Pesticide confirmation by triple stage quadrupole mass spectrometry: etrimfos and dimethoate

The production of a protonated molecular ion, MH+, for a pesticide under investigation is often preferred for primary identification purposes. However, the lack of fragment ions under such chemical ionization conditions can place the burden of proof on a single ion species for confirmation. Although a single ion representing the molecule at the correct retention time on a packed column or high-resolution capillary column might seem to have furnished sufficient evidence for unambiguous confirmation, in a number of cases additional specificity can improve the analytical result. With the introduction into commerce of triple stage quadrupole (TSQ) instruments, the possibility of improving the degree of specificity by chemical ionization has emerged for practical pesticide residue confirmation analysis. Use of collision-activated dissociation (CAD) experiments to form daughter ions from the protonated molecular ion of 2 representative organophosphorus pesticides has provided a second dimensional plane of characterization for confirmatory purposes at incurred residue levels.     

Determination of carbadox-related residues in swine liver by gas chromatography/mass spectrometry with ion trap detection

The ion trap detector (ITD), in combination with a capillary gas chromatograph and under chemical ionization conditions, offers sufficient sensitivity to determine carbadox-related residues as the methyl ester derivative of quinoxaline-2-carboxylic acid at 3 micrograms/kg or higher in porcine liver. A tetradeuterated internal standard of QME effectively compensates for losses incurred during sample preparation. The method produced mean levels of 3.3 (+/- 0.5), 5.5 (+/- 0.8), and 10.1 (+/- 0.9) micrograms/kg for liver fortified at 3, 5, and 10 micrograms/kg. When applied to analysis of samples containing incurred residues of 14C-carbadox at the low microgram/kg level, results were comparable to those obtained by reverse isotope dilution analysis.     

Quantitative determination and structure elucidation of type A- and B-trichothecenes by HPLC/ion trap multiple mass spectrometry.

A method is presented for the quantification and structure confirmation of trichothecenes in wheat by high-performance liquid chromatography combined with multiple mass spectrometry (MS(n)()). Nine type A- and B-trichothecenes were determined (nivalenol, deoxynivalenol, fusarenon-X, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, neosolaniol, diacetoxyscirpenol, HT-2 toxin, and T-2 toxin). Extraction was carried out with acetonitrile/water. The extract was purified on a MycoSep column. Quantification was based on an internal standard and atmospheric pressure chemical ionization in the positive ion mode. Recoveries from spiked wheat were in the range of 80-106% at levels of 500 ppb. The limits of quantification for the whole method were between 10 and 100 ppb. Ion adduct formation with ammonium and acetate ions and MS(n) experiments provided information about substitution and fragmentation behavior of the mycotoxins. A scheme has been established for the partial structure elucidation of type A- and B-trichothecenes in fungal cultures.     

Collisionally activated decomposition mass spectrometry/mass spectrometry determination of organophosphorus pesticide residues in foods

Representative collisionally activated decomposition mass spectrometry/mass spectrometry spectra of omethoate, parathion, and azinphos-methyl pesticides are described. Crude and cleaned up extracts of strawberries or lettuce fortified at the 0.2 ppm level with omethoate, parathion, and azinphos-methyl were examined using the direct exposure probe. Cleaned up extracts produced better data because the large overburden of interfering coextractives was removed.     

Quantitative confirmation of dimetridazole and ipronidazole in swine feed by capillary gas chromatography/mass spectrometry with multiple ion detection

Extracts from 4 types of swine feed containing 0.11 ppm each of dimetridazole (DMZ) and ipronidazole (IPR) were analyzed by capillary gas chromatography/mass spectrometry (GC/MS) using multiple ion detection (MID) techniques. We demonstrate in this paper that the quantitative results obtained by capillary GC/MS with MID are comparable for both compounds to results obtained by liquid chromatography and have a lower coefficient of variation for DMZ. Moreover, consistency in the ion ratios (5 ions in DMZ and 6 ions in IPR) permits identification of these compounds by electron ionization MS.     

Determination of trinexapac in wheat by liquid chromatography-electrospray ionization tandem mass spectrometry

A quantitative and confirmatory method for the analysis of trinexapac (free acid metabolite of trinexapac-ethyl) in wheat is described. Residues were extracted from wheat with acetonitrile in aqueous phosphate buffer (pH 7) overnight. The extract was directly injected into the HPLC system. Chromatographic separation was achieved on an octadecylsilica column, and detection was performed by negative ion electrospray ionization tandem mass spectrometry. The precursor ion of trinexapac [M - H](-) at m/z 223 was subjected to collisional fragmentation with argon to yield two intense diagnostic product ions at m/z 135 and 179, respectively. Accuracy and specificity for routine analysis of trinexapac were demonstrated. The validated concentration range was 10-200 microg/kg based on a 0.10 g/mL wheat sample extract. Recoveries were within the range of 71-94%, with associated relative standard deviations better than 10%. The limit of detection for trinexapac in wheat was estimated at 5 microg/kg. The method has been applied to a survey of 100 samples of wheat. In 46% of the samples analyzed, a quantifiable amount of trinexapac was detected, ranging from 10 to 110 microg/kg. It has been demonstrated that analyses of trinexapac accurately reflect the total amount of residues of the plant growth regulator, trinexapac-ethyl, in the wheat samples following field application. No residues of the parent compound, trinexapac-ethyl, in wheat were detected.     

Quantitation of dityrosine in wheat flour and dough by liquid chromatography-tandem mass spectrometry

A method for the quantitation of dityrosine in wheat flour and dough by high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) using an isotope dilution assay with the internal standard 3,3'-(13)C(2)-dityrosine in the single-reaction monitoring mode was developed. The method consisted of the release of protein-bound dityrosine by hydrolysis in 4 mol/L hydrochloric acid/8.9 mol/L propionic acid for 24 h at 110 degrees C after addition of the internal standard, cleanup by C(18) solid-phase extraction, and HPLC-MS/MS. The limit of detection of dityrosine was 80 ng/g of sample (0.22 nmol/g), and the limit of quantitation was 270 ng/g of sample (0.75 nmol/g). The method was sensitive enough to analyze wheat flour and dough and to study the effect of flour improvers on the dityrosine content. Furthermore, the effect of the mixing time was studied. The dityrosine concentration in the flour was 0.66 nmol/g. After we mixed a dough to peak consistency, the dityrosine concentration doubled and remained constant on further mixing. Overdoses of hydrogen peroxide and hexose oxidase (HOX, E.C. 1.1.3.5) resulted in a strongly increased dityrosine content, whereas no increase of the dityrosine concentration was found after the addition of ascorbic acid and potassium bromate. Calculation of the percentage of dimeric tyrosine showed that less than 0.1% of the tyrosine residues of wheat protein were cross-linked. Therefore, dityrosine residues seem to play only a very minor role in the structure of wheat gluten.     

Direct determination of paclobutrazol residues in pear samples by liquid chromatography-electrospray tandem mass spectrometry

A rapid and sensitive liquid chromatography/electrospray ionization/tandem mass spectrometry (LC-ESI-MS-MS) method has been developed for the determination of the plant growth regulator paclobutrazol in pear samples. Extraction was performed with methanol by using a high-speed blender Ultra-Turrax, and 10 microL of pear extract was directly injected in the LC-ESI-MS-MS system without any previous sample treatment. The highest sensitivity of the method was achieved under MS-MS conditions obtaining a limit of detection of 0.7 microg/kg and a quantification limit of 5 microg/kg, with a run time of only 5.5 min. Recoveries for paclobutrazol from spiked pear samples at 0.005, 0.05, and 0.5 mg/kg were around 82-102% with relative standard deviations between 2 and 7%. The method was applied to real treated and untreated samples of pears, using quality control samples as a evaluation of the method reliability. Two MS-MS transitions were selected, one for quantification (294 > 70) and the other for confirmation of the analyte (296 > 70). All the experiments were performed in compliance with good laboratory practices.     

蜂蜜中26种磺胺及其增效剂类药物残留检测方法研究

利用QuEChERS前处理技术和超高效液相色谱-串联质谱(UHPLC-MS/MS),建立了可同时检测蜂蜜中23种磺胺和3种磺胺增效剂类药物残留的分析方法.蜂蜜样品经水溶解,以乙腈为提取溶剂,提取液经乙二胺-N-丙基硅烷(PSA)和C18固相分散萃取吸附剂净化后,采用多反应监测模式(MRM)进行测定.26种药物在0.5～...     

Determination of alpha-amanitin in serum and liver by multistage linear ion trap mass spectrometry

This paper describes a rapid LC-MS/MS/MS method for the analysis of alpha-amanitin in serum and liver. Serum was initially prepared by precipitation of proteins with acetonitrile and subsequent removal of acetonitrile with methylene chloride. Liver was prepared by homogenization with aqueous acetonitrile and subsequent removal of acetonitrile using methylene chloride. For both matrices, the aqueous phase was then extracted using mixed-mode C18/cation exchange SPE cartridges and analyzed on a linear ion trap LC-MS system. Standards were prepared in extracts of control matrix. Seven replicate fortifications of serum at 0.001 mug/g (1 ng/g) of alpha-amanitin gave a mean recovery of 95% with 8.8% CV (relative standard deviation) and a calculated method detection limit of 0.26 ng/g. Seven replicates of control liver fortified at 1 ng/g gave a mean recovery of 98% with 17% CV and a calculated method detection limit of 0.50 ng/g. This is the first report of a positive mass spectrometric identification and quantitation of alpha-amanitin in serum and liver from suspect human and animal intoxications.     

Determination of olive oil oxidative status by selected ion flow tube mass spectrometry

The emergence of primary and secondary oxidation products in New Zealand extra virgin olive oil during accelerated thermal oxidation was measured and correlated with the concentrations of 13 headspace volatile compounds measured by selected ion flow tube mass spectrometry (SIFT-MS). SIFT-MS is a mass spectrometric technique that permits qualitative and absolute quantitative measurements to be made from whole air, headspace, or breath samples in real-time down to several parts per billion (ppb). It is well-suited to high-throughput analysis of headspace samples. Propanal, hexanal, and acetone were found at high concentrations in a rancid standard oil, while propanal, acetone, and acetic acid showed marked increases with oxidation time for the oils used in this study. A partial least-squares (PLS) regression model was constructed, which allowed the prediction of peroxide values (PV) for three separate oxidized oils. Sensory rancidity was also measured, although the correlations of headspace volatile compounds with sensory rancidity score were less satisfactory, and too few results were available for the construction of a PLS regression model. A fast (approximately 1 min), reliable method for prediction of olive oil PVs by SIFT-MS was developed.     

Speciation of arsenic in different types of nuts by ion chromatography-inductively coupled plasma mass spectrometry

In this work the quantitative determination and analytical speciation of arsenic were undertaken in different types of nuts, randomly purchased from local markets. The hardness of the whole nuts and high lipid content made the preparation of this material difficult for analysis. The lack of sample homogeneity caused irreproducible results. To improve the precision of analysis, arsenic was determined separately in nut oil and in the defatted sample. The lipids were extracted from the ground sample with the two portions of a mixture of chloroform and methanol (2:1). The defatted material was dried and ground again, yielding a fine powder. The nut oil was obtained by combining the two organic extracts and by evaporating the solvents. The two nut fractions were microwave digested, and total arsenic was determined by inductively coupled plasma mass spectrometry (ICP-MS). The results obtained for oils from different types of nuts showed element concentration in the range 2.9-16.9 ng g(-)(1). Lower levels of arsenic were found in defatted material (<0.1 ng g(-)(1) with the exception of Brazil nuts purchased with and without shells, 3.0 and 2.8 ng g(-)(1) respectively). For speciation analysis of arsenic in nut oils, elemental species were extracted from 2 g of oil with 12 mL of chloroform/methanol (2:1) and 8 mL of deionized water. The aqueous layer, containing polar arsenic species, was evaporated and the residue dissolved and analyzed by ion chromatography-ICP-MS. The anion exchange chromatography enabled separation of As(III), dimethylarsinic acid (DMAs(V)), monomethylarsonic acid (MMAs(V)), and As(V) within 8 min. Several types of nuts were analyzed, including walnuts, Brazil nuts, almonds, cashews, pine nuts, peanuts, pistachio nuts, and sunflower seeds. The recovery for the speciation procedure was in the range 72.7-90.6%. The primary species found in the oil extracts were As(III) and As(V). The arsenic concentration levels in these two species were 0.7-12.7 and 0.5-4.3 ng g(-)(1), respectively. The contribution of As in DMAs(V) ranged from 0.1 +/- 0.1 ng g(-)(1) in walnuts to 1.3 +/- 0.3 ng g(-)(1) in pine nuts. MMAs(V) was not detected in almonds, peanuts, pine nuts, sunflower seeds, or walnuts, and the highest concentration was found in pistachio nuts (0.5 +/- 0.2 ng g(-)(1)).     

Determination of 24 pesticide residues in fortified wines by solid-phase microextraction and gas chromatography-tandem mass spectrometry

The present work describes a solid-phase microextraction (SPME) gas chromatography-tandem mass spectrometry (MS/MS) method to quantify 24 pesticides in fortified white wine and fortified red wine. In this study "fortified wine" refers to a wine in which fermentation is arrested before completion by alcohol distillate addition, allowing sugar and alcoholic contents to be higher (around 80-100 g/L total sugars and 19-22% alcohol strength (v/v)). The analytical method showed good linearity, presenting correlation coefficients (R(2)) ≥ 0.989 for all compounds. Limits of detection (LOD) and quantitation (LOQ) in the ranges of 0.05-72.35 and 0.16-219.23 μg/L, respectively, were obtained. LOQs are below the maximum residue levels (MRL) set by European Regulation for grapes. The proposed method was applied to 17 commercial fortified wines. The analyzed pesticides were not detected in the wines tested.     

Analysis of matrix-bound nitrofuran residues in worldwide-originated honeys by isotope dilution high-performance liquid chromatography-tandem mass spectrometry

A sensitive and selective isotope dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESIMS/MS) method is presented for the simultaneous analysis of the metabolites of four nitrofuran veterinary drugs, that is, furazolidone, furaltadone, nitrofurantoin, and nitrofurazone, in honey samples. The method entails a combined hydrolysis of protein-bound drug metabolites and derivatization of the resulting metabolites with 2-nitrobenzaldehyde (NBA) during an overnight incubation, followed by a liquid-liquid extraction and a cleanup on a polymeric solid-phase extraction cartridge. Mass spectral acquisition is carried out in the positive ion mode by applying multiple reaction monitoring (MRM) of three diagnostic transition reactions for each analyte under survey. A reliable quantification is obtained by the use of one deuterated analogue per analyte (NBA-d(4) derivative). The method has been validated in honey according to the European Union criteria for the analysis of veterinary drug residues in food. Expressed in underivatized nitrofuran metabolite concentrations, the decision limits (CCalpha) ranged within 0.07-0.46 microg/kg, and the detection capabilities (CCbeta) were within 0.12-0.56 microg/kg. The method has been successfully applied in a survey of honeys of various geographical origins, showing that furazolidone is the main nitrofuran antibiotic administered to treat bacterial diseases of bees.     

高效液相色谱-串联质谱同时测定有机肥料中9种抗生素药物残留

采用高效液相色谱-串联质谱法(HPLC-MS/MS),同时测定有机肥料中3类9种抗生素(土霉素、四环素、金霉素、强力霉素、青霉素G和普鲁卡因青霉素、磺胺嘧啶、磺胺二甲基嘧啶、磺胺噻唑)残留,对于有机肥料中抗生素残留的快速检测具有重要的意义。样品用Na2EDTA-Mc Ilvaine缓冲液超声振荡提取后,采用固相萃取小柱净化,高效液相色谱-串联质谱法检测,标准曲线外标法定量。采用多反应监测模式检测,除负离子扫描青霉素G外其他均用正离子扫描。方法在0.1、0.5、1.0 mg/kg添加水平下,样品平均回收率为63.1%~93.4%;相对标准偏差为1.7%~9.5%;四环素类药物的方法检出限均可达到0.05 mg/kg,磺胺类和青霉素类药物的检出限可达0.02 mg/kg。本方法简便、快速,重现性良好,可用于有机肥料样品中抗生素残留的快速确证检测。     

Confirmation of levamisole residues in cattle and swine livers by capillary gas chromatography-electron impact mass spectrometry

Capillary gas chromatography-electron impact mass spectrometry is used to confirm the presence of levamisole in cattle and swine livers at the 0.1 ppm tolerance level. Use of a fused silica capillary column from injector to detector solved chromatographic problems encountered with the analyte. Of the mass spectrometric techniques evaluated, electron impact mass spectrometry provided the most satisfactory data for a confirmatory method. Recoveries from swine and cattle livers fortified at 0.1 ppm averaged 74.9 and 72.7%, respectively, indicating potential utility of this methodology as a quantitative method. Apparent levamisole residues in control livers were less than 0.01 ppm.     

Determination of furaltadone and nifursol residues in poultry eggs by liquid chromatography-electrospray ionization tandem mass spectrometry

The use of nitrofurans as veterinary drugs has been banned from intensive animal production in the European Union (EU) since 1993. The objective of the present study was to evaluate the accumulation and depletion of furaltadone and nifursol and their side-chain metabolites 5-methylmorpholino-3-amino-2-oxazolidinone (AMOZ) and 3,5-dinitrosalicylic acid hydrazide (DNSAH) in eggs after administration of therapeutic and subtherapeutic doses of the drugs to laying hens during three consecutive weeks. LC-MS/MS, with positive and negative electrospray ionization methods, was used for the determination of parent compounds and metabolites in yolk and egg white and was validated according to criteria established by Commission Decision 2002/657/EC. The decision limit (CCα) and the detection capability (CCβ) of the analytical methodology for metabolites were 0.1 and 0.5 μg/kg for AMOZ and 0.3 and 0.9 μg/kg for DNSAH, respectively. For the parent compounds, CCα and CCβ were 0.9 and 2.0 μg/kg for furaltadone and 1.3 and 3.1 μg/kg for nifursol, respectively. The data obtained show that the parent compounds are much less persistent than their side-chain metabolites in either yolk or egg white. Between the studied metabolites, AMOZ is the most persistent and could be detected in either yolk or egg white three weeks following withdrawal from treatment.     

液相色谱串联质谱法测定有机肥料中磺胺甲噻二唑 残留量的不确定度评定

依据《有机肥料中19种兽药残留量的测定液相色谱串联质谱法》（GB/T 40462—2021）对有机肥料中磺胺甲噻二唑（SMT）的残留量进行测定,对测量结果进行不确定度评定。不确定度来源包括标准溶液配制、样品制备、测量重复性、回收率及仪器等分量。相对标准不确定度计算结果表明标准曲线拟合、标准物质纯度和标准曲线配制是影响不确定度的主要因素,应在实际试验过程中加以重点关注与控制。在95%置信水平下,取扩展因子k=2,待测肥料样品中最终结果表示为：X(SMT)=(189.82±20.12) mg/kg。