Structure analysis and degree of substitution of chitin, chitosan and dibutyrylchitin by FT-IR spectroscopy and solid state 13C NMR

Chitin, an important constituent of the exoskeleton of many organisms such as crustacea and insects, and its derivates promote the ordered healing of tissues and are therefore very suitable for use in wound dressings. The degree of substitution (DS) is an important parameter when assessing the conversion of chitin into one of its derivates. The degree of acetylation of chitin and chitosan and the degree of butyrylation of dibutyrylchitin was evaluated. It is found that FT-IR spectroscopy is a relatively easy but indirect way of determining the DS. FT-IR spectroscopy proved to be very useful for comparing the degrees of conversion and -substitution, as well as for differentiating between different chitin types. Absolute DS determinations by FT-IR however are only reliable when a calibration, using a direct technique such as 13C-NMR, is made.