Multiresidue analysis of 16 pesticides in jujube using gas chromatography and mass spectrometry with multiwalled carbon nanotubes as a sorbent

Although jujube is a minor crop and very few pesticides are registered on it, the application of pesticides during the growth stage of jujube is inevitable to control the pests or diseases. This situation has led to pesticide misuse. A modified quick, easy, cheap, effective, rugged, and safe method using a novel sorbent, multiwalled carbon nanotubes, as a dispersive solid‐phase extraction sorbent combined with gas chromatography with mass spectrometry, was developed for the determination of 16 pesticides in jujube. Under the optimized conditions, recoveries of 76.7–112.4% were obtained for the target analytes at three spiked concentration levels. The relative standard deviations ranged from 1.2 to 12.3%. Limits of detection and limits of quantification for 16 pesticides ranged from 1 to 10 and 3 to 30 μg/kg, respectively. The residues of chlorpyrifos, hexaconazole, tebuconazole, and cyhalothrin were detected from samples obtained from the market.     

Rapid analysis of pesticide residues in drinking water samples by dispersive solid‐phase extraction based on multiwalled carbon nanotubes and pulse glow discharge ion source ion mobility spectrometry

An analytical method based on dispersive solid‐phase extraction with a multiwalled carbon nanotubes sorbent coupled with positive pulse glow discharge ion mobility spectrometry was developed for analysis of 30 pesticide residues in drinking water samples. Reduced ion mobilities and the mass–mobility correlation of 30 pesticides were measured. The pesticides were divided into five groups to verify the separation capability of pulse glow discharge in mobility spectrometry. The extraction conditions such as desorption solvent, ionic strength, conditions of adsorption and desorption, the amounts of multiwalled carbon nanotubes, and solution pH were optimized. The enrichment factors of pesticides were 5.4‐ to 48.7‐fold (theoretical enrichment factor was 50‐fold). The detection limits of pesticides were 0.01～0.77 μg/kg. The linear range was 0.005–0.2 mg/L for pesticide standard solutions, with determination coefficients from 0.9616 to 0.9999. The method was applied for the analysis of practical and spiked drinking water samples. All results were confirmed by high‐performance liquid chromatography with tandem mass spectrometry. The proposed method was proven to be a commendably rapid screening qualitative and semiquantitative technique for the analysis of pesticide residues in drinking water samples on site.     

Analytical method for 44 pesticide residues in spinach using multi‐plug‐filtration cleanup based on multiwalled carbon nanotubes with liquid chromatography and tandem mass spectrometry detection

Spinach is one of the most commonly planted vegetables worldwide. A high chlorophyll content makes spinach a complicated matrix in pesticide residue analysis. In this study, a rapid clean‐up method was developed for the analysis of pesticide multi‐residues in spinach followed by liquid chromatography with tandem mass spectrometry. A modified QuEChERS method with multiwalled carbon nanotubes and carbon material was adopted in the multi‐Plug Filtration Cleanup procedure. This method was validated for 44 representative pesticides spiked at two concentration levels of 10 and 100 μg/kg. The pesticides of different physicochemical properties were registered on spinach in China. The recoveries were between 76 and 114% for major pesticides with relative standard deviations of less than 15%, except for quizalofop‐P‐ethyl, pyrimethanil, and carbendazim. Matrix‐matched calibration curves were performed with the coefficients of determination higher than 0.995 for the studied pesticides for concentration levels of 10–500 μg/kg. The limits of quantitation ranged from 2 to 10 μg/kg. The developed method was successfully applied to determine pesticide residues in Chinese market spinach samples.     

Determination of multi‐pesticide residue in tobacco using multi‐walled carbon nanotubes as a reversed‐dispersive solid‐phase extraction sorbent

A multi‐pesticide residue determination method based on a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method using multiwalled carbon nanotubes as reversed‐dispersive solid‐phase extraction material was validated in 37 representative pesticides in tobacco. Determination was performed using liquid chromatography with tandem mass spectrometry in multiple reaction monitoring mode. Three major types of tobacco leaf samples, namely, flue‐cured, burley, and oriental tobacco were studied and compared. Three factors (extraction time, external diameter, and amount of extraction material used) that could affect the performance of multi‐walled carbon nanotubes were investigated. Optimization of sample preparation and determination allowed recoveries between 70.8 and 114.8% for all 37 pesticides with < 20.0% relative standard deviations at three spiking levels of 20, 50, and 200 μg/kg. The limits of quantification and limits of detection for the 37 pesticides ranged within 0.46–28.57 and 0.14–8.57 μg/kg at a signal‐to‐noise ratio of 10 and 3, respectively.     

Multiresidue analysis and probabilistic dietary risk assessment of 241 pesticides in wheatgrass (Triticum sp.) using LC–MS/MS in combination with QuEChERS extraction

Wheatgrass is consumed as an important nutritious herbal food supplement across the globe; however, limited studies have been reported analyzing multiclass pesticides in this complex, nutrient-rich natural product. An analytical method was developed for the estimation of 241 pesticides in random wheatgrass samples collected from Delhi Northern Capital Region (Delhi-NCR). Extraction was performed by QuEChERS, cleaning was performed by dispersive solid-phase extraction and the extracts were analyzed using triple quadrupole liquid chromatography mass spectrometry. The limit of quantification was 0.5 μg/kg, which is well below the European Union Maximum Residue Level. The coefficient of determination was >0.991 across a calibration range of 0.5–100 μg/kg. The relative standard deviation values for 231 pesticides based on 10 replicates of samples spiked at 10 μg/kg were <5%. Among random samples, 54% confirmed the presence of at least one pesticide. The results indicated the presence of eight different pesticides among 38% of the total population with metribuzin at 299.7 μg/kg and carfentrazone-ethyl at 19.47 μg/kg exceeding the permissible limits among 6% of the total estimated population. The chronic and acute risk quotients as calculated were <1, indicating nonsignificant dietary risk to consumers. However, the presence of pesticides above the permissible limit is likely to result in adverse health effects to the consumers of herbal supplements from an urban population and incorporating measures would be useful to ensure the quality and safety of wheatgrass consumption.     

Multiresidue determination of 29 pesticide residues in pepper through a modified QuEChERS method and gas chromatography–mass spectrometry

This study describes the development and use of a modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method coupled with gas chromatography with mass spectrometry to determine 29 pesticide residues in green, red and dehydrated red peppers. Pesticides were extracted with acetonitrile (1% acetic acid), partitioned with sodium chloride and purified with primary secondary amino and octadecyl silane in acetone. The QuEChERS extraction conditions were optimized, and the matrix effects that might influence recoveries were evaluated and minimized using matrix‐matched calibration curves. Under the optimized conditions, the calibration curves for 29 pesticides showed good linearity in the concentration range of 0.1–10 μg/mL with determination coefficient R² > 0.998. The limits of quantification of the 29 pesticides were 0.006–0.06 mg/kg for green pepper, 0.005–0.039 mg/kg for red pepper and 0.014–0.25 mg/kg for dehydrated red pepper. These values are below the suggested regulatory maximum residue limits. The mean recoveries ranged between 70.1 and 110%, and the relative standard deviations were <13%. The developed method was successfully applied to commercial samples. Some samples were found to contain the 29 pesticides with levels below the legal limits. Copyright © 2016 John Wiley & Sons, Ltd.     

Rapid multiplug filtration cleanup method for the determination of 124 pesticide residues in rice,wheat, and corn

A simple and rapid multiplug filtration cleanup method based on multiwalled carbon nanotubes was developed to determine 124 pesticide residues in rice, wheat, and corn, which could be done in a few seconds without conditioning and elution steps. Various combinations of sorbents were optimized for each matrix with a dispersive solid‐phase extraction procedure to get a satisfactory recovery and clean‐up performance. Good linearity was obtained for all pesticides with calibration curve coefficients larger than 0.9958. Most recoveries for the majority pesticides were between 70 and 120% (n = 5) with relative standard deviations below 20%. The limit of detection was 0.1–1.3 μg/kg, and the limit of quantification was 0.2–4.3 μg/kg for the pesticides in all matrices. The work suggests that the multiplug filtration cleanup method is better than the dispersive solid‐phase extraction method and it could be applied to routinely monitor pesticide residues in market samples.     

Determination of bisphenol A and bisphenol B in canned seafood combining QuEChERS extraction with dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A new simple and reliable method combining an acetonitrile partitioning extractive procedure followed by dispersive solid-phase cleanup (QuEChERS) with dispersive liquid–liquid microextraction (DLLME) and further gas chromatography mass spectrometry analysis was developed for the simultaneous determination of bisphenol A (BPA) and bisphenol B (BPB) in canned seafood samples. Besides the great enrichment factor provided, the final DLLME extractive step was designed in order to allow the simultaneous acetylation of the compounds required for their gas chromatographic analysis. Tetrachloroethylene was used as extractive solvent, while the acetonitrile extract obtained from QuEChERS was used as dispersive solvent, and anhydride acetic as derivatizing reagent. The main factors influencing QuEChERS and DLLME efficiency including nature of QuEChERS dispersive-SPE sorbents, amount of DLLME extractive and dispersive solvents and nature and amount of derivatizing reagent were evaluated. DLLME procedure provides an effective enrichment of the extract, allowing the required sensitivity even using a single quadropole MS as detector. The optimized method showed to be accurate (>68?% recovery), reproducible (<21?% relative standard deviation) and sensitive for the target analytes (method detection limits of 0.2?μg/kg for BPA and 0.4?μg/kg for BPB). The screening of several canned seafood samples commercialized in Portugal (total?=?47) revealed the presence of BPA in more than 83?% of the samples with levels ranging from 1.0 to 99.9?μg/kg, while BPB was found in only one sample at a level of 21.8?μg/kg.     

Multiresidue determination of pyrethroid pesticide residues in pepper through a modified QuEChERS method and gas chromatography with electron capture detection

This study developed and used a modified quick, easy, cheap, efficient, rugged and safe (QuEChERS) method coupled with gas chromatography with electron capture detection to determine eight pyrethroid pesticide residues in green, red and dehydrated red peppers. Pyrethroids were extracted with acetonitrile, partitioned with sodium chloride and purified with primary secondary amino and graphitized carbon black in hexane. The QuEChERS extraction conditions were optimized, and the matrix effects that might influence recoveries were evaluated and minimized using matrix‐matched calibration curves. Under the optimized conditions, the calibration curves for pyrethroid pesticides showed good linearities in the concentration range of 0.05–20 µg/mL with determination coefficients (R²) >0.997. The limits of quantification of eight pyrethroids were 0.004–0.04 mg/kg for green and red pepper and 0.04–0.5 mg/kg for dehydrated red pepper. These values are below the suggested regulatory maximum residue limits. The mean recoveries ranged between 79.0 and 104%, and the relative standard deviations were <11%. The developed method was successfully applied to commercial samples. Some samples were found to contain pyrethroid pesticides with levels below the legal limits. Copyright © 2015 John Wiley & Sons, Ltd.     

Rapid and sensitive detection of the phenoxy acid herbicides in environmental water samples by magnetic solid‐phase extraction combined with liquid chromatography–tandem mass spectrometry

Phenoxy acid herbicides are widely used herbicides that play an important role in improving the yield and quality of crops. However, some research has shown that this kind of herbicide is poisonous to human and animals. In this study, a rapid and sensitive method was developed for the detection of seven phenoxy acid herbicides in water samples based on magnetic solid‐phase extraction followed by liquid chromatography and tandem mass spectrometry. Magnetic amino‐functionalized multiwalled carbon nanotubes were prepared by mixing bare magnetic Fe₃O₄ nanoparticles with commercial amino‐functionalized multiwalled carbon nanotubes in water. Then the amino‐functionalized multiwalled carbon nanotubes were used to enrich phenoxy acid herbicides from water samples based on hydrophobic and ionic interactions. The effects of experimental variables on the extraction efficiency have been studied in detail. Under the optimized conditions, the method validation was performed. Good linearities for seven phenoxy acid herbicides were obtained with squared regression coefficients ranging from 0.9971 to 0.9989. The limits of detection ranged from 0.01 to 0.02 μg/L. The method recoveries of seven phenoxy acid herbicides spiked at three concentration levels in a blank sample were from 92.3 to 103.2%, with inter‐ and intraday relative standard deviations less than 12.6%.     

Simultaneous analysis of indaziflam and its metabolites in pitaya using dispersive solid phase extraction coupled with liquid chromatography coupled with tandem mass spectrometry

A simple and efficient multiresidue method using dispersive solid phase extraction and liquid chromatography coupled with tandem mass spectrometry was developed for the targeted analysis of indaziflam and its five metabolites (indaziflam‐diaminotriazine, indaziflam‐carboxylic acid, indaziflam‐triazine indanone, indaziflam‐hydroxyethyl, and indaziflam‐olefin) in pitaya samples (including roots, plants, flowers, peels, pulp, and whole fruit). The analytes were extracted with acetonitrile, and the extracts were purified using multiwalled carbon nanotubes. The method was validated using pitaya samples spiked at 0.5, 5, and 50 µg/kg, and the average recoveries varied from 61.1 to 103.7% with relative standard deviations lower than 12.7% (n = 5). This method exhibited sufficient linearity within the concentration range of 0.1–100 µg/L. The limits of detection and quantification were in the ranges of 0.001–0.1 and 0.003–0.3 µg/kg, respectively. The method was successfully applied to analyze pitaya samples in Nanning, and no indaziflam or its metabolites were detected in the samples analyzed.     

气相色谱-三重四极杆串联质谱结合QuEChERS测定三七中有机磷农药残留

建立了改良的QuEChERS样品前处理法,结合气相色谱-三重四极杆串联质谱(GC-MS/MS)同时测定三七中18种有机磷农药残留的方法。样品经1%乙酸-乙腈提取,改良QuEChERS技术净化,利用GC-MS/MS采取多反应离子监测模式测定,基质匹配校准曲线外标法定量。18种有机磷农药残留在2.5~120.0μg/kg范围内线性良好,相关系数(R2)大于0.99;检出限为0.4~1.5μg/kg,定量限为0.8~2.5μg/kg。在3个加标水平(2.5,8.0,60.0μg/kg)下平均回收率为70.5%~118.9%,相对标准偏差为1.0%~9.8%。     

Determination of 11 priority pollutant phenols in wastewater using dispersive liquid—liquid microextraction followed by high-performance liquid chromatography—diode-array detection

Dispersive liquid—liquid microextraction coupled with high-performance liquid chromatography—diode-array detection was applied for the extraction and determination of 11 priority pollutant phenols in wastewater samples. The analytes were extracted from a 5-mL sample solution using a mixture of carbon disulfide as the extraction solvent and acetone as the dispersive solvent. After extraction, solvent exchange was carried out by evaporating the solvent and then reconstituting the residue in a mixture of methanol–water (30:70). The influences of different experimental dispersive liquid—liquid microextraction parameters such as extraction solvent type, dispersive solvent type, extraction and dispersive solvent volume, salt addition, and pH were studied. Under optimal conditions, namely pH 2, 165-μL extraction solvent volume, 2.50-mL dispersive solvent volume, and no salt addition, enrichment factors and limits of detection ranged over 30–373 and 0.01–1.3 μg/L, respectively. The relative standard deviation for spiked wastewater samples at 10 μg/L of each phenol ranged between 4.3 and 19.3% (n = 5). The relative recovery for wastewater samples at a spiked level of 10 μg/L varied from 65.5 to 108.3%.     

基于QuEChERS提取方法优化的液相色谱-串联质谱法测定蔬菜中51种氨基甲酸酯类农药残留

采用气相色谱-质谱（GC-MS）全扫描结合NIST谱库检索方法分析6种蔬菜（番茄、青刀豆、大葱、青花菜、姜、胡萝卜）提取液中的基质干扰物,以蒸发残渣重量法探讨乙二胺N-丙基硅烷（PSA）、十八烷基硅烷（C18）及两者组合对6种蔬菜提取液基质干扰物的净化效果及吸附机理,考察了原创QuEChERS方法及AOAC 2007.01方法对蔬菜中51种氨基甲酸酯类农药提取的适用性,并建立了液相色谱-串联质谱法测定蔬菜中51种氨基甲酸酯类农药残留的方法。结果表明,C18与PSA组合进行分散固相萃取的净化效果最好;AOAC 2007.01方法适用于二氧威以外的50种农药残留的提取,而原创QuEChERS方法对二氧威残留的提取可获得满意结果。经电喷雾正离子电离及多反应监测模式来测定目标化合物,采用基质匹配标准溶液曲线法进行定量。结果表明：51种农药在6种基质中3个添加水平（10、20、100 μg/kg）的回收率为58.4%~126%,相对标准偏差为3.3%~26%;以信噪比（S/N）≥10计,久效威及杀螟丹的定量限（LOQ）为50 μg/kg,其他49种农药的LOQ为0.2~10 μg/kg。本文方法有效、灵敏,适用于不同蔬菜基质中51种氨基甲酸酯类农药残留的测定。     

气相色谱-负化学源质谱法测定蔬菜中17种拟除虫菊酯类农药残留量

建立了气相色谱-负化学源质谱检测蔬菜中17种拟除虫菊酯类农药残留量的方法。样品中的目标物经乙腈提取后,用乙二胺-N-丙基甲硅烷(PSA)和石墨化炭黑填料进行分散固相萃取净化,气相色谱-负化学源质谱选择离子监测模式测定,同位素内标法定量。在甜豌豆、绿花菜和大葱基质中均未见干扰所有农药测定的现象。17种拟除虫菊酯类农药的定量限均为0.02～5 μg/kg。在10、20、30和100 μg/kg等4个添加水平下,所有农药的回收率均为71.0%～139.0%,相对标准偏差≤12.8%。该方法可作为蔬菜中17种菊酯类农残检测的确证方法。     

Determination of 19 sulfonamides residues in pork samples by combining QuEChERS with dispersive liquid–liquid microextraction followed by UHPLC–MS/MS

A new simple and rapid pretreatment method for simultaneous determination of 19 sulfonamides in pork samples was developed through combining the QuEChERS method with dispersive liquid–liquid microextraction followed by ultra‐high performance liquid chromatography with tandem mass spectrometry. The sample preparation involves extraction/partitioning with QuEChERS method followed by dispersive liquid–liquid microextraction using tetrachloroethane as extractive solvent and the acetonitrile extract as dispersive solvent that obtained by QuEChERS. The enriched tetrachloroethane organic phase by dispersive liquid–liquid microextraction was evaporated, reconstituted with 100 μL acetonitrile/water (1:9 v/v) and injected into an ultra‐high performance liquid chromatography with a mobile phase composed of acetonitrile and 0.1% v/v formic acid under gradient elution and separated using a BHE C₁₈ column. Various parameters affecting the extraction efficiency were investigated. Matrix‐matched calibration curves were established. Good linear relationships were obtained for all analytes in a range of 2.0–100 μg/kg and the limits of detection were 0.04–0.49 μg/kg. Average recoveries at three spiking levels were in the range of 78.3–106.1% with relative standard deviations less than 12.7% (n = 6). The developed method was successfully applied to determine sulfonamide residues in pork samples.     

Dual‐layer column filtration cleanup and gas chromatography‐tandem mass spectrometry detection for the analysis of 39 pesticide residues in porcine meat

A rapid and effective method was developed for the analysis of 39 pesticide residues in porcine meat with dual‐layer multiplug filtration cleanup and gas chromatography‐tandem mass spectrometry detection. The cleanup process was performed with columns packed with two layers, namely multiwalled carbon nanotubes, C18 and anhydrous magnesium sulfate (MgSO₄) as top layer, while mixture of florisil and MgSO₄ as bottom layer. A single‐layer method was tested in parallel, with columns packed with the same amount of absorbents. Extraction conditions and filtration cleanup process were optimized to obtain satisfied method performance. Method linearity was calculated with coefficients of determination more than 0.995. The limits of quantitation were verified with acceptable accuracy at the lowest spiked concentration of 0.01 mg/kg (except pyrimethanil). The recoveries at three fortified levels (0.01, 0.05, and 0.1 mg/kg) in five replicates were between 74 and 118% (except pyrimethanil) with relative standard deviations range from 1 to 16%. The matrix effects were in the range of 1.01 to 2.84. This new method was applied for the analysis of multipesticide residues in market samples of porcine meat. This study showed the dual‐layer multiplug filtration cleanup demonstrated better performance than that with the single‐layer columns in cleanup of porcine meat.     

Determination of Pesticide Residues in Teas via QuEChERS Combined with Dispersive Liquid–Liquid Microextraction Followed by Gas Chromatography–Tandem Mass Spectrometry

In this study, an effective gas chromatography–tandem mass spectrometry method was developed to determine 47 pesticide residues in tea. Sample preparation involved a quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure, wherein the sample is extracted by acetonitrile and cleaned up with multiwalled carbon nanotubes and primary secondary amine adsorbents; dispersive liquid–liquid microextraction (DLLME) was subsequently performed using carbon tetrachloride as extractive solvent and the extract obtained by QuEChERS as dispersive solvent. Factors influencing DLLME efficiency, including type and volume of extractive solvent, volume of dispersive solvent, and extraction time were evaluated. For validation purposes, recovery studies were performed using matrix blanks fortified with pesticides at three concentrations, namely, 10, 50, and 100 μg kg^?1. Most of the analytes were recovered at an acceptable range of 70?120% and RSDs ≤ 20% were acquired for green tea, oolong tea, black tea, and puer tea. Limits of quantification of pesticides obtained for these teas were sufficiently low, and most pesticides levels were lower than 10 μg kg^?1, which satisfies the requirements for maximum residue levels (MRLs) as prescribed by the European Community. Twenty-four commercially available tea samples were analyzed using this optimized method. Results revealed that the contents of chlorpyrifos and alpha-HCH from different green tea samples exceed the MRLs, and chlorpyrifos, bifenthrin, lambda-cyhalothrin, and cypermethrin are among the most frequently detected pesticides in teas.     

基于QuEChERS法提取液相色谱-串联质谱法测定新会陈皮中的9种真菌毒素和农药残留

建立了Qu ECh ERS-改性多壁碳纳米管提取净化结合液相色谱-质谱联用同时检测新会陈皮中6种真菌毒素和3种农药残留的分析方法,并对影响提取、净化、检测效率的因素进行了优化。以乙腈-水(80∶20)提取样品,适量改性多壁碳纳米管净化后,净化液直接用HPLC-MS/MS进行测定,选择多反应监测模式,基质匹配标准溶液外标法定量。在优化实验条件下,9种目标化合物在各自线性范围内均具有良好的线性关系,相关系数为0.983 8~0.998 2,检出限(S/N=3)为0.18~10μg/kg。在低、中、高3个加标水平的平均回收率为72.4%~106%,相对标准偏差为2.2%~7.4%。该法准确、灵敏度高﹑操作简单﹑快速,可满足新会陈皮中上述9种化合物同时测定的要求,应用于真菌毒素和农药残留的快速筛查和确证,结果满意。     

Multiresidue pesticides analysis in soils using modified QuEChERS with disposable pipette extraction and dispersive solid‐phase extraction

QuEChERS original method was modified into a new version for pesticides determination in soils. The QuEChERS method is based on liquid–liquid portioning with ACN and was followed by cleanup step using dispersive SPE and disposable pipette tips. Gas chromatographic separation with MS detection was carried out for pesticides quantification. The method was validated using recovery experiments for 36 multiclass pesticides. Mean reco‐veries of pesticides at each of the four spiking levels between 10–300 μg/kg of soil ranged from 70–120% for 26 pesticides with RSD values less than 15%. The method achieved low limit of detection less than 7.6 μg/kg. Matrix effects were observed for 13 pesticides. Matrix effects were compensated by using matrix‐matched calibration. The method was applied successfully using d‐SPE or DPX in the analysis of the pesticides in soils from organic farming and integrated pest management.