Strategy to improve the characterization of chitosan by size exclusion chromatography coupled with multi angle laser light scattering

Abstract Here we present SEC-MALLS study for chitosan samples with weight average molar mass M w between 33 and 427 kg/mol on columns packed with 8 μm porous particles. A low injection concentration on the order of 0.1–0.2 mg/mL must be used to avoid overloading of the SEC columns, due to the extended coil conformation of cationic chitosan in the dilute acid buffer as compared to neutral polymers. Additionally, SEC must be performed at an eluent flow rate no more than 0.5 mL/min for high molar mass chitosan samples. At flow rates of 1.0 and 1.5 mL/min, the elution of the largest chitosan species is delayed, which leads to a distortion of the molar mass distribution towards lower molar mass region. Such an abnormal behavior is due to a chromatographic mode transition from SEC to slalom chromatography, originated from the coil–stretch transition of chitosan chains in elongational flow through the packed columns.