Comparison between size exclusion chromatography and micro-batch analyses of corn starches in DMSO using light scattering detector

The molecular structure of corn starches different in amylose content (waxy, normal, and high-amylose) was analyzed in 90% dimethyl sulfoxide (DMSO) solution by refractive index (RI) and multi-angle laser light scattering (MALLS) detectors. The starch sample solutions were measured either by medium-pressure size exclusion chromatography (MPSEC) or by the micro-batch mode. For waxy corn starch, the average molar mass (M_w) and radius of gyration (R _g) values were similar in both methods. However, for normal and high-amylose corn starches, M_w measured by the micro-batch mode was 2-4 times greater than that by the chromatographic method, although R _g values obtained from both methods were not very different. The M_w difference was the greater the higher the amylose content of starch.