High-performance liquid chromatographic determination of amezinium in human plasma.

A method with internal analogue standardization is described for the determination of 4-amino-6-methoxy-1-phenyl-pyridazinium methyl sulphate (ameziniummetilsulfate, Regulton, LU 1631) in plasma. The method involves a cation-exchange filtration, a dequaternization reaction and subsequent determination by high-performance liquid chromatography. There is no interference by plasma components or amezinium metabolites found in plasma extracts. When using a 2-ml sample the lower limit of detection is 0.75 ng/ml; the lower limit of determination is about 2 ng/ml. Interassay coefficients of variation decrease from about 14% at the lowest concentration to about 5% at 20 ng/ml and above.