[Determination of oxolinic acid residues in baked and fresh eels by high performance liquid chromatography without...

A method for rapid determination of oxolinic acid residues in baked eels and fresh eels by high performance liquid chromatography without derivatization was studied. The samples were triturated, and extracted with methylene dichloride. The extracted solutions were evaporated to dryness, and then was dissolved by using the mobil phase. The solutions were cleaned-up by partition with n-hexane before analysis. The components were analysed on a Nova-Pak C18 column (150 mm x 3.9 mm i.d., 5 microm), with methanol-diluted phosphoric acid (pH 2.5) (40:60, V/V) as the mobile phose at a flow rate of 0.8 mL/min and detected by a fluorescence detector at the excitation wavelength (lambdaex) 254 nm and the emission wavelength (lambdaem) 375 nm. The detection limit was 0.01 mg/kg (S/N = 3). The recoveries were over 80 %, and the relative standard deviations (RSDs) were less than 3.8%.