SOLID-PHASE EXTRACTION AND HPLC DETERMINATION OF LEVAMISOLE HYDROCHLORIDE IN SHEEP PLASMA

The anthelmintic, levamisole, was determined in sheep plasma by means of ion-pair solid-phase extraction (SPE) and reverse-phase liquid chro matography. The SPE columns were conditioned with 2 ml of methanol fol lowed by 1 ml of octane sulphonic acid buffer. After sample applicatio n, the columns were washed with 2 ml of the same buffer, followed by e lution with 90/10 acetonitrile: buffer. A phenyl reverse-phase column (Spherisorb S5 Phenyl, 250 x 4,6 mm) was used with a mobile phase of a cetonitrile: 0,005 M of octane sulphonic-acid sodium salt and 0,2% tri ethylamine in water, pH 3,5, 38/62. Extrac tion recoveries of 89-94% w ere achieved over the range from 100-3 750 ng/ml. Accuracy and precisi on were better than 96% and 2,6%, respectively, over said range, with a limit of quantitation of 50 ng/ml.