Determination of morphine and 6-acetylmorphine in plasma by high-performance liquid chromatography with fluorescence detection.

A method is described for the simultaneous determination of morphine and 6-acetylmorphine in small volumes of human plasma by normal-phase high-performance liquid chromatography using solid-phase extraction, dansyl derivatisation and fluorescence detection. The lower limits of quantitation in a 0.1-ml plasma sample are 10 ng/ml for morphine and 25 ng/ml for 6-acetylmorphine. The method has been applied to determine concentrations of morphine and 6-acetylmorphine in plasma samples from premature babies administered an intravenous infusion of diamorphine.