The best structures of LC columns-A theoretical perspective

Abstract

The largest peak capacity (n) that LC analysis can generate in isocratic or gradient elution analysis of a given sample in a given time at a given pressure is proportional to the quality factor (q_max) of its column structure. In this study, the multi-channel structures with open pseudo-planar channels (OPPC) and open circular channels (OCC) where compared with PC2 - a typical core-shell column packed with 2 μm particles. These columns have q_max of 1.27, 1.17 and 0.41, respectively. The former two q_max are the highest among all known column structures - about 3 times higher than q_max of PC2. This means that the OPPC and OCC can generate about 3 times higher n compared to what a PC2 can in the same analysis time (t_anal) at the same pressure, or they require about 81 times shorter t_anal (81 is the 4th power of 3) to generate the same n as a PC2 can at the same pressure. However, while PC2 is a commercially available column, there are substantial challenges in manufacturing the OPPC and OCC that can compete with PC2 in practical applications. In order to be competitive with PC2, the OPPC and OCC should have sub-1μm characteristic dimensions (e.g., the inter-pillar distance, g, in OPPC-based pillar array columns, internal diameters of OCC). Thus, in order to compete with PC2 in one scenario, an OPPC requires g ≤ 0.14 μm. Additionally, to be competitive with PC2, OPPC and OCC should be able to sustain the same high pressure. Highlighting the challenges of their design and manufacturing might help to develop the manufacturable columns substantially superior to the packed ones.

Keywords: Multi-channel columns; Open circular columns; Open pseudo-planar columns; Quality factor of a column structure; Transport diameter; Transport efficiency.