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A method was developed for the simultaneous determination of seven high risk pesticides in the royal jelly, eg. tau-fluvalinate, triadimenol, coumaphos, haloxyfop, carbendazim, thiophanate-ethyl and thiophanate-methyl by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). First, the royal jelly samples were extracted with acetonitrile under alkaline conditions. After dehydration by anhydrous sodium sulfate, the extracts were enriched and purified through solid-phase extraction (SPE) with Oasis HLB cartridges. Finally, the pesticides were detected by HPLC-MS/MS method. The separation was carried out on a Venusil MP C18 column with gradient elution. Methanol (containing 0.1% (v/v) formic acid) and 0.5 mmol/L ammonium acetate aqueous solution (containing 0.1% (v/v) formic acid) were used as the mobile phases. The detection was achieved using electrospray ionization in positive ion (ESI+) mode and multiple reaction monitoring (MRM) mode for data collection. Quantification was carried out using internal standard method. The results showed that the seven high risk pesticides were linear in the range of 5-100 μg/kg. The linear correlation coefficients (r2) were 0.9921-0.9996. The limits of detection (LODs) and limits of quantification (LOQs) of the seven high risk pesticides were 0.5-2.0 μg/kg and 1.0-5.0 μg/kg, respectively. The average recoveries at the three spiked levels were 80.5%-101.3%, and the relative standard deviations were 3.6%-9.4% (n=3). This method is simple, effective and sensitive, and is suitable for the determination of the pesticide residues in royal jelly.

A simple and rapid capillary electrophoresis (CE) method was developed for the determination of trace thiophanate-methyl, carbendazim and benomyl in fruits and vegetables. Herein, bacterial cellulose (BC) was used as additive in running buffer to improve the separation efficiency. CE experimental parameters such as detection wavelength, concentration and pH of the running buffer, separation voltage as well as the contents of BC in running buffer were systematically investigated. Under the optimized conditions, three benzimidazole fungicides could be accurate quantified in 8 min using H3BO3/Na2B4O7 (4 mmol/L, pH 9.0) containing 0.3% (mass fraction) BC for background electrolyte, 15 kV for the separation voltage, 25℃ for the column temperature and 275 nm for detection wavelength. Good linearities for the three benzimidazole fungicides were obtained with correlation coefficients (r2) ≥ 0.997. The limits of detection (LODs) of the three benzimidazole fungicides were between 5.0 and 10.0 μg/L. The relative standard deviations (RSDs, n=5) of inter-day were 0.82%-1.0% for retention times and 2.4%-2.9% for peak areas. The proposed method was further applied to determine the residues of the three benzimidazole fungicides in fruits and vegetables. The recoveries were in the range of 93.5%-103.0% with RSDs no more than 8.0%. These results indicated that the proposed method can serve as an efficient tool for the simultaneous determination of the three benzimidazole fungicides in fruits and vegetables.

A QuEChERS-liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of pyraclostrobin, thiophanate-methyl and its metabolite carbendazim in soil and citrus. The samples were extracted with methanol or acetonitrile, purified by primary secondary amine (PSA), then separated by LC, detected in multiple reaction monitoring (MRM) mass spectrometry mode via positive electrospray ionization. The analytes were quantified by matrix-matched standard solutions with external standard method. The limits of quantification (LOQs) of pyraclostrobin, thiophanate-methyl and carbendazim in different matrices were 5.8-7.0 μg/kg, 9.3-14.1 μg/kg and 2.1-2.6 μg/kg, respectively. For all the samples, the spiked recoveries ranged from 75.48% to 109.18%, and the relative standard deviations (RSDs) were 0.60%-5.11% (n=5). The method is quick, easy, effective, sensitive and accurate. The matrix-matched calibration solutions can efficiently compensate matrix effects of the pyraclostrobin, thiophanate-methyl and carbendazim in LC-MS/MS analysis. The established method can be applied to the residue analysis of the real samples of soil, citrus peel, citrus pulp and citrus fruits.

A method was developed for the determination of thiophanate-methyl and carbendazim residues in cucumber and soil by using QuEChERS-high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The residues in the samples were extracted by acetonitrile, cleaned up by developed QuEChERS method, and then analyzed by using LC-MS/MS in multiple reaction monitoring (MRM) mode via positive electrospray ionization with an Agilent ZORBAX SB-C, column (30 mm x 2.1 mm, 5 microm) as the analytical column. The recoveries of thiophanate-methyl spiked at four levels of 0.01, 0.05, 0.1 and 1.0 mg/kg were from 87.3% to 96.0% with the relative standard deviations (RSDs) of 8.0%-9.3% in cucumber, from 88.8% to 93.4% with the RSDs of 5.3%-9.9% in soil; the recoveries of carbendazim spiked at the same levels as those of thiophanate-methyl were from 87.1% to 92.3% with the RSDs of 5.2%-7.5% in cucumber, from 85.8% to 90.9% with the RSDs of 5.3%-13.2% in soil. The method is simple, rapid and characterized with acceptable sensitivity and accuracy to meet the requirements of the pesticide residue analysis. This method is applicable to confirm the residues of thiophanate-methyl and carbendazim

An ultra performance liquid chromatography-tandem mass spectrometric method (UPLC-MS/MS) was established for the simultaneous determination of imidacloprid, carbendazim, thiophanate-methyl, propamocarb, methomyl and dimethomorph residues in tomato paste. The samples were extracted by methanol-water (1: 1, v/v) containing 0.1% (v/v) acetic acid. The separation was performed on a Waters Acquity UPLC system with a BEH C18 column with the gradient elution of methanol and water (containing 10 mmol/L ammonium acetate). The six pesticides were determined in the modes of electrospray positive ionization (ESI+) and multiple reaction monitoring (MRM). The analytes were quantified by matrix-matched standard solution, and the calibration curves showed good linearity within the concentrations of 0.005 to 0.2 mg/L and the correlation coefficients (r) were more than 0.995. The average recoveries of the six pesticides ranged from 66.8% to 102.9% in the three spiked levels of 0.02, 0.05 and 0.2 mg/kg. The relative standard deviations (RSDs) were all less than 15%. The limits of quantification (LOQ, S/N10) were 0.02 mg/kg for the all analytes. The results indicate that the method is easier, faster, more sensitive, and suitable for the qualitative and quantitative confirmation of the six pesticide residues from tomato paste.