Determination of the degree of acetylation of chitosan by UV spectrophotometry using dual standards

Determination of the degree of acetylation of chitosan by UV spectrophotometry using dual standards is investigated. The UV absorbance of a pure chitosan solution is contributed additively by the N-acetylglucosamine and glucosamine residues; the absorbance divided by the total molar concentration of the residues (A/ct) is linearly related to the degree of acetylation (DA). Using acetyl glucosamine and glucosamine hydrochloride as standards in 0.1 M hydrochloric acid solution, the equation obtained by linear regression is A/ct = 3.3615DA + 0.0218, R2 = 0.9958. The DA of the analytical sample (m milligram of chitosan in V liters solution) can be calculated byDA=161.1·A·V-0.0218m3.3615m-42.1·A·V.

The degree of acetylation (DA) of a sample of chitosan can be calculated by the equation:DA=161.1·A·V-0.0218m3.3615m-42.1·A·Vwhere m is the number of milligrams of chitosan, V is the volume of the solution in liters, and A is the UV absorbance of the solution.