Selection of a practical assay for the determination of the entire range of acetyl content in chitin and chitosan: UV spectrophotometry with phosphoric acid as solvent.

The rapidly expanding use of chitomaterials in biomedical applications demands accurate and precise analytical methods to determine physico-chemical characteristics, especially the acetyl content of the sample. The analytical methods available for the determination of the acetyl content of the biomaterials are quite different in efficiency, accuracy and precision. Out of 22 analytical methods reviewed, XRD, DSC, FTIR (KBr pellet), solid state (13)C CP/MAS NMR, and acid hydrolysis-HPLC and the spectrophotometry assay using phosphoric acid as solvent (PUV) were selected in this study. The validity and applicability of these methods were investigated with a wide range of chitin and chitosan samples varying acetyl content, preparation methods, and sources. The XRD, DSC, and FTIR (KBr pellet) methods showed poor accuracy with the samples of diverse preparations and sources. The PUV method was modified and accuracy of the method was examined against absolute methods: solid state (13)C CP/MAS NMR and acid hydrolysis-HPLC methods. The correlations between these three methods were >0.9. Therefore, the PUV method was selected as the most generally acceptable method based on its accuracy, reliability, simplicity, and instrument availability.