T/ZNX 031-2023 Determination of Residues of 23 Triazole Fungicides in Water and Fish by Liquid Chromatography-Tandem Mass Spectrometry

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Main technical content: 8 Analysis Steps 8.1 Extraction Method for Water Samples: Transfer 10 mL of the sample into a 50 mL centrifuge tube containing 1 g of sodium chloride and 4 g of sodium sulfate. Add 10 mL of acetonitrile and mix on a vortex mixer for 1 minute. After 15 minutes of standing, extract the upper clear solution of 2 mL and filter it through a 0.22 μm microporous membrane for liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. For fish samples: Weigh 2 g of the sample and place it in a 50 mL centrifuge tube. Add 20 mL of acetonitrile and use a high-speed tissue homogenizer to homogenize the sample at 15,000 r/min for 30 seconds, followed by ultrasonic extraction for 15 minutes. Centrifuge at 4,000 r/min for 3 minutes. Evaporate the extract almost completely at 40 °C in a water bath using a rotary evaporator. Add 5 mL of methanol/water (5:95, v/v) for purification. 8.2 Purification Method: Pre-rinsing the HLB (200 mg × 6 mL) solid phase extraction column with 4 mL of methanol and 4 mL of pure water. Add the extracted solution from 8.1 to the HLB column, followed by washing with 5 mL of methanol/water solution (methanol:water = 3:7, v/v). Finally, elute with 5 mL of methanol/water solution (methanol:water = 8:2, v/v) at a flow rate of approximately 1.0 mL/min. Collect the eluate in a 40 °C water bath and rotary evaporate until approximately 0.5 mL. Dry under nitrogen at 35 °C and dissolve the residue in 2 mL of methanol. Filter through a 0.22 μm microporous membrane and analyze by LC-MS/MS. 8.3 Liquid Chromatography-tandem Mass Spectrometry Analysis 8.3.1 Liquid Chromatography Conditions: Use an HSS Cyano column (1.8 μm, 100 mm × 2.1 mm ID) or equivalent. Set the column temperature to 40 °C, with an injection volume of 5 μL. The mobile phase and gradient elution conditions are shown in Table 1.

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