Ion-exchange HPLC of cheese-related organic acids in comparison with reverse-phase HPLC

Sixteen cheese-related organic acids were analysed by an ion-exchange HPLC protocol developed in this study. The proposed technique was compared to a typical reverse-phase separation of the same organic acid mixture to establish the most satisfactory HPLC methodology. The ion-exchange method yielded best results for the concentration of compounds analysed, resolution, duration of separation and ease of analysis. A number of compounds co-eluted with the proposed ion-exchange HPLC protocol but could be individually distinguished and quantified using spectral array UV detection and three-dimensional Spectacle software. Isoplot graphs were found to be valuable for the more detailed analysis of HPLC chromatograms. The reverse-phase method succeeded in eluting all the polar and more non-polar organic acids in a single chromatographic run with the aid of a buffer-methanol gradient. However, resolution was not as good as with the ion-exchange method. The reverse-phase methodology was found to be more laborious, requiring column re-equilibration and longer run time, and could not accomplish analysis of diacetyl. (C) 1999 Elsevier Science Ltd. All rights reserved.