Ionic Liquid Microextraction/High Performance Liquid Chromatography For Determination Of Veterinary Drugs In Animal Derived Foods

Ionic liquid is a class of “green” and excellent solvents that can be used to develop new extraction methods to replace the traditional extraction methods. The objective of this study is to develop the ionic liquid based microextraction methods and combine high performance liquid chromatography for the determination of four classes of veterinary drugs in animal derived foods(penicillins, quinolones, tetracyclines, and sulfanamides).Firstly, an ionic liquid dispersive liquid-liquid microextration method(IL- DLLME) was developed to extract the residues of penicillins in milk: 0.02 mol/L phosphate buffer 5 m L, 60 μL of ionic liquid([C4MIM][PF6]), 1 m L of acetonitrile/formic acid(99.8:0.2,v/v) as disperser solvent, extraction time of 1.5 min and centrifuge time of 8 min. Results showed that the satisfactory purification effects and the high enrichment factors for penicillin V(35 folds) and cloxacillin(82 folds) were obtained. The limits of detection for the two analytes in milk were 0.2 and 1.5 ng/m L respectively, and the recoveries from the standards fortified blank milk were in the range of 84.1%-96.7% with coefficients of variation lower than 4.9%.Secondly, an IL- DLLME was developed to extract the residues of tetracyclines in egg: 5 m L deionized water(p H=3), 50 μL of ionic liquid([C4MIM][PF6]), 400 u L of acetonitrile as disperser solvent, extraction time of 30 s and centrifuge time of 5 min. Results showed that the satisfactory purification effects and the high enrichment factors for oxytetracycline(12 folds), tetracycline(29 folds), chlorotetracycline(38 folds) and doxycycline(44 folds) were obtained. The limits of detection for the four analytes in egg were in the range of 2.0-12 ng m L-1, and the recoveries from the standards fortified blank egg were in the range of 58.6%-95.3% with coefficients of variation lower than 6.2%.Thirdly, an IL- DLLME was developed to extract the residues of quinolons in meat: 5 m L deionized water, 50 μL of ionic liquid([C4MIM][PF6]), 300 u L of acetonitrile as disperser solvent, extraction time of 30 s and centrifuge time of 5 min. Results showed that the satisfactory purification effects and the high enrichment factors for norfloxacin(12 folds), clprofloxacin(29 folds), lomefloxacin(38 folds) and enrofloxacin(44 folds) were obtained. The limits of detection for the four analytes in meat were in the range of 0.5-1.1 ng m L-1, and the recoveries from the standards fortified blank meat were in the range of 60.4%-96.3% with coefficients of variation lower than 11.8%.Finally, an ionic liquid single drop microextraction method(IL-SDME) was developed to extract the residues of sulfonamides in meat: deionized water(p H = 4.5) 15 m L, 20 μL of [C6MIM][PF6], immersing the needle tip about 0.5 cm below the surface of the solution, pushing the piston to make needlepoint suspension including 10 μL,extraction time of 20 min(700rpm), then suction the ionic liquid drop. Results showed that the satisfactory purification effects and the high enrichment factors for sulphadiazine(6 folds), sulfadimidine(5 folds), sulfamethoxypyridazine(11 folds), sulfamonomethoxine(10 folds), sulfamethoxazole(22 folds) and sulfadimethoxine(26 folds) were obtained. The limits of detection for the six analytes in meat were in the range of 0.3-1.0 ng/m L, and the recoveries from the standards fortified blank samples were in the range of 71.7%-90.7% with coefficients of variation lower than 7.1%.Therefore, the ionic liquid based microextraction methods can be used as the rapid, simple and effective tools for the extraction and enrichment of the residues of veterinary drugs in animal derived foods.