Table 1: XPS-determined binding energies (eV) of Ca 2p, P 2p, and (Ca 2p, P 2p); atomic concentrations (at. %); and Ca/P ratios for hydroxyapatite (HAP) and HAP treated with 10%, 20%, 30%, 40%, 50%, or 60% phosphoric acid (HAP—10% PA, HAP—20% PA, HAP—30% PA, HAP—40% PA, HAP—50% PA, and HAP—60% PA).

SampleBinding energy (eV)At. %Ca/P
Ca 2pP 2p (Ca 2p, P 2p)C 1sO 1sCa 2pP 2p

HAPMean 214.06a 1.65
SD 0.05 0.02
HAP—10% PAMean 214.07a 1.54c
SD 0.05 0.01
HAP—20% PAMean 214.05a 1.51b
SD 0.05 0.02
HAP—30% PAMean 214.07a 1.50b
SD 0.05 0.03
HAP—40% PAMean 214.06a 1.56c,d
SD 0.05 0.02
HAP—50% PAMean 214.03a 1.57c,d
SD 0.05 0.04
HAP—60% PAMean 214.05a 1.58d
SD 0.05 0.02

The presence of the same superscript letter for the values indicates that there were no significant differences among the samples (P > 0.05).