Determination of drugs in serum by high performance liquid chromatography with automated sample preparation

Abstract

In analysis of drugs in human serum by high performance liquid chromatography (HPLC), preparation of sample is essential due to complexity of sample composition. Manual preparation of sample is time-consuming work. Automated sample preparation using pre-column extraction and column switching was examined. The system consists of two flow lines which are connected each other by a flow changeover valve. The system is controlled by microprocessors. Drugs of interest are trapped by hydrophobic interaction on pre-column (4 mm i. d.×30 mm L.: tetramethylolmethanetriacrylate resin packing) which is then introduced to the analytical column by column switching. Hydrophilic interaction is suppressed in this column. Weak hydrophilic interaction prevents proteins from irreversible adsorption. Proteins in serum can be shunted by base such as triethylamine. When elution of the drugs from the pre-column is completed, the flow changeover valve is switched back to its initial position and then the pre-column is regenerated for the subsequent sample. Preparation mobile phases which can extract anticonvulsants, theophylline and lidocaine selectively were chosen. Baseline stability was examined using blank serum. This system made direct injection of serum and stable automated analysis possible. The analysis by this system was free of interference from serum. Good recovery and reproducibility were obtained for all components analyzed. © 1986, The Japan Society for Analytical Chemistry. All rights reserved.