[Separation and characterization of millet starch based on asymmetrical flow field-flow fractionation]

A method based on asymmetrical flow field-flow fractionation (AF4) coupled with a multi-angle light scattering detector and a differential refractive detector was developed for the separation and characterization of millet starch. In this study, the effects of sample loading, cross-flow rate, half-life, and ionic strength and pH value of the carrier liquid on the AF4 analysis of millet starch were investigated. In addition, the molecular structure of millet starch was determined under the optimum conditions. The optimized operation conditions for the AF4 analysis of millet starch were as follows:injection mass concentration, 0.50 g/L; injection volume, 50 μL; cross-flow rate, 1.2 mL/min; half-life, 3 min; and the carrier liquid, demonized water containing 10 mmol/L pH 7.00 NaNO₃ (add 3 mmol/L NaN₃). The method developed in this study showed good reproducibility. The relative standard deviations for the radius of gyration (R_g) and molar mass (M_w) were 3.4% and 7.0%, respectively.