Gel permeation chromatography on unmodified silica using aqueous solvents

Ionic liquids enable accurate chromatographic analysis of polyelectrolytes

The molecular weight distribution of polyelectrolytes was determined with high performance liquid chromatography using ionic liquids as eluents, because the electrostatic repulsion among polyelectrolytes was entirely suppressed in it. A mixed sample of polycation and polyanion was also analysed to detect them independently.

Interference prevention in size-exclusion chromatographic analysis of debranched starch glucans by aqueous system

Branch chain-length distribution of amylopectin plays an important role on the characteristics of starch. One of the adapted protocols for determining the chain-length distribution and mass proportion of starch molecules is that starch is debranched with isoamylase and then analyzed by using high-performance size-exclusion chromatography coupled with multiangle laser-light scattering and refractive index detection (HPSEC-MALS-RI). However, ammonium sulfate in commercial isoamylase and acetate in debranching buffer give significant interferences on the chromatograms because of their undesirable ionic interactions with column sorbent materials. This study deals with development for correcting those interferences. A weak anion-exchange resin or selective precipitation with barium acetate was employed to remove sulfate prior to HPSEC determination. The interference of acetate was overcome by means of high ionic strength eluent, 0.3 M sodium nitrate. The specific refractive index increment (dn/dc) of amylodextrin was determined to be 0.147 using the modified conditions and was applied to calculate the molecular weight distribution of debranched starch molecules.

High-pressure size-exclusion chromatography of anticoagulant materials

A comparative determination of molecular weights of anticoagulant materials is made on different types of high-performance liquid chromatographic stationary phases in aqueous media. The influence of different elution parameters is reported. Narrow-molecular-weight-distribution polystyrenesulphonates are used as standards for the calibration curves. Slight retentions are observed on unmodified silica supports. The commercially available grafted silica columns give similar results for the molecular weight values of heparin. A retention of pentosan polysulphate is observed on a TSK column. However, the size of this anticoagulant polymer is determined on the other grafted silica columns.