Beyond helium: hydrogen as a carrier gas in multiresidue pesticide analysis in fruits and vegetables by GC-MS/MS.

In this comprehensive study, we evaluated the feasibility of using hydrogen instead of helium as a carrier gas in a GC-MS/MS system for pesticide residue analysis, spanning three matrices: pepper, tomato, and zucchini. Initial assessments focused on the ion source's chemical inertness, employing nitrobenzene as a benchmark to monitor the hydrogenation process. A method with a duration of less than 12 minutes was developed, achieving good chromatographic peak resolution attributable to the enhanced chromatographic performance of hydrogen as a carrier gas. The study emphasized the optimization of system parameters, testing various ion source temperatures, detector voltages, and injection volumes. Sensitivity assessments, based on the DG-SANTE criteria, indicated that the majority of compounds were identifiable at a concentration of 5 µg kg-1 (81% in tomato, 84% in pepper and 73% in zucchini). Detailed validation for reproducibility, matrix effects, and linearity across 150 pesticides unveiled generally favorable outcomes, with a notable majority of compounds displaying low matrix effects, satisfactory linearity ranges and good reproducibility with most compounds returning a relative standard deviation (RSD) below 10%. When applied to 15 real samples, the hydrogen-based system's performance was juxtaposed against a helium-based counterpart, revealing that results are very comparable between both systems. This comparative approach highlights hydrogen's potential as a reliable and efficient carrier gas in pesticide residue analysis for routine food control laboratories, overcoming difficulties resulting from the lack of helium supplies.

Determination of highly polar anionic pesticides in beehive products by hydrophilic interaction liquid chromatography coupled to mass spectrometry.

The analysis of highly polar pesticides is challenging due to their unique physicochemical properties, requiring specialized chromatographic techniques for their accurate and sensitive detection. Furthermore, the high level of co-extracted polar matrix components that can co-elute with the analytes can interfere with the analysis. Consequently, there is lack of pesticide monitoring data, as the European Food Safety Authority has pointed out. This article explores the overcoming of such difficulties in the analysis of these compounds. Analytical methodologies for the extraction, clean-up, and direct determination of 11 highly polar anionic pesticides, including glyphosate, glufosinate, ethephon, fosetyl-aluminium, and their related metabolites in complex food matrices such as honey and pollen by hydrophilic interaction liquid chromatography coupled to tandem mass spectrometry were successfully developed and validated. Solid-phase extraction and micro-solid-phase extraction employing strong anion exchange (SAX) cartridges were implemented for clean-up. The automation and miniaturization of SAX clean-up for these compounds were achieved for the first time. For method validation, SANTE/11312/2021 guideline was followed. Recoveries were between 70 and 120%, with RSDs below 20%. Limits of quantitation ranged from 0.005 to 0.020 mg kg-1. Linearity was evaluated from 0.002 to 0.200 mg kg-1. Matrix effects were assessed, showing medium to low signal suppression for most compounds. AMPA and glufosinate presented the highest signal suppression, but it was reduced after SAX clean-up. Analysis of real honey and pollen samples revealed the occurrence of the studied compounds in beehive products and showed the applicability of the validated methodologies for routine control of these complex samples.

Analysis by LC-MS/MS of polar pesticides in fruits and vegetables using new hybrid stationary phase.

Highly polar pesticides are frequently used in agriculture. However, their physicochemical properties make very difficult the analysis of these compounds following common procedures. Polar pesticides show poor retention and peak shapes in the common stationary phases used for multiresidue methods of pesticides. For this reason, multiple columns with different stationary phases have been developed to perform the analysis of these particular compounds. The column evaluated in this method uses a new hybrid stationary phase with a mixed-mode between hydrophilic interaction liquid chromatography (HILIC) and ion exchange interactions. The retention modes are dependant on mobile phase conditions and can be easily switched. The aim of this study can be summarized in the next bullet points: • Performance evaluation of 10 anionic compounds in different column sizes of the hybrid stationary phase. • Validation of the method in terms of sensitivity, linearity, and matrix effects in four different matrices: tomato, orange, onion and quince. • Improvement of the retention time robustness.

Liquid chromatography versus supercritical fluid chromatography coupled to mass spectrometry: a comparative study of performance for multiresidue analysis of pesticides.

Abundant studies have been published evaluating different parameters of reverse-phase liquid chromatography (LC) and supercritical fluid chromatography (SFC), both coupled to electrospray (ESI)/mass spectrometry (MS) for pesticide residue analysis. However, there is a lack of a comprehensive comparative study that facilitates deep knowledge about the benefits of using each technique. In the present study, the same mass spectrometer was used coupled to both liquid and supercritical fluid chromatographies with a multiresidue method of 215 compounds, for the analysis of pesticide residues in food samples. Through the injection of the spiked extracts, separate experiments were conducted. A study of the optimum ion source temperature using the different chromatography modes was performed. The results were evaluated in terms of sensitivity with tomato, leek, onion, and orange as representative fruit and vegetable matrices. The compounds which reported the highest area values in each chromatography were evaluated through their substance groups and polarity values. The impact of matrix effects obtained in tomato matrix was similar for both cases; however, SFC clearly showed better results in analyzing matrices with a higher number of natural co-extracted compounds. This can be explained by the combination of two effects: (i) chromatography separation and (ii) ion source efficiency. The chromatographic elution presented different profiles of matrix components, which had diverse impact on the coelution with the analytes, being more beneficial when SFC was used in the matrices studied. The data showed that the best results obtained in SFC are also related to a higher ionization efficiency even when the ESI emitter tip was not optimized for SFC flow. In the present study a comprehensive evaluation of the benefits and drawbacks of these chromatography modes for routine pesticide residue analysis related to target compounds/commodities is provided.

Supercritical fluid chromatography separation of chiral pesticides: Unique capabilities to study cyhalothrin and metalaxyl as examples.

Evaluation of chiral pesticides remains a frequently neglected matter in routine food control laboratories. This fact is due to the existence of many residue definitions but also due to the lack of robust instrumental methods for the evaluation of these isomeric compounds. However, supercritical fluid chromatography coupled to mass spectrometry (SFC-ESI-MS/MS) has been demonstrated to perform fast and highly efficient separations without the need to change the mobile phase employed in multiresidue pesticide analyses. Regarding chiral stationary phase columns, the polysaccharide-based ones clearly demonstrate the best separation technology. Two polysaccharide-based columns were tested in this study, and the robustness of their combination with SFC was verified. The enantiomers of lambda-cyhalothrin and metalaxyl were studied precisely due to their markedly distinct toxicity and enantioselectivity. Furthermore, the acute reference dose for gamma-cyhalothrin is half in comparison with its enantiomer (0.0025 and 0.005 mg/kg respectively), which is present in the lambda-cyhalothin residue definition. These enantiomers were analyzed in terms of linearity, reproducibility, and matrix effects in four representative matrices (tomato, orange, leek, and cayenne). Additionally, field tests under greenhouse conditions for these compounds were performed. The results obtained after different sample collections revealed a similar degradation in lambda-cyhalothrin enantiomers (R, S, S, and S, R, R) but not in the case of metalaxyl-M (mefenoxam) where the degradation in tomato was 2 to 6 times less in comparison with its S-enantiomer.

Supercritical Fluid Chromatography and Gas Chromatography Coupled to Tandem Mass Spectrometry for the Analysis of Pyrethroids in Vegetable Matrices: A Comparative Study.

This study describes a comprehensive comparison between supercritical fluid chromatography (SFC) and gas chromatography (GC) coupled to mass spectrometry for the analysis of pyrethroids in vegetable matrices. The ionization process used was electrospray ionization (ESI) in SFC and electron ionization in GC. In general, liquid chromatography coupled to mass spectrometry with ESI sources provides poor results for pyrethroid detection, as described in previous literature. A total of 14 pyrethroids were selected, together with 6 representative matrices. The differences in chromatographic separation and ionization process were assessed. Similar results were obtained in terms of sensitivity (limits of quantification close to 2 µg/kg, injecting the same amount of sample), matrix effect, and linearity. A total of 17 real samples were analyzed by both systems, obtaining similar results. These data suggest that SFC offers a suitable alternative to GC in the analysis of pyrethroids and allows for their inclusion in a wider multiresidue method.

Sensitive Detection of Neonicotinoid Insecticides and Other Selected Pesticides in Pollen and Nectar Using Nanoflow Liquid Chromatography Orbitrap Tandem Mass Spectrometry.

In this work, a new method based on nanoflow LC with high-resolution MS was developed for the determination of eight pesticides in pollen and nectar samples, including neonicotinoid insecticides and other selected pesticides commonly found in bees and beeswax. Detection was undertaken with a hybrid quadrupole-Orbitrap mass spectrometer (Q Exactive™) equipped with a commercial nanospray ion source. The extraction of pesticides from pollen samples was performed by a modified micro-QuEChERS method scaled down to Eppendorf tubes, whereas nectar samples were simply diluted with a water-methanol (95 + 5, v/v) solution. Good linearity (>0.999 in all cases) was obtained between 0.05 and 500 µg/kg and between 0.04 and 400 µg/kg for pollen and nectar, respectively. Recovery rates in pollen ranged from 85 to 97%, with RSDs <12%. Matrix effect was evaluated and showed negligible effects for all studied pesticides. The lowest concentration levels tested and validated were 0.5 and 0.4 µg/kg for pollen and nectar matrixes, respectively. In addition, selected incurred samples were studied, obtaining several positive findings in pollen and nectar samples, demonstrating the sensitivity and applicability of the proposed method.

Coupling Ion Chromatography to Q-Orbitrap for the Fast and Robust Analysis of Anionic Pesticides in Fruits and Vegetables.

Ion chromatography coupled to a quadrupole Orbitrap mass analyzer was used to develop a multiresidue method for the determination of highly polar pesticides and their metabolites (chlorate, perchlorate, fosetyl-aluminum, glyphosate, aminomethylphosphonic acid (AMPA), phosphonic acid, N-acetyl AMPA, and N-acetyl glyphosate) in fruits and vegetables. After extraction with methanol, samples were diluted 5× with water. No derivatization was applied. Pesticides were separated in an anion-exchange column. Water was used as the ion chromatography mobile phase. A gradient was created by increasing the concentration of KOH in the mobile phase. Ion chromatography provided good and stable retention and separation for all studied compounds. All investigated pesticides had an LOQ of 0.01 mg/kg and a linear range of 0.01-0.50 mg/kg. The ion ratio of the m/z ions produced was stable and adequate (deviation <30%) in all cases. The obtained mass errors (always in full-scan MS and MS2 mode) were <0.2 mDa. The high resolution (>100 000) provided by the Orbitrap analyzer with the low m/z ions obtained (e.g., m/z 80) was effective in obtaining low background matrix signals. The influence of postcolumn infusion of organic solvent on sensitivity was investigated. Acetonitrile was found to be more effective than methanol, increasing the sensitivity 3× with respect to water. The method was validated for five vegetable-based matrixes. Both the sample processing and the analytical measurement were very fast. Hence, the methodology is ideal for high-throughput work.

Determination of pesticides in edible oils by liquid chromatography-tandem mass spectrometry employing new generation materials for dispersive solid phase extraction clean-up.

The goal of this work was to evaluate the efficiency of several sorbents on removal fats from edible oils (olive, soya and sunflower) during the clean-up step for posterior determination of 165 pesticides by UHPLC-QqQ-MS/MS system. The extraction procedure employed in this work was the citrate version of QuEChERS method followed by a step of freezing out with dry ice and clean-up evaluation using i) PSA with magnesium sulfate (d-SPE); ii) magnesium sulfate and Z-sep sorbent (d-SPE); iii) Z-sep (column SPE) and iv) Agilent Bond Elut QuEChERS Enhanced Matrix Removal-Lipid (EMR-Lipid). After evaluation of the recovery results at 10, 20 and 50µgkg(-1), the EMR-Lipid showed important advantages comparing to the other sorbents evaluated, such as better recovery rates and RSD%. The method was validated at the three concentrations described above. Analytical curves linearity was evaluated by spiking blank oil samples at 10, 20, 50, 100 and 500µgkg(-1). The method demonstrated good recoveries values between the acceptable range of 70-120% and RSD%<20 for most of evaluated pesticides. In order to evaluate the performance of the method, this same procedure was employed to other oils such as soya and sunflower with very good results.