Two-dimensional High Performance Liquid Chromatography (2DHPLC) affords greater separation power and peak capacity compared to a 1DHPLC system. The combinations of various stationary and mobile phases are countless and the combination of certain phases in a 2DHPLC system can provide a unique elution profile (chemical signature) for the sample
To ensure optimal peak capacity, the two dimensions must be as different as possible. However, this often results in the transport of solute from the first dimension in a solvent that is not ideally compatible with the solvent in the second dimension, often resulting poor peak shape, loss of efficiency and subsequently a decrease in total peak capacity.
A new column format known as Active Flow Technology (AFT) provides a means to transport solute between the two dimensions using smaller transport volumes, but at the same time sampling the first dimension at exactly the same modulation frequency. This reduces the substantially the effects of incompatible solvent mixing in the second dimension. This improved solute transport stems from the design of the column format: In AFT columns the column inlet and outlet end fittings are replaced with a multi-channel end fitting with a special purpose-built frit that separates flow from the centre of the column from that of the wall. The active management of the solvent entering and exiting the column improves separation efficiency and sensitivity, minimising the effects of bed heterogeneity and importantly reducing the volume of the peak that is extracted from the column since the diffuse tailing section of the band is removed [1]. Thus, the peak volume is decreased in proportion to the segmentation ratio.