An analytical method was developed for determination of residual avoparcin in chicken muscle by measuring a-and b-avoparcin, major components of the pharmaceutical preparation avoparcin, using HPLC with UV and amperometric detectors. The analytical HPLC was run on a Cosmosil 5C18-AR column (4.6 mm25 cm) with a gradient formed from A: 2.5 acetic acid, 0.01 mol/L sodium heptane sulfonic acidῌacetonitrile (88.5 : 11.5) (pH 4.0) and B: 2.5 acetic acidῌ acetonitrile (10 : 90), using UV and amperometric detection (AMD) with glassy-carbon electrode (ΐ 900 mV). Avoparcin was extracted from chicken muscle by homogenization with methanolῌ0.2 mol/L sulfuric acid (6 : 4) followed by centrifugation after pH adjustment to 4 with 1 mol/L sodium hydroxide. The supernatant was evaporated to dryness, and the residue was dissolved in water. The aqueous layer was adjusted to pH 4 by adding 1 mol/L sodium hydroxide. Then it was purified on a Sep-Pak tC18 plus ENV cartridge. The cartridge was washed with water, and retained substances were eluted with 50 methanol. The eluate was evaporated to dryness under reduced pressure. The residue was dissolved in water and determined by HPLC. Recoveries of avoparcin spiked in chicken muscle were 73.1ῐ88.1 at levels of 2ῐ10 mg/g. The detection limits were 0.5 mg/g (UV) and 0.2 mg/g (AMD). ῌ QῘQῠῦQῸ 60 ̯ 10 QῲQ`Q̱̮̳ῦ ῤQ̮῝Ὺ̯ 6), 7) ῍ ῩQΰῢQQQQῗQ 5) ῠQ`῝Ὺ̯ Ῑ̯Ῐῌ ̯ῥQῌ ῐQQῥQQ̰ῒῘ̮̰ῡ῞̯ῨQ 9Q῞ῌ ̯ῥQ`ΎQQ῞̯῍ ῞ῗ῞ῌ ῨQ 10 ̯ῡ 11 ̯

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