Progress over the past few years in LC has been rather slow. But this does not mean we have reached the end of the journey. My personal favorite discovery in the past two years has been the work of Ta-Chen Wei, Xiaoli Wang and Bill Barber from Agilent Technologies (1). By making core-shell particles with mesopores that are purely radially oriented (instead of the conventional randomly connected mesoporous network) they could make the minimum of the van Deemter curve drop by 0.5 plate height units from roughly hmin=1.5 to hmin=1. The spectacular drop is caused by the fact that the radially-oriented pores strongly suppress the B-term, while the C-term is not altered at all. This discovery could be the next big revolution (given the other big drop from hmin=2 to hmin=1.5 when core-shell particles were introduced). It remains to be seen whether these particles have the same mechanical stability and mass loadability as conventional particles, but it does show how a small change in shape can have a remarkable impact.
As for the future, with new possibilities in materials engineering such as silicon micromachining and 3D printing becoming increasingly available, it seems inevitable that we will one day see columns that are no longer densely packed with particles, but rather filled with a perfectly ordered, low flow resistance material permeated by a sub-micron maze of flow-through channels. In the years to come, I expect more (r)evolutions in the shape of the supports, rather than further reduction of the size of our spherical particles. The latter only seems useful for ultra-rapid separations (a few seconds) needed in the final dimension of the best possible 3D-LC separations – but this is likely to remain a niche application for many years.
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References
- T Wei et al., J Chromatogr A, 1440, 55–65 (2016).