3.5. Determination of the N-Deprotection Degree of the Aspartate

The amount of N-deprotection in the aspartate grafts in the modified celluloses was measured by using a ninhydrin method previously reported [22]. Celluloses with N-deprotected aspartates react with a ninhydrin solution developing a blue-purple color due to Schiff base formation [52]. The deprotection level in each sample was calculated by comparing the UV absorbance values at 575 nm, with the values from a calibration curve of valine at different concentrations (2, 4, 6, 8 and 10 mM).