Simultaneous Analysis of Herbicide Metribuzin and Quizalofop-p-ethyl Residues in Potato and Soil by GC-ECD

A robust and sensitive method was developed for the simultaneous analysis of metribuzin and quizalofop-p-ethyl residues in potato and soil, based on solid-phase extraction (SPE) coupled to capillary gas chromatography with electron capture detector (GC-ECD). Residues of two herbicides were extracted from potato and soil with acetone and methanol–water, followed by SPE to remove coextractives, before analysis by GC-ECD. SPE procedures were performed on Florisil cartridges (500 mg, 3 mL), the analytes from potato and soil matrix were eluted with petroleum ether-acetic ether (9:1 v/v, 5 mL) and petroleum ether-acetic ether (8:2 v/v, 2 mL), respectively. Limits of quantification of the method were 0.01 mg kg^?1, and the mean recoveries ranged from 72.9 to 109.5% with relative standard deviation ranging from 0.7 to 9.2% at the three spike levels (0.01, 0.1, and 0.5 mg kg^?1). The proposed method was successfully applied to the analysis of metribuzin and quizalofop-p-ethyl residues in potato and soil samples from an experimental field. Direct confirmation of the analytes in real samples was achieved by gas chromatography-mass spectrometry (GC–MS).     

Determination of the Insecticide Imidacloprid in Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) and Onion (<Emphasis Type="Italic">Allium cepa</Emphasis>) by High-Performance Liquid Chromatography with Diode-Array Detection

A high-performance liquid chromatography (HPLC) method has been proposed for the determination of imidacloprid residues in fortified potato (Solanum tuberosum L.) and onion (Allium cepa) and in treated potato and onion samples. Sample preparation consisted of dichloromethane extraction of imidacloprid from the plant material, followed by purification of the obtained onion extract on an LC-Florisil disposable cartridge. The obtained potato extracts were further analyzed without purification. The HPLC-diode-array-detection (DAD) method has been developed on reversed phase for separation of imidacloprid with isocratic elution with a mixture of 0.01 M phosphate buffer (pH 3.15) and acetonitrile (75 : 25, v/v). Spectral data obtained with DAD allow the identification of imidacloprid residue. Detector response showed a linear dynamic range from 0.0125 to 0.500 μg/mL. Imidacloprid was recovered from fortified samples in a range of 94–99%. The within-day RSD of repeatability of the retention time of imidacloprid standard solution was less than 0.1% and of the obtained peak area less than 5%. For potato and onion samples, the limits of detection were 0.0075 and 0.0060 mg/kg and the limits of determination were 0.015 and 0.012 mg/kg, respectively. __________ From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 12, 2005, pp. 1273–1278. Original English Text Copyright ? 2005 by Mandic, Lazic, Okresz, Gaal. The text was submitted by the authors in English.     

Multiplug filtration clean‐up with multiwalled carbon nanotubes in the analysis of pesticide residues using LC–ESI‐MS/MS

A novel design for a rapid clean‐up method was developed for the analysis of pesticide residues in fruit and vegetables followed by LC–ESI‐MS/MS. The acetonitrile‐based sample extraction technique was used to obtain the extracts, and further clean‐up was carried out by applying the streamlined procedure on a multiplug filtration clean‐up column coupled with a syringe. The sorbent used for clean‐up in this research is multiwalled carbon nanotubes, which was mixed with anhydrous magnesium sulfate to remove water from the extracts. This method was validated on 40 representative pesticides and apple, cabbage, and potato sample matrices spiked at two concentration levels of 10 and 100 μg/kg. It exhibited recoveries between 71 and 117% for most pesticides with RSDs < 15%. Matrix‐matched calibrations were performed with the coefficients of determination >0.995 for most studied pesticides between concentration levels of 10–500 μg/L. The LOQs for 40 pesticides ranged from 2 to 50 μg/kg. The developed method was successfully applied to the determination of pesticide residues in market fruit and vegetable samples.     

Development and independent laboratory validation of a simple method for the determination of paraquat and diquat in potato, cereals and pulses

A new sensitive, fast and robust method for the determination of paraquat and diquat residues in potatoes, cereals and pulses is presented. Different extraction conditions (solvent, time and temperature) have been evaluated using barley grain, potatoes and dry lentils containing incurred residues of diquat and paraquat. The finalised procedure involves extraction with a mixture of methanol/water/hydrochloric acid at 80?°C and analysis by liquid chromatography–tandem mass spectrometry. Diquat D4 and Paraquat D6 internal standards were added to the test portions prior to extraction. A small-scale inter-laboratory validation of the developed method for diquat and paraquat using potato and barley samples was conducted by three laboratories. The precision and accuracy of the method were determined from recovery experiments (five replicates) at 0.01 and 0.1?mg?kg^?1. The recoveries obtained (n?=?180) were in the range of 92–120?% with associated relative standard deviation (RSD) between 1.4–10?% for all compound/commodity/spiking concentration combinations.     

Rapid determination of fluoroquinolone residues in honey by a microbiological screening method and liquid chromatography

A rapid and efficient method was developed for the simultaneous determination of seven fluoroquinolone (FQ) residues: norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin, orbifloxacin, sarafloxacin, and difloxacin in honey. The samples were first screened with a microbiological method by using test plates made from metal-free purified agar seeded with Bacillus subtilis BGA. When a sample was found to contain FQ residues by using the microbiological method, it was analyzed by LC with fluorescence detection (LC/FL). FQs were extracted with Na2EDTA-McIlvaine buffer and purified by a dual SPE method in which a cation-exchange cartridge was connected to an anion-exchange cartridge. The overall recoveries of the seven FQs ranged from 70.0 to 92.1%. The intra-assay and interassay CVs were < or = 7.8 and < or = 5.1%, respectively. For the microbiological method, the LOD values ranged from 2 to 9 microg/kg. For LC/FL, the LOQ values ranged from 2 to 7 microg/kg. The developed method was used to analyze 70 honey samples. In 14 samples in which the microbiological method detected the presence of FQ residues, norfloxacin, ciprofloxacin, and enrofloxacin were identified by LC/FL.     

Simple and sensitive method for determination of glycoalkaloids in potato tubers by high-performance liquid chromatography with chemiluminescence detection

A novel, simple and sensitive high-performance liquid chromatographic method for the determination of the potato glycoalkaloids, alpha-solanine and alpha-chaconine, based on the chemiluminescent reaction of tris(2,2'-bipyridine)ruthenium(III) has been developed. The calibration graph was linear in the range of 5 ng/ml-10 microg/ml for both alpha-solanine and alpha-chaconine. The detection limits of alpha-solanine and alpha-chaconine were 1.2 and 1.3 ng/ml, respectively. This method was successfully applied to a potato tuber sample without cleanup, pre-concentration, and derivatization steps. The recoveries (mean +/- standard deviation, %) of alpha-solanine and alpha-chaconine spiked in tuber pith at 10 microg/g (n = 6) were 101.0 +/- 4.4% and 103.6 +/- 7.1%, respectively.     

Determination of thiabendazole in orange juice and rind by liquid chromatography with fluorescence detection and confirmation by gas chromatography/mass spectrometry after extraction by matrix solid-phase dispersion

A method was developed for the determination of thiabendazole (TBZ) in orange juice and rind based on matrix solid-phase dispersion (MSPD). TBZ was extracted with ethyl acetate and the extract was subsequently cleaned up on a solid-phase extraction column. Fungicide residues were determined by liquid chromatography with fluorescence detection. Recoveries through the method ranged from 87 to 97% with relative standard deviations < or = 11%. The detection and quantitation limits were 0.15 and 0.50 microg/kg, respectively. The confirmation of TBZ residues in positive samples was performed by solid-phase microextraction followed by gas chromatography with mass spectrometric detection using selected ion monitoring. The developed method was applied to determine TBZ levels in commercial orange juices and in juice and rind of fresh oranges. The influence of storage and washing of fruits on TBZ residues was also studied.     

Development and single-laboratory validation of a reversed-phase liquid chromatography-electrospray-tandem mass spectrometry method for identification and determination of acrylamide in foods

A rapid and accurate method using reversed-phase liquid chromatography-tandem mass spectrometry interfaced with electrospray was developed for determination of acrylamide in cooked food samples. A simplified sample treatment procedure using an extraction step with acidified water without cleanup was developed. A C18 column with an aqueous formic acid-methanol mixture as the mobile phase was used under isocratic conditions. The method was validated in-house for robustness, limits of detection (LOD) and quantitation (LOQ), linearity, recovery, and accuracy both on standard and baked-product and potato flour matrixes. Good results in the low ppb level were obtained for LOD (< 15 microg/kg) and LOQ (< 25 microg/kg) of acrylamide in samples. Excellent linearity (r2 = 0.999-1.000) was established over 2 orders of magnitude by performing statistical tests. The absence of both constant and proportional systematic errors demonstrated good method accuracy. Excellent results were obtained for intraday repeatability (RSD < 1.5%) and between-day precision (RSD < 5%). Extraction recoveries from food products were calculated in the 97 +/- 3-99 +/- 2% (n = 6) range with a labeled internal standard (13C3-acrylamide). The applicability of the method to determination of acrylamide in cooked food products was demonstrated.     

高效液相色谱法测定番茄酱中辛硫磷残留

建立了高效液相色谱(HPLC)法测定番茄酱中辛硫磷残留量的方法。番茄酱样品经乙腈提取盐析,弗罗里硅土固相萃取小柱净化,样液浓缩过滤膜后用乙腈溶解定容。采用C18色谱柱,流动相为体积比4∶1的乙腈∶0.15%甲酸水溶液,检测波长285nm,外标法定量。结果表明:在0.01～1mg/kg范围内辛硫磷的线性关系良好(r=0.9999)。方法检出限为0.01mg/kg,平均回收率为86.1%～102.7%,相对标准偏差为2.0%～6.5%。该法简便、快速、灵敏、准确,各项技术指标均满足农药残留检测的要求。     

液质联用法测定纺织品中烷基酚和烷基酚聚氧乙烯醚

采用高效液相色谱-质谱法测定了纺织品中残留的辛基酚、壬基酚、辛基酚聚氧乙烯醚和壬基酚聚氧乙烯醚,对提取方式、提取溶剂等前处理条件进行了优化,对质谱监测离子进行了选择。该方法检出限(S/N=5)为0.010~0.025 mg/kg,回收率为93%~106%,相对标准偏差为1.0%~5.0%,方法简便、准确,灵敏度高。     

纺织品、皮革及其制品中五氯苯酚残留量的气相色谱-质谱法测定

介绍应用气相色谱-质谱法测定纺织品、皮革及其制品中防霉剂五氯苯酚的残留量,试样经硫酸溶液酸化后用正己烷提取,用气相色谱-质谱选择离子测定。方法简便、快速、灵敏,检出限20μg／kg,添加回收率86．7％～93．1％,变异系数4．1％～5．9％。     

气相色谱法检测西兰花和荷兰豆中嘧菌酯残留量

建立了气相色谱法检测西兰花和荷兰豆中嘧菌酯残留量的快速分析方法。样品用V(乙酸乙酯)∶V(环己烷)=1∶1超声波萃取,气相色谱-氮磷检测法测定。外标法定量,结果表明,嘧菌酯在0.01~1.0 mg/kg范围内呈线性关系,其相关系数r>0.99。在低、中、高3个添加水平,嘧菌酯的回收率为85%~110%,相对标准偏差为3.8%~11.4%,检出限为0.01 mg/kg。     

Solid-phase extraction and cleanup procedures for determination of acrylamide in fried potato products by liquid chromatography/mass spectrometry

In response to recent discoveries of acrylamide in heated foods, a solid-phase extraction and cleanup protocol was developed for the determination of acrylamide in fried or baked potato samples by liquid chromatography/mass spectrometry (LC/MS). The analyte was extracted from the matrix by using 2M NaCl, and an aliquot of the initial extract was loaded onto a reversed-phase cartridge. After the analyte was eluted from the cartridge, the eluate was cleaned up on a mixed-mode cation-exchange cartridge. The eluate was then evaporated, and the residue was reconstituted in mobile phase before LC/MS analysis. Recoveries, based on the recovery of an added internal standard, ranged from 96 to 101% with relative standard deviations (RSDs) of 5-11%. The response was linear for a concentration range of 100-2000 ng/g with a coefficient of determination (R2) of 0.992 (n = 25). An interday study showed good accuracy and precision of the method over a 3-day period with a recovery of 98% and an RSD of 9.5% (n = 15). The analyses of 6 potato chip samples showed concentrations of incurred acrylamide ranging from 260 to 1500 ng/g.     

高效液相色谱-串联质谱法测定食品中20种氨基甲酸酯类农药残留

建立了食品中20种氨基甲酸酯类农药残留量的高效液相色谱-串联质谱联用(HPLC-MS/MS)测定与确证方法。20种氨基甲酸酯类农药在0.005～0.1 mg/kg范围内线性良好,相关系数为0.991 7～0.999 6;在0.005～0.025 mg/kg范围内, 20种目标物的回收率为51.2%～125.0%,相对标准偏差为1.4%～19.8%。该方法准确、灵敏、快速,可满足国际上对食品中这20种氨基甲酸酯类农药残留量的检测需要。     

Application of liquid chromatography with electrospray tandem mass spectrometry to the determination of a new generation of pesticides in processed fruits and vegetables

This paper describes a method for the sensitive and selective determination of 24 new pesticide residues (azoxystrobin, trifloxystrobin, kresoxim-methyl, fenazaquin, indoxacarb, fenothiocarb, furathiocarb, benfuracarb, imidachloprid, dimethomorph, fenpyroximate, hexythiazox, tebufenpyrad, tebufenozide, difeconazole, fenbuconazole, flusilazole, paclobutrazol, tebuconazole, tetraconazole, bromuconazole, etofenprox, fenhexamid, pyridaben) in apple puree, concentrated lemon juice and tomato puree. A miniaturized extraction-partition procedure requiring small amounts of non-chlorinated solvents was used. The extracts are analyzed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS) without any further clean-up step. The pesticides are separated on a reversed-phase polar column using a gradient elution. Fifty-five simultaneous MS-MS transitions of precursor ions were monitored (two or three for each pesticide). Studies at fortification levels of 0.001-0.020 and 0.010-0.200 mg/kg gave mean recoveries ranging from 76 to 106% for all compounds, except for imidacloprid, with (R.S.D.s) < or = 15%. The excellent sensitivity and selectivity of LC-MS-MS method allowed quantitation and identification at low levels also in difficult matrices with a run time of 20 min. With the developed method almost 100 samples of commercial fruit products (nectars, juices, purees) were analyzed. None of samples contained residues higher than 0.010 mg/kg.     

Distribution and Degradation of 14C-Ethyl Prothiofos in a Potato Plant and the Effect of Processing

Prothiofos and some of its degradation products have been synthesized in our laboratory for investigation purposes. The residual fate of ¹⁴ C-ethyl prothiofos in different parts of potato plant was studied. The highest level of insecticide residues was detected in and on the leaves of potato plants. The residues of prothiofos insecticide were mainly located in the peels of potato tubers (peeling process removed 85% of the total residue after one month of the treatment), small amount penetrated into the pulp of potato tubers. The degradation products in the extracts of both peel and pulp of potato tubers were identified as prothiofos, prothiofos oxon, desethyl prothiofos, O-ethyl-S-propyl phosphorodithioate, O-ethyl phosphorothioate, O-ethyl-S-propyl phosphoric acid, O-ethyl phosphoric acid, despropylthio prothiofos, and prothiofos oxon sulfoxide. In addition 2,4-dichlorophenol was identified as such and in conjugated metabolites.

Potatoes are processed in three ways: frying, boiling, and baking, which is simulated in home preparation. The amount of prothiofos residues was found to decrease on boiling (70%) and further on baking (82%) and frying (100%). The results indicated that frying process is the most effective method for reducing the amount of pesticide residues. Detectable residues were found in boiled potatoes (2.64 ppm), in the boiling water (0.24 ppm), and in the frying oil (0.71 ppm). From these results we concluded that the processed potatoes are safely used for human consumption.     

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.     

Headspace liquid phase microextraction for quantitation of hexanal in potato crisps by gas chromatography

A simple and rapid method using headspace liquid-phase microextraction (HS-LPME) was developed for the determination of hexanal at low levels in potato crisp samples. Parameters such as extraction solvent, agitation of the sample, salt addition, organic drop volume, exposure time, and extraction time were controlled and optimised. The developed protocol was found to yield a linear calibration curve in the concentration range from 0.001 to 2 mg/L and a limit of detection of 0.1 microg/L with a good enrichment factor of > 107 for the analyte. The repeatability of the method was satisfactory (4%). The results demonstrate that HS-LPME is a rapid, accurate, and effective preparation method and could be successfully used for the determination of hexanal in potato crisp samples.     

Multiclass,multiresidue method for the detection of antibiotic residues in distillers grains by liquid chromatography and ion trap tandem mass spectrometry

The increased production of ethanol in the US has resulted in large amounts of distillers grains (DG) which is an excellent feed supplement for livestock. However, the use of antimicrobials during ethanol fermentation has led to a growing concern over the possibility of their residues remaining in DG. To enable the detection of antimicrobial residues, a robust LC–MS/MS method was developed that included 13 antibiotics of diverse chemistries, ampicillin, penicillin G, tetracycline, oxytetracycline, chlortetracycline, bacitracin A, virginiamycin M1, chloramphenicol, erythromycin A, clarithromycin, tylosin A, monensin A and streptomycin. The residues were extracted with an aqueous solution of EDTA and trichloroacetic acid followed by methanol. The combined extract was subjected to a two-track cleanup and concentration on either hydrophilic polymeric or weak cation exchange solid phase extraction cartridges. The extracts are analyzed by LC/ion trap tandem mass spectrometry. The method was validated in dry DG matrix. Absolute recoveries of the analytes ranged from 50 to 100%. Accuracy ranged from 89 to 111% based on calibration by processed standards. The limits of detection and relative standard deviation are satisfactory to support future surveillance studies. The method was subsequently tested in three different end-products of DG: distillers dry grains, distillers wet grains and distillers grains solubles.     

固相萃取-气相色谱/质谱法分析水果和蔬菜中残留的嘧菌酯

建立了多种水果和蔬菜中嘧菌酯残留的气相色谱/质谱分析方法。首先用乙酸乙酯-环己烷(体积比为1∶1)对样品中的嘧菌酯进行超声波提取,经硅胶固相萃取小柱对样品提取液进行净化、富集,采用气相色谱/质谱法以选择离子监测模式(m/z 344,372,388,403定性,m/z 344定量)进行检测。实验结果表明,嘧菌酯在0.01～1.0 mg/kg浓度范围内呈线性,其相关系数r>0.99。在低、中、高3个添加水平,嘧菌酯的回收率为85.2%～98.2%,相对标准偏差为5.8%～21.5%。方法的检测限不大于0.01 mg/kg,定量限不大于0.05 mg/kg。