Method Development,Optimization and Validation of Matrix Hydration Effect on Pesticide Residues in Cocoa Beans Using Modified QuEChERS Method and Gas Chromatography Tandem Mass Spectrometry

Modified QuEChERS method combined with gas chromatography tandem mass spectrometry (GC-MS/MS) was developed and validated to determine pesticide residues in dried cocoa beans. Extraction efficiency of matrix hydration effect on 19 pesticide residues was studied and optimized using 2³ full factorial design with percentage recoveries as the response variable. The optimized hydration method was validated for 24 pesticides, and recoveries obtained were in the range of 70–120% with relative standard deviations of less than 20% for most pesticides. Limit of quantification was obtained at 10 μg/kg for all pesticides, and this value was lower than national maximum residue levels (MRLs). Finally, the developed and optimized method was applied to real cocoa bean samples and the results from incurred residues were compared between method with and without matrix hydration. These results suggest that the addition of water to the dry and high-fat cocoa bean samples is crucial in pesticide residue analysis.     

Multi-residual Pesticide Monitoring in Commercial Chinese Herbal Medicines by Gas Chromatography–Triple Quadrupole Tandem Mass Spectrometry

To investigate multi-residual pesticide monitoring data in commercial Chinese herbal medicines on major markets, an easy, rapid, and selective gas chromatography with mass spectrometry (GC/MS/MS) method was established for simultaneously determining multi-residual pesticides including organochlorine, pyrethroid, carbamate, and organophosphorus pesticides in Chinese herbal medicines. The analytical method was based on an efficient extraction procedure and further cleanup steps by solid-phase extraction columns, yielding recovery rates in the range of 70.0–120.0 % for the majority of pesticides, except for hexachlorobenze, diazinon, β-HCH, δ-HCH, and omethoate, with precision values expressed as relative standard deviation of 0.1–14.7 %. The limits of detection of the established GC/MS/MS method for all investigated pesticides ranged from 0.01 to 3.6 μg kg^?1 and limits of quantification from 0.03 to 11.88 μg kg^?1. With this validated method, multi-residual pesticides of 132 Chinese herbal medicine samples were analyzed. The monitoring results indicated that pesticide residue was found in 74 samples. In total, 51 pesticides were found with detection rate ranging from 0.76 to 18.94 %. An 82.3 % of positive pesticides were found in less than 6 % of samples. Hexachlorobenzene was found in 25 samples, quintozene in 15 samples, and acephate and simazine in 13 samples. Concentrations of pesticide residue from monitoring data obtained ranged from 0.5 to 203.5 μg kg^?1. The simple and rapid method can be used as routine analysis method in multi-residual pesticide monitoring of Chinese herbal medicines.     

Optimization of QuEChERS Procedure Coupled to GC-ECD for Organochlorine Pesticide Determination in Carrot Samples

An optimised version of the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for simultaneous determination of 14 organochlorine pesticides in carrots was developed using gas chromatography coupled with electron-capture detector (GC-ECD) and confirmation by gas chromatography tandem mass spectrometry (GC-MS/MS). A citrate-buffered version of QuEChERS was applied for the extraction of the organochlorine pesticides, and for the extract clean-up, primary secondary amine, octadecyl-bonded silica (C18), magnesium sulphate (MgSO₄) and graphitized carbon black were used as sorbents. The GC-ECD determination of the target compounds was achieved in less than 20 min. The limits of detection were below the EU maximum residue limits (MRLs) for carrots, 10–50 μg kg^?1, while the limit of quantification did exceed 10 μg kg^?1 for hexachlorobenzene (HCB). The introduction of a sonication step was shown to improve the recoveries. The overall average recoveries in carrots, at the four tested levels (60, 80, 100 and 140 μg kg^?1), ranged from 66 to 111 % with relative standard deviations in the range of 2–15 % (n?=?3) for all analytes, with the exception of HCB. The method has been applied to the analysis of 21 carrot samples from different Portuguese regions, and β-HCH was the pesticide most frequently found, with concentrations oscillating between less than the limit of quantification to 14.6 μg kg^?1. Only one sample had a pesticide residue (β-HCH) above the MRL, 14.6 μg kg^?1. This methodology combines the advantages of both QuEChERS and GC-ECD, producing a very rapid, sensitive and reliable procedure which can be applied in routine analytical laboratories.     

Occurrence of pesticide residues and transformation products in different types of dietary supplements

The purpose of this study was to evaluate the presence of pesticide residues and transformation products in dietary supplement products. Thirty-two samples were analysed to determine 177 pesticides by gas chromatography–tandem mass spectrometry (GC-MS/MS) and 333 pesticides by liquid chromatography–high-resolution mass spectrometry (LC-HRMS). Pesticides were extracted from different kinds of dietary supplements by the use of a modified QuEChERS extraction method. Six samples contained pesticide residues at concentration up to 92.7 µg kg^?1, but only butralin exceeded the maximum residue limits set for raw material. In addition to target compounds, LC-HRMS enables the simultaneous detection of non-target pesticides. In this case, transformation products of pesticides were detected in the analysed samples using HRMS analyser (Exactive-Orbitrap). These compounds were not included in the original method, and they were monitored as post-target compounds, knowing their molecular formula and exact mass. Mass accuracy was always < 2 ppm, corresponding to a maximum mass error. The positive findings endorse the idea that a deeper and continuous investigation of pesticide residues and transformation products in dietary supplement products is necessary in order to guaranty consumer’s safety.     

Screening of Over 600 Pesticides,Veterinary Drugs,Food-Packaging Contaminants,Mycotoxins, and Other Chemicals in Food by Ultra-High Performance Liquid Chromatography Quadrupole Time-of-Flight Mass Spectrometry (UHPLC-QTOFMS)

In this article, an accurate mass multiresidue screening method has been developed for the determination of over 630 multiclass food contaminants in different matrices using ultra-high performance liquid chromatography/(quadrupole)-time-of-flight mass spectrometry. The compounds included in the study were 426 pesticides, 117 veterinary drugs, 42 food-packaging contaminants, 21 mycotoxins, 10 perfluorinated compounds, 9 nitrosamines, and 5 sweeteners. The separation was carried out by liquid chromatography using a C₁₈ column (50 mm × 2.1 mm, 1.8 μm particle size). The identification of the targeted species was accomplished using accurate masses of the targeted ions (protonated or deprotonated molecule) along with retention time data and characteristic fragment ion for reliable identification, using specific software for automated data mining and exploitation. The performance of the screening method was validated in terms of linearity, matrix effect, and limits of quantification for three representative food matrices (tomato, orange, and baby food) using a generic sample treatment based on liquid partitioning with acetonitrile (QuEChERS). The overall method performance was satisfactory with limits of quantification lower than 10 μg kg ^?1 for the 44 % of studied compounds. In some cases (ca. 10–15 % of the pesticides depending on the matrix tested, maximum residue levels were not fulfilled). In orange, 15 % of the compounds displayed LOQs above the maximum residue levels (MRLs) set for the studied pesticides, which can be partially attributed to matrix effects. Moderate signal suppression was observed in the three matrices tested in most cases, being orange the matrix which produced the highest matrix effect and baby food the lowest one.     

Determination of multi-class pesticide residue in dietary supplements from grape seed extracts by ultra-high-performance liquid chromatography coupled to triple quadrupole mass spectrometry

A new method was developed and validated for the determination of multi-class pesticide residues in nutraceutical products obtained from grape seed extracts. The extraction procedure was based on QuEChERS methodology using ethyl acetate as solvent and a dispersive solid-phase extraction (dSPE) clean-up stage with C₁₈ was included to minimise matrix effects. Pesticides determination was achieved using ultra-high-performance liquid chromatography coupled to triple quadrupole mass spectrometry (UHPLC-QqQ-MS/MS); total running time was 11 min. Pesticides were quantified using matrix-matched calibration. The developed method was validated in terms of matrix effect, linearity, selectivity, limits of detection and quantification, trueness, repeatability and inter-day precision at three concentration levels (10, 50, 100 µg kg^?1). Suitable recovery values were obtained for 76% of analysed pesticides at the lowest concentration (10 µg kg^?1). For most of the compounds, relative standard deviation values were lower than 20% and 25% for intra- and inter-day precision, respectively. Finally, 106 pesticides were determined, and the method was applied to seven dietary supplements from grape seed extract, obtaining various positive results for piperonyl butoxide, cyromazine and diniconazole at concentrations ranging from 2.0 to 13.4 µg kg^?1.     

Simultaneous determination of three pesticides and their metabolites in unprocessed foods using ultraperformance liquid chromatography-tandem mass spectrometry

We have developed a rapid, multi-compound analytical method for measuring residues of the pesticides thiamethoxam and its metabolite, clothianidin; fipronil and its three metabolites, fipronil sulfone, fipronil sulfide, and fipronil desulfinyl; and pyraclostrobin in unprocessed foods (rice, corn, cucumbers, tomatoes, apples, and bananas) by ultra-performance liquid chromatography coupled to tandem mass spectrometry. Acetonitrile was used as the extraction solvent, and an octadecylsilane-dispersive SPE was used to clean up the analytes, which were then separated through a UPLC HSS T3 column connected to a tandem mass spectrometer via an electrospray ionisation source. The linearity of this method for the target analytes was excellent (R² ≥0.990) in the concentration range of 5–1000 μg kg^–1. The average recoveries of the seven compounds at concentrations of 10, 100, and 1000 μg kg^–1 from six spiked matrix samples ranged from 73.6 to 110.6%, all with RSD values of ≤19.7%. The limit of quantification was 10 μg kg^–1. The method validated the effectiveness of the method for routine monitoring the residue of these pesticides and their metabolites in foods.     

Quantitative analysis of pesticide residues in vegetables and fruits by liquid chromatography quadrupole time-of-flight mass spectrometry

The applicability of liquid chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) for the quantitative analysis of pesticide residues in vegetables and fruits was demonstrated. The LC-QTOF-MS parameters, such as cone voltage, capillary voltage, collision energy and mass extraction window, were carefully optimised for the analysis of pesticide residues. The LC-QTOF-MS method was validated for 149 pesticides in four vegetables and fruits, i.e. apple, potato, cabbage and spinach, at a spiking level of 0.01 mg kg^?1. The samples were prepared according to the Japanese official multi-residue method with a modification to the column clean-up procedure. Of the 149 pesticides, recoveries in the range of 70–120% were achieved for 147 pesticides in apple, 145 in potato, 141 in cabbage and 131 in spinach, with intra-day precisions (RSDs) of < 25% and inter-day precisions (RSDs) of < 30%, which are within the acceptable range given in the Japanese method validation guideline. Matrix effects were negligible for the majority of the target pesticides. Except for spiroxamine in spinach, no interfering peaks were observed in the blank samples. The target pesticides, except those with low sensitivity, achieved calibration curves with satisfactory linearity, with correlation coefficients (r) greater than 0.995 in the concentration range of 0.002–0.1 μg ml^?1. Furthermore, the majority of the target pesticides provided more than one fragment ion or isotope ion that could be used for confirmation. The overall results suggest that LC-QTOF-MS is a powerful tool for the quantification of pesticide residues in vegetables and fruits at the level of 0.01 mg kg^?1.     

Effect of paste processing on residue levels of imidacloprid,pyraclostrobin, azoxystrobin and fipronil in winter jujube

The changes of imidacloprid, pyraclostrobin, azoxystrobin and fipronil residues were studied to investigate the carryover of pesticide residues in winter jujube during paste processing. A multi-residue analytical method for winter jujube was developed based on the QuEChERS approach. The recoveries for the pesticides were between 87.5% and 116.2%. LODs ranged from 0.002 to 0.1 mg kg^–1. The processing factor (Pf) is defined as the ratio of pesticide residue concentration in the paste to that in winter jujube. Pf was higher than 1 for the removal of extra water, and other steps were generally less than 1, indicating that the whole process resulted in lower pesticide residue levels in paste. Peeling would be the critical step for pesticide removal. Processing factors varied among different pesticides studied. The results are useful to address optimisation of the processing techniques in a manner that leads to considerable pesticide residue reduction.     

Determination of Over 350 Multiclass Pesticides in Jams by Ultra-High Performance Liquid Chromatography Time-of-Flight Mass Spectrometry (UHPLC-TOFMS)

In this study, a screening method was developed using ultra-high performance liquid chromatography time-of-flight mass spectrometry (UHPLC-TOFMS) for multiclass pesticide analysis in jam samples. The method was based on an experimental database with retention time/accurate mass data for the 353 selected analytes. Compound identification was based on retention time and the accurate mass measurements of the protonated molecules. The limits of detection were below 10 μg kg^?1 for 90 % of the studied compounds. The proposed method was successfully applied to evaluate the presence and concentration levels of over 350 multiclass pesticides in a total of 54 jam market samples collected in Spain from different companies. Results found were in compliance with the current regulations with the exception of a sample, which contained monocrotophos. Forty-one percent of the samples were found free of pesticides; 26 % of the samples contained only one pesticide while 33 % contained at least two or more pesticides.     

Optimization of the QuEChERS Method for Determination of Pesticide Residues in Chicken Liver Samples by Gas Chromatography-Mass Spectrometry

The goal of this research was to evaluate the application of Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) method for the determination of organochlorine, organophosphate, and carbamate pesticides in fatty animal matrices such as liver of chicken obtained from National Research Institute of Animal Production in Balice (Poland). Pesticides extraction effectiveness was evaluated at two different spiking levels (0.010 and 0.020 mg kg^?1) and efficiency of the dispersive solid-phase extraction (d-SPE) clean-up step was evaluated by comparison adding different d-SPE sorbent combinations (PSA?+?GCB, PSA?+?C₁₈, PSA?+?SAX, and PSA?+?NH₂). The analysis of pesticide residues was performed by gas chromatography ion trap mass spectrometry (GC/IT-MS). The linear relation was observed from 0 to 400 ng mL^?1 and the determination coefficient R ²?>?0.997 in all instances for all target analytes. Better recoveries were obtained in samples at 0.020 mg kg^?1 spiking level. The recoveries were in the range 70–120 %, with relative standard deviation (RSD) values lower than 15 % at 0.020 mg kg^?1 spiking level for most pesticides. Similar recovery ratios were obtained with the four different combinations of sorbents tested in the clean-up step, with better precision when the (PSA?+?SAX) combination was tested. Limits of detection (LODs) ranged from 0.001 to 0.005 mg kg^?1 and limits of quantification (LOQs) ranged from 0.003 to 0.015 mg kg^?1. The proposed method was successfully applied analyzing pesticide residues in real chicken liver samples; detectable pesticide residues were observed, but in all of the cases, the contamination level was lower than the default maximum residue levels (MRLs) set by European Union (EU), Regulation (EC) N 396/2005.     

Rapid multiresidue determination of pesticides in livestock muscle and liver tissue via modified QuEChERS sample preparation and LC-MS/MS

ABSTRACT

Many multiresidue methods for the determination of pesticides in vegetables and fruits have been reported to date. However, few such methods have been employed to investigate pesticide residues in animal tissue. In this study, an LC-MS/MS multiresidue method coupled with modified QuEChERS extraction was developed and validated for the investigation of eight pesticide residues: prallethrin (PR), resmethrin (RMT), imidacloprid (IMC), diflubenzuron (DFB), cyromazine (CYR), etofenprox (EFP), dinotefuran (DNT) and phthalthrin (PTLT). This method involves initial extraction in a water/acetone system, the addition of salts and a subsequent extraction/partitioning step and, finally, a clean-up step utilising dispersive solid-phase extraction (SPE). The mean recoveries of seven of the pesticides (the exception being CYR) ranged between 74.7% and 113.5%, and the CVs of the livestock tissue – bovine, swine, and chicken muscle and liver tissue spiked at 10 ng g^–1 (50 ng g^–1 for RMT and DNT) and 100 ng g^–1 – were < 13.8%. The recoveries of CYR in all muscle and liver spiked samples ranged from 56.9% to 78.3%, while those of RMT in swine liver were > 120%. Therefore, this method was considered as being unsuitable for the investigation of these samples. The limits of quantitation (LOQs) of seven of the investigated pesticides (the exception being swine liver) in the tissue samples ranged from 0.9 to 15.2 ng g^–1. We therefore concluded that this LC-MS/MS multiresidue method is a valid and suitable for the investigation of seven pesticides in animal tissue, but it is unsuitable for the analysis of CYR in all animal tissues and RMT in swine liver tissue.     

西安市猕猴桃主产区农药残留风险评估

目的通过对西安市猕猴桃进行系统的农药残留情况及膳食暴露风险分析,明确猕猴桃农药残留风险状况。方法对2018年西安市周至县14个猕猴桃主产乡镇共200批次样品进行农药残留定量检测分析,用每日允许摄入量和急性参考剂量进行慢性膳食摄入风险评估和急性膳食摄入风险评估,利用猕猴桃大份餐、每日允许摄入量和人均参考体重计算最大残留限量估计值。并参照兽药残留风险排序矩阵方法(英国兽药残留委员会)对农药和样品进行风险排序。结果 200个猕猴桃样品中有137个样品检出了农药残留,未有超标农药和禁用农药检出;在检出的14种农药中,慢性膳食摄入风险和急性膳食摄入风险均值远远小于100%;将14种检出农药按照风险得分分为Ⅲ类,第Ⅰ类为高等风险农药,共1种;第Ⅱ类为中等风险农药,共0种;第Ⅲ类为低等风险农药,共有13种;以风险指数排序,低风险样品占35.5%,极低风险样品占64.5%,检出农药残留种类为3个以上的样品有占比5.5%,检出农药残留种类为1～2个的样品占比61.5%,未检出农药残留有66个样品,占比33%。结论西安市周至县猕猴桃农药残留处于低风险状态,但仍然要加强日常监管工作。     

Evaluation of the QuEChERS Method with GC-MS Detection for the Determination of Organochlorine Pesticides in Food of Animal Origin

This paper reports the evaluation of the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for the determination of organochlorine pesticide residues in food of animal origin with gas chromatography–mass spectrometry detection. There is a very little information about sample preparation method for the determination of pesticide residues in food of animal origin in the literature. Moreover, any example of application of the QuEChERS method for the determination of pesticide residues in food of animal origin has not been reported as yet. The results showed that the best recovery ratios from 75 to 112 % were obtained for the method with primary secondary amine, C₁₈ sorbents and evaporation to dryness and dissolving the residues in hexane with relative standard deviation lower than 10 % for most compounds. The limit of quantification ranged from 0.0015 to 0.0071 mg kg^?1. This method was also used for the determination of pesticide residues in 15 samples of pork ham. In 12 samples, low concentrations of DDT or its metabolites and isomers of hexachlorocyclohexane were detected. Heptachlor epoxide and α-chlordane were determined in one sample and HCB in two samples. There were no exceedances of maximum residue levels (MRLs) for the determined pesticides in any of the analysed samples.     

食用植物油中农药残留检测技术的研究进展

我国农产品中农药残留的中毒事件和进出口贸易中农药残留超标事件时有发生,已成为影响农业可持续发展的重要问题,因此农药残留检测技术也在迅速发展。文章综述了现阶段对植物油中农药残留检测技术的研究进展。主要从前处理和检测方法 2方面进行分析,根据前处理方法和检测方法的不同,分别介绍了各类前处理方法如液液萃取法(liquid-liquid extraction,LLE)、固相萃取法(solid phase extraction,SPE)、基质固相分散萃取法(matrix solid phase dispersion,MSPD)、分散固相萃取(disperse solid phase extraction,d SPE)法、凝胶渗透色谱法(gel permeation chromatography,GPC)等方法的原理和过程,以及各类检测方法如气相色谱法、气相色谱-质谱联用法(gas chromatography-mass spectrometry,GC-MS)、液相色谱法和液相色谱-串联质谱联用法(liquid chromatography-tandem mass spectrometry,LC-MS/MS)等的特点和应用范围。文章总结各类方法的优缺点,并提出了食用植物油中农药残留分析方法的发展趋势。     

Multi-residue analysis of pesticides in traditional Chinese medicines using gas chromatography-negative chemical ionisation tandem mass spectrometry

In this study, a residue analysis method for the simultaneous determination of 107 pesticides in traditional Chinese medicines (TCMs), Angelica sinensis, A. dahurica, Leonurus heterophyllus Sweet, Pogostemon cablin and Lonicera japonica Thunb., was developed using gas chromatography coupled with tandem mass spectrometry in negative chemical ionisation mode (GC-NCI-MS/MS). NCI has advantages of high sensitivity and selectivity to chemicals with electron-withdrawing groups, and yields low background interference. For sample preparation, QuEChERS (quick, easy, cheap, effective, rugged and safe) was applied. Due to the unique characteristics of TCMs, the clean-up step was optimised by adjusting amounts of primary secondary amine, C18, graphitised carbon black and silica sorbents. Validation was mainly performed by determining analyte recoveries at four different spiking concentrations of 10, 50, 100 and 200 ng g^?1, with seven replicates at each concentration. Method trueness, precision, linearity of calibration curves, lowest calibrated levels (LCLs) and matrix effects were determined to demonstrate method and instrument performance. Among the 107 pesticides tested, approximately 80% gave recoveries from 80% to 110% and < 10% relative standard deviation (RSD). The LCLs for nearly all pesticides were 5 ng g^?1, and as low as 0.1 ng g^?1 for dichlofenthion, endosulfan sulphate, flumetralin, isofenphos-methyl, methyl-pentachlorophenyl sulphide and trifluralin. The results indicate that GC-NCI-MS/MS is an excellent technique for quantitative and qualitative analysis of targeted GC-amenable pesticides at ultra-trace levels, especially in complex matrices such as TCMs.     

Multiresidue method for detection of pesticides in beef meat using liquid chromatography coupled to mass spectrometry detection (LC-MS) after QuEChERS extraction

Beef meat is an important food that can be contaminated by pesticides. This study aimed to optimize a multiresidue method for identification and quantification of pesticides in beef meat by liquid chromatography coupled to mass spectrometry detection (LC-MS). The extraction and clean-up procedures were adapted from the QuECHERS method. From the 188 analytes tested, the method was validated as qualitative method for 19 compounds and as quantitative method for 152 compounds. The results were satisfactory, yielding coefficients of variation of less than 20% and recoveries ranging from 70% to 120% and expanded uncertainty of less than 50%. The quantification limit was typically 10 µg kg^?1 (but 25 µg kg^?1 for 12 of the compounds) and the detection limit was 5.0 µg kg^?1. Thirty-two real samples of commercialized beef meat were analyzed without any residual pesticide being found. Thus, the results showed that the multiresidue method for detecting 171 pesticides, using adapted QuECHERS for extraction and LC-MS for detection, is suitable for analyzing beef meat.     

Rapid Determination of Organonitrogen, Organophosphorus and Carbamate Pesticides in Tea by Ultrahigh-Performance Liquid Chromatography–Tandem Mass Spectrometry (UPLC-MS/MS)

A rapid and effective multiresidue method has been developed for the determination of 18 pesticide residues (selected from organonitrogen, organophosphorus, and carbamate pesticides) in tea by ultrahigh-performance liquid chromatography–tandem mass spectrometry. Tea samples were extracted with acetonitrile and purified by a novel multilayer solid-phase extraction cartridge—Cleanet TPT. Evaluation of the influence of the mobile phase on the ionization efficiency, resolution, and sensitivity was carried out by comparing the acetonitrile–water and methanol–water with different modifiers. The recoveries of all the pesticides varied from 70 to 110 % with a relative standard deviation of less than 15 %, and the determination coefficient for each pesticide was R ²?>?0.99. Matrix-matched standard calibration curve was used to reduce errors associated with matrix-induced enhancement or suppression effects. The limit of detection for all targeted pesticides ranged from 0.03 to 1.5 μg/kg. Applicability of this analytical approach was confirmed by successful determination of tea samples from different regions of China.     

Multiresidue Analysis of 113 Pesticides in Different Maturity Levels of Mangoes Using an Optimized QuEChERS Method with GC-MS/MS and UHPLC-MS/MS

In this study, a simple and high-throughput multiresidue pesticide analysis method based on the quick, easy, cheap, effective, rugged, safe (QuEChERS) extraction combined with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) and ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) is presented for the determination of 113 pesticides in green and ripe mangoes. Different buffer systems and purification sorbents were optimized to get better recovery. Extracts from mangoes after acid acetonitrile and ammonium acetate extraction were directly injected to UHPLC-MS/MS analysis, whereas other GC-amenable compounds were treated with cleanup approaches with a mixture of sorbents [400 mg primary-secondary amine (PSA) and 400 mg graphitized carbon black (GCB)] for GC-MS/MS analysis. Recoveries for the majority of pesticides at spike levels of 10, 50, and 100 μg/kg were ranged between 70 and 120% with RSD values below 20%. Limits of detection (LODs) were below 4 μg/kg, whereas limits of quantification (LOQs) were below 10 μg/kg. Response linearity was good in the range between 5 and 500 μg/kg. The matrix effect for 56 pesticides by GC-MS/MS analysis exhibited a non-significant matrix effect (≤?25%) in green and ripe mangoes. For 57 pesticides used for UHPLC-MS/MS analysis, the optimized method in green mango provided no significant matrix effect (≤?25%) for 63% of the compounds, whereas only for 16 and 21% compounds, the matrix effect was medium (25–40%) and strong (>?40%); the optimized method in ripe mango provided no significant matrix effect (≤?25%) for 61% of the compounds, whereas only for 26 and 12% compounds, the matrix effect was medium (25–40%) and strong (>?40%). Following the application of a “top-down” approach, the expanded measurement uncertainty was both 21% on average (coverage factor k =?2, confidence level 95%) in green and ripe mangoes. The application of GC-MS/MS and UHPLC-MS/MS coupled with the modified QuEChERS extraction procedures was proved to adequately quantitate these pesticides in different maturity levels of mangoes.     

Determining pesticide residues in wheat flour by ultrahigh-performance liquid chromatography/quadrupole time-of-flight mass spectrometry with QuEChERS extraction

ABSTRACT

Pesticides are used to increase crop yields and preserve quality by protecting crops against pests; however, their overuse can adversely affect human health and the environment. Herein, we report the development of a multi-pesticide screening method using optimized QuEChERS coupled with liquid chromatography/quadrupole time-of-flight (QTOF) mass spectrometry for the analysis of 13 pesticides in wheat flour. Mass accuracies with errors of less than 2.4 ppm were obtained for all analysed pesticides, and the method provided satisfactory recovery and linearity. Repeatabilities of 0.3–12.7% and reproducibilities of 2.5–15.2% were observed in full-scan TOF mode. The performance of the developed full-scan TOF method was compared to that obtained in high-resolution multiple reaction monitoring (MRM-HR) mode. The limits of quantification for the full-scan TOF and MRM-HR modes ranged from 2 to 10, and 3 to 9 μg kg^?1, respectively. The two quantification methods exhibited high sensitivities (limit of detections: 1–3 μg kg^?1 in full-scan TOF, and 1–3 μg kg^?1 for MRM-HR mode). No pesticide residues were detected when the developed method was applied to 22 real wheat flour samples.