A novel method for determining surface charge and isoelectric point of leather

Surface charge and isoelectric point of leather play an important role in the production of leather. However, a precise and rapid method for the determination of leather surface charge and isoelectric point is unavailable nowadays due to the complexity of the structure of leather, especially for chromefree tanned leather. Therefore, it is necessary to develop a quantitative determination method to provide technical support for tanning and post-tanning processes. In this study, a novel method for determining zeta potential (to characterize the surface charge of leather) and isoelectric point of leather was established using a zeta potential analyzer based on the principle of streaming potential. The test conditions such as suspension concentration, sampling time, settling time and equilibrium time after pH adjustment were optimized. Then various chrome-free tanned leathers as well as chrome tanned leather were used for determination. Based on the optimal parameters identified above, the zeta potentials of the leathers at different pH values were measured, and the isoelectric points of the leathers, which were the pH values at the zero point of zeta potentials, could be obtained. It was found that this determination method was rapid (3 min for one measurement), well repeatable and universal, suggesting that it is useful in the formulation of chrome-free tanning and post-tanning processes.