ABSTRACT: Purpose of the paper was the optimization of mobile phase in natrium chloride gradient in the chromatographic separation of butyrylcholinesterase from human plasma. Materials/Methods. Butyrylcholinesterase (BuChE) was isolated from human plasma using a diethylamminoethyl-cellulose column, by elution with 0.02M acetate buffer pH=4.0, gradually increasing NaCl percentage from 10% to 80%. The procedure lasted approximately 28 days. Results.