[Determination of clavulanic acid residue in milk by high performance liquid chromatography-tandem mass spectrometry].

An analytical method was developed for the determination of clavulanic acid (CLAV) in milk by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). A 2 g milk sample was deproteinized by ethanol. The supernatant was transferred into a pear-shaped bottle to be evaporated to about 0.5 mL, and the residue was dissolved with ammonium acetate solution. The sample was determined by HPLC-MS/MS after the purification. The chromatographic separation was achieved on a Luna 5u C8 column using 0.1% formic acid in water and acetonitrile as mobile phases with gradient elution. The identification of CLAV was carried out by MS/MS equipped with electrospray ionization in negative scanning and multiple reaction monitoring (MRM) modes. Matrix-matched calibration standard was used for the quantification. The calibration curve showed perfect linear in the range of 10 - 400 microg/kg with the correlation coefficient of 0.999. The limit of detection (LOD, S/N > or = 3) was 10 microg/kg in milk, and the limit of quantification (LOQ, S/N > or = 10) was 20 microg/kg. The mean recoveries varied from 80.00% to 91.25% at the four spiked levels of LOQ, 1/2MRL (the maximum residue limit), MRL, and 2MRL with the relative standard deviations of 5.60% -8.77%. In conclusion, the established method can be applied for the determination of CLAV residues in milk.

[Determination of imidocarb residue in swine tissues by high performance liquid chromatography].

A quantitive method for the determination of imidocarb residue in edible tissues of swine by high performance liquid chromatography (HPLC) was developed. The analyte was digested by beta-glucosidase first, and then extracted with 1 mol/L hydrochloric acid. The aqueous phase was back-extracted with the mixture of hexane-isoamyl alcohol (3: 2, v/v) for the purification. The mobile phases were acetonitrile (phase A) and 0.007 5 mol/L 1-pentansulfonic acid sodium aqueous solution containing 0.1% triethylamine, adjusted to pH 3.0 with glacial acetic acid (phase B). The analyte was detected by ultraviolet absorption spectroscopy after the separation was achieved on a C18 RP column. The linear range was 10 - 10 000 micog/L, and the correlation coefficient was more than 0.999. The limit of detection (LOD) was 10 microg/kg, and the limit of qualification (LOQ) was 20 microg/kg. The mean recoveries of imidocarb in swine tissues at the added levels of LOQ, MRL (maximum residue limit) and 2MRL ranged from 80.04% to 110.32%, and the relative standard deviations (RSDs) of intra- and inter-day analyses ranged from 0.82% to 10.00%. The method is simple and sensitive for the quantification of imidocarb residue in swine tissues.