Abstract

An ion-pair reversed phase HPLC method is described to quantitatively determine individual chromium complexes in chrome tanning solutions. Separations are achieved within 12-40 minutes in contrast to 6-7 hours with the currently used ion-exchange method. Sample sizes of about one microlitre, as opposed to 10 milliliters with the ion-exchange method, are adequate for a separation, thus producing minimum waste. As described below in detail, precautions are taken in order to minimise any perturbation to complex equilibria that exist in chrome liquor so that the true composition of chrome liquor is obtained. Since the analysis can be performed within a very short time, monitoring the composition of tanning solution with time is possible without having to freeze-dry samples from each stage. The method described here is extremely flexible and simple requiring only a basic HPLC system and a reversed phase column which is temporarily modified to an ‘ion-exchange’ mode during separations but which is regenerated to the reversed phase mode at the end of the separations.