On-column visualization of sample migration in liquid chromatography

A quantitative on-column visualization technique for evaluating solute migr ation in liquid chromatography columns was described. This technique employ ed a matched refraction index phase system in high-pressure glass columns. In this case, the mobile phase was carbon tetrachloride and the stationary phase was a C18 silica, Because the refractive indexes of the two phases we re the same, the column bed, otherwise opaque, was transparent to the eye. Zones of colored solutes could be injected (iodine for instance) and their migration studied along the column. Photographing the sample band during it s migration allowed chromatographic information to be extracted using digit al technology. As an example of applications for this technique, we show th e sample entry through various inlet fittings, The results demonstrate that chromatographers should pay more attention to the selection of inlet frits . Importantly, the frit porosity should be matched to the particle size of the packing.