Table 3.
FTIR spectra of buffer and stabilizers in the presence of sodium copper chlorophyllin (SCC) at pH = 3.5.
| Peak assignment | Wavenumber (cm−1) of components (original / affected by SCC) |
||||||
|---|---|---|---|---|---|---|---|
| Sodium citrate (1)* | Citric acid (1) | CMC (2) | Gum Arabic (3) | Pectin (4) | Xanthan Gum (5) | Polysorbate 80 (6) | |
| Skeletal mode vibrations of the pyranose rings | – | – | – | 400–700 / Re, LW | – | – | – |
| C–C O in-plane bending | – | – | – | – | – | 468 and 413 / Removed | – |
| CH2 twisting modes | 412.3 / Removed | – | – | – | – | – | – |
| OH torsion modes | 528.5 / Re or Removed | – | – | – | – | – | – |
| CH2 twisting modes | 547.3 / Re or Removed | – | – | – | – | – | – |
| O–CO in-plane bending | – | – | – | – | – | 591.2 (400–830) / 599.4 Re and 650 / 651.3 Re | – |
| 1–4 linkage of galactose and 1–6 linkage of mannose | – | – | – | 775.0 / Overlap, Re | – | – | – |
| C—O of epoxy rings | – | – | 894.4 / 891.67 In | 840.1 / 835 Lin and 902.6 / 890.8 In | 838.4 / 827 Re | 820.9 / 806.2 Re | 845.8 / Removed |
| Skeletal C—C stretching and bending | 755.6–945 / Re | 722.8 – 935 / Re | 1016.9 / Re | 710.56 / 711 Re | 775.8 / 803.9 Re or Removed | 820.9 / 806.2 Re | 722.8 / 722 Lre |
| Carboxylate ion bending | 843.8 / removed and 907.7 / 891.6 Re or Removed | – | – | – | – | – | – |
| The degree of methyl esterification | – | – | – | – | 915.8 / 892.2 Re or Removed | – | – |
| Polysaccharides fingerprint region | – | – | – | 900–1050 (arabinogalactan) / Re, LW | 950–1200 (glycosidic bonds and pyranoid rings) / Re, LW | – | – |
| Vinyl C—H out-of-plane bending | – | – | – | – | – | – | 950.3 (CH = CH) / 946.65 Re |
| C—C stretching | 1262.2 weak / Masked | – | – | – | |||
| Skeleton C—H rocking motions | 1271.4 / Removed and 1419.6 / 1355 Re | 1291.2 / Removed | – | – | – | – | |
| Skeleton C—H rocking of the CH2 | 1305.6 / Re | 1319.1 / Re | – | – | – | – | |
| C—H bending | – | – | – | – | 1368.4 / Overlap | 1350.9 / 1352.2 Lre | |
| C—H stretching | 2970.3 / Lre, 2925.3 (In phase CH2) / 2930.7 Lin and 2864.0 (out of phase CH2) / 2860 In | 2669.0 / 2615 Re and 3040.5 / Removed | 2914.0 / 2936.1 Overlap | 3000–2800 / Br, Lin | 2895, 2913.6 and 2944.2 / 2936.2 Br, Re | 2915.1 aliphatic (aldehyde, CH2 or CH3) / Removed | 2864.0 (–CH2) / 2872.2 Re and 2923.3 (–CH3) (acyl chain of fatty acid) / 2926.1 Re |
| C—H bending mode of the –CH3 | – | – | 1380.7 symmetric / 1350 In | 1381 symmetric / Disappeared | – | – | |
| Acetal groups bending | – | – | – | – | 1024.0 strong (–C–OH) / 1050 Re | – | |
| C—O—C and secondary alcohol C–OH stretching | 1079.3 (C–OH) / 1080.6 Re | – | 1328.9 (C—O—C) / 1350 In and 1057.8 (R–CH2OCOO–) CH–O–CH2 / Lin |
1071.5 (asymmetric –C—O—C) / 1076 LW, Re | 1024.4 / 1017.0 Re, 1225.2 (saccharide C—O—C), and 1149.9 (glycosidic linkages C—O—C) / 1143 Re |
1057.9 (glycosidic ether bond C—O—C) / 1079.2 LW, Re |
1045 –C—O of ethoxy (C—O—C) moiety / 1024 Re |
| C—O stretching | 1157.1 (COO–) / Removed | – | 1106.9 (R–CH2OCOO–) / 1116 In | – | – | 1156.0 (C—O—C glycosidic ether bond) / Disappeared | 1109.1 (C—O—C ethoxy moiety) / 1108.58 Re |
| C—O—H bending | 1200 (COOH) / Overlap, 1282.6 / Disappeared and 1419.6–1425 (hydroxyl group) / 1345 Re | 1214.4 (COOH) / 1229.17 Re | – | – | – | – | – |
| Symmetric C—O stretching vibrations of COO− | 1394.6 / 1345 Re | 1392.4 / 1345 Re | 1426.6 / 1403.59 Br, In | 1428.0 / 1405.32 Br, In | 1460.5 / ∼1454 Re | 1414.9 / 1402.93, Br | – |
| Asymmetric C—O stretching vibrations of COO− | 1592.3 / 1591.4 Re | – | – | – | – | – | – |
| OH-bending from water molecules, asymmetric C O stretch and N—H bending | 1666.7 (COO– C O) / 1620 Re | 1690.2 (COO– C O) / 1620 Re | 1625.1 (COO– C O) / 1586.1 In | 1612.2 (COO– C O and N—H bending) / 1592.4 | 1605.5 (COO– C O) / 1591.61 In | 1619.6 (COO– C O and acetate) / 1590.8 LW, Re | 1644.1C = O / 1593.8 Br, In |
| Symmetric C
O stretching of the uncharged carboxylic acid |
– | 1728.7 (COOH) / 1725.4 LW, Re | – | 1728.0 (COOH) / 1728.3 Br, In | 1744.4 (methyl ester of carboxylic acid) / 1729.7 Br, In | – | 1735.1 (ester moiety)/ 1731.9 Br, In |
| Free carboxyl groups negatively charged | 2925.3 / 2930.7 Lin | 2913.9 / 2936.1 Br, In | 2928.3 / 2940.56 Br, In | 2913.6 / 2936.2 Br, Re | 2915.1 / 2929.4 LW, Re | – | |
| O—H stretching (H-bonded hydroxyls) | 3274.8 / Re or Removed | 3227.7 and 3293.1 / Re or Removed | – | – | 3311.4 / Re or Removed | – | – |
| O—H stretching, and intermolecular or intramolecular H-bonding | 3452.5 / 3455.3 Re | 3369.7 and 3495.6 / 3455.3 Re | 3429.6 / 3463.1 Br, In | 3394.4 / 3450.6 LW | 3410.4 / 3450.9 LW, Re | 3420.1 / 3463.0 LW, Re | 3443.7 / 3446.8 In |
| N—H stretch | – | – | – | 3310–3350 secondary amine, 3400–3500 primary amine | – | – | – |
SCC: Sodium copper cholorophyllin, Re: Reduced intensity, In: Increased intensity, Lre/in: Little reduced/increased intensity, Br: Broadened band.
*References: (1) Noerpel and Lenhart, 2015, Bichara et al., 2012, Sritham and Gunasekaran, 2017. (2) Mazuki et al., 2020, Jeong et al., 2020; (3) Mazuki et al., 2020, Gopi et al., 2019, Mansour et al., 2020, Banerjee and Chen, 2007. (4) Santos et al., 2020, Ninčević Grassino et al., 2020, Hosseini et al., 2019. (5) Coates, 2006, Abu Elella et al., 2020, Saravanan and Subramanian, 2016, Kura et al., 2014. (6) Coates, 2006, Joshi et al., 2016, Kura et al., 2014, Roacho-Pérez et al., 2020.