DETERMINATION OF RESIDUAL AVOPARCIN IN CH ICKEN MUSCLE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

An analytical method was developed for residual avoparcin in chicken m uscle by measuring alpha- and beta-avoparcin, major components of the pharmaceutical preparation of avoparcin, using high performance liquid chromatography (HPLC). Alpha- and beta-avoparcin were used as authent ic samples after isolation by preparative HPLC. The analytical HPLC wa s achieved by using a Cosmosil 5C18-AR column (4.6 mm X 25 cm), a mobi le phase of 2.5% acetic acid, 0.01 M sodium heptane sulfonic acid-acet onitrile (88.5: 11.5) (pH 4.0) with UV detection at 280 nm. Since the values obtained by HPLC as the sum of alpha- and beta-avoparcin were h ighly correlated to those obtained by bioassay (r=0.95, n=24), it was suggested that the proposed HPLC method may substitute for the time-co nsuming bioassay. Avoparcin was extracted from chicken muscle by homog enization in methanol-0.2 M sulfuric acid (6:4) followed by centrifuga tion after pH adjustment to 3 by 1 N sodium hydroxide. The supernatant was evaporated to dryness, and the residue was dissolved in water. Th e aqueous layer was adjusted to pH 3 by adding 1 N sodium hydroxide. T hen it was purified on a Sep-pak C18 cartridge. The cartridge was wash ed with water, and retained substances were eluted with 50% methanol. The eluate was evaporated to dryness under reduced pressure. The resid ue was dissolved in water and determined by HPLC. Recoveries for avopa rcin spiked in chicken muscle were 104-99.5% at 2-16 mug/g. The detect ion limit is 0.5 mug/g.