Clean-up of cereal extracts for gas chromatography–tandem quadrupole mass spectrometry pesticide residues analysis using primary secondary amine and C18

Residue behavior and efficacy of benzothiazole in grains under different fumigation conditions

BACKGROUND

Benzothiazole is a potential grain fumigant for Tribolium castaneum. However, its safety profile and suitable fumigation conditions remain unknown. We therefore investigated the insecticidal efficacy, accumulation and dissipation of benzothiazole in grains (wheat, corn and rice) under different temperatures.

RESULTS

We established a universal detection method (modified QuEChERS coupled with GC-MS/MS) of benzothiazole residues in three grains, which provided high linearity (R2  > 0.999), sensitivity (limits of detection = 0.001 mg/kg, limits of quantification = 0.002-0.005 mg/kg), accuracy (recoveries = 88.18-118.75%) and precision (relative standard deviations < 4.78%). The insecticidal efficacy order of benzothiazole was 30 ≥ 10 > 20 °C and corn > wheat > rice. Temperature positively affected the accumulation/dissipation rate of benzothiazole. Rice was the most easily accumulated and dissipated grain for benzothiazole residues, while corn accumulated benzothiazole more than wheat but less than rice, with dissipation slower than wheat and rice.

CONCLUSION

Our results provide important references for the application of benzothiazole and other fumigants. © 2023 Society of Chemical Industry.

Development of a colloidal gold immunochromatographic test strip for the rapid detection of iprodione

Iprodione is a dicarboximide fungicide that is widely used in agriculture around the world. A reliable and rapid detection method is needed for the on-site monitoring of iprodione residues in a variety of agricultural products. Herein, a colloidal gold immunochromatographic test strip was developed based on a selected coating antigen and a specific monoclonal antibody against iprodione. The particle size of colloidal gold, the preparation technique of the conjugate pad, the composition of the loading buffer, and the extraction solvent were comprehensively optimized for the test strip. A cut-off value of 0.9 mg kg^-1 (50 ng mL^-1) and a visual limit of detection of 0.09 mg kg^-1 (5 ng mL^-1) were achieved in a complex matrix of tobacco. No cross-reactivity was observed for iprodione metabolite and four other widely used pesticides during tobacco growth. Furthermore, the developed colloidal gold immunochromatographic test strip was applied to determine iprodione residues in tobacco samples, and the obtained results were in good agreement with those obtained by liquid chromatography tandem mass spectrometry. Additionally, the test strip was found to be stable afterlong-term storage at 37 °C for two months. The developed colloidal gold immunochromatographic test strip showed excellent accuracy, sensitivity, specificity, and stability, therefore, it is suitable for the rapid detection of iprodione residues in complex matrices.

Validation of a Multi-Residue Analysis Method for 287 Pesticides in Citrus Fruits Mandarin Orange and Grapefruit Using Liquid Chromatography-Tandem Mass Spectrometry

Since the introduction of the positive list system (PLS) for agricultural products in the Republic of Korea, the demand for a quick, easy multi-residue analysis method increased continuously. Herein, the quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique combined with liquid chromatography−tandem mass spectrometry was employed to optimize a method for the multi-residue analysis of 287 pesticide residues in mandarin orange and grapefruit. Method validation was conducted in terms of selectivity, limit of quantitation (LOQ), linearity, accuracy, precision, and matrix effect. All the compounds at low spiking levels (1, 2.5, 5, or 10 mg/kg) could be quantified at LOQs lower than 0.01 mg/kg (PLS level). The linearity of the matrix-matched calibration curve for each compound is in the range 0.5−50 μg/L, and its coefficient of determination (R2) is >0.990. Satisfactory recovery values of 70−120% with a relative standard deviation of ≤20% are obtained for all compounds in the mandarin orange and grapefruit samples. A negligible matrix effect (−20−20%) is observed for more than 94.8% and 85.4% of the pesticides in mandarin orange and grapefruit, respectively. Therefore, this analytical method can contribute to pesticide residue analyses of citrus fruits for routine laboratory testing.

Rapid Simultaneous Determination of 43 Pesticide Residues in Schizonepeta tenuifolia by Gas Chromatography Mass Spectrometry

A simple, fast, and reliable method was established for simultaneous determination of 43 pesticides in Schizonepeta tenuifolia. The samples were prepared using solid-phase extraction (SPE) method. Pesticides were extracted from Schizonepeta tenuifolia using acetonitrile, cleaned with Pesticarb/NH₂, and eluted by mixed solvents of acetonitrile and toluene (3 : 1, v/v). Selected pesticides were identified using DB-35MS capillary column and detected by gas chromatography mass spectrometry. Samples were quantified by external standard method. Recoveries for the majority of pesticides at spike levels of 0.2, 0.5, and 1 mg kg⁻¹ ranged between 70 and 120% (except for Chlorothalonil, Thiamethoxam, and Dicofol), and the relative standard deviations (RSDs n = 6) were 1.32%–13.91%. Limits of detection (LODs) were 0.0011–0.0135 mg kg⁻¹, whereas limits of quantification (LOQs) were 0.0038–0.0451 mg kg⁻¹. The satisfactory accuracy and precision, in combination with a good separation and few interferences, have demonstrated the strong potential of this technique for its application in Schizonepeta tenuifolia analysis.

Determination of Avermectins Residues in Soybean, Bean, and Maize Using a QuEChERS-Based Method and Ultra-High-Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry

Soybean, maize, and bean are crops of great economic importance, but in recent years have suffered with infestations of the caterpillar Helicoverpa armigera, with the main reason being the resistance of this pest to most pesticides. Avermectin emamectin benzoate was recently released to control this pest. Other avermectins, like abamectin, doramectin, eprinomectin, and ivermectin are used in large scale because they potent acaricidal, anthelmintic, and insecticidal activities. Thus, a simple and fast method for the determination of avermectins in these crops based on a quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction procedure and ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) analysis was developed and validated. For extraction, water followed by acetonitrile:isopropanol and a partition step with salts was stablished. With the clean-up step using activated EMR-Lipid, limits of detection of 1.2 μg kg−1 for abamectin, doramectin, emamectin benzoate, and ivermectin, and of 2.4 μg kg−1 for eprinomectin were achieved. The validation showed satisfactory results and the method was successfully applied to commercial samples, indicating that it is suitable for routine analysis.

Evaluation of the automated micro-solid phase extraction clean-up system for the analysis of pesticide residues in cereals by gas chromatography-Orbitrap mass spectrometry

Food analysis is a tremendously broad field that is constantly evolving. New methods have emerged to increase productivity, such as modern miniaturized and robotic analytical techniques. In this paper, a micro-solid-phase extraction system (µ-SPE) for clean-up was combined with a robotic autosampler to yield ready-to-analyze extracts. The system was evaluated for its applicability in routine laboratories. The new, automated, high-throughput µ-SPE clean-up method was applied to acetonitrile extracts and was developed for the analysis of pesticide residues in cereals by gas chromatography-Orbitrap mass spectrometry (GC-Orbitrap-MS). The µ-SPE clean-up efficiency was demonstrated in the removal of matrix-interfering components and in the recovery of pesticides. The sorbent bed mixture consisted of magnesium sulfate, primary-secondary amine, C₁₈, and CarbonX, and effectively retained matrix components without loss of target analytes. Analysis of five types of cereals (barley, oat, rice, rye, and wheat) by GC-Orbitrap-MS showed that the method removed more than 70% of matrix components. The clean-up method was validated for 170 pesticides in rye, 159 pesticides in wheat, 142 pesticides in barley, 130 pesticides in oat, and 127 pesticides in rice. Spike recovery values were 70-120% for all pesticides and the repeatability, calculated as the relative standard deviation, was less than 20%. The limits of quantitation achieved were 0.005 mg kg^-1 for almost all analytes, ensuring compliance with the maximum residue limits.

Residual behavior of the potential grain fumigant 1-octen-3-ol in wheat during fumigation and ventilation processes

BACKGROUND

Our previous works indicated that 1-octen-3-ol has promising potential as an alternative grain fumigant. However, aside from its insecticidal efficacy, the presence of 1-octen-3-ol residues in grains must be investigated to assess its food safety profile.

RESULTS

A convenient and sensitive QuEChERS based GC-MS/MS method was developed to detect residues of 1-octen-3-ol in wheat. The sample pretreatment procedures were optimized. The developed method showed good linearity (R²  = 0.9999) and negligible matrix effects. The limit of detection (LOD) and limit of quantification (LOQ) for 1-octen-3-ol were 0.003 and 0.01 mg kg^-1 , respectively. Recoveries at spiked concentration levels of 0.01, 0.5, 10, 100 and 200 mg kg^-1 ranged from 90.8% to 112.4%, with relative standard deviations (RSDs, n = 5) ranged from 1.2 to 7.5%. In the fumigation process during wheat storage, there were positive correlations between the accumulation rate and fumigation concentration as well as between the accumulation amounts and fumigation time. In the ventilation process, temperature significantly affected the dissipation dynamics of 1-octen-3-ol in wheat, and the t_1/2 values at ventilation temperatures of 30 and 5 °C for 0.1 μL mL^-1 were 0.16 and 21.80 days, respectively, representing a 136-fold difference.

CONCLUSION

Preservers can regulate the ventilation temperature to achieve different goals, with either a long duration period for long-term storage or rapid dissipation for quick food consumption. This study provides guidance on the reasonable usage of 1-octen-3-ol on wheat and other stored grains. © 2021 Society of Chemical Industry.

Uptake and Translocation of Triflumezopyrim in Rice Plants

A new type of mesoionic insecticide triflumezopyrim is mainly used to control rice planthoppers, leafhoppers, etc. In order to study the uptake and translocation characteristics of this new insecticide in rice (Oryza sativa), a method for the detection of triflumezopyrim in rice, soil, and water was established using liquid-liquid extraction and QuEChERS sample pretreatment combined with liquid chromatography-triple quadrupole tandem mass spectrometry. The distribution of triflumezopyrim in rice was investigated after hydroponic treatment and foliar treatment at the concentrations of 2.5 and 5 mg·L^-1 within the ranges of 24, 48, and 72 h. The results showed that triflumezopyrim could be absorbed by roots and form a systematic distribution in rice by hydroponic treatment; meanwhile, it could also be absorbed by leaves and transported to the bottom leaves under foliar treatment, but no triflumezopyrim was detected in the roots. Thus, triflumezopyrim exhibited high acropetal translocation within the rice plant. This study provides an important scientific basis for the development of an application strategy of triflumezopyrim to control planthoppers and leafhoppers as well as for the residue detection method and safety evaluation.

Selective pressurized extraction as single-step extraction and clean-up for the determination of organophosphate ester flame retardant in Citrus aurantium leaves by gas chromatography-tandem mass spectrometry

In this work, an analytical method has been developed and validated for the determination of organophosphate esters (OPEs) in urban ornamental tree leaves. OPEs are flame retardants and plasticizers which are classified as health and environmental hazards substances. Their presence in urban air has been previously described. The method proposed in this work would allow the use of urban tree leaves as simple, cheap, and widely distributed in urban areas alternative to the existing active and passive sampler for sample collection. The method was based on sample treatment by selective pressurized liquid extraction (SPLE) and determination by gas chromatography with triple quadrupole mass spectrometry detector. After the optimization of the extraction solvent, the key parameters applied to SPLE (clean sorbent and sorbent amount applied for the sample clean-up, temperature, extraction cycles, and time) were optimized using a Box-Behnken response surface design. The method achieves high recoveries (higher than 60% for most of the target compounds), accuracies between 70 and 109%, and method detection and quantification limits ranged 0.05-4.96 ng/g dw (dry weight) and 0.15-14.4 ng/g dw, respectively. The method allowed the proper biomonitoring of OPE in tree leaves. Concentrations measured in analyzed samples were from 47.5 to 5477 ng/g dw (TEP). The most frequently detected compounds were triethyl phosphate tri-n-butyl phosphate, triphenyl phosphate, and tris(1-chloro-2-propyl)phosphate, while tris(2-ethylhexyl)phosphate was not detected in the analyzed samples. The proposed analytical method constitutes a starting point for the use of ornamental urban trees as passive sampler for the evaluation of OPE as air pollutants. Graphical Abstract.

Role of Sample Processing Strategies at the European Union National Reference Laboratories (NRLs) Concerning the Analysis of Pesticide Residues

The guidance document SANTE 11945/2015 recommends that cereal samples be milled to a particle size preferably smaller than 1.0 mm and that extensive heating of the samples should be avoided. The aim of the present study was therefore to investigate the differences in milling procedures, obtained particle size distributions, and the resulting pesticide residue recovery when cereal samples were milled at the European Union National Reference Laboratories (NRLs) with their routine milling procedures. A total of 23 NRLs participated in the study. The oat and rye samples milled by each NRL were sent to the European Union Reference Laboratory on Cereals and Feedingstuff (EURL) for the determination of the particle size distribution and pesticide residue recovery. The results showed that the NRLs used several different brands and types of mills. Large variations in the particle size distributions and pesticide extraction efficiencies were observed even between samples milled by the same type of mill.