LOW CONCENTRATION DRUG ANALYSIS BY SEMI-MICROCOLUMN LIQUID-CHROMATOGRAPHY WITH A POLYMER-COATED MIXED-FUNCTION PRECOLUMN

The construction and performance of dual- and triple-column systems fo r the analysis of dilute drug samples are described. The systems are b ased on the following two separation processes: (1) deproteinization a nd analyte fractionation using a short polymer-coated mixed-function ( PCMF) phase (10 mn x 4.0 mm i.d. column) and, (2) final separation usi ng a C18 semi-microcolumn (1.5 to 2.0 mm i.d.). The surface structure of the MF phase and the geometry of the packed column for the primary separation made it possible to inject hundreds of microliters of serum samples into the system. Analytes separated in the primary chromatogr aphy are transferred to the main column with or without an intermediat e column (35 mm x 1.0 mm i.d.). A system using an intermediate column was designed to save time of analysis when a 1.5-mm i.d.(and smaller) main column was used. The systems showed an increased concentration se nsitivity for drug molecules, such as diazepam, carbamazepine, and phe nobarbital, without any loss in chromatographic efficiency. Carbamazep ine and phenobarbitalat 12.5 ppb and 50 ppb, respectively, in human se rum were detected with good S/N ratio.