Table 1 Summary of characteristic peaks in the FTIR spectra of leather

3600–3200

O–H stretch

Adsorbed water

3100–2800

C–H stretch

3220 (broad)

N–H stretching

2925 (broad)

C–H₃ stretching

Protein chain, lipids

2900

C–H bending

Protein chain, lipids

2830

O=C–H stretch

Aldehyde from degradation

2350 (broad)

Sulfur (possibly from contamination)

2360/2340 doublet

Carbon dioxide

1740–1750

R–C=O

Esters in collagen, lipids

1660

C=O stretching

Amide I

1656–1500

C–N–H bending

Amide II

1380

C–O–C

Amino acid side chains

1490–1300

C–H bending

Deformation of protein and lipids

1258–1273

Protein backbone

Amide III

1150

C–O–C stretch

Cyclic ethers in tannins

1033

C–O–C=O

Esters in tannins

990

C–O stretch

976

C=C

Amide III