Characterizing molar mass distributions and molecule structures of different chitosans using asymmetrical flow field-flow fractionation combined with multi-angle light scattering

Abstract

We investigated various chitosan types and batches successfully with a combination of asymmetrical flow field-flow fractionation and multi-angle light scattering using a customized separation method. Advantageous were the separation capability of a broad applicable molar mass range, the injection of unpurified solutions and the determination of absolute molar masses. Most of the measured samples followed molar mass distributions of monomodal logarithmic Gaussian type. Only one sample showed a very broad distribution caused by either high molar mass amounts or aggregate formation. It was also found that batch-to-batch variations were quite high, which is a common problem for nature-derived products. Thus, especially pharmaceutical products and semi-synthetic derivates should benefit from the development of products with a predictable average molar mass and a narrow distribution. On the basis of received data for each slice eluting from the channel, molar mass–gyration radius relationships could be generated for every single measurement. The hereof received molecule structure parameters were verified to be molar mass dependent, ranging from open structures of rinsed thoroughly molecules to theta coil conditions or an even more compact conformation.