Starch molecular mass and size by size-exclusion chromatography in DMSO-LiBr coupled with multiple angle laser light scattering

The weight average molar mass (M-w) and root mean square radii of starches from waxy maize (Amioca), waxy rice flour, cassava, Hylon V, Hylon VII, and potato amylose were determined by size-exclusion chromatography (SEC) and multiple-angle laser light scattering (MALLS). Dimethylsulfoxide (DMSO) containing 50 mM LiBr was used to dissolve the starches and also served as the mobile phase. SEC with large particle size polystyrene divinylbenzene packing materials and MALLS instrumentation were evaluated for the ability to separate and determine molar mass (MM) of starch polymers, respectively The determination of M-w by MALLS is necessary because the M-w of many cereal starches exceeds the available molecular standards by one or two orders of magnitude. The M-w depends on the method of calculation. The M-w (Berry method) of starch from waxy corn was 2.27 x 10(8) Da, waxy rice 8.9 x 10(7) Da, cassava 5.7 x 10(7) Da, Hylon V 2.7 x 10(7) Da, Hylon VII 4.8 x 10(6) Da, and potato amylose 1.9 x 10(5) Da. Recovery dropped dramatically for molecules with root mean square radii >209 nm.