Table 2 Characteristic bands of the typical FT-IR spectrum obtained on the sample extracts (see text for details)

3600–3000

O–H stretching

3400

O–H stretching (adsorbed water in silicates)

2950

C–H asymmetric stretching (methyl groups)

2925

C–H asymmetric stretching (methylene groups)

2855

C–H symmetric stretching (methylene groups)

1705

C=O stretching (esters and acids)*

1670

C=O stretching (esters and acids)*

1590

C=C stretching (aromatics)

1455

C-H asymmetric deformation (methyl groups)/scissoring (methylene groups)

1375

C-H symmetric deformation (methyl groups)

1295

Not assigned

1100–1000

Si–O stretching (silicates)/ring deformations

875

C-H out of plane deformation (aromatics)

835

C-H out of plane deformation (aromatics)