Table 1.

Assignment of ATR-FTIR peaks for phosphates in solution based on Guan et al.³², Lu et al.³³, Michelmore et al.³¹, Socrates³⁴, and Wan et al.³⁵.

Phosphate type	pH	Species	Wavenumber (cm−1)	Assignment (free in solution)
Orthophosphate	3.7	H2PO4−	1157	vas(P–O)
			1075	vs(P–O)
			940	vas(P–OH)
			872	vs(P–OH)
	9.1	HPO42−	1075	vas(P–O)
			990	vs(P–O)
			850	vs(P–OH)
	12.5	PO43−	1008	vas(P–O)
Tripolyphosphate	6–9		1212	vas(P–O)
			1191–1199	vas(P–O in terminal HPO3 and H2PO3)
			1120	vas(P–O) in PO3
			1101	vas(P–OH in H2P3O10)
			1060	vs(P–OH H2P3O10)
			1029	vs(P–O in terminal PO3)
			1002	vs(P–OH)
			975	vas(P2O74−)
			905	vas(P–O–P)
Trimetaphosphate	6–9		1260	vas(P–O)
			1150	vs(P–O)
			1086	vs(P–O)
			1002	vb(P–O)
			902	vas(P–O–P)
Hexametaphosphate	6–9		1260	vas(P–O)
			1115	vs(P–O)
			1090	vas(P–O)
			1030	vb(P–O)
			1008	vb(P–O)
			882	vas(P–O–P)
			868	vs(P–O–P) in long chain

v_as—asymmetric stretching vibration, v_s—symmetric stretching vibration, v_b—bending vibration.