Hi, I'm functionalizing crystal nanocellulose (CNC) in order to increase the number of carboxyl molecules on the surface, however, the carboxyl signal on the FTIR is barely visible.

According to Chem. Soc. Rev., 2018, 47, 2609 the acidification of the medium with dilute HCl before the analysis is necessary for the band observation.

Has anyone done it before? Which concentration of HCl is the best? How much cellulose should i use?

Thanks a lot for your time.