HPLC determination of 5-hydroxypropafenone in plasma with electrochemical detection

A high pressure liquid chromatographic (HPLC) method with internal analogue standardization for the determination of 5-hydroxypropafenone in plasma is described. The method comprises extraction from plasma at pH 9 with diethyl-ether and quantification after HPLC separation using a reverse phase by means of electrochemical (reductive) detection after electrochemical preoxidation. When using 1 ml plasma the lower limit of detection is 0.5 ng/ml. Under routine conditions the limit of determination is estimated to be lower than 2 ng/ml. The variation coefficients of duplicates drop from about 10% in the range of the determination limit to about 3% at 5 ng/ml and above. The determination of 5-hydroxypropafenone is not impaired by other known metabolites of propafenone.