ABSTRACT
High-performance liquid chromatography (HPLC) is a powerful technique to separate chemicals from matrices in modern analytical sciences. For more powerful analytical capacity and to increase resolution and sensitivity, HPLC has been further developed. For example, to improve resolution for the separation of chemicals, ultra-high pressure was adapted into a very small, particles-packed (<5 μm) column, such as the ultra-performance liquid chromatography (UPLC) system. Also, mass spectrometry (MS), such as HPLC-MS, has been used to enhance the sensitivity of the HPLC system. In general, HPLC uses one separation column with a simple §ow-through course. When additional columns are branched and switching devices (valves) are adapted to control or adjust the §ow of a chromatographic network, the HPLC system is able to increase its already powerful separation ability. In 1982, Riley and his colleague [1] reported analysis of platinum in urine using HPLC automated column switching. They used platinum complexes retained on anion exchangers, and automated column switching was applied for recovery of puried cisplatin fractions. Werkhoven-Goewie and his colleague [2] also used the column-switching technique to automatically separate the drug secoverine from blood by enzymatic hydrolysis of blood samples with subtilisin-A. The column-switching technique was applied to decrease the analysis time. In 1984, Little et al. [3] explained the role of column switching in analyzing complex samples. They proposed the column-switching technique for sample and column clean-up followed by column reequilibration to minimize analysis time.
