Modified QuEChERS Extraction Research Articles

Pesticides in widely consumed vegetables in Bangladesh and its health risk

ABSTRACT This study analysed pesticide residues in cauliflower (Brassica oleracea botrytis) and bitter gourd (Momordica charantia), two widely consumed vegetables in Bangladesh, and assessed the associated human health risks. Vegetables were analysed using a modified QuEChERS extraction, followed by gas chromatography with flame thermionic and electron capture detectors. Results showed that in 36.7% of the samples pesticide residues were detected, 90.9% of which exceeding the MRLs of the European Commission, so highlighting serious food safety concerns. Multiple residues were detected in some samples, with chlorpyrifos being the most common present, followed by diazinon, dimethoate and quinalphos. Human health risks, calculated by estimated daily intake and hazard index, indicated potential non-carcinogenic risks from the present pesticides. This study may assist policymakers and authorities in developing strategies for safe vegetable production and quality monitoring to ensure food safety.

Contamination and pesticide multiresidue analysis in cotton production systems in Benin

High quantity of chemical pesticides spraying in conventional cotton production systems may affect negatively natural ecosystems components. This study examined the contamination levels of soil in Benin's cotton production system in West Africa by residues of pesticides used in cotton farming. One hundred and fourteen soil samples from six conventional and organic cotton production systems were collected and analysed. Multi-class pesticide residues were extracted from the soil samples, and analysed using respectively modified QuEChERS extraction and LC–MS/MS chromatography methods. Results showed an overall soil contamination to emamectin benzoate (18.5 μg/kg), imidacloprid (116.3 μg/kg), profenofos (12.7 μg/kg), acetamiprid (10.8 μg/kg), triasophos (12.6 μg/kg), abamectin (14.3 μg/kg), and deltamethrin (10.4 μg/kg). Especially, emamectin benzoate was detected with a high contamination in Banikoara district (18.5 μg/kg). Nevertheless, these contaminations were not deemed threatening from a toxicological perspective. Soils in conventional cotton cultivation displayed lower organic matter levels but higher concentrations of pesticides, whereas soils in organic cotton cultivation were less degraded and contaminated. Consequently, it is imperative to conduct environmental risk assessments and monitor key pesticide metabolites to establish sustainable cotton production systems in Benin.

Quantitation of pesticides in bee bread collected from honey bee colonies in an agricultural environment in Switzerland

Pesticide contamination of bee products is a widespread phenomenon. Due to its composition, bee bread is affected by both lipophilic and hydrophilic substances. As proof of concept of a monitoring campaign and to better understand the extent of contamination, we developed an analytical method based on a modified QuEChERS extraction, with subsequent separation by liquid chromatography and detection by mass spectrometry. This allowed for the quantitation of 51 agricultural- or beekeeping-associated pesticides in bee bread. The workflow was applied to 60 samples taken biweekly throughout spring to autumn 2022 from five colonies at a Swiss apiary in an agricultural area. In total, 30 pesticides were identified (> LOD), among which 26 pesticides were quantitated. The total number of pesticides detected per colony ranged from 11 to 19. The most prevalent substances (> LOQ) were two neonicotinoid insecticides, acetamiprid and thiacloprid (max. 16 μg/kg and 37 μg/kg, respectively); seven fungicides, azoxystrobin (max. 72 μg/kg), boscalid (max. 50 μg/kg), cyprodinil (max. 1965 μg/kg), difenoconazole (max. 73 μg/kg), mandipropamid (max. 33 μg/kg), pyraclostrobin (max. 8 μg/kg) and trifloxystrobin (max. 38 μg/kg); and two herbicides, prosulfocarb (max. 38 μg/kg) and terbuthylazine (max. 26 μg/kg). The study revealed strong variability in pesticide occurrence and concentrations among colonies sampled at the same site and date. The applied biweekly sampling of bee bread from March to August was shown to be reliable in capturing peak contaminations and revealing the onset of certain pesticides in bee bread. The study provides an adequate practical approach for pesticide monitoring campaigns.

Development of a simple HPLC procedure for the determination of prochloraz residues in mushrooms

Abstract A simple HPLC-UV procedure is described in our paper which is suitable for the rapid and cost-efficient determination of prochloraz in mushrooms. Prochloraz is the only fungicide in EU which use is allowed in mushroom production. The aim of our work was the development of a simple method that is suitable for the control of this pesticide in everyday analyses during mushroom production. The procedure involves a simple sample preparation method based on solid-liquid extraction (modified QuEChERS extraction method EN 15662) followed by an HPLC-UV determination (recovery: 97–99%; limit of detection LOD: 0.01 mg/kg; limit of quantification LOQ: 0.05 mg/kg).

Pesticide residues in dates using a modified QuEChERS method and GC-MS/MS

ABSTRACT The aim of this study was to develop a convenient, fast, effective and safe analytical method (QuEChERS) to determine 198 pesticide residues in multi-source date palm fruits using gas chromatography-tandem mass spectrometry (GC-MS/MS). The calibration curves for most pesticides were linear in the range of 15–150 µg/kg, with r2 values higher than 0.9934 and the relative standard deviation for all pesticides was ≤20%. The mean recovery rate of pesticides was 70–120% and limits of detection (LODs) and limits of quantification (LOQs) were in the range of 5–14 µg/kg and 14–40 µg/kg, respectively. The validated procedure was used to monitor pesticide residues in 30 fresh date samples. It could be concluded that the modified QuEChERS extraction method was efficient in analysing pesticide residues in dates palm and none of the samples contained residues above the MRLs.

Seasonal and geographical variations in insecticide and miticide residues in hop samples produced across three hop-growing regions in the Czech Republic during the years 2018–2020

The aim of this study was to determine the presence of zoocide (insecticide and miticide) residues in hops collected in three hop-growing regions located in the Czech Republic, and to assess their zoocide profiles and residue levels in terms of variability in temperature and precipitation across the 2018–2020 seasons. Furthermore, the weather factors that influenced the occurrence of hop pests are described and discussed. During our 3-year survey, a total of 120 samples of whole-cone hops samples harvested in three hop-growing regions were analysed for the presence of 29 insecticides and miticides using the modified QuEChERS extraction method, followed by liquid chromatography-tandem mass spectrometry and gas chromatography-tandem mass spectrometry. A majority, 119 of 120 samples, contained a residue of at least one of the active substances surveyed in this study, and 34 analysed samples contained multiple residues with three to four zoocides presented. Concerning the most frequently detected zoocide residues, spirotetramat and/or its metabolites were found in 94.2% of the samples at levels ranging from 0.02 to 1.08 mg/kg. Of the other zoocides surveyed, residues of fenpyroximate, hexythiazox, bifenazate and lambda-cyhalothrin were routinely found in hop cone samples. Obtained data were then used for evaluating seasonal and geographical variations in the profile of zoocide residues among the hop-growing regions in the years 2018–2020, and the compliance with legal regulations concerning the use of zoocides on hops was ascertained. The results showed that (1) the profile and levels of zoocide residues found in the samples reflected seasonal prevalence of pest infestation on hop plants; (2) the strategy to control pests (especially aphids) used in most of hop yards was consistent across the seasons; and (3) a concentration of spirotetramat residues less than 1 mg/kg was typical for hops grown in the Czech Republic.

Fipronil and Fipronil Sulfone Distribution in Chicken Feathers and Eggs after Oral and Dermal Exposure.

This work aimed to investigate the bio-distribution and the persistence of fipronil and its primary metabolite fipronil sulfone after oral and dermal administration by simulating natural farming conditions. Fipronil and fipronil sulfone detection and quantification were performed in different poultry matrices using an LC-MS/MS method coupled with modified QuEChERS extraction. After oral administration, fipronil was detected in feathers at each sampling time, in eggs for 28 days, and in the internal organs at the end of the experiment. After dermal administration, high levels of fipronil were detected in feathers, accounting for 195.85 ± 8.54 mg/kg, which were reduced by a third after 60 days. No traces of fipronil were detected in the eggs or internal organs. In addition, fipronil sulfone showed remarkable residues in all samples in trial 2. The data obtained confirmed that inappropriate use of unauthorized pesticides can lead to severe contamination of entire poultry farms. The contemporary presence of fipronil sulfone in feathers and eggs associated with the lack of fipronil in eggs suggests recent dermal contamination or past oral contamination. Moreover, simultaneous analysis of hens’ feathers and eggs could represent a new method to improve large-scale monitoring programs and animal welfare, limiting their slaughter.

Evaluation of pesticide residues and risk assessment in apple and grape from western Azerbaijan Province of Iran

West Azerbaijan, especially the city of Urmia, is the center of Iranian apple and grape production hence the importance of this, residues of 85 pesticides in these products were investigated using modified QuEChERS extraction followed by UHPLC-MS/MS technique. Residues of 17 different pesticides detected in some apple samples. In grape sample only 7 pesticides detected. The levels of the residues found in all apple and grape samples were below the maximum residue levels (MRLs) of Iran, except for iprodione. Health risk assessment associated with pesticide residues in apples and grapes were estimated by hazard quotient (HQ) and hazard index (HI), which indicated that the HI value was lower than 1 in adults and children due to apple and consumption. HI in adults and children were 0.012 and 0.054 in apple; 0.001 and 0.003 in grape samples, respectively. Although the health risk assessment showed that the consumers are not at considerable risk but due to pesticide residue, implement control plans to manage the proper application of this pesticide, or replace it with safer alternatives in apple and grape is required.

Dietary exposure assessment to macrolide antimicrobial residues through infant formulas marketed in Brazil

ABSTRACT Macrolides are critically important antimicrobials for both human and animal health and should be prioritized in risk assessments, as inappropriate use may result in antimicrobial resistance. The antimicrobials erythromycin, oleandomycin, spiramycin, tilmicosin and tylosin were analysed in infant formula samples by HPLC-MS/MS using a validated analytical method based on a modified QuEChERS extraction. The results of the occurrence study were employed to perform a dietary exposure assessment of infants to residues. In a total of 30 analysed samples, 73% contained spiramycin residues and 27%, tilmicosin residues. Calculated daily intakes ranged from 1.47 × 10−6 to 2.71 × 10−4 mg kg−1 body weight considering all analytes, representing 0.01–0.59% of acceptable daily intakes. The results of the dietary exposure assessment were all below acceptable daily intakes, indicating low potential health concerns. However, according to Brazilian regulations, infant formulas containing residues of one or more of the investigated analytes were deemed as non-compliant.

Development and optimization of a method based on QuEChERS-dSPE followed by UPLC-MS/MS for the simultaneous determination of 21 mycotoxins in nutmeg and related products

Nutmeg (Myristica fragrans), a popular spice and traditional medicine worldwide, is susceptible to fungal and mycotoxin contamination. Hence, it is important to monitor the residual levels of multiple mycotoxins in nutmeg and related products. However, analysts are continuously faced with the challenges of quantifying mycotoxin concentrations in complex matrices such as spices and traditional Chinese medicines. To develop a simple and sensitive mycotoxin analysis method encompassing the total workflow from sample preparation to quantitative analysis, a simple, robust, and sensitive method for the simultaneous identification and quantification of 21 mycotoxins in nutmeg and related products was described. The method is based on sample preparation by modified QuEChERS extraction and dispersive solid-phase extraction (dSPE) cleanup followed by ultrahigh-performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-MS/MS). Matrix-matched calibration was applied for the quantification of the investigated mycotoxins. The limits of detection of the target analytes ranged from 0.04 μg/kg to 6.0 μg/kg. Recovery rates ranged from 60.49% to 97.46% at three spiking levels, with relative standard deviations<13%. This method was applied to 45 samples of nutmegs, mace and related products. Three nutmeg samples and one nutmeg powder were contaminated with aflatoxins with residue levels of 1.76 ~ 3.39 μg/kg for AFB1 and 2.51 ~ 8.77 μg/kg for AFs (the sum of AFB1, AFB2, AFG1, AFG2 and AFM1). No mycotoxins were detected in mace. All of the contamination levels were below the regulatory maximum residue limits suggested by the European Commission and China.

Development of analytical protocol for the investigation of transformation products of pre-harvest fungicides in fruits using LC-MS/MS methods

ABSTRACT Chemical protection of plants is critical to permit all-year-long availability of plant products. These chemical agents are transformed both biotically and abiotically after spraying. Our purpose was to develop a workflow which is suitable to investigate those transformation products from plant matrices. Two field trials were set up in two years in two different plant matrices (apples, cherries) to develop a workflow to map the transformation products (TP) of three selected pre-harvest fungicides (boscalid, fluopyram, pyraclostrobin) in the fruits. Modified QuEChERS extraction method was applied for the extraction of TPs from the fruit matrices. We used liquid chromatograph-mass spectrometers to identify and confirm the transformation products of fungicides. LC-QTOF-MS method was suitable to map the key fragmentation routes of parent fungicides. Based on fragmentation pathways, MRM (multiple-reaction monitoring) transitions of fungicide-metabolites mentioned in the literature were predicted. HPLC-QTRAP-MS in target mode was successfully applied to monitor trace level of metabolites and in some cases their isomers. For confirmation of the identified metabolites, LC-QTOF-MS was used. Five earlier-documented as well as one novel transformation product (deschloro-FLP) were found in the investigated fruit samples, the latter has not been reported in plant matrices so far. Area-normalisation method was used to follow the relative concentration of the transformation products in the fruits as a function of time.

Determination of organophosphorus and synthetic pyrethroid pesticide residues and their variability in large size fruit crops

Variability of pesticide residues in food item plays a key role for the evaluation of consumer food safety. However, variability factors (VFs) derived from the large size fruit crops are still scarce. Therefore, the present work was aimed to quantify pesticide residues and to estimate VFs in large size fruit crops of mango and guava. A total of 140 mango and 130 guava samples from different marketplaces in Bangladesh were collected to estimate the variability of pesticide residues (acephate, diazinon, malathion, fenitrothion, chlorpyrifos, quinalphos, dimethoate and cypermethrin) by in-house validated methods based on modified QuEChERS extraction and gas chromatography coupled with electron capture detector (ECD) and flame thermionic detector (FTD). The method was validated at three fortification levels (0.01, 0.10 and 0.30 mg kg-1 ) and satisfactory recoveries (80-111%) with relative standard deviation (RSDr ) ≤ 13% were achieved. A wide variation of residues was found in the analyzed samples. In the case of mango, the ranges of residues were 0.011-0.314, 0.015-0.04, and 0.05-0.291 mg kg-1 , respectively, for cypermethrin, chlorpyrifos, and dimethoate, while in the case of guava, the ranges were 0.04-0.113, and 0.03-0.290 mg kg-1 , respectively, for cypermethrin and acephate. The average VF for mango was 4.06 and it was 5.70 for guava. VFs originating from the marketed samples of mango and guava are reported in this study for the first time. The estimated VFs were higher than the default value of 3, therefore, the default VFs should be reconsidered when more data are obtained regarding large size crops. © 2021 Society of Chemical Industry.

Multiresidue Method for Analysis of 240 Pesticides in Soils of Tomato Planting by Ultra Performance Liquid Chromatography Coupled to Mass Spectrometry

In this work, an analytical method for the determination of residues for the pesticides-focus was optimized: Azoxystrobin, Boscalide, Carbendazim, Chloranthranilprole, Clothianidin, Diafentiuron, Difenoconazole, Dimetomorfe, Espinetoram, Espinosade A, Espinosade D, Fenurox, Metalaxyl M, Methoxyfenozide, Tiametoxan in soil derived from tomato planting, in order to compare the levels of contamination of these compounds in soil samples. The modified QuEChERS extraction method and Ultra Performance Liquid Chromatography coupled with Sequential Mass Spectrometry were used, with ionization source by Electronebulization in ESI mode (+/-). The method consisted of extracting 15.0 g of soil with 15 ml of saturated calcium hydroxide solution pH 12.3 and 15 ml of acetonitrile, with a consequent partition in the “salting out” effect through 6.0 g of sulfate of anhydrous magnesium and 1.5 g of sodium chloride. The phases were separated by centrifugation at 3700 rpm for 7 min. The extracts were diluted with MeOH licrossolv® grade and injected in a chromatograph. The method was validated based on the parameters of linearity, LOD, LOQ, precision and accuracy. Linearity between 0.2 and 20.0 µg L-1, determination coefficients greater than 0.99. The LOQ values ​​for the method were 13 µg kg-1 for Spinosad and 7.0 µg kg-1 for the other pesticides. The method showed good precision, with RSD values ​​&lt;20%, and accuracy, with recoveries between 70 and 120% for the vast majority of the analyzed compounds. The analytical curves were prepared with reference white soil extracts, in order to minimize the Matrix Effect. The method was considered adequate for the analysis of pesticide residues in soil, since it satisfies the validation parameters of chromatographic methods (European Commission, 2018). After validation, the method was used to analyze the residues of these pesticides in soil samples from conventional, organic and sustainable tomato plantations. Making it possible to compare the levels of environmental impacts generated. In addition to validating the analytical method for the pesticides-focus of the study, it was also possible to validate 240 more compounds, between authorized and unauthorized for use in tomato planting.

Free Amino Acid Analysis in Honey Samples by Hydrophilic Interaction Liquid Chromatography with UV Detection Using Precolumn Derivatization with Dansyl Chloride

A new hydrophilic interaction chromatography (HILIC) method was developed for free amino acid analysis in honey samples after pre-column derivatization of amino acids with dansyl chloride (Dns-Cl). This method consisted of the sample pretreatment with a modified QuEChERS extraction and liquid chromatographic analysis with UV detection. The derivatized amino acids were separated on a HILIC column (NH2-HILIC 150 × 4.6 mm). The separation of 9 derivatized amino acids was successfully achieved with gradient elution. The derivatization process allowed high sensitivity for the amino acids while the rapid analysis in the HILIC mode within 17 min of elution time was obtained. Full separation and determination of the Dns-amino acids were achieved in relevant honey samples. Mean percentage recoveries of Dns-amino acids from the samples were 82.4% or higher with a good standard deviation of < 4%.

Chemometrics Assisted QuEChERS Extraction Method for the Residual Analysis of Organophosphate Insecticides: Application to Their Dissipation Kinetics in Open Field Ecosystem

The present study aimed to investigate the dissipation kinetics and residual levels of five organophosphate pesticides in a carrot- and potato-field ecosystem by sensitive and selective liquid chromatography-tandem mass spectrometry method. The optimization of the modified QuEChERS extraction method was carried out using the cost-effective chemometric tool equipped with Plackett-Burman and central composite designs. Based on the response surface methodology the optimized conditions were found to be 56.5 mg of primary secondary amine sorbent, 1.53 g of sodium chloride, and 213 mg of C18. The average recoveries of the method were obtained over the range of 81.6 to 96.0 % with a relative standard deviation < 14.7 %. The detection and quantification limit ranged from 0.7 to 1.0 μg/kg and 1.0 to 5.0 μg/kg, respectively. The data showed that the first-order model was the best fit for the dissipation of five organophosphate pesticides with a regression coefficient of more than 0.99. The half-lives for all the studied pesticides were below 6.6 and 5.1 days for carrot and potato, respectively. The harvesting intervals for pesticides on the carrot and potato fields were within 28 and 21 days, respectively. The study results contribute to establishing the scientific basis of the dosage for organophosphate pesticide use in the vegetable field.

Modified QuEChERS extraction and GC-MS analysis of selected cannabinoids from human urine

The aim of this work is to apply a modified QuEChERS method to extract cannabinoids from urine, using a mixture of salts for extraction in an appropriate ratio instead of commercially available cartridges. The analysis was performed on blank urine to which a known concentration of tetrahydocannabinol (THC), cannabinol (CBN) and cannabidiol (CBD), 11-hydroxy-Δ9-tetrahydrocannabinol (THC-OH) and 11-nor-9-carboxy-Δ9-tetrahydrocannnabinol (THC-COOH) was added. Six solvents, as well as four solvent mixtures, were tested for extraction and the solvent mixture acetonitrile : dichloromethane (1:3) was selected for which the best recovery factor was obtained. Derivatization of all samples was done with MSTFA (N-trimethylsilyl-N-methyl trifluoroacetamide) + 1% TMCS (2,2,2-Trifluoro-N-methyl-N-(trimethylsilyl)-acetamide, chlorotrimethylsilane) at room temperature. The prepared extracts were analyzed by a coupled system, gas chromatography-mass spectrometry (GC-MS) in full-scan mode. Peaks of selected cannabinoids are wellseparated indicating that there was no interference with the selected analytes. The results were calculated from a calibration curve ranging from LOQ to 1000 ng/mL for selected cannabinoids with a correlation factor over 0.998. The LOD and LOQ for THC are (3.0 ng/mL; 9.0 ng/mL), for CBN (5.0 ng/mL; 18.0 ng/mL) for CBD (5.0 ng/mL, 16.0 ng/mL), for THC-OH (2.6 ng/mL; 8.7 ng/mL) and for THC-COOH (5.0 ng/mL; 15.0 ng/mL). The recovery factor was recorded in the range of 79.40% for THC-COOH to 94.86% for CBN.

Development of “Quick-DB forensic”: A total workflow from QuEChERS-dSPE method to GC–MS/MS quantification of forensically relevant drugs and pesticides in whole blood

Trends in forensic toxicology show the advancement of rapid and sensitive analytical methods for qualitative and quantitative analysis of drugs of abuse. However, forensic toxicologists are continuously faced with the challenges of identifying and quantifying drug blood concentration while simultaneously struggling with manpower shortage. In view of developing a simple and productive toxicological analysis method encompassing total workflow from sample preparation to quantitative analysis, here we describe a simple, robust, and sensitive method for the simultaneous determination and quantification of 63 forensically relevant drugs and pesticides in human whole blood. The method is based on sample preparation by a modified QuEChERS extraction and dispersive solid-phase extraction (dSPE) clean-up followed by gas chromatography–tandem mass spectrometry (GC–MS/MS) analysis. Limits of detection of the target analytes in whole blood ranged in the few ng/mL-order levels. Intra- and inter-day validation result ranges were 0–24% for accuracy (% error) and 0.8–26% for precision (%RSD). Recovery rates ranged from 66% to 84% for barbiturates, 36% to 110% for benzodiazepines, 41% to 86% for tri/tetracyclic antidepressants, 15% to 81% for drugs of abuse, 28% to 44% for phenethylamines, and 25% to 118% for pesticides. The validated results were used to develop a user-friendly, systematic, and quantitative toxicological GC/MS/MS system and software “Quick-DB Forensic”.

Screening of multi-class antibiotics in pork meat by LC-Orbitrap-MS with modified QuEChERS extraction.

The quantification capability of high resolution mass spectrometry is of great interest to analysts. We described a method for analysis of multi-class antibiotics in pork meat by UPLC-quadrupole (Q)-Orbitrap-MS. The QuEChERS approach with a clean-up step using a sorbent of primary-secondary amine (PSA) and C18 was adopted for sample preparation, and 37 antibiotics including beta-lactams, tetracyclines, sulfonamides, fluoroquinolones and macrolides were analyzed. The Q-Orbitrap method showed high sensitivity with limits of detection (LODs) ranging from 0.8 μg kg−1 to 2.9 μg kg−1. The method was further validated by intra and inter-day tests with fortified samples. Recovery (85–105.6%) and precision values (RSDs < 15%) for all analytes were obtained. The result indicates that UPLC-Q-Orbitrap-MS coupled with QuEChERS preparation can serve as a routine method for multi-class antibiotic analysis in pork meat.

Combination of Modified QuEChERS Extraction Method and Dispersive Liquid–Liquid Microextraction as an Efficient Sample Preparation Approach for Extraction and Preconcentration of Pesticides from Fruit and Vegetable Samples

In this study, a combination of modified quick easy cheap effective rugged and safe extraction and dispersive liquid–liquid microextraction has been proposed for the extraction and preconcentration of some widely used pesticides (diazinon, chlorpyrifos, penconazole, oxadiazon, and diniconazole) from fruit and vegetable samples prior to their determination by gas chromatography–flame ionization detection. In the proposed method, firstly, an aliquot of sample is crushed and then its refuse and juice are separated by centrifuging. The juice is transferred to a conical glass test tube. Then acetonitrile as an extraction/disperser solvent is added into the tube containing the refuse. The analyte residues are extracted into acetonitrile after vortexing. The obtained acetonitrile is mixed with an extraction solvent (1,2–dibromoethane) at microliter level and rapidly injected into the juice. As a result, a cloudy state is formed, and the tiny droplets of the extractant containing the extracted analytes are sedimented at the bottom of the tube after centrifugation. Finally, an aliquot of the sedimented organic phase is removed and injected into the separation system for the quantitative analysis. In this study, several significant factors affecting the performance of the introduced method were investigated and optimized. Under the optimum experimental conditions, enrichment factors ranged from 240 to 375 for apricot nectar and 96–150 for solid samples. The relative standard deviations were ≤ 7% for intra-(n = 6) and inter-day (n = 4) precisions at a concentration of 100 μg L−1 of each analyte. Limits of detection were in the ranges of 0.27–0.48 μg L−1 in the solution and 0.68–1.2 μg kg−1 in the solid samples. Finally, several fruit and vegetable samples were analyzed by the proposed method, and penconazole was found in grape at μg kg−1 level.

Analysis of multiple pesticide residues in polyphenol-rich agricultural products by UPLC-MS/MS using a modified QuEChERS extraction and dilution method

An efficient method for the rapid extraction and clean-up of 20 pesticide residues from polyphenol-rich agricultural samples (tea, apple, broccoli, and shallot) for analysis by UPLC-MS/MS was developed. Following extraction, PVPP was used to precipitate polyphenols, supernatant was diluted to minimize matrix effects. Homogenized samples were vortexed in acetonitrile prior to cleanup with a combination of PVPP (150 mg), PSA (50 mg) and GCB (10 mg). Supernatant (1 mL) was filtered and diluted 10-fold before analysis. In 4 agricultural products that usually produce high interference, the matrix effects were overcome for all pesticides expect in green and oolong tea for acephate, omethoate, dinotefuran and nitenpyram. Mean recoveries ranged from 73% to 106%, and RSD ≦ 13%. Limits of quantification ranged from 0.01 to 0.02 mg kg−1. PVPP as one of excellent QuEChERS material combined with dilution was verified as a promising method for multiple pesticide residues analysis in complex matrices.