Application of Liquid Chromatography‐Time‐of‐Flight‐Mass Spectrometry for the Analysis of Urea Herbicides Residues in Soybean

Gas chromatography-isotope dilution mass spectrometry method validation for target pesticides in soybeans

The production of certified reference materials requires the application of highly accurate methods for characterisation. A gas chromatography-isotope dilution mass spectrometry method, setting ambitious performance criteria, was developed for eight selected pesticides in soybeans. Pressurised liquid extraction was followed by automated gel-permeation chromatography and solid-phase extraction clean-up. Pesticides identification respected a Commission Decision and guidelines of the Directorate General for Health and Food Safety (DG SANTE). Reliable quantification involved stable isotopically labelled analogues as internal standards. Validation, according to ISO/IEC 17,025 and DG SANTE guidelines, assessed linearity, LOD/LOQ, trueness, selectivity, precision, stability and robustness. Mean recoveries ranges (83-109%, relative standard deviations < 3%), repeatability (2.2-4.8%), day-to-day variation (0.6-4.2%) and combined uncertainty (1.2-4.2%) were fit for purpose. The method is highly accurate and suitable for certification of the selected pesticides in soybean matrix reference material. Chemical compounds studied in this article: Diazinon (PubChem CID: 3017); malathion (PubChem CID: 4004); chlorpyrifos (PubChem CID: 2730); captan (PubChem CID: 8606); endosulfan (PubChem CID: 3224); tebuconazole (PubChem CID: 86,102); iprodione (PubChem CID: 37,517); cypermethrin (PubChem CID: 2912).

Matrix solid-phase dispersion coupled with magnetic ionic liquid dispersive liquid-liquid microextraction for the determination of triazine herbicides in oilseeds

A novel method was developed for the determination of six triazine herbicides from oilseeds by matrix solid-phase dispersion combined with magnetic ionic liquid dispersive liquid-liquid microextraction (MSPD-MIL-DLLME), followed by ultrafast liquid chromatography with ultraviolet detection (UFLC-UV). The MIL, 1-butyl-3-methylimidazolium tetrachloroferrate ([C4mim][FeCl4]), was used as the microextraction solvent to simplify the extraction procedure by magnetic separation. The effects of several important experimental parameters, including type of dispersant, ratio of sample to dispersant, type and volume of collected elution solvent, type and volume of MIL, were investigated. Using the present method, UFLC-UV gave the limits of detection (LODs) of 1.20-2.72 ng g(-1) and the limits of quantification (LOQs) of 3.99-9.06 ng g(-1) for triazine herbicides. The recoveries were ranged from 82.9 to 113.7% and the relative standard deviations (RSDs) were equal or lower than 7.7%. The present method is easy-to-use and effective for extraction of triazine herbicides from oilseeds and shows the potentials of practical applications in the treatment of the fatty solid samples.

Chromatography and high-resolution mass spectrometry for the characterization of the degradation products of the photodegradation of amidosulfuron: an analytical approach

Simulated sunlight irradiation causing degradation of amidosulfuron, a pyrimidinylsulfonylurea herbicide, has been investigated in aqueous solution. The main degradation products were followed up by ultrahigh-pressure liquid chromatography with a UV detector (UHPLC-UV) and identified by combining ultrahigh-pressure liquid chromatography-mass spectrometry (UHPLC-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). On the basis of the retrosynthetic analysis, the most identified degradation products were mainly due to the losses of methylsulfamic acid (CH₅NO₃S), sulfocarbamic acid (CH₃NO₅S), carbamic acid (CH₃NO₂), methyl(methylsulfonyl)sulfamic acid (C₂H₇NO₅S₂), N-methylmethanesulfonamide (C₂H₇NO₂S), and sulfonic acid (H₂SO₄) molecules. Accordingly, O and S-demethylation as well as hydroxylation processes were also observed. Sum formulas of the main degradation products were assigned, and a mechanical pathway is proposed.

Current mass spectrometry strategies for the analysis of pesticides and their metabolites in food and water matrices

Analysis of pesticides and their metabolites in food and water matrices continues to be an active research area closely related to food safety and environmental issues. This review discusses the most widely applied mass spectrometric (MS) approaches to pesticide residues analysis over the last few years. The main techniques for sample preparation remain solvent extraction and solid-phase extraction. The QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) approach is being increasingly used for the development of multi-class pesticide residues methods in various sample matrices. MS detectors-triple quadrupole (QqQ), ion-trap (IT), quadrupole linear ion trap (QqLIT), time-of-flight (TOF), and quadrupole time-of-flight (QqTOF)-have been established as powerful analytical tools sharing a primary role in the detection/quantification and/or identification/confirmation of pesticides and their metabolites. Recent developments in analytical instrumentation have enabled coupling of ultra-performance liquid chromatography (UPLC) and fast gas chromatography (GC) with MS detectors, and faster analysis for a greater number of pesticides. The newly developed "ambient-ionization" MS techniques (e.g., desorption electrospray ionization, DESI, and direct analysis in real time, DART) hyphenated with high-resolution MS platforms without liquid chromatography separation, and sometimes with minimum pre-treatment, have shown potential for pesticide residue screening. The recently introduced Orbitrap mass spectrometers can provide high resolving power and mass accuracy, to tackle complex analytical problems involved in pesticide residue analysis.

Mass spectrometry of the photolysis of sulfonylurea herbicides in Prairie waters

This review of mass spectrometry of sulfonylurea herbicides includes a focus on studies relevant to Canadian Prairie waters. Emphasis is given to data gaps in the literature for the rates of photolysis of selected sulfonylurea herbicides in different water matrices. Specifically, results are evaluated for positive ion electrospray tandem mass spectrometry with liquid chromatography separation for the study of the photolysis of chlorsulfuron, tribenuron-methyl, thifensulfuron-methyl, metsulfuron-methyl, and ethametsulfuron-methyl. LC-MS/MS is shown to be the method of choice for the quantification of sulfonylurea herbicides with instrumental detection limits ranging from 1.3 to 7.2 pg (on-column). Tandem mass spectrometry coupled with the use of authentic standards likewise has proven to be well suited for the identification of transformation products. To date, however, the power of time-of-flight MS and ultrahigh resolution MS has not been exploited fully for the identification of unknown photolysis products. Dissipation of the herbicides under natural sunlight fit pseudo-first-order kinetics with half-life values ranging from 4.4 to 99 days. For simulated sunlight, radiation wavelengths shorter than 400 nm are required to induce significant photolytic reactions. The correlation between field dissipation studies and laboratory photolysis experiments suggests that photolysis is a major pathway for the dissipation of some sulfonylurea herbicides in natural Prairie waters.