spinach found 94-95% of pesticides fortified for analysis at 10 ng/g with GC/MS/MS or LC/MS/MS using multiple reaction monitoring (MRM) procedures. Orbitrap-MS successfully found 89% of 177 fortified pesticides in spinach at 25 ng/g using a targeted search of accurate mass pseudomolecular ions in the positive electrospray ionization mode. A comprehensive GCxGC/TOF-MS system provided separation and identification of 342 pesticides and metabolites in a single 32 min acquisition with standards. Only 67 or 81% of the pesticides were identified in ginseng and spinach matrixes at 25 ng/g or 10 ng/g, respectively. MS/MS or qTrap-MS operated in the MRM mode produced the lowest false-negative rates, at 10 ng/g. Improvements to instrumentation, methods, and software are needed for efficient use of nontargeted screens in parallel with triple quadrupole MS.     

A reliable analytical approach based on gas chromatography coupled to triple quadrupole and time‐of‐flight mass analyzers for the determination and confirmation of polycyclic aromatic hydrocarbons in complex matrices from aquaculture activities

The potential of gas chromatography coupled to tandem mass spectrometry (GC/MS/MS) with a triple quadrupole analyzer (QqQ) has been investigated for the quantification and reliable identification of sixteen polycyclic aromatic hydrocarbons (PAHs) from the EPA priority list in animal and vegetable samples from aquaculture activities, whose fat content ranged from 5 to 100%. Matrices analyzed included fish fillet, fish feed, fish oil and linseed oil. Combining optimized saponification and solid‐phase extraction led to high efficiency in the elimination of interfering compounds, mainly fat, from the extracts. The developed procedure minimized the presence of these interfering compounds in the extracts and provided satisfactory recoveries of PAHs. The excellent sensitivity and selectivity of GC/(QqQ)MS/MS in selected reaction monitoring (SRM) allowed to reach limits of detection at pg/g levels. Two SRM transitions were acquired for each analyte to ensure reliable identification of compounds detected in samples. Confirmation of positive findings was performed by GC coupled to high‐resolution time‐of‐flight mass spectrometry (GC/TOFMS). The accurate mass information provided by GC/TOFMS in full acquisition mode together with its high mass resolution makes it a powerful analytical tool for the unequivocal confirmation of PAHs in the matrices tested. The method developed was applied to the analysis of real‐world samples of each matrix studied with the result of detecting and confirming the majority of analytes at the µg/kg level by both QqQ and TOF mass spectrometers. Copyright © 2009 John Wiley & Sons, Ltd.     

固相萃取–气相色谱–串联质谱法测定茶叶中9种农药残留量

建立固相萃取净化–气相色谱–串联质谱法同时测定茶叶中9种农药残留量的方法。茶叶样品用乙腈均质提取,提取液经固相萃取净化处理后,采用DB–5MS毛细管色谱柱分离,在多反应监测模式下测定,外标法定量。9种农药组分的质量浓度在0.01~0.50 mg/L范围内与其色谱峰面积呈良好线性,相关系数r~2大于0.998,方法测定下限(10 S/N)为0.002~0.01 mg/kg。以空白绿茶、红茶、普洱茶和乌龙茶为基体,在0.05,0.1,0.2 mg/kg 3个添加水平进行加标回收试验,加标回收率在73.6%~99.7%之间,相对标准偏差为4.2%~8.7%(n=6)。该法操作简便、快速,适用于茶叶中多种农药残留的测定。     

Simultaneous determination of 103 pesticide residues in tea samples by LC‐MS/MS

A simple and sensitive method was developed and validated for the simultaneous determination of 103 pesticide residues in tea by LC‐MS/MS. For the analysis of the pesticide with polarity, thermal lability or low volatility, this LC‐MS/MS method has an advantage over GC. In this work, residual pesticides were extracted from the tea sample with ACN and then purified using Carb‐NH₂ SPE cartridges. Using the multiple reaction monitoring mode, the pesticides were quantified and identified by the most abundant and characteristic fragment ions. The recoveries obtained for each pesticide ranged between 65 and 114% at three spiked concentration levels. The intra‐day precisions were lower than 19.6%. Good linear relationships were observed with the correlation coefficients r² >0.996 for all analytes. The established method was successfully applied to the determination of pesticide residues in real tea samples.     

Quantification,confirmation and screening capability of UHPLC coupled to triple quadrupole and hybrid quadrupole time‐of‐flight mass spectrometry in pesticide residue analysis

The potential of three mass spectrometry (MS) analyzers (triple quadrupole, QqQ; time of flight, TOF; and quadrupole time of flight, QTOF) has been investigated and compared for quantification, confirmation and screening purposes in pesticide residue analysis of fruit and vegetable samples. For this purpose, analytical methodology for multiresidue determination of 11 pesticides, taken as a model, has been developed and validated in nine food matrices for the three mass analyzers coupled to ultra high pressure liquid chromatography. In all cases, limits of quantification around 0.01 mg/kg were reached, fulfilling the most restrictive case of baby‐food analysis. Regarding absolute sensitivity, the lower limits of detection were obtained, as expected, for QqQ (100 fg), whereas slightly higher limits (300 fg) were obtained for both TOF and QTOF. Confirmative capacity of each analyzer was studied for each analyte based on the identification points (IPs) criterion, useful for a comprehensive comparison. QTOF mass analyzer showed the highest confirmatory capacity, although QqQ normally led to sufficient number of IPs, even at lower concentration levels. The potential of TOF MS was also investigated for screening purposes. To this aim, around 50 commercial fruits and vegetables samples were analyzed, searching for more than 400 pesticides. TOF MS proved to be an attractive analytical tool for rapid detection and reliable identification of a large number of pesticides thanks to the full spectrum acquisition at accurate mass with satisfactory sensitivity. This process is readily boosted when combined with specialized software packages, together with theoretical exact mass databases. Several pesticides (e.g. carbendazim in citrus and indoxacarb in grape) were detected in the samples. Further unequivocal confirmation of the identity was performed using reference standards and/or QTOF MS/MS experiments. Copyright © 2010 John Wiley & Sons, Ltd.     

High- and low-resolution mass spectrometry coupled to liquid chromatography as confirmatory methods of anabolic residues in crude meat and infant foods

Within the European Union the use of anabolic steroids for promoting growth and improving meat-to-fat ratio in food-producing animals has been banned since 1988. For the unequivocal identification of hormone residues in a complex matrix such as meat we have developed a rapid, specific and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method, in combination with a simple extraction procedure based on the matrix solid-phase dispersion (MSPD). The performances of a triple quadrupole (QqQ) and a quadrupole/time-of-flight (QqTOF) were compared: the QqQ mass spectrometer was found to be more sensitive for almost all studied analytes, but the selectivity was superior using the QqTOF system; the full-scan spectra (acquired without losing sensitivity), mass accuracy and resolution of the hybrid instrument enabled a more probatory analyte identification than that obtained selecting two multiple-reaction monitoring (MRM) transitions with a QqQ. Average recoveries ranged from 80 to 100%, and the detection capabilities (CCbetas) were less than 1.06 ppb with the QqQ instrument and less than 5.20 ppb with the QqTOF instrument for the bovine meat, which proved to be the most complex matrix.     

Screening method for pesticides in air by gas chromatography/tandem mass spectrometry

A multiresidue method for determining more than 70 pesticides in air has been validated using a single injection with gas chromatography/tandem mass spectrometry (GC/MS/MS). The method validation considered both stages of sampling and analysis. The sampling method, based on active sampling using sorption in sorbent cartidges, was validated by generating standard atmospheres. Performance parameters of the method were evaluated, with a reduction in the limits of quantification by injecting a higher volume of sample extract, and increase of selectivity by the use of MS/MS detection mode. The method was based on solid-phase extraction, which permits a degree of automation. The best adsorbents were found to be Chromosorb 106 and Tenax TA. The retention capacity of these sampling sorbents allows up to 1440 L of air to be sampled without any breakthrough for most of the compounds. Data were generated for assessing the potential exposure of bystanders. The application of the method to the analysis of the air in urban locations near agricultural areas showed that pesticides were present in most of the samples.     

Application of gas chromatography/tandem quadrupole mass spectrometry to the multi-residue analysis of pesticides in green leafy vegetables

A new, sensitive and specific method has been developed for the simultaneous determination of 129 pesticides in lettuce and other green leafy vegetables. The samples were extracted with acetonitrile and co-extractives such as fatty acids and pigments were removed using dispersive solid-phase extraction (dispersive-SPE) with primary secondary amine (PSA) and graphitized carbon black (GCB). All pesticides were analyzed in a single injection gas chromatography/tandem quadrupole mass spectrometry (GC/MS/MS) acquisition method. Two multiple reaction monitoring (MRM) transitions of precursor ions fragmenting into product ions were recorded for the targeted pesticides, thus fulfilling the EU identification points system criteria for the identification of contaminants (2002/657/EC). Calibration curves were determined using matrix-matched standards, and exhibited excellent linearity at two orders of magnitude from 0.005 to 0.5 mg/kg for almost all the pesticides studied (R(2) > or = 0.99). The analytical performance was demonstrated by the analysis of lettuce samples spiked at five concentration levels ranging from 0.005 to 0.5 mg/kg for each pesticide. The recovery and repeatability results satisfied SANCO/2007/3131 criteria (i.e. average recoveries were in the range 70-120% with RSDs < or =20%) for 114 of the 129 pesticides at the 0.005 mg/kg spiking level, and for almost all pesticides at the higher spiking levels. The methodology was applied successfully to identify and quantify pesticide residues in leafy vegetable samples such as lettuce, cabbage and leek.     

气相色谱-柱后分流-反吹技术测定含脂羊毛中有机氯和有机磷类杀虫剂残留

建立了同时测定含脂羊毛中20种有机氯和有机磷类杀虫剂残留的气相色谱-柱后分流-反吹检测方法.通过二氧化碳超临界萃取技术提取含脂羊毛样品中的杀虫剂残留并经中性氧化铝固相萃取柱净化,采用气相色谱-柱后分流技术,可以同时得到3个检测器信号(MSD、μECD和NPD),可对两类杀虫剂准确定性和定量分析.同时运用反吹技术,减少样品中高沸点杂质对色谱系统的污染.3个添加水平的回收率为85.6%～120.9%,相对标准偏差在1.2%～17.3%之间.方法干扰小、重现性好、自动化程度高,能够对含脂羊毛中有机氯和有机磷类杀虫剂残留准确地定性定量分析.     

Investigating the presence of pesticide transformation products in water by using liquid chromatography-mass spectrometry with different mass analyzers

Many pesticide transformation products (TPs) can reach environmental waters as a consequence of their normally having a higher polarity than their parent pesticides. This makes the development of analytical methodology for reliable identification and subsequent quantification at the sub-microgram per liter levels necessary, as required under current legislation. In this paper we report the photodegradation of several pesticides frequently detected in environmental waters from the Spanish Mediterranean region using the high-resolution and exact-mass capabilities of hybrid quadrupole time-of-flight mass spectrometry (QTOF MS) hyphenated to liquid chromatography (LC). Once the main photodegradation/hydrolysis products formed in aqueous media were identified, analytical methodology for their simultaneous quantification and reliable identification in real water samples was developed using on-line solid-phase extraction (SPE)-LC-tandem MS with a triple-quadrupole (QqQ) analyzer. The methodology was validated in both ground and surface water samples spiked at the limit of quantification (LOQ) and 10 x LOQ levels, i.e. 50 and 500 ng/l, obtaining satisfactory recoveries and precision for all compounds. Subsequent analysis of ground and surface water samples resulted in the detection of a number of TPs higher than parent pesticides. Additionally, several soil-interstitial water samples collected from the unsaturated zone were analyzed to explore the degradation/transformation of some pesticides in the field using experimental plots equipped with lisimeters. Several TPs were found in these samples, with most of them having also been detected in ground and surface water from the same area. This paper illustrates the extraordinary potential of LC-MS(/MS) with QTOF and QqQ analyzers for qualitative/structural and quantitative analysis, respectively, offering analytical chemists one of the most powerful tools available at present to investigate the presence of pesticide TPs in water.     

Evaluation of low-pressure gas chromatography linked to ion-trap tandem mass spectrometry for the fast trace analysis of multiclass pesticide residues

A rapid multiresidue method for the analysis of 72 pesticides has been developed using a single injection with low-pressure gas chromatography/tandem mass spectrometry (LP-GC/MS/MS). The LP-GC/MS/MS method used a short capillary column of 10 m x 0.53 mm i.d. x 0.25 microm film thickness coupled with a 0.6 m x 0.10 mm i.d. restriction at the inlet end. Optimal LP-GC conditions were determined which achieved the fastest separation in MS/MS detection mode. Also MS/MS conditions were optimized in order to increase sensitivity and selectivity. The analytical parameters of the LP-GC/MS/MS method were compared with those obtained by GC/MS/MS using a conventional capillary column (30 m x 0.25 mm i.d. x 0.25 microm film thickness). Better precision and sensitivity values were obtained with the LP-GC/MS/MS approach. The limits of detection (LOD) of the compounds ranged from 0.1 to 14.1 microg L(-1) for LP-GC/MS/MS, lower than those obtained for conventional GC/MS/MS that ranged from 0.1 to 17.5 microg L(-1). The peak widths obtained with the short column in LP-GC are similar to those obtained using conventional capillary GC columns, and the peaks can be successfully identified by MS/MS detection with the conventional scan speed of ion-trap instruments. In addition, the analysis time was significantly reduced with LP-GC/MS/MS (32 min) versus GC/MS/MS (72 min), allowing the number of samples analyzed per day in a routine laboratory to be doubled.     

Application of high-performance liquid chromatography–tandem mass spectrometry with a quadrupole/linear ion trap instrument for the analysis of pesticide residues in olive oil

This article describes the development of an enhanced liquid chromatography-mass spectrometry (LC-MS) method for the analysis of pesticides in olive oil. One hundred pesticides belonging to different classes and that are currently used in agriculture have been included in this method. The LC-MS method was developed using a hybrid quadrupole/linear ion trap (QqQ(LIT)) analyzer. Key features of this technique are the rapid scan acquisition times, high specificity and high sensitivity it enables when the multiple reaction monitoring (MRM) mode or the linear ion-trap operational mode is employed. The application of 5 ms dwell times using a linearly accelerating (LINAC) high-pressure collision cell enabled the analysis of a high number of pesticides, with enough data points acquired for optimal peak definition in MRM operation mode and for satisfactory quantitative determinations to be made. The method quantifies over a linear dynamic range of LOQs (0.03-10 microg kg(-1)) up to 500 microg kg(-1). Matrix effects were evaluated by comparing the slopes of matrix-matched and solvent-based calibration curves. Weak suppression or enhancement of signals was observed (<15% for most-80-of the pesticides). A study to assess the identification criteria based on the MRM ratio was carried out by comparing the variations observed in standard vs matrix (in terms of coefficient of variation, CV%) and within the linear range of concentrations studied. The CV was lower than 15% when the response observed in solvent was compared to that in olive oil. The limit of detection was < or =10 microg kg(-1) for five of the selected pesticides, < or =5 microg kg(-1) for 14, and < or =1 microg kg(-1) for 81 pesticides. For pesticides where additional structural information was necessary for confirmatory purposes-in particular at low concentrations, since the second transition could not be detected-survey scans for enhanced product ion (EPI) and MS3 were developed.     

Multiresidue liquid chromatography tandem mass spectrometry determination of 52 non gas chromatography-amenable pesticides and metabolites in different food commodities

A multiresidue method is developed for the screening, quantification and confirmation of 43 pesticides, belonging to different chemical families of insecticides, acaricides, fungicides, herbicides and plant growth regulators, and 9 pesticide metabolites in four fruit and vegetable matrices. Pesticide residues are extracted from the samples with MeOH:H2O (80:20, v/v) 0.1% HCOOH, and then a cleanup step using OASIS HLB SPE cartridges is applied. The SPE eluate is concentrated and the final volume adjusted to 1 mL with MeOH:H2O (10:90, v/v) before injection into LC-MS/MS. Analyses are performed using electrospray ionization (ESI) and triple quadrupole (QqQ) analyzer. The method has been validated based on the SANCO European Guidelines for representative samples that were chosen to study the influence of different matrices: high water content (tomato), high acidic content (lemon), high sugar content (raisin) and high lipidic content (avocado). Special attention has been given to minimize the degradation of some pesticides into their metabolites and the losses observed in the evaporation step. Under the optimized conditions, the recoveries were, with a few exceptions, in the range 70-110% with satisfactory precision (CV < or = 15%). The quantification of analytes was carried out using the most sensitive transition for every compound and by "matrix-matched" standards calibration. The method can be used for the accurate determination of 52 pesticides and metabolites in one single determination step at the 0.01 mg/kg level. Confirmation of residues detected in samples is performed by an independent injection into the LC-MS/MS system by acquiring additional MS/MS transitions to that used for quantification. The acquisition of the highest number of available transitions is suggested for unequivocal confirmation of the analyte.     

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.     

Analysis of pesticide residues in fruit and vegetables with ethyl acetate extraction using gas and liquid chromatography with tandem mass spectrometric detection

A multiresidue method based on extraction with ethyl acetate has been used at the Swedish National Food Administration since 1989 to monitor pesticide residues in fruit and vegetables. The method has been continuously adjusted, resulting in simple and quick analyses of pesticide residues. To recover basic pesticides, the addition of an alkali is necessary. The addition of sodium hydrogen carbonate has been shown to recover all pesticides effectively without any degradation. The liquid chromatography (LC) with tandem mass spectrometry (MS/MS) technique has made it possible to analyse more polar pesticides and to replace many single methods. The latest development in the multiresidue method, comprising the use of gas chromatography (GC) with MS/MS, has further improved the analysis by replacing the conventional GC detectors. The need for cleanup has been reduced or eliminated entirely. Consequently, the method has been simplified in a way that makes it possible to recover all included analytes in many different matrices in one single extraction and to detect them either with GC-MS/MS or with LC-MS/MS.     

Determination of polar organophosphorus pesticides in vegetables and fruits using liquid chromatography with tandem mass spectrometry: selection of extraction solvent

A method based on liquid chromatography (LC)-mass spectrometry (MS)/MS was developed for sensitive determination of a number of less gas chromatography (GC)-amenable organophosphorus pesticides (OPs; acephate, methamidophos, monocrotophos, omethoate, oxydemeton-methyl and vamidothion) in cabbage and grapes. For extraction, several solvents were evaluated with respect to the possibility of direct injection, matrix-induced suppression or enhancement of response, and extraction efficiency. Overall, ethyl acetate was the most favourable solvent for extraction, although a solvent switch was required. For some pesticide/matrix combinations, reconstitution of the residue after evaporation required special attention. Extracts were analysed on a C18 column with polar endcapping. The pesticides were ionised using atmospheric pressure chemical ionisation on a tandem mass spectrometer in multiple reaction monitoring mode. The final method is straightforward and involves extraction with ethyl acetate and a solvent switch to 0.1% acetic acid/water without further cleanup. The method was validated at the 0.01 and 0.5 mg/kg level, for both cabbage and grapes. Recoveries were between 80 and 101% with R.S.D. < 11% (n = 5). The limit of quantification was 0.01 mg/kg and limits of detection were between 0.001 and 0.004 mg/kg.     

Application of gas chromatography-triple quadrupole mass spectrometry in the quantification-confirmation of pesticides and polychlorinated biphenyls in eggs at trace levels

A new multiresidue method has been developed and validated for the simultaneous analysis of 57 compounds, including organochlorine and organophosphorus pesticide residues (OCPs and OPPs) and polychlorinated biphenyls (PCBs), in eggs at trace levels by gas chromatography coupled to triple quadrupole mass spectrometry (GC-QqQ-MS/MS). Egg samples were extracted by a simple and fast matrix solid phase dispersion (MSPD) procedure using C18 as sorbent, and ethyl acetate and acetonitrile saturated in n-hexane (85:15, v/v) as elution solvent with a simultaneous clean up with Florisil in-line. The QqQ analyzer acquired data in selected reaction monitoring (SRM) mode, permitting both quantification and confirmation in a single injection with a running time reduced up to 17.70 min. Recovery was in the range of 70-110% and 70-106% at 15 and 50 microg/kg, respectively. Precision values expressed as relative standard deviation (RSD) were lower than 20%. Linearity in the range of 10-150 microg/kg provided determination coefficients (R(2)) higher than 0.98 for all compounds. Limits of detection (LODs) for pesticides were < or =2.25 microg/kg and limits of quantification (LOQs) ranged from 0.02 to 7.78 microg/kg. LODs for PCBs were < or =0.41 microg/kg and LOQ were < or =0.71 microg/kg. The method was applied to real samples. Endosulfan sulphate and p,p'-DDE were found in two samples at concentrations below the first calibration level.     

High-throughput GC/MS and HPLC/MS/MS techniques for the multiclass, multiresidue determination of 653 pesticides and chemical pollutants in tea

An efficient and sensitive method has been established for simultaneous determination of 653 pesticides in teas by GC/MS and HPLC/MS/MS. The method involved extraction with acetonitrile followed by cleanup using Cleanert-TPT SPE and subsequent identification and quantitation of 490 pesticides by GC/MS and 448 pesticides by HPLC/MS/ MS. The LODs for pesticides determined by GC/MS were between 1.0 and 500 microg/kg, and those determined by HPLC/MS/MS were between 0.03 and 4820 microg/kg. At the low fortification levels of 0.01-100 microg/kg, the average recoveries of 94% of the pesticides determined by GC/MS were between 60 and 120%, 77% of which had an RSD below 20%. For 91% of pesticides determined by HPLC/MS/MS, the average recoveries were between 60 and 120%, 76% of which had an RSD below 20%. The paper also reports a novel SPE column, Cleanert TPT, which comprised graphitized carbon black (PestiCarb), polyamine silica, and amide polystyrene for purifying the tea samples. The results indicated good repeatiblity and reproducibility.     

蔬菜、水果中多农药残留的筛查

近年来,食品安全问题引起了人们的高度重视,农药残留污染是制约食品安全的重要因素.在食品农药残留检测方法中,农药残留检测的种类越来越多,农药残留的限量标淮越来越严,人们对食品中农药残留的检测正在不断地探索快速准确的有效方法[1].解卷积报告软件(DRS)是由安捷伦公司研发,其目的主要用于农药和可疑内分泌干扰物的筛查.该软件由安捷伦质谱工作站、自动质谱解卷积和鉴定系统(AMDIS)以及NIST检索三部分组成.AMDIS需要使用包含有保留时间的自动质谱解卷积和鉴定系统.DRS能大大提高复杂基质中痕量化合物的定性能力,并且在SCAN和SIM两种模式下均可采用DRS进行数据处理.保留时间锁定(RTL)和RTL数据库是DRS的一个组成部分,它无需使用标样,只需采用数据库中建立的GC/MS条件,即可实现对农药和一些内分泌干扰物分析鉴定.