Simultaneous determination of propafenone and 5-hydroxypropafenone in plasma by means of high pressure liquid chromatography.

A high pressure liquid chromatographic (HPLC) method with internal analogue standardization for the simultaneous determination of propafenone and 5-hydroxypropafenone in plasma is described. The method comprises extraction from plasma at pH 9 with toluene/dichloromethane/isopropanol, derivatization with dansylhydrazine and subsequent elimination of fluorescent byproducts via silica gel disposable columns followed by quantification by means of fluorescence detection after HPLC separation using a normal phase. With a sample volume of 1 ml the lower limit of detection for propafenone and 5-hydroxypropafenone is approximately 0.2 ng/ml, the limit of determination (precision limit 10%) is approximately 1 ng/ml. The variation coefficients decrease from approximately 10% in the low range to 6-9% for propafenone and 3-7% for 5-hydroxypropafenone at 2 ng/ml and above. For both substances a mean weighted relative error of 6% has to be expected.