From Chitin to Chitosan - Chitosan Based Hydrogels: Functions and Applications - page 16

1650

2890 1595

1379

1152

3430

1080

4000 3500 3000 2500 2000 1500 1000 500

CM -1

Figure 1.8
FTIR spectra of chitosan.

unique, at 1650 cm −1 , indicating that the N -acetyl amino still exists in chitosan and its
absorption intensity is weaker than that of chitin. The band at 1595 cm −1 is assigned to
-NH 2 and does not exist in chitin. The other bands of chitosan are similar to those of chi-
tin: 3430 cm −1 for O-H stretching, 2890 cm −1 for C-H stretching, 1379 cm −1 for symmetric
distortion vibration bands of -CH 3 , 1152 cm −1 for C-O-C stretching, and 1080 cm −1 for C-O
stretching.
Figure 1.9 [63] gives the 1 HNMR spectrum obtained for chitosan dissolved in D 2 O con-
taining DCl (pD approximately 4). The signal at 1.95 ppm allows determination of the
acetyl content by reference to the H-1 signal at 4.79 ppm for the d-glucosamine residue and
at 4.50 ppm for the H-1 of the N -acetyl-d-glucosamine unit at 85°C.

2 3 4

1

5.0 4.0 3.0 2.0

ppm

Figure 1.9
1 HNMR spectrum of chitosan in D 2 O, pH 4, T = 85°C, conc. 5 g/L: (1) H-1 of glucosamine units, (2) H-1 of
N -acetylglucosamine, (3) H-2, and (4) protons of the acetyl group of N -acetylglucosamine.