Sample preparation for anthocyanins and betacyanins HPLC determination. The effect of the sample solvent

Abstract

The paper is devoted to the explanation of artefacts appearance on the chromatograms. Thus the artefacts may be the consequence of the high concentration of the organic component in the sample solvent if the elution strength of the solvent exceeds that of the mobile phase utilized for solutes separation. In this case sample will be distributed between the mobile and stationary phases with a smaller distribution constant, at least in the initial phase of the chromatographic column. The phenomenon will result in solute peak repelling before the peak equilibrium position of on the chromatogram. The idea was confirmed by a series of experimental data. So, the appearance of "false" peaks was proved to be the consequence of the high concentration of acetonitrile in the sample of the betacyanin extract of the fruit of Chenopodium foliosum L. For a series of samples of the extract of the fruit of Ribes rubrum L. and Ribes nigrum L. with different concentration of acetonitrile it has been shown that in the case of the mismatch of the elution powers of the sample solvent and of the mobile phase initially a decrease in the efficiency of the chromatographic system (expressed by number of theoretical plates) is observes, and then false peaks may appear. In some (but not in all) cases, the effect can be partially suppressed by volume of injected sample reducing.