Dissipation behavior of phorate and its toxic metabolites in the sandy clay loam soil of a tropical sugarcane ecosystem using a single‐step sample preparation method and GC–MS

The dissipation of phorate in the sandy clay loam soil of tropical sugarcane ecosystem was studied by employing a single‐step sample preparation method and gas chromatography with mass spectrometry. The limit of quantification of the method was 0.01 μg/g. The recoveries of phorate, phorate sulfoxide, phorate sulfone, and phorate oxon were in the range 94.00–98.46% with relative standard deviations of 1.51–3.56% at three levels of fortification between 0.01 and 0.1 μg/g. The Half‐life of phorate and the total residues, which include phorate, phorate sulfoxide and phorate sulfone, was 5.5 and 19.8 days, respectively at the recommended dose of insecticide. Phorate rapidly oxidized into its sulfoxide metabolite in the sandy clay loam soil. Phorate sulfoxide alone accounted for more than 20% of the total residues within 2 h post‐application and it was more than 50% on the fifth day after treatment irrespective of the doses applied. Phorate sulfoxide and phorate sulfone reached below the detectable level on 105 and 135 days after treatment, respectively as against 45 days after treatment for phorate residues at the recommended dose. Thus, the reasonably prolonged efficacy of phorate against soil pests may be attributed to longer persistence of its more toxic sulfoxide and sulfone metabolites.     

Development and validation of a multiresidue method for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection

A multiresidue method has been developed and validated for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection. Limits of quantification of the method varied between 0.007 and 0.01 μg/g. Ethyl acetate based extraction followed by dispersive solid‐phase extraction cleanup with primary secondary amine yielded internationally acceptable recoveries of acephate, chlorpyrifos, dichlorvos, monocrotophos, malathion, malaoxon, phorate, phorate‐sulfoxide, phorate‐oxon, phorate‐sulfone, and quinalphos from selected matrices. The recoveries of target analytes from cane juice were 75.55 ± 0.5–102.57 ± 4.2, 77.45 ± 4.7–103.33 ± 3.3, and 80.55 ± 6.6–105.82 ± 9.8% at 0.01, 0.02, and 0.1 μg/g levels of fortification, respectively. The recoveries from cane sugar were 73.24 ± 3.5–104.47 ± 1.9, 75.23 ± 1.5–116.10 ± 3.7, and 70.75 ± 5.7–110.15 ± 2.7%, respectively at 0.01, 0.02, and 0.1 μg/g levels of fortification. Matrix effect and measurement uncertainty were within the permissible limit (less than 20%) as prescribed for pesticide residue analysis.     

Simultaneous determination and method validation of clethodim and its metabolites clethodim sulfoxide and clethodim sulfone in tobacco by LC‐MS/MS

A simple method was developed and validated for the simultaneous determination of clethodim, clethodim sulfoxide, and clethodim sulfone in soil and tobacco by liquid chromatography with tandem mass spectrometry. The three target compounds were extracted from tobacco and soil with acetonitrile, and the extracts were purified using octadecyl silane. The proposed method showed satisfactory linearity (R² ≥ 0.9973) for the target compounds. The limits of detection and quantitation of the three analytes in all matrices were 0.024−0.06 and 0.08−0.2 mg/kg, respectively. The recovery was tested in blank soil and tobacco leaf samples and calculated to be 74.8–104.4% with relative standard deviations of 1.9–12.1%. The developed method was successfully applied to the analysis of residues of clethodim, clethodim sulfoxide and clethodim sulfone in real soil and tobacco samples. The results indicated that the developed method can meet the requirements for the analysis of trace amounts of all three analytes in soil and tobacco.     

Determination of low-level pesticide residues in soft drinks and sports drinks by liquid chromatography with tandem mass spectrometry: collaborative study

A collaborative study was conducted on a method for the measurement of 11 low-level pesticide residues in soft drinks and sports drinks by liquid chromatography with tandem mass spectrometry. The pesticide residues determined in this study were alachlor, atrazine, butachlor, isoproturon, malaoxon, monocrotophos, methyl paraoxon, phorate, phorate sulfone, phorate sulfoxide, and 2,4-dichlorophenoxyacetic acid (2,4-D). Blind fortification solutions containing 3 different levels of pesticide residues were provided to 9 collaborating laboratories to create test samples at concentrations of 0, 0.1, and 0.5 microg/L with a 10-fold concentration for phorate in a total of 6 matrixes (2 colas, 1 diet cola, 1 clear lemon-lime soft drink, 1 orange soft drink, and 1 sports drink). Good qualitative performance of the method was demonstrated for all pesticide residues. Reproducibility relative standard deviation (RSDR) ranged from 7 to 151% for alachlor, atrazine, butachlor, isoproturon, malaoxon, monocrotophos, methyl paraoxon, phorate, phorate sulfone, phorate sulfoxide, and 2,4-D at the 0.1 microg/L level (1.0 microg/L for phorate). At 0.5 microg/L (5.0 microg/L for phorate), RSDR ranged from 9 to 57% for alachlor, atrazine, butachlor isoproturon, malaoxon, monocrotophos, methyl paraoxon, phorate, phorate sulfone, phorate sulfoxide, and 2,4-D in all matrixes. Repeatability relative standard deviation (RSDr), applicable to the diet cola and sports drink, ranged from 0 to 124% for the 11 pesticide residues at the 0.1 microg/L level (1.0 microg/L for phorate). At 0.5 microg/L (5.0 microg/L for phorate), RSDr ranged from 4 to 26%. Recoveries for the 11 pesticide residues in all matrixes ranged from 84 to 300% at the 0.1 microg/L level (1.0 microg/L for phorate) and from 66 to 127% at the 0.5 microg/L (5.0 microg/L for phorate) level. Coefficients of determination (r2) of the matrix-matched calibration curves were > or = 0.95. It is recommended that the method be accepted by AOAC as Official First Action with a limit of quantification of 0.5 microg/L for alachlor, atrazine, butachlor, isoproturon, malaoxon, methyl paraoxon, monocrotophos, phorate sulfone, phorate sulfoxide, and 2,4-D and 5.0 microg/L for phorate.     

Determination of albendazole and its metabolites in the muscle tissue of hybrid striped and largemouth bass using liquid chromatography with fluorescence detection

A liquid chromatographic method was developed for the determination of albendazole and its metabolites albendazole sulfoxide, albendazole sulfone, and albendazole-2-aminosulfone from largemouth and hybrid striped bass muscle tissue with adhering skin. The muscle tissue samples were made alkaline with potassium carbonate and extracted with ethyl acetate. The extracts were further subjected to cleanup by using a series of liquid-liquid extractions. After solvent evaporation, the residue was reconstituted in mobile phase and chromatographed. The chromatography was carried out on a reversed-phase Luna C18 column, using acetonitrile-methanol buffer as the mobile phase. The analytes were detected by fluorescence with excitation and emission wavelengths of 290 and 330 nm, respectively. The average recoveries from the fortified muscle tissue of the 2 fish species for albendazole (25-100 ppb), albendazole sulfoxide (8.75-52.5 ppb), albendazole sulfone (1-10 ppb), and albendazole-2-aminosulfone (10-100 ppb) were 89, 82, 99, and 74%, respectively. The coefficient of variation for each compound was <20% in all cases. The procedure was applied to the determination of albendazole and its 3 metabolites in the muscle tissue of the 2 fish species after orally dosing them with albendazole.     

A simple LC-MS/MS method to determine plasma and cerebrospinal fluid levels of albendazole metabolites (albendazole sulfoxide and albendazole sulfone) in patients with neurocysticercosis

The development and validation of an LC-MS/MS method for the simultaneous determination of albendazole metabolites (albendazole sulfoxide and albendazole sulfone) in human plasma are described. Samples of 200 μL were extracted with ether-dichloromethane-chloroform (60:30:10, v/v/v). The chromatographic separation was performed using a C(18) column with methanol-formic acid 20 mmol/L (70:30) as the mobile phase. The method was linear in a range of 20-5000 ng/mL for albendazole sulfoxide and 10-1500 ng/mL for albendazole sulfone. For both analytes the method was precise (RSD < 12%) and accurate (RE <7%) with high recovery (>90%). The method was successfully applied to determine the plasma and cerebrospinal fluid levels of albendazole sulfoxide and albendazole sulfone in patients with subarachnoidal neurocysticercosis who received albendazole at 30 mg/kg per day for 7 days. This LC-MS/MS method yielded a quick, simple and reliable protocol for determining albendazole sulfoxide and albendazole sulfone concentrations in plasma and cerebrospinal fluid samples and is applicable to therapeutic monitoring.     

Simultaneous determination of benzimidazoles and their metabolites in plasma using high-performance liquid chromatography/tandem mass spectrometry: application to pharmacokinetic studies in rabbits

An HPLC/MS/MS method was developed for the simultaneous determination of the following benzimidazole anthelmintics and metabolites in plasma: flubendazole, albendazole, fenbendazole, mebendazole, thiabendazole, hydrolyzed flubendazole, albendazole sulfoxide, albendazole sulfone, albendazole aminosulfone, oxfendazole, fenbendazole sulfone, aminomebendazole, hydroxymebendazole, and 5-hydroxythiabendazole. The sample preparation process involved a pH-dependent extraction of the analytes. Chromatographic separation was performed on a C18 column with a mobile phase gradient starting with methanol-water (20 + 80, v/v) containing 0.1% formic acid. The overall average recoveries of the analytes based on a matrix-matched calibration ranged from 75.0 to 120.0%, with RSD values of <20.0%. The LODs ranged from 0.08 to 2.0 microg/kg and the LOQs from 0.3 to 5.0 microg/kg. The validated method was used in pharmacokinetic studies of benzimidazole compounds in rabbits, and the elimination of the metabolites was measured quantitatively.     

Determination of low-level agricultural residues in soft drinks and sports drinks by liquid chromatography/tandem mass spectrometry: single-laboratory validation

In this study, sponsored by PepsiCo Inc., a method was validated for measurement of 11 pesticide residues in soft drinks and sports drinks. The pesticide residues determined in this validation were alachlor, atrazine, butachlor, isoproturon, malaoxon, monocrotophos, paraoxon-methyl, phorate, phorate sulfone, phorate sulfoxide, and 2,4-dichlorophenoxyacetic acid (2,4-D) when spiked at 0.100 microg/L (1.00 microg/L for phorate). Samples were filtered (if particulate matter was present), degassed (if carbonated), and analyzed using liquid chromatography with tandem mass spectrometry. Quantitation was performed with matrix-matched external standard calibration solutions. The standard curve range for this assay was 0.0750 to 10.0 microg/L. The calibration curves for all agricultural residues had coefficient of determination (r2) values greater than or equal to 0.9900 with the exception of 2 values that were 0.9285 and 0.8514. Fortification spikes at 0.100 microg/L (1.00 microg/L for phorate) over the course of 2 days (n=8 each day) for 3 matrixes (7UP, Gatorade, and Diet Pepsi) yielded average percent recoveries (and percent relative standard deviations) as follows (n=48): 94.4 (15.2) for alachlor, 98.2 (13.5) for atrazine, 83.1 (41.6) for butachlor, 89.6 (24.5) for isoproturon, 87.9 (24.4) for malaoxon, 96.1 (9.26) for monocrotophos, 101 (25.7) for paraoxon-methyl, 86.6 (20.4) for phorate, 101 (16.5) for phorate sulfone, 93.6 (25.5) for phorate sulfoxide, and 98.2 (6.02) for 2,4-D.     

多壁碳纳米管滤过型净化柱净化-超高效液相色谱/串联质谱法同时测定生姜中的涕灭威及其代谢物

建立了多壁碳纳米管滤过型净化柱净化-超高效液相色谱/串联质谱联用技术同时测定生姜中涕灭威及其代谢物的分析方法。生姜样品经乙腈提取后,用多壁碳纳米管滤过型净化柱进行2次反复抽提净化,净化液用氮气吹干,用乙腈-水（5：95,v/v）溶解,采用正离子多反应监测（MRM）模式进行分析,外标法定量。结果表明：涕灭威、涕灭威砜及涕灭威亚砜在0.5~200 μg/L浓度范围内呈线性,其相关系数（r²）均大于0.99;在2、20、200 μg/kg添加水平下,回收率为71.4%~89.8%,相对标准偏差范围为0.7%~13.2%;3种目标物的定量限为1.0~2.0 μg/kg。本方法操作简单,灵敏度、准确度和精密度均满足农药多残留检测技术的要求,适用于生姜中涕灭威及其代谢物残留的快速测定。     

Determination of albendazole and its main metabolites in ovine plasma by liquid chromatography with dialysis as an integrated sample preparation technique

Albendazole is a benzimidazole derivative with a broad-spectrum activity against human and animal helminth parasites. In order to determine the main pharmacokinetic parameters in sheep after oral and intravenous administration of a new formulation of albendazole (an aqueous solution), a fully automated method was developed for the determination of this drug and its main metabolites, albendazole sulfoxide (active metabolite) and sulfone in ovine plasma. This method involves dialysis as purification step, followed by enrichment of the dialysate on a precolumn and liquid chromatography (LC). All sample handling operations were executed automatically by means of an ASTED XL system. After conditioning of the trace enrichment column (TEC) packed with octadecyl silica with pH 6.0 phosphate buffer containing sodium azide, the plasma sample, in which a protein releasing reagent (1 M HCl) containing Triton X-100 was automatically added, was loaded in the donor channel and dialysed on a cellulose acetate membrane in the static-pulsed mode. The dialysis liquid consisted of pH 2.5 phosphate buffer. By rotation of a switching valve, the analytes were eluted from the TEC in the back-flush mode by the LC mobile phase and transferred to the analytical column, packed with octyl silica. The chromatographic separation was performed at 35°C and the analytes were monitored photometrically at 295 nm. Due to the differences in hydrophobic character between albendazole and its metabolites, a gradient elution was applied. The mobile phase consisted of a mixture of acetonitrile and pH 6.0 phosphate buffer. The proportion of organic modifier was increased from 10.0 to 50.1% in 12.30 min, then from 50.1 to 66.9% in 1.70 min. First, the gradient conditions and the temperature were optimised for the LC separation using the DryLab software. Then, the influence of some parameters of the dialysis process on analyte recovery was investigated. Finally, the method developed was validated. The mean recoveries for albendazole and its metabolites were about 70 and 65%, respectively. The limits of quantification for albendazole and its metabolites were 10 and 7.5 ng/ml, respectively.     

Pesticide analysis in toasted barley and chickpea flours

Analytical potentiality of a modified version of the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method has been studied and validated for the extraction of a group of 11 pesticides (ethoprophos, cadusafos, dimethoate, terbufos, disulfoton, chlorpyrifos‐methyl, fenitrothion, pirimiphos‐methyl, malathion, chlorpyrifos and fensulfothion) and some of their metabolites (malaoxon, disulfoton sulfoxide, terbufos sulfone and disulfoton sulfone) in toasted barley and chickpea flours. The method involves separation and quantification by gas chromatography (GC) with nitrogen phosphorus detection (NPD) using triphenylphosphate as the internal standard. Matrix‐matched calibration was carried out for both flours due to the existence of a matrix effect. Linearity, recovery, precision and accuracy studies of the proposed QuEChERS‐GC‐NPD method were evaluated in each sample matrix. Mean recovery values were in the range of 73–118% with relative standard deviation values below 10%. Limits of detection of the whole method were between 0.07 and 57.39 μg/kg. The method was finally applied for the analysis of 14 samples collected in different zones of the Tenerife island. The residues of pirimiphos‐methyl were found in 13 of them, confirming its unequivocal presence by mass spectrometry.     

Gas chromatographic analysis of methiocarb and its metabolites in soil and rice

Summary A new method to determine the amount of methiocarb and its two metabolites, the sulfoxide and sulfone in soil and rice plant is described. The method consists of extraction of samples with acetone, filtration, separation of methiocarb and its metabolites through a Florisil column, and gas chromatographic determination. Since the degradation of methiocarb to 3,5-dimethyl-4-methylthiophenol (DMMP) is commonly observed during GC analysis, methiocarb was converted to DMMP via chemical hydrolysis after column chromatography. Reasonable recoveries for routine analysis were obtained and the limit of quantitation (LOQ) with GC/FPD were 0.5, 2 and 2 ng for DMMP sulfoxide and sulfone, with a signal to noise ratio of 4. In all rice samples, no detectable residues were found, however DMMP and methiocarb sulfoxide were found in some straw samples. In field soil samples, no sulfone was detected in all samples and methiocarb showed typical degradation curves with a half life of 8 days after treatment. A five-fold longer half life was observed in indoor studies.     

超高效液相色谱-串联质谱法测定草鱼肉中阿苯达唑及其代谢物残留

建立了同时测定草鱼肉中阿苯达唑及其3种代谢物阿苯达唑亚砜、阿苯达唑砜、阿苯达唑-2-氨基砜的超高效液相色谱-串联质谱(UPLC-MS/MS)分析方法。草鱼肉样品通过碱性乙酸乙酯提取,正己烷净化,超高效液相色谱分离,串联质谱检测,氘代同位素内标定量。本方法分析时间短,在4 min内即可完成4种被分析物的液质联用分析。本方法在0.1～10μg/kg范围内各物质线性良好,线性系数在0.9991～0.9996之间。阿苯达唑、阿苯达唑亚砜、阿苯达唑砜、阿苯达唑-2-氨基砜在0.5～5.0μg/kg添加水平下的平均回收率分别为98.4%～102.6%,97.1%～103.4%,98.8%～103.7%和101.1%～104.2%检出限分别为0.2,0.1,0.2和0.1μg/kg;日内精密度小于4.77%,日间精密度小于3.03%。本方法为阿苯达唑及其代谢物的检测及监控提供了一种快速、灵敏度高、重现性好的定量分析方法。     

Use of XAD-2 Macroreticular Resin for the Recovery of Aldicarb and its Metabolites in Drinking Water

Abstract

A simplified method for the determination of aldicarb and its oxidation products, aldicarb sulfoxide, and aldicarb sulfone, in water has been developed. Aldicarb and its metabolites are adsorbed on Amberlite XAD-2 polymer resin and then eluted with acetone. The eluate is analyzed for aldicarb and aldicarb sulfoxide by high performance liquid chromatography (HPLC) with UV detection at 254 nm. Total aldicarb residues can be determined by a colorimetric method. Typical detection limits in drinking water are 1 μg/1.     

Application of ultra-performance columns in high-performance liquid chromatography for determination of albendazole and its metabolites in turkeys

Methods for determination of albendazole (ALB), albendazole sulfoxide (SOX) and albendazole sulfone (SON) in turkey blood plasma, using high‐performance liquid chromatography (HPLC) with fluorescence detection, were developed. Moreover, comparison of HPLC columns with ultra‐performance liquid chromatography (UPLC) columns was performed. Albendazol was administered orally in 5‐week‐old birds (n = 18) at a dose of 25 mg/kg b.w. Accuracy and precision of the developed method were satisfactory and stability studies showed acceptable variation (below 15%) in ALB, SOX and SON concentrations when the samples were stored at –75°C for 15 days. UPLC® columns gave higher peaks from typical HPLC columns retaining high quality of analysis. Pharmacokinetic analysis indicated quick elimination of ALB from turkey blood plasma. The mean residence time of SON was at least two times longer than that of SOX and four times longer than that of ALB. The elimination half‐lives for ALB, SOX and SON were 0.7 ± 0.27, 5.37 ± 6.03, 9.17 ± 5.12 h, respectively. The obtained results indicate that the described method allows for precise determination of albendazole and its metabolites in turkey plasma. Moreover, using UPLC columns in HPLC apparatus results in higher sensitivity as compared with the classical HPLC columns. Copyright © 2011 John Wiley & Sons, Ltd.     

Degradation study of selected organophosphorus insecticides in natural waters

The degradation of 15 organophosphorus insecticides was studied in drinking, ground, and surface waters under different laboratory-controlled and environmental conditions. Surface waters originated from rivers Savinja (near the city of Celje) and Kamniska Bistrica (at the spring), which both belong to the Danube river basin. Groundwater was collected from wells (70?m deep) in Ljubljana, which are the direct source of drinking water for the capital. These matrices were selected on the basis of their different chemical composition and microbial activity. Major factors influencing the degradation were determined, such as temperature, oxygen, sunlight, pH, and type of water. The degradation of atrazine, present in many water sources in Slovenija, was followed simultaneously as a reference under the same conditions. The degradation kinetics was followed by gas chromatography with mass-selective detection, which also allowed the identification of some degradation by-products, such as oxon analogues paraoxon, dyfoxon, malaoxon, phenyl-methyl sulfoxide, fenthion sulfone, phorate sulfoxide, and phorate sulfone. The results show that the half-lives of the selected organophosphorus insecticides varied from 4 to 192 days or more, depending on the water source and experimental conditions. As a result, kinetically constants and half-lives were calculated for every tested insecticide, and major degradation products were determined.     

固相萃取-同位素稀释-超高效液相色谱-串联质谱法测定水中涕灭威、涕灭威亚砜和涕灭威砜

采用同位素稀释结合固相萃取对水样进行预处理,建立了环境水体中涕灭威及其代谢物(涕灭威亚砜、涕灭威砜)的超高效液相色谱-串联质谱分析方法.水样加同位素内标涕灭威-D3、涕灭威亚砜-D3和涕灭威砜-D3,经HLB固相萃取柱富集净化后,用Waters ACQUITYTM BEH C18色谱柱(2.1 mm×100 mm,1....     

Simultaneous determination of erlotinib and its isomeric major metabolites in human plasma using isocratic liquid chromatography–tandem mass spectrometry and its clinical application

This study developed a method for the simultaneous determination of erlotinib and its isomeric major metabolites, OSI‐413 and OSI‐420, in human plasma using an isocratic liquid chromatography–tandem mass spectrometry. Plasma specimens deproteinized with acetonitrile were separated using a 3‐µm particle size octadecylsilyl column. The m/z values of the precursor and product ions for the analytes were as follows: erlotinib, 394.2/278.2; and OSI‐413 and OSI‐420, 380.2/278.2. The total run time was 21 min and no peaks interfering with the analytes and internal standard (d₆‐erlotinib) in human plasma were observed. The calibration curves of erlotinib, OSI‐413 and OSI‐420 were linear over the concentration ranges of 10–3000, 2–500 and 2–100 ng/mL, respectively. The pretreatment recovery ratios were >86.1%. The intra‐ and inter‐assay precisions and accuracies were <12.7 and 89.0–108.9% for all analytes. This validated method was applied to the determination of plasma samples in lung cancer patients receiving 150 mg of oral erlotinib. The plasma concentration ranges of erlotinib, OSI‐413 and OSI‐420 were 373–2354, 15.7–379 and 2.5–43.6 ng/mL, respectively. In conclusion, the present method can be helpful for evaluating the plasma exposures of erlotinib and its major isomeric metabolites in clinical settings. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous determination of pantoprazole and its two metabolites in dog plasma by HPLC

A simple and sensitive high-performance liquid chromatography (HPLC) method is developed and validated for simultaneous determination of pantoprazole and its two metabolites (pantoprazole sulfone and pantoprazole thioether) in dog plasma and applied to a pharmacokinetic study in Beagle dogs. Following a protein precipitation procedure, the samples are separated using reversed-phase HPLC (C18) by a gradient of acetonitrile and ammonium acetate (pH 6.0) at a flow rate of 1.0 mL/min and quantitated using UV detection at 290 nm. Omeprazole is selected as the internal standard. The method has a lower limit of quantitation of 0.025 microg/mL for pantoprazole and its two metabolites, using 0.1-mL aliquots of plasma. The linear calibration curves are obtained in the concentration range of 0.025-10.0 microg/mL for three analytes. The intra- and interrun precision (relative standard deviation), calculated from quality control (QC) samples, is less than 13% for three analytes. The accuracy determined from QC samples is between -6.4% and 12%.