Small-Angle X-Ray Scattering Studies on Nucleation Formation of Dextran Precipitation in the Presence of Boron

In the present study, the nucleation formation process of dextran precipitation in the presence of boron was investigated by small-angle X-ray scattering (SAXS) techniques. The formation mechanism of aggregates or nuclei is very important in the initial step of crystallization. SAXS measurement is an excellent technique for observing these processes. The results of SAXS measurement suggest that boron, as a trace impurity, induces the aggregating of dextran molecules intermolecularly as a process in the nucleation formation of dextran precipitate nuclei and causes precipitation of dextran through an elongation process. These reactions occur readily at low boron concentrations. In fact, boron, which was detected at low levels in dextran solutions, was concentrated in the precipitates. Therefore, an aqueous solution of boron-free dextran should be resistant to precipitation. Copyright 2000 Academic Press.