Table 2.

FTIR-absorption-band assignments for minerals components in bone cortex and osteoid

Assignments	Wavenumber at the resonance ($c{m}^{-1}$)	Type of bonds
A. FTIR-absorption-band assignments for minerals
Carbonate: ${\nu }_2$ ${\text{CO}}_3^{2-}$	850–870	C–O bend (${\nu }_2$) [35]
Type B	~872
Type A	~880
Labile	~865
Carbonate: ${\nu }_3$ ${\text{CO}}_3^{2-}$	1355–1485	O–C–O stretch (${\nu }_3$) [24]
Type A1 doublet	1534–1545 & 1465–1459
Type A2 doublet	1505 & 1565
Type B doublet	1408–1423 & 1455–1459
Labile	~1413 & 1500
Acid phosphate ${\nu }_3$ ${\text{HPO}}_4^{2-}$	870–875	P–OH stretch (${\nu }_3$)[32]
Acid phosphate: ${\nu }_2$ ${\text{HPO}}_4^{2-}$	988–1005	P–O stretch (${\nu }_2$)
free	~988
in HA	~987 & 1000
Acid phosphate: ${\nu }_6$ ${\text{HPO}}_4^{2-}$	1037–1130	P–O stretch (${\nu }_6$) [12, 32, 39]
free	~1076
in HA	~1058 & ~1037 & 1,145
in HA	~1127 & ~1110
Acid phosphate : ${\nu }_5$ ${\text{HPO}}_4^{2-}$	1230	P–O–H bend (${\nu }_5$) [32]
Phosphate: ${\nu }_1$ ${\text{PO}}_4^{3-}$	950–970	P–O stretch (${\nu }_1$) [17, 36]
ACP	~950
OCP	~955
Phosphate in HA	~960
Phosphate: ${\nu }_3$ ${\text{PO}}_4^{3-}$	980–1200	P–O stretch (${\nu }_3$) [12, 17]
in well-crystallized HA	~1030, 1055, 1096, 1116
in poorly crystallized HA	~1020, 1040
Hydroxyl in HA	3570	P–O stretch (O–H)
B. Mineral indexes defined for bone’s cortex
Mineral-to-matrix ratio (MM)	$\frac{{\nu }_3{\text{PO}}_4^{3-}}{\text{Amide}I}$	Mineral content per collagen amount [5, 31, 35]
Crystallinity (XST)	$\frac{1030}{1020}$	Poorly crystallized into more crystallized [39]
Mineral maturity (CM)	$\frac{1030}{1110}$	Non-apatite transformation into apatite [12, 39]
Acid phosphate substitution (APS)	$\frac{1130}{1096}$	Acid phosphate content in HA [39]

HA hydroxylapatite, OCP Octacalcium phosphate, ACP: amorphous calcium phosphate