Table 1 Assignment of main infrared peaks (cm−1) of standard materials and compounds
Absorption maximum (cm−1) | Assignment* | |
|---|---|---|
Collagenous materials | ||
Collagen | Parchment | |
3315 s, br | 3302 | Amide A: first component of vN–H in Fermi resonance with the amide II overtone (overlapping with v as O–H (3447 br) and v s O–H (3240 br) of structural H2O) |
3072, m–w, br | 3072 | Amide B: (second component of vN–H in Fermi resonance with the amide II overtone) |
2958 | 2926 | vC–H |
1640 s | 1644 | Amide I: vC=O with small contributions from vC–N and δN–H)* [overlapping with δH–O–H (approx. 1610) of structural H2O]*** |
1545 s | 1538 | Amide II: (vC–N with contributions from δ ip N–H)** |
1454 m–w | 1448 | δCH2 of Pro- |
1405 w | 1408 | δ ip C–O–H (carboxylic side chains) and δNH2 |
1340 w | 1334 | wCH2/δC–H (methine) |
1241 m–w | 1230 | Amide III: (vC–N + δN–H with contributions from vC–C and δipC=O)** |
1082, 1032 | 1084, 1031 | Breathing of proline ring [69] with carbohydrate vC–O and vC–O–C (glycosylation sites) [70]/parchment: additional esters [66] |
Gallic acid [40, 73, 74] | ||
3498 | vO9H, vO11H | |
3366 | vO10H | |
3284 | vO14H (COOH) | |
3065, 2996, 2844 | vC2–H, vC6–H | |
2673, 2632, 2575, 2512 | vO14H (–COOH dimers) | |
1703 | vC=O | |
1668, 1648 | vC=O (–COOH dimers) | |
1612,1542,1484, 1468, 1427, 1387, 1321 | vC=C (aromatic ring vibrations) | |
1268 | vC–O | |
1221 | δ(i–p) C–O–H | |
1184 | vC1–C7 + vC–H | |
1099 | vC1–C7 + δC–O–H | |
1028 | Aromatic asym-, sym- breathing, vC1–C7 + vC–OΗ (phenol) | |
904 | vC–O +δ(o–o–p) C–O–Η (dimer band) + δ(o–o–p) of ring | |
867 | δ(i–p) C–H | |
767 | δ(o–o–p) C–H (out-of-phase) | |
735 | δ(o–o–p) C–H (out-of-phase) + τC–OΗ (torsion) | |
703 | Aromatic ring puckering | |
636 | Aromatic ring puckering + δ(o–o–p) C–Ο–H (phenolic) | |
559 | δ(o–o–p) C–Ο–H (phenolic) | |
492 | τC—aromatic ring | |
Gum Arabic | ||
3352 | vOH | |
2932 | vC–H | |
1604 | v as COO− | |
1418 | v s COO− | |
1146(sh), 1068, 1035(sh) | vC–O | |
Iron (II) sulfate heptahydrate | ||
3336 | vOH | |
1652 | δOH in water | |
1092 | v 1 SO4 2− | |
977 | v 3 SO4 2− | |
619 | v 4 (asym-) SO4 2− | |
LIG ink formulation | ||
3415 | vOH in water | |
1645 | δOH in water | |
1094 | v 1 SO4 2− | |
977 | v 3 SO4 2− | |
628 | v 4 (asym-) SO4 2− | |
LIGG ink formulation | ||
3439 | vH–O in polysaccharide (gum Arabic) and water | |
2931 | vC–H | |
1640 | δOH in water overlapping with v asCOO− in polysaccharide (gum Arabic) | |
1424 | v s COO− in gum Arabic | |
1083 | v 1 SO4 2− overlapping with vC–O in gum Arabic | |
1146(sh), 1035(sh) | vC-O in gum Arabic | |
604 | v 4 (asym-) SO4 2− | |