Determination of 8 Quinolone Drugs in Fish with Sin-QuEChERS Purification

The crushed fish sample (2.00 g) was placed in a 50 mL-centrifuge tube, and 200 μL of 100 μg·L^-1 internal standard solution and 5 mL of water were added. After vortex for 1 min, the above mixture was extracted ultrasonically for 10 min with 10 mL of acetonitrile solution containing 5% (φ) acetic acid, and the salts (6 g of anhydrous magnesium sulfate and 1.5 g of sodium chloride) were added to separate the aqueous phase and acetonitrile phase. After vortex and centrifugation, Sin-QuEChERS rapid filtration column was directly inserted into the centrifuge tube. When the extract rose to the purifying column through the purifying layer, 5 mL of the extract was transferred into a 15 mL-centrifuge tube, a mixture of acetonitrile and n-hexane at the volume ratio of 1:1 was added, and then the mixture was mixed well and settled. The upper n-hexane layer of was taken, then swirl, centrifuged and blown to nearly dry at 40℃ with nitrogen. The residue was made its volume to 1 mL with 0.2% (φ) formic acid solution. After filtration, 8 quinolones residues were determined by ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) under multi-reaction monitoring mode. As shown by the results, the consumption of the solvent was reduced to 10 mL and the pretreatment time was shortened to 20-25 min by this purification method. The linear ranges of the standard curves of ciprofloxacin, pefloxacin, norfloxacin, difloxacin and danofloxacin were 1.00-500.0 μg·L^-1, with the same detection limits (3S/N) of 1.0 μg·kg^-1. The linear ranges of the standard curves of ofloxacin, enrofloxacin and sarafloxacin were 0.50-500.0 μg·L^-1, with the same detection limits (3S/N) of 0.5 μg·kg^-1. The same sample was determined 7 times in parallel by this method, with RSDs of the determined values in the range of 1.3%-6.3%. Test for recovery was made by standard addition method, giving results in the range of 92.0%-108%. This method was applied for sampling inspection of 3 kinds of fish from 4 supermarkets in Lanzhou, and 8 quinolones were not detected, showing that drug residues in fish food in Lanzhou were relatively safe. At the same time, the results were basically consistent with those of the method in Proclamation No. 1077-1-2008 of the State Ministry of Agriculture.