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.
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