Statistical approach to the spectroscopic determination of the deacetylation degree of chitins and chitosans

The objective of the study is to elucidate the effect of reaction temperature and time during heterogeneous alkali reaction on degree of deacetylation (DD) of chitin. Two different analytical methods namely 1st derivative ultraviolet and Fourier transform infrared spectroscopies have been adopted to determine and compare the DD values of the prepared chitin derivates. Statistical analysis indicates that the most significant variable is the temperature followed by the time with slight interdependence between the two. By applying the developed statistical model, using temperature and time as the process variables, chitosan with 80% DD can be obtained in 9 h using 50% (v/v) NaOH and a reaction temperature of 100 °C. Thermal analysis both in air and nitrogen showed that thermodegradation occurs in two steps in the 200–600 °C range. The 1st derivative ultraviolet method has been advocated as a suitable method for the assessment of chitin derivates.