Recent Advances in Online Column-Switching Sample Preparation

Abstract

Sample preparation is an important step for the extraction, isolation and pre-concentration of desired analytes. It is the most labor-intensive and error-prone process in analytical methodology and greatly influences the reliability and accuracy of analyte determination. Column-switching techniques, using two or more stationary phase columns, multiport valves and one or more pumps, are useful for trace enrichment, automated sample cleanup, and rapid online analysis by dynamic extraction or transfer of the extract to the chromatographic column. These techniques can be used to determine the analytes in complex matrices by direct sample injection or merely by simple sample treatment such as filtration. Sample preparation by online column-switching is usually combined with high-performance liquid chromatography. Solid-phase extraction and turbulent flow chromatography using a cartridge column and in-tube solid-phase microextraction using a capillary column have been developed for convenient column-switching sample preparation. Furthermore, various sorbent materials, including conventional hydrophobic supports, restricted-access media, immunosorbents, molecularly imprinted polymers, and monolithic materials, have been developed to improve extraction efficiency. This chapter critically evaluates these column-switching sample preparation systems, including the strategies underlying the development of these methods, as well as recent applications in biological, pharmaceutical, food and environmental analyses.