Solid-phase extraction and HPLC determination of levamisole hydrochloride in sheep plasma

Abstract

The anthelmintic, levamisole, was determined in sheep plasma by means of ion-pair solid-phase extraction (SPE) and reverse-phase liquid chromatography. The SPE columns were conditioned with 2 ml of methanol followed by 1 ml of octane sulphonic-acid buffer. After sample application, the columns were washed with 2 ml of the same buffer, followed by elution with 90/10 acetonitrile: buffer. A phenyl reversephase column (Spherisorb S5 Phenyl, 250 x 4,6 mm) was used with a mobile phase of acetonitrile: 0,005 M of octane sulphonic-acid sodium salt and 0,2% triethylamine in water, pH 3,5, 38/62. Extraction recoveries of 89-94% were achieved over the range from 100-3 750 ng/ml. Accuracy and precision were better than 96% and 2,6%, respectively, over said range, with a limit of quantitation of 50 ng/ml.