Table 1.

Specific surface area (SSA_BET), Ca/P ratio, citrate and carbonate content of samples synthesized in the absence (HA) and presence of citrate (cit-HA) at different maturation times. The citrate surface density is also provided, as both n _cit/nm²and 1cit/(n nm)².

Sample	SSABET (m2·g−1)	Ca/Pb	Citrate content			Carbonate content (wt%)
			(wt%)	Surface density
				n cit/nm2	1cit/(n nm)2
HA1a	130 ± 6		0	0	0	1.0 ± 0.1
HA2a	160 ± 10		0	0	0	1.8 ± 0.2
Cit–HA–4 h	160 ± 10	1.51 ± 0.02	2.4 ± 0.1b	0.47 ± 0.1	1.46 ± 0.3	1.1 ± 0.1b
Cit–HA–24 h	145 ± 7	1.52 ± 0.03	1.9 ± 0.1b	0.41 ± 0.1	1.56 ± 0.4	1.0 ± 0.1b
Cit–HA–96 h	114 ± 5	1.54 ± 0.03	2.0 ± 0.1b	0.55 ± 0.1	1.35 ± 0.2	1.0 ± 0.1b

^aCitrate-free hydroxyapatite studied in ref. 26.

^bref. 25.