Figure 4
Comparison between the C:N ratio and 1660:1690 cm−1. Below the threshold value, indicated by the dashed blue line, the quality of collagen determined by the C:N criterion reveals the relationship with the alteration of the secondary structure of collagen by the ratio of the main two Amide I sub-bands. The figure highlights that above the value of 1.30, obtained from the ratio between 1660:1690 cm−1, the collagen samples show C:N atomic ratios within the 2.9–3.6 range, meaning a good preservation state.
