Simple method on determination of deacetyllation degree for chitosan

Abstract

The simple method of comparative study has been carried out for the determination of DDA chitosan by infrared spectrometry and titrimetric. Determination of DDA by infrared spectrometry has the data quantification technique with 4 different equations This study aims to determine the significance of the DDA value with these equations. Including the titration method, there are 4 techniques to determine the endpoint that has been reported in the previous studies. The endpoint is indicated by phenolphthalein, methyl orange, and Conway (methyl red-bromocresol green) indicators, and potentiometric titration. This study was conducted by measuring DDA for chitosan with 7 replications using FTIR and titration using phenolphthalein, methyl orange, and Conway (methyl red-bromocresol green) indicators, and potentiometric titration. The DDA has been determined using the baseline method with absorption at wavenumber 3450 cm−1 from –OH aliphatic groups and 1655 cm−1 from –CO groups with Eq. 2 and Eq. 3; absorption at wavenumber 2870 cm−1 from –CH stretching band with Eq. 4; and absorption at wavenumber 1420 cm-1 from –CH2 stretching band with Eq. 5. The significance testing of the DDA values using infrared spectrometry and titrimetric methods was carried out using ANOVA. Based on the study, infrared spectrometry with Eq. 2 - Eq. 5 recommended as the method for rough estimation of DDA for chitosan and its derivatives. The DDA values from Eq. 2 and Eq. 3 with the absorption at 3450 and 1655 cm−1 and Eq. 5 with absorption at 1320 and 1420 cm-1 is not significantly different but the determination of DDA with Eq. 4 with the absorption at 2870 cm-1 is a significant difference. The calculation of DDA values with good precision and good accuracy is calculated using Eq. 5. The method allows for dry samples and calculation of DDA requires carefulness in determining the baseline to get the good precision and good accuracy. The determination of DDA using volumetric is recommended using potentiometric titration. Titration with phenolphthalein, methyl orange, Conway indicators have limitations on observing the endpoint. Chitosan has limitation solubility at low pH and observation of the endpoint of the titration must be carried out rapidly before chitosan is precipitated. Potentiometric titration has good precision and good accuracy for the determination of DDA using the simple, available equipment, inexpensive, good precision, accurate, and reliable for routine analysis.