Nachweis von Organophosphorinsecticiden durch Gas-Chromatographie-Massenspektrometrie

Zusammenfassung Die Elektronenstoß-Massenspektren (EI-MS) von 49 Organophosphorinsecticiden wurden in Gas-Chromatographie-Massenspektrometrie-Kopplung unter Bedingungen gemessen, die denen in der Rückstandsanalyse entsprechen. Die EI-MS der Vertreter der 4 Substanzklassen Dithiophophorsäureester, Thiono- und Thiolphosphorsäureester und Phosphorsäureester wurden in Gruppen nach Dimethyl- und Diäthylester unterteilt. Für diese 8 Substanzgruppen wurden die 5 Ionenm/e 93, 97, 109,121 und 125 als gruppentypisch erkannt. Mit diesen Fragmenten ist eine Zuordnung der Verbindungen zu den einzelnen Gruppen möglich.Zusätzlich zu den gruppentypischen Ionen wurden für alle 49 Pesticide aus den EI-MS substanztypische Ionen ausgewählt, die eine Identifizierung der einzelnen Organophosphorinsecticide in der Rückstandsanalyse ermöglichen. Die Auswahl der substanztypischen Ionen wird diskutiert unter Betonung der Frage, ob in den EI-MS anderer Phoshorpesticide die gleichen Ionen gefunden werden.Für die eindeutige Identifizierung wird die GC-MS-Kopplung mit Einfach- und Mehrfachmassenregistrierung der ausgewählten Ionen unter Berücksichtigung von Retentionszeit und des Phosphornachweises mit dem Alkaliflammenionisationsdetektor vorgeschlagen.

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Detection of organophosphorus insecticides by gas chromatography/mass spectrometry

Summary The Electron impact mass spectra (EI-MS) of 49 organophosphorus insecticides were measured in gc-ms mode under conditions generally used in residue analysis. The EI-MS of compounds of the 4 substance classes phosphorodithioates, phosphorothionates, phosphorothiolates, and phosphates were further divided into the groups of dimethyl esters and diethyl esters. For these 8 substance groups the 5 ions atm/e 93, 97, 109, 121, and 125 were found to be indicative for the corresponding structure. With these 5 fragments individual compounds can be classified into the different structure groups.In addition, to these group typical ions for each of the 49 pesticides a series of ions was selected which are characteristic for each individual pesticide allowing an unequivocal identification of these compounds in residue analysis. The choice of the ions characteristic for individual pesticides is discussed accentuating the question whether the same ions may be found in the EI-MS of other organophosphorus pesticides.As an identification procedure gc-ms with single ion detection and multiple ion detection in combination with the retention time and the positive response of the alkaliflame detector is proposed.

Photokopien der in Tabelle 1 in der Spalte Ref. mit einem + versehenen Massenspektren können vom Autor angefordert werden.     

热解吸低温等离子体质谱技术直接快速筛查蔬菜中的有机磷农药

在传统低温等离子体质谱技术的基础上引入热解吸装置,建立了一种直接快速筛查蔬菜中有机磷农药的新方法。白菜样品经乙腈提取,离心取上清液进行质谱检测,在正离子检测模式下,将承载样品的载玻片置于加热块上进行解吸,被低温等离子体射流离子化后进入质谱检测。结果表明,在优化实验条件下,8种有机磷农药在0.005～0.200 mg/L质量浓度范围内线性良好,相关系数均大于0.99,检出限为0.001～0.010 mg/L,加标回收率为90.5%～119%,相对标准偏差(RSD,n=6)为12%～17%。与无热解吸条件相比,检测灵敏度提高了9.3～41.7倍。该方法操作简单,无复杂的样品前处理,灵敏度高、准确性好,可用于蔬菜中8种有机磷农药残留的同时测定,在大批量样品的非靶向分析中有较大的应用前景。     

Identification tree based on fragmentation rules for structure elucidation of organophosphorus esters by electrospray mass spectrometry

Organophosphorus compounds have played important roles as pesticides, chemical warfare agents and extractors of radioactive material. Structural elucidation of phosphonates poses a particular challenge because their initial forms can be hydrolyzed, thus, degradation products may predominate in samples acquired in the field. The analysis of non‐volatile organophosphorus compounds and their degradation products is possible using electrospray tandem mass spectrometry ESI‐MS/MS. Here, we present a generic strategy that allows the unambiguous identification of substituents for two families of organophosphorus compounds: the phosphonates and phosphates. General fragmentation rules were deduced based on the study of decomposition pathways of 55 organophosphorus esters, including examples found in the literature. Multistage MS (MSⁿ) experiments at high resolution in a hybrid mass spectrometer provide accurate mass measurements, whereas collision‐induced dissociation experiments in a triple quadrupole give access to small fragment ions. The creation of a specific nomenclature for each possible structure of organophosphorus compound, depending on the alkyl side chain linked to the oxygen, was achieved by applying these fragmentation rules. This led to the creation of an ‘identification tree’ based upon the unique consecutive decomposition pathways uncovered for each individual compound. Hence, seven structural motifs were created that orient an unequivocal identification using the ‘identification tree’. Despite the similar structures of the ensemble of phosphate and phosphonate esters, distinct identifications based upon characteristic neutral losses and diagnostic fragment ions were possible in all cases. Copyright © 2013 John Wiley & Sons, Ltd.     

Chemische Ionisations-Massenspektrometrie von Organophosphors?ureinsecticiden mit verschiedenen Reaktantgasen

Zusammenfassung Chemische Ionisations-Massen-spektren (CI-MS) wurden mit einer Kopplung Dünnfilmcapillar-Gas-Chromatographie-Massenspektrometrie von 23 Organophosphorsäurepesticiden mit Isobutan als Reaktantgas gemessen. Alle Substanzen zeigten im CI-MS ein intensives Ion bei M + 1. Die CI-MS der einzelnen Substanzen werden diskutiert und mit Elektronenstoß-MS und CI-MS, die mit Methan oder Methanol als Reaktantgas erhalten wurden, verglichen. Die MS werden beim Übergang von Elektronenstoßionisation zu CI mit den Reaktantgasen Methan, Isobutan und Methanol in dieser Reihenfolge einfacher. Mit Methanol wird nur noch das M + 1-Ion gefunden. Für die praktische Rückstandsanalyse wird Isobutan als Reaktantgas vorgeschlagen.

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Chemical ionization mass spectrometry of organophosphorus pesticides with various reagent gases

Summary Chemical ionization mass spectra (CI-MS) of 23 organophosphorus pesticides with isobutane as reagent gas were obtained by a combination of open tubular column gas chromatography-mass spectrometry. All substances show intense M + 1 ions in the CI-MS. The CI-MS of the individual substances obtained with isobutane were discussed and compared with their electron impact mass spectra (EI-MS) and CI-MS obtained with methane or methanol as reagent gases. The spectra became simpler applying CI-MS instead of EI-MS. In CI-MS the extent of fragmentation decreased changing the reagent gas from methane to isobutane and methanol. With methanol, usually only the M + 1 ion was observed in the spectra. For routine residue analysis, isobutane as reagent gas is recommended.

     

Direct determination of alkyl phosphates in human urine by liquid chromatography/electrospray tandem mass spectrometry

A novel and rapid procedure based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the determination of dialkyl phosphates (metabolites of organophosphorus pesticides) in human urine has been developed. After addition of 40 mM tetrabutylammonium acetate, 10 microL of urine sample were directly injected into the LC/MS/MS system. The method was validated yielding calibration curves with correlation coefficients greater than 0.997 and repeatability coefficient of variation (CV) lower than 9%. The accuracy and precision were evaluated by direct injection of spiked samples at 10 and 100 microg/L obtaining recoveries between 78 and 119% with coefficients of variation below 12%. Limits of detection of 1 microg/L for diethyl phosphate (DEP), diethylthiophosphate (DETP) and diethyldithiophosphate (DEDTP) and 2 microg/L for dimethyldithiophosphate (DMDTP) were achieved, all the analytes being detected in negative ion mode. The fragmentation pathway of dialkyl phosphates allowed us the use of an additional transition for confirmation in order to improve their identification in real-world samples. The applicability of the LC/MS/MS method was demonstrated by applying it to the analysis of urine samples of farmers exposed to the organophosphorus pesticide chlorpyrifos. Good correlation between application of the product in the field (citrus orchards), concentration levels of dialkyl phosphates and levels of the chlorpyrifos-specific metabolite (1,3,5-trichloro-2-pyridinol) was obtained.     

Felddesorptions-Massenspektrometrie von Biociden des Phenylharnstoff-, Carbamat- und Thiocarbamattyps

Zusammenfassung Das Verhalten von Herbiciden und Insecticiden aus den Verbindungsklassen der Phenylharnstoffe und Carbamate in der Felddesorptions-Massenspektrometrie wurde untersucht. Die erhaltenen Spektren zeichnen sich durch hohe Molekülionenintensitäten und ein charakteristisches Fragmentierungsverhalten aus. Im Hinblick auf die Identifizierung der Biocide in Umweltproben (z. B. aus Gewässern) wurden die Nachweisgrenzen für Standardverbindungen und Testgemische ermittelt. Die günstigsten methodischen Voraussetzungen für die niedrig- und hochauflösende Felddesorptions-Massenspektrometrie in der Spurenanalyse dieser Verbindungen werden beschrieben. Beim elektrischen Nachweis ergibt sich aus der Akkumulierung der FD-Massenspektren mit einem Vielkanalanalysator und der damit erreichbaren Aufzeichnung der Isotopenverteilung eine weitere Information für die Zuverlässigkeit des Nachweises.

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Field desorption mass spectrometry of biocides of the phenylurea and carbamate type

Summary Herbicides, insecticides and fungicides of the phenylurea, carbamate-, and thiocarbamate type have been investigated by field desorption mass spectrometry. The spectra obtained show high molecular ion intensities and a characteristic fragmentation pattern. In view of the identification of these biocides in environmental samples (e.g. from surface water) the limits of detection for standard compounds and test mixtures were evaluated. The optimal methodological parameters for trace analyses of these compounds in low and high resolution field desorption mass spectrometry are described. For electrical detection the accumulation of the spectra with a multichannel analyser and the thus available registration of the isotopical distribution of the molecular ions yield an additional information which further improves the reliability of the identification of environmental chemicals.

     

Screening organophosphorus nerve agent degradation products in pesticide mixtures by GC-ICPMS

Gas chromatography inductively coupled plasma mass spectrometry (GC-ICPMS) was utilized for the analysis of four organophosphorus nerve agent degradation products in the presence of mixtures of common organophosphorus pesticides. The first degradation products of sarin (isopropyl methylphosphonic acid, GB acid), cyclosarin (cyclohexyl methylphosphonic acid, GF acid), and soman (pinacolyl methylphosphonic acid) as well as their common final hydrolysis product methyl phosphonic acid were utilized throughout these experiments. Due to the non-volatile nature of these alkyl phosphonic acid degradation products, derivatization was performed to generate the volatile tert-butyl dimethylsilyl species. Degraded organophosphorus pesticide standards were obtained for acephate, chlorpyrifos, dichlorvos, ethion, and parathion ethyl. Mixtures consisting of three pesticides in the presence of a single nerve agent degradation product were prepared. GC-ICPMS allowed for the separation and detection of all four degradation products in the presence of pesticide mixtures in just over 12 minutes. This is the first study analyzing pesticides as interfering species for analysis of nerve agent degradation products by GC-ICPMS.     

Tip-assisted ambient electric arc ionization mass spectrometry for rapid detection of trace organophosphorus pesticides in strawberry

In this study, an ambient mass spectrometry (AMS) based method was developed for rapid detection of organophosphorus pesticides in strawberry. This method combines an electric arc and a microsyringe tip to realize tip-assisted ambient electric arc ionization (TAAEAI). A high-voltage electric arc can be applied to the microsyringe tip to generate an electric field, which results in corona discharge at the microsyringe tip. The juiced strawberry sample loaded on the tip could be directly ionized with TAAEAI and then analyzed by a mass spectrometer. TAAEAI-MS was successfully applied to analyze 6 organophosphorus pesticides in three strawberry samples. Malathion and profenofos were detected from the investigated strawberry samples. This method could quantitatively determine the contents of organophosphorus pesticides in strawberry with high reproducibility, high precision, and high sensitivity. Sample matrices did not interfere with the pesticide analysis. The recoveries of organophosphorus pesticides spiked in strawberry samples varied between 82.6% and 116% with relative standard deviations (RSDs) less than 9.2%. The limits of detection (LODs) varied between 0.0124 µg/g and 0.0245 µg/g, while the limits of quantification (LOQs) varied between 0.0413 µg/g and 0.0817 µg/g. The coefficients of determination (R²) of the method were determined to be >0.995. The method established here may have potential application in the detection of organophosphorus pesticides in vegetables and fruits.     

Field desorption mass spectra of phthalocyanines

Mass spectr of phthalocyanines are readily obtainable by field desorption mass spectrometry. Molecular ions are normally the base peaks in the spectra and minimal fragmentation is observed. The technique provides a rapid method for the qualitative exmination of mixtures of phthalocyanines.     

Detecting trace pesticides in real time using single particle aerosol mass spectrometry

Pesticides are toxic substances and may cause unintentional harm if improperly used. The ubiquitous nature of pesticides, with frequent use in agriculture and the household, and the potential for harm that pesticides pose to non-target organisms such as wildlife, humans, and pets, demonstrate the need for rapid and effective detection and identification of these compounds. In this study, single particle aerosol mass spectrometry (SPAMS) was used to rapidly detect compounds from four classes of pesticides commonly used in agricultural and household applications. These include permethrin (pyrethroid class), malathion and dichlorvos (organophosphate class), imidacloprid (chloronicotinyl class), and carbaryl (carbamate class). Analytical standards of each compound were diluted and aerosolized using a nebulizer to create particles for analysis in the SPAMS instrument. The resultant dual-polarity time-of-flight mass spectra were then analyzed to identify the characteristic peaks of the compound in each sample. In addition, samples of commercial products containing pesticides, a commercial insecticide spray, containing permethrin, and a canine flea collar, containing carbaryl, were analyzed in their original form using SPAMS without any significant sample preparation. The characteristic mass spectral peaks of the active pesticides in these samples were identified using the mass spectra obtained earlier from the pesticide analytical standards. By successfully identifying pesticides in analytical standards and in commercial products, it is demonstrated herein that the SPAMS system may be capable of pesticide detection in numerous environmental and agricultural situations.     

High-resolution field desorption mass spectrometry: Part VII. Explosives and Explosive Mixtures4

Standard explosives and technical mixtures of explosives have been investigated by field desorption mass spectrometry. The compounds investigated gave intense molecular ions or protonated molecules and structurally significant fragmentation. For comparison, the corresponding electron impact and chemical ionization mass spectrometry data are reported. Emission-controlled field desorption, photographic detection, and accurate mass measurements enabled the components of the technical mixtures to be identified. An example of the determination of an additive in a technical product by field desorption mass spectrometry and stable isotope dilution is given. The use of these techniques for quality control of explosives and for forensic investigations appears to be promising.     

Gas chromatographic determination of pesticides in vegetable samples by sequential positive and negative chemical ionization and tandem mass spectrometric fragmentation using an ion trap analyser

A selective and sensitive chromatographic method is described for the determination of nine organochlorine and organophosphorus pesticides in vegetable samples by gas chromatography-mass spectrometry. The proposed method combines the use of positive and negative chemical ionisation and tandem mass spectrometric fragmentation, resulting in a significant increase in selectivity and allowing the simultaneous confirmation and quantification of trace levels of pesticides in complex vegetable matrices. Parameters relative to ionisation and fragmentation processes were optimised to obtain maximum sensitivity. Repeatability and reproducibility studies yielded relative standard deviations lower than 25% in all cases. Identification criteria, such as retention time and relative abundance of characteristic product ions, were also evaluated in order to guarantee the correct identification of the target compounds. The method was applied to real vegetable samples to demonstrate its use in routine analysis.     

Gas‐phase copper and silver complexes with phosphorothioate and phosphorodithioate pesticides investigated using electrospray ionization mass spectrometry

Efforts to improve agricultural productivity have led to a growing dependency on organophosphorus pesticides. Phosphorothioate and phosphorodithioate pesticides are organophosphorus pesticide subclasses with widespread application for the control of insects feeding on vegetables and fruits. However, even low doses of these pesticides can cause neurological problems in humans; thus, their determination and monitoring in agricultural foodstuffs is important for human health. Phosphorothioate and phosphorodithioate pesticides may be poorly ionized during electrospray, adversely affecting limits of detection. These pesticides can form complexes with Cu²⁺ and Ag⁺, however, potentially improving ionization. In the present work, we used electrospray ionization/mass spectrometry (ESI/MS) to study fenitrothion, parathion, diazinon, and malathion coordination complexes with silver and copper ions. Stable 1 : 1 and 1 : 2 metal/pesticide complexes were detected. Mass spectra acquired from pesticide solutions containing Ag⁺ or Cu²⁺ showed a significant increase in signal‐to‐background ratio over those acquired from solutions containing only the pesticides, with Ag⁺ improving detection more effectively than Cu²⁺. Addition of Ag⁺ to a pesticide solution improved the limit of detection by ten times. The relative affinity of each pesticide for Ag⁺ was related to complex stability, following the order diazinon > malathion > fenitrothion > parathion. The formation of Ag⁺–pesticide complexes can significantly improve the detection of phosphorothioate and phosphorodithioate pesticides using ESI/MS. The technique could potentially be used in reactive desorption electrospray ionization/mass spectrometry to detect phosphorothioate and phosphorodithioate pesticides on fruit and vegetable skins. Copyright © 2015 John Wiley & Sons, Ltd.     

Multiple-stage mass spectrometry analysis of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether and their derivatives

The fragmentation of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE) and their derivatives was studied by electrospray ionization tandem mass spectrometry. Multiple-stage mass spectrometry and accurate mass measurements were combined to establish the fragmentation pathways. BADGEs and BFDGEs tend to form ammonium adducts under electrospray conditions which fragmented easily. The fragmentation of [M+NH(4)](+) for BADGEs started with the cleavage of the phenyl-alkyl bond, which was followed by the α-cleavage of the ether group to generate the characteristic product ions at m/z 135, [C(9)H(11)O](+), and m/z 107, [C(7)H(7)O](+). The fragmentation of the BFDGE isomer mixtures was studied by on-line reversed-phase liquid chromatography coupled to multiple-stage mass spectrometry (LC/MS(n)). Information obtained from product ion spectra for each BFDGE isomer and its comparison with the fragmentation pathway of BADGE allowed each isomer and the chromatographic elution order to be identified.     

陈皮中农药残留分析及风险评估研究

通过分析中药陈皮的农药残留问题开展风险评估研究。采用气相色谱-串联质谱(GC-MS/MS)和高效液相色谱-串联质谱(HPLC-MS/MS)对198批陈皮中的117种农药进行检测;采用点评估方式计算陈皮中农药残留的急性和慢性摄入风险;采用英国兽药残留委员会提出的兽药残留风险排序矩阵计算各农药的风险得分;采用危害指数(HI)法计算有机磷农药的慢性累积风险。198批陈皮中共检出30种农药(含13种禁用农药),总检出率为98.5%,农药检出量为0.001~11.7 mg/kg。检出农药的慢性膳食摄入风险(%ADI)为0.003%~3.142%,急性膳食摄入风险(%ARfD)为0.022%~26.667%,风险均远低于100%,表明陈皮中农药的膳食暴露风险处于较低水平。6种有机磷农药的慢性累积暴露危害指数为0.942,略小于1,表明风险虽可控但需要关注。风险排序结果表明,陈皮中有16种为中高风险农药,应在生产和安全监管中重点关注。     

表面解吸化学电离质谱法快速检测蔬菜中痕量氨基甲酸酯

采用自行研制的表面解吸常压化学电离源（SDAPCI）,首次在无需样品预处理的前提下用质谱法直接测定了多种蔬菜表面残留的痕量氨基甲酸酯,并用串联质谱对所获得的不同氨基甲酸酯农药的离子进行了结构鉴定,排除了检测结果的假阳性。该方法对待测样品无污染,方法检测限低于10－14g/cm2,单个样品的测定时间平均少于1 s,特别适合于对批量样品进行快速检测。     

Rapid identification of pesticides in human oral fluid for emergency management by thermal desorption electrospray ionization/mass spectrometry

Self‐poisoning with pesticides accounts for approximately one‐third of all suicides worldwide. To expedite rescue in the emergency department, it is essential to develop a point‐of‐care analytical method for rapid identification of ingested pesticides. In this study, five of the most common pesticides ingested by self‐poisoning patients in Taiwan were analyzed from oral fluid samples. Pesticide‐oral fluid mixtures were applied on a cotton swab and then transferred into methanol. A metallic probe was used to sample the methanol solution for subsequent thermal desorption‐electrospray ionization mass spectrometry analysis. Altogether, pesticide sampling, transfer, desorption, ionization, and detection took less than 1 min. The reproducibility of this method (n = 6) was shown in the observed low‐relative standard deviation (<7%) in the detection of pesticide in oral fluid. The detection limits of the pesticides in oral fluid obtained from four human subjects by thermal desorption‐electrospray ionization mass spectrometry were between 1–10 ppb with relative standard deviation 10.7%. Moreover, in this study, linear responses of five pesticides in oral fluid with concentrations between 1 ppb–1 ppm (R2 between 0.9938 and 0.9988) were observed. As the whole analytical process is extremely short, this technique allows for early non‐invasive point‐of‐care identification of pesticides in the oral fluid of self‐poisoning patients in the emergency room, providing important toxicological information for decision‐making during critical resuscitation. Copyright © 2016 John Wiley & Sons, Ltd.     

Applications of high-pressure liquid chromatography and field desorption mass spectrometry in studies of natural porphyrins and chlorophyll derivatives.

Mixtures of porphyrins derived from natural sources can be readily separated by high-pressure liquid chromatography both analytically and on a preparative scale. A variety of procedures have been developed not only for the esters but also for free acids, and on the analytical scale quantitation is easily achieved by visible absorption. The retention times are largely characteristic of the number of carboxylic acid side chains (or other polar groups) but further information can be obtained by mass spectrometric studies of the various fractions. Field desorption mass spectrometry is particularly useful for this purpose because the emitter wire can be dipped directly into the eluates. The field desorption spectra of porphyrin free acids and esters as well as their metal complexes give essentially molecular ions with little or no fragmentation in most cases, whereas electron-impact mass spectrometry, particularly of free acids, is impeded by the low volatility of porphyrins. Mixtures can also be analysed by field desorption mass spectrometry, and this provides not only a rapid qualitative assessment of the components of a mixture, but also a check on the subsequent chromatographic separations.     

Laser Mass Spectrometry of Organophosphorus Pesticides and Related Compounds

Abstract

Laser mass spectra obtained for 20 organophosphorus (OP) compounds were systematically evaluated for groups containing analogous structural features. Variations in fragmentation can be understood based on simple organic reactions. While detailed mechanistic interpretations of the laser mass spectra (LMS) were not possible, the qualitative features in the LMS obtained from five compounds, not in the original set, could be predicted based on the characteristics of the other OP compounds studied. The success of the prediction lends credence to the qualitative models developed for rationalizing the LMS. A specific feature in the LMS of aromatic thionophosphates is a thiono-thiolo rearrangement. Detailed investigation into the phenomena involved comparison of LMS obtained from aromatic thionophosphates with spectra from electron impact, chemical ionization, field desorption, and secondary ion mass spectrometry. These results led to the conclusion that the rearrangement in laser mass spectrometry must occur during volatilization while the molecule/ion is in the “cloud” present immediately above the laser impact area.     

Analysis of amino acid mixtures by plasma desorption mass spectrometry

Plasma desorption mass spectrometry (PDMS) was investigated as a means of analysing mixtures of three, four and five amino acids in both positive- and negative-ion modes. Fifteen mixtures were tested; each mixture contained equimolar amounts of selected amino acids. The PD mass spectra exhibited MH⁺ and [M – H]^? molecular ions for all the aminoacids with different desorption–ionization yields. The spectra were more easily interpreted in the negative- than the positive-ion mode. The desorption order of the amino acids was progressively established by comparing the molecular ion desorption–ionization yields for each mixture. This desorption order was well correlated in both the positive- and negation-ion modes with the acid–base thermodynamic data for the amino acids in the gas phase. This observation gives some insight into the desorption–ionization mechanisms under PDMS conditions.