Unstable biopolymer solutions inevitably lead to mis-characterization of macromolecular properties and
irreproducible results. Even under stable or quasi-stable conditions, persistent aggregates can hamper
reliable characterization, especially using light scattering methods. Various pitfalls in characterizing
biopolymers were worked through, including determination of solution stability zones, dissolution kinetics,
estimation of fraction of aggregate populations, and the relationship between batch and fractionation
methods. Chitosans, polyampholytic biopolymers with isoelectric point around pH=6.0, with varying
degrees of carboxymethylation were studied. Instability was determined vs. pH and ionic strength using a
high throughput screening method, simultaneous multiple sample light scattering (SMSLS). With stable
solution conditions determined, equilibrium batch and multi-detector GPC characterization of molecular
weight, intrinsic viscosity, and polyelectrolyte properties was made. Finally, a first attempt at continuous
online monitoring of the modification reaction itself was made and compared to FTIR analysis of
carboxymethylation on discrete aliquots. Given the range of possible characterization problems, multiple
approaches with independent instruments may be required for reliable natural product characterization.
Online monitoring of modification reactions may lead to rapid advances in understanding and preparation of
natural products.
