Dear Bachir,

Chitosan for NMR analysis must be purified prior to the analysis in order to avoid solution aggregates and foreign particles presence during analysis. A typical purification procedure you will find it in attached paper.

For H NMR you will need 20mg/ml of chitosan and for C13 NMR you will need 70mg/ml of chitosan (maybe a lower amount in 600MHz equipment). Then you can prepare a mixture of D2O containing CD3COOD at 1.5% v/v. Every 850 microliters of D-water you can add 150 microliters of D-acetic acid and put the solvent  in a 5ml glass vial with cap. Then added chitosan carefully to the solvent  under magnetic stirring. If chitosan have high Mw then you will have a highly viscous solution and you can heat the mixture at 60-80°C until a fully dissolved chitosan is obtained.  Then put the mixture in NMR tube for analysis.

In case you don´t have D-acetic acid you can try first dissolving chitosan in the same volume and proportion of a mixture D2O -HCl (p.a. grade) . Once dissolved the mixture is freeze dried to form the corresponding chitosan hydrochloride salt (it will looks like a cotton piece). Then redissolve chitosan salt only in D2O (1ml) at the same concentration (20 or 70 mg/ml) depending of the type of analysis. The convenience to use a glass vial with cap is you can use the same vial during all the process. 

Hope it could be useful for you.

Best regards,

Gustavo

Thank you 

Gustavo