Figure 6
13C CP/MAS NMR spectra of shrimp shell and different chitin. The spectra were measured under 10 kHz MAS spinning at a 13C resonance frequency of 75 MHz. a) Biologically purified chitin, b) Shrimp shells before biological treatment and c) Commercial chitin. The signal at 48 ppm is a spinning sideband of the carbonyl signal at 175 ppm. The weak signals in the regions of 20–40 ppm, near 120 ppm and the up field shoulder of the carbonyl peak at 175 ppm in Figure 6b are attributed to aliphatic, aromatic and carbonyl resonances of residual protein contaminations, respectively.