Landmark Literature: 2015 (part3)

Practically and Fundamentally Excellent

By Peter Schoenmakers, Education Director COAST; Editor, Journal of Chromatography A; Professor, Analytical Chemistry/Forensic Science, University of Amsterdam, The Netherlands

A recent paper by Fabrice Gritti, Thomas McDonald and Martin Gilar struck me for several reasons. Firstly, it is an immensely important publication for liquid chromatographers. Such steadfast folk tend to strive for high efficiencies and excellent separations by making or using better columns with very small and uniform particles, perfectly homogeneous monoliths, and so on. But, unfortunately, they forget that long or poorly designed connectors and extra-column apparatus cause them to lose what they aim to gain – a problem the paper attempts to correct. In addition, the paper describes ingenious and original methods. It is a practical liquid chromatography (LC) paper, with theory supporting the experiments that aim to capture the causes of “misdemeanors” by short pieces of connection tubing. The results from the tedious experiments are consistent and rather surprising, the latter being mandatory for an interesting paper.

The paper contains some recommendations that will not surprise you, such as using the narrowest possible tubing and elevated temperatures, and voices a suggestion that we hear with increasing frequency, “Shouldn’t we all convert to supercritical-fluid chromatography (SFC)?” When we replace conventional water-acetonitrile mixtures in LC with mixtures of carbon dioxide and methanol for SFC, it is possible to perform faster separations (which we already know) and extra-column band broadening may be less of a threat (which is more remarkable than it seems – see SFC Star). Therefore, it will be interesting to see whether SFC will begin to catch up with LC. SFC has fundamental properties on its side (faster diffusion, lower viscosity), but aqueous-organic mixtures have proven to be fantastic eluents for all kinds of samples.