The technique of column-switching could alter the connections between injection valve and column,column and column, column and detector. The column-switching high performance liquid chromatography was a powerful technique for the separation and clean-up of multicomponent mixtures. The samples were directly injected after simple pretreatment. Analytes of interest were concentrated, cleaned and derivated on-line, and so on. The method could decrease organic solvent volume, improve recovery and lower detect li...