Comprehensive two-dimensional liquid chromatography.

Having nearly exhausted the possibilities for generating peak capacity through improvements in column technology, chromatographers are increasingly looking to alternative ways of maximising chromatographic separation. In recent years there has been increasing activity in the field of comprehensive multidimensional separations to meet analysis demands. Comprehensive two-dimensional liquid chromatography (LCxLC) approaches offer high peak capacity which leads to significantly improved analytical performance over single-column liquid chromatography. There are several closely related avenues available for achieving an LCxLC separation and this review pays special attention to the different valve-based interfaces that have been used to comprehensively couple the first and second dimension columns in LCxLC systems. A brief discussion of column choices for selected applications and the conditions employed is also presented.