Constant composition study of crystal growth of dicalcium phosphate dihydrate. The influence of polyphosphates, phosphonates, and phytate

1988 ◽  
Vol 66 (9) ◽  
pp. 2181-2187 ◽  
Author(s):  
Zahid Amjad
Keyword(s):  
Crystal Growth ◽  
Phosphonic Acid ◽  
Structural Features ◽  
Dicalcium Phosphate Dihydrate ◽  
Constant Composition ◽  
Seed Crystals ◽  
Langmuir Adsorption ◽  
Inhibitor Complex ◽  
Phosphate Dihydrate ◽  
Mechanism Of Inhibition

The influence of inhibitors of varying functional groups on the crystal growth of calcium phosphate dihydrate (CaHPO4•2H2O, DCPD) on DCPD seed crystals at pH 6.00, 37 °C, has been studied using the constant composition technique. The inhibitors studied include: (a) polyphosphate (sodium pyrophosphate, sodium hexametaphosphate, SHMP), (b) phosphonates (nitrilotris(methylene phosphonic acid), NTMP; 1-hydroxyethylidene-1,1-diphosphonic acid, HEDP; ethylenediaminetetra (methylene phosphonic acid), ETMP; hexamethylenediaminetetra(methylene phosphonic acid), HMDP); and (c) myoinositol hexaphosphoric acid (phytic acid). The effect of these inhibitors on the growth kinetics have been studied at several inhibitor concentrations. The retarding effect of these inhibitors is discussed in relation to calcium–inhibitor complex formation on the DCPD seed crystals and the structural features of the inhibitor molecules. The fit of the Langmuir adsorption to experimental data supports a mechanism of inhibition through molecular adsorption of the inhibitor ions on the surface of growing crystals. Based upon the kinetic data, the overall order of inhibitors effectiveness is[Formula: see text]

The Growth of Calcium Phosphates on Hydroxyapatite Crystals. The Effect of Fluoride and Phosphonate

1978 ◽  
Vol 57 (5-6) ◽  
pp. 735-742 ◽  
Author(s):  
J.P. Barone ◽  
G.H. Nancollas
Keyword(s):  
Crystal Growth ◽  
Calcium Phosphate ◽  
Calcium Phosphates ◽  
Fluoride Ion ◽  
Dicalcium Phosphate Dihydrate ◽  
Phosphate Dihydrate ◽  
Phosphate Phase ◽  
Calcium Phosphate Phase ◽  
Basic Phase ◽  
Hydroxyapatite Crystals

The nature of the calcium phosphate phase which precipitates on hydroxyapatite seed crystals can be controlled by varying the HAP seed concentration. At low seed concentrations, dicalcium phosphate dihydrate (DCPD) is formed while at high seed levels a more basic phase precipitates. It has been found that fluoride ion increases the percentage of basic phase that crystallizes while ethylidenediphosphonic acid encourages the formation of DCPD. This behavior is explained by the competition between the nucleation of DCPD and the crystal growth on sites already present on the HAP seeds.

Seeded Growth of Calcium Phosphates: Effect of Different Calcium Phosphate Seed Material

1976 ◽  
Vol 55 (4) ◽  
pp. 617-624 ◽  
Author(s):  
G.H. Nancollas ◽  
J.S. Wefel
Keyword(s):  
Calcium Phosphate ◽  
Tricalcium Phosphate ◽  
Calcium Phosphates ◽  
Octacalcium Phosphate ◽  
Dicalcium Phosphate ◽  
Dicalcium Phosphate Dihydrate ◽  
Seeded Growth ◽  
Seed Crystals ◽  
Phosphate Dihydrate ◽  
Supersaturated Solutions

The growth of calcium phosphates on seed materials, dicalcium PhosPhate dihydrate (DCPD), tricalcium phosphate (TCP), octacalcium phosphate (OCP), and hydroxyapatite (HAP) in stable supersaturated solutions has been studied under conditions of pH and concentration for which the predominant phases are 1, DCPD, and II, HAP. All seed crystals are good nucleators for DCPD in system I, but, aside from HAP itself, only OCP will readily induce growth under condition II.

Sign in / Sign up

Export Citation Format

Share Document