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A method of rapid analysis of multi-class residual veterinary drugs in milk, fish and shellfish was validated in accordance with Japanese guidelines for the validation of analytical methods for residual agricultural chemicals in food. Using LC-MS/MS, 43 multi-class veterinary drugs, including sulfonamides, quinolones, coccidiostats and antiparasites, could be analyzed in one injection. Analytes were extracted from samples with two kinds of solvent, acetonitrile containing 1 vol% formic acid and anhydrous acetonitrile, and salted out with 4.0 g of magnesium sulfate, 1.5 g of trisodium citrate and 2.0 g of sodium chloride. This method was assessed by performing recovery tests in retail milk and 4 kinds of fresh cultured fish and shellfish (salmon, tiger shrimp, red sea bream and bastard halibut) spiked with the 43 target analytes at the levels of 10 and 100 μg/kg. Using this method, 40 out of 43 drugs satisfied the guideline criteria in milk, 37 drugs in salmon, 42 drugs in tiger shrimp, 41 drugs in red sea bream and 39 drugs in bastard halibut.

LC/MS/MS was developed to determine the residues of bithionol (BTN), bromofen (BMF), nitroxynil (NTX), oxyclozanide (OCZ), and tribromsalan (TBS) in milk. Samples were extracted with ethyl acetate and cleaned up by liquidliquid separation with acetonitrile and n-hexane. The compounds were determined by RP-LC using a C18 column with 0.1 formic acidmethanol. Mass spectral acquisition was performed in the negative mode by applying selected-reaction monitoring. The method was validated in milk spiked with these compounds at 5600 g/kg; average recoveries were in the range 83.897.1, with RSD values of 1.48.0. The interassay RSDs were less than 11. The LODs of these compounds in milk were 0.1 g/kg. The method was applied to 24 raw milk samples. The concentration of these compounds in all samples was lower than the Japanese maximum residue limits. The method is rapid, sensitive, and specific for monitoring residues of BTN, BMF, NTX, OCZ, and TBS in milk.

A method for rapid analysis of multi-class residual veterinary drugs in livestock products was developed and validated in accordance with the Japanese guideline for pesticides. Using LC-MS/ MS, 43 multi-class veterinary drugs, including sulfonamides, quinolones, coccidiostats and antiparasites, could be analyzed simultaneously in only 18 minutes. The extraction process was developed by modifying the QuEChERS approach to provide faster and less expensive extraction. The samples were extracted by using two kinds of solvent, acetonitrile and acetonitrile including 1 vol formic acid, and salted out with magnesium sulfate, trisodium citrate and sodium chloride. Using these two extractants, 40 out of 43 drugs satisfied the guideline criteria in bovine muscle and swine muscle, 39 drugs were found in chicken muscle, and 37 drugs were found in eggs. The limit of quantification was less than the MRL for all analytes.

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