Bioactive Surface Modification of Hydroxyapatite

Table 2

XPS-determined binding energies (eV) of Ca 2p, P 2p, and Δ(Ca 2p, P 2p), and Ca/P ratios for hydroxyapatite (HAP), HAP treated with 30% phosphoric acid (HAP—30% PA), and HAP—30% PA in storage for 12 hours (HAP—30% PA—12 h) at each incidence angle of the X-ray (90, 75, 60, 45, 30, or 15 degrees).

Sample	Angle of incidence (degrees)	Binding energy (eV)			Ca/P
		Ca 2p	P 2p	Δ(Ca 2p, P 2p)
HAP	90	346.60	132.55	214.05	1.65
	75	346.70	132.60	214.10	1.59
	60	346.60	132.50	214.10	1.63
	45	346.65	132.55	214.10	1.66
	30	346.60	132.50	214.10	1.69
	15	346.60	132.55	214.05	1.68
	Mean	346.63	132.54	214.08^a	1.65^b
	SD	0.04	0.04	0.03	0.04
HAP—30% PA	90	346.80	132.75	214.05	1.45
	75	346.80	132.75	214.05	1.44
	60	346.85	132.75	214.10	1.45
	45	346.85	132.80	214.05	1.44
	30	346.90	132.95	213.95	1.46
	15	346.90	132.65	214.25	1.45
	Mean	346.85	132.78	214.08^a	1.45^b
	SD	0.04	0.10	0.10	0.01
HAP—30% PA—12 h	90	347.30	133.40	213.90	1.11
	75	347.25	133.40	213.85	1.10
	60	347.30	133.45	213.85	1.10
	45	347.30	133.40	213.90	1.09
	30	347.30	133.35	213.95	1.11
	15	347.30	133.30	214.00	1.06
	Mean	347.29	133.38	213.91	1.09^b
	SD	0.02	0.05	0.06	0.02

^a𝑃>0.05 indicates no significant difference between the samples.
^b𝑃<0.01 indicates significant differences among the samples.