Several types of chitin, chitosan and DBC were studied with FT-IR in order to establish differences in structure and degree of substitution (and thus degree of conversion).
FT-IR peak analysis confirmed that indeed the desired reactions had taken place but FT-IR done as suggested in literature did not provide accurate absolute DA values. FT-IR DA determinations are clearly dependent upon the followed method and especially sample form and treatment.
So great care should be taken when assessing the DA value of chitin by FT-IR measurements, and a calibration with respect to a direct technique such as 13C NMR should be performed. This calibration is then only useable for one certain combination of FT-IR method and sample form. A
formula for the quantitative determination of the degree of acetylation by FT-IR is proposed in this article. Should one however want to compare different chitin or chitosan types qualitatively, FT-IR without calibration may prove to be a very useful tool for determining differences in DA and crystalline structure