Determination of drugs in untreated body fluids by micellar chromatography with fluorescence detection

Direct serum and urine injection, without sample extraction or protein precipitation steps, into a liquid chromatographic system using sodium dodecyl sulfate (SDS) with 10% added propanol as the mobile phase, is described for measurement of drug levels. The ability of SDS micelles to form soluble protein-SDS complexes, with no on-column precipitation, provides a simple, rapid method for routine determination of quinine, quinidine, propranolol, morphine and codeine at concentration levels found in serum and urine following administration of therapeutic doses. Absolute limits of detection ranged from 0.2 to 6 ng. Variation of the surfactants mobile phase concentration allows control of selectivity and analysis time, although a minimum concentration is required to prevent protein precipitation. Chromatographic efficiencies are improved by the addition of propanol to the micellar mobile phase, and sensitivities improved by use of fluorescence detection. The sensitivities are more than adequate for therapeutic drug monitoring of concentration ranges normally encountered in serum and urine.