NOVEL PRECOLUMN DEPROTEINIZATION METHOD USING A HYDROXYAPATITE CARTRIDGE FOR THE DETERMINATION OF THEOPHYLLINE AND DIAZEPAM IN HUMAN PLASMABY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH ULTRAVIOLET DETECTION

The deproteinization of human plasma was carried out using a hydroxy a patite cartridge as a precolumn. After human plasma had been passed th rough the cartridge followed by suitable elution, protein-free eluate was obtained within only 1 min without the need for centrifugation. De proteinization was evaluated by the determination of albumin, gamma-gl obulin and transferrin in the eluate by high-performance liquid chroma tography (HPLC) with UV detection. Determination of theophylline and d iazepam in human plasma was performed by HPLC with UV detection. The p roposed method was suitable for the determination of these two drugs i n human plasma, because it is simple and rapid (retention time of each drugs approximate to 15 min) and microamounts of sample are required (50-100 mu l) The calibration graphs for theophylline and diazepam wer e linear in the range 0.1-10 mu g and 0.1-65 ng, respectively. Recover ies of both drugs were over 90% by the standard addition method.