Abstract
The usability of column-switching techniques of high performance liquid chromatography is reviewed with special interest given to the enrichment and cleanup of biological samples. In Section 2, band broadening and a fully automated operation system are especially noted. In Sections 3 and 4, it is emphasized that the recovery of on-line solid extraction in a precolumn is quantitative (100%), depending upon the combination of the stationary phase and the mobile phase. In Section 5, are elucidated the deproteinization and recovery from protein-bound entities by a size exclusion coupled with internal-surface reversed-phase techniques or by hydrophobic interaction. These methods are extensively applied to the biological samples, such as whole blood and tissue homogenates, which contain minute particles, by using a large-bore endfitting filter for the precolumn.