Rapid determination of degree of deacetylation of chitosan by a headspace analysis based Titrimetric technique

This paper reports on a novel method for rapid determination of the degree of deacetylation (DD) of chitosan samples by headspace gas chromatography (HS-GC). In this method, overdose of an acid is added to protonate the free amino groups in chitosan, which further reacts with bicarbonate (as an alkali titrant) in a close vial. Based on measuring the HS-GC signal for CO2 vs. the volume of HCO3- added by a stepwise titration, two transition points can be obtained. The DD value is calculated by net volume of HCO3- consumed, i.e., by the R-NH3+ groups in chitosan. The results showed that the present method has a good measurement precision (RSD < 0.82%) and accuracy (relative differences < 6.46% when compared with the results measured by a reference method). Since the HS-GC can perform an automated sample reaction equilibration and measurement, it could be much more efficient than the existing methods in the batch sample analysis.