Abstract:

A sensitive and rapid analytical method was developed for the determination of chitosan based on the fact that the absorbance of reactive red 4/chitosan complex at 574 nm has linear relationship with the added concentration of chitosan in both B-R buffer solution (pH 4.5) and HAc-NaAc buffer solution (pH 4.5). The linear equation of the method was A = 0.3434c－0.0355 (the unit of c: μg/mL, hereinafter the same) (R2 = 0.9996) in B-R buffer solution and A = 0.3229c－0.03 (R2 = 0.9992) in HAc-NaAc buffer solution with a linear range from 0 to 4.0 μg/mL. The determination results obtained using the above two kinds of buffer solutions had no significant difference and were not affected by the molecular weight of chitosan. This method was utilized to determine the content of chitosan in a commercial brand of chitosan capsules, and the result was consistent with the indicated one. The relative standard deviation (RSD, n = 6) of precision of this method was 1.43% and the mean recovery rate was 101.1%. This method possesses good selectivity and therefore can be applied to the determination of chitosan in complex samples.

Key words: chitosan, reactive red 4, spectrophotometry