Evaluation of a single step extraction procedure for enzymatic assay of levamisole in calf serum

A single step extraction procedure for recovery of the anthelmintic drug levamisole (LEV) from aqueous solutions and calf serum was evaluated. Levamisole was extracted from aqueous solutions and calf serum with 1.5 ml of ethyl acetate. After evaporation to dryness, the LEV content of extracts was estimated by measuring LEV inhibition of bovine milk fat globule membrane alkaline phosphatase. Lipid interference with absorbance readings was eliminated by the addition of 1.0 ml of chloroform to the assay mixtures. The recovery of LEV from both aqueous samples and serum samples by this single step extraction procedure coupled with enzymatic assay was 90%. The effective range for serum LEV determination was 0.3 to 20 micrograms/ml.