Dicalcium phosphate dihydrate

Dicalcium Phosphate Dihydrate (DPD). Dicalcium phosphate cHhydrate is completely nonreactive at room temperature. At 65—71°C and in the presence of water, it dehydrates and decomposes into hydroxyapatite and acidic monocalcium phosphate, or a free phosphoric acid (18). It is used to some extent in cake mixes in combination with faster acting acid. Its primary function is to provide acidity late in the baking cycle and thus produce a neutral and palatable product. DPD has an NV of 33. It provides sufficient acidity only in products requiring long baking times. 

An abrasive is usually chemically inert, neither interacting with other dentifrice ingredients nor dissolving in the paste or the mouth. Substances used as dentifrice abrasives include amorphous hydrated silica, dicalcium phosphate dihydrate [7789-77-7] anhydrous dicalcium phosphate [7757-93-9] insoluble sodium metaphosphate [10361-03-2], calcium pyrophosphate [35405-51-7], a-alumina trihydrate, and calcium carbonate [471-34-1]. These materials are usually synthesized to specifications for purity, particle size, and other characteristics naturally occurring minerals are used infrequently. Sodium bicarbonate [144-55-8] and sodium chloride [7647-14-5] have also been employed as dentifrice abrasives. 

Fig. 9 The FT-Raman spectra of a paracetamol-dicalcium phosphate dihydrate mixture A, spectrum of pure paracetamol B, spectrum of pure dicalcium phosphate dihydrate C, spectrum of a mixture of paracetamol (5% w/w) in dicalcium phosphate dihydrate D, spectrum C minus spectrum B to identify pure paracetamol (compare with A). 

Monocalcium phosphate monohydrate reacts almost as quickly as cream of tartar (potassium acid tartrate). Anhydrous monocalcium phosphate has four-fifths of the reactivity. At ambient temperatures dicalcium phosphate dihydrate, sodium aluminium phosphate and some grades of sodium acid pyrophosphate are essentially unreactive. 

Despite the importance of the precipitation of calcium phosphates, there is still considerable uncertainty as to the nature of the phases formed in the early stages of the precipitation reactions under differing conditions of supersaturation, pH, and temperature. Although thermodynamic considerations yield the driving force for the precipitation, the course of the reaction is frequently mediated by kinetic factors. Whether dicalcium phosphate dihydrate (CaHPO HoO, DCPD), octacalcium phosphate (Ca HfPO, 2.5 H20, OCP), hydroxyapatite (Cag (PO fOH), HAP), amorphous calcium phosphate (ACP), or a defect apatite form from aqueous solution depends both upon the driving force for the precipitation and upon the initiating surface phase. Thermodynamically, the relative supersaturation, o, is given by... 

Landin, M., Casalderrey, M., Martinez-Pacheco, R., Gomez-Amoza, J.L., Souto, C., Concheiro, A., and Rowe, R.C., Chemical stability of acetylsalicyclic acid in tablets prepared with different particle size fractions of a commercial brand of dicalcium phosphate dihydrate, Int. ]. Pharm., 123, 143,1995. 

Tablets were prepared either with an insoluble (dicalcium phosphate dihydrate), a soluble (6-lactose) or a moderately soluble filler-binder (a-lactose monohydrate). As a disintegrant four different starches (com, rice, potato and tapioca) were used. As a comparison the effect of two super-disintegrants (crospovidone and sodium starch glycolate) was studied. The disintegrants were added at two concentration levels. The compression load was adjusted in order to obtain tablets with comparable initial cmshing strengths.

Tablets prepared with dicalcium phosphate dihydrate increased in crushing strength due to increasing temperatures (A,sir(s) ). The relative humidity had a negative effect on the SIR of crushing strength of the tablets prepared with dicalcium phosphate dihydrate, except for the tablets prepared with potato starch. Also a significant interaction between the temperature and relative humidity effect was seen (A3,sir(S) 0), indicating that the effect of the relative humidity on the SIR of crushing strength of dicalcium phosphate dihydrate tablets depended on the level of temperature and vice versa.

The a-lactose tablets were influenced by the relative humidity too (y5, siR(S) is significant) but the effect was smaller than for the dicalcium phosphate dihydrate tablets. From the tablets investigated, the 6-lactose tablets were least influenced by storage. 

Each combination behaves differently after storage. In all cases there was an effect of the starch concentration (y i sir(d) is significant). In most cases the relative humidity as well as the interaction between the relative humidity and the disintegrant concentration plays a role in the disintegration time of tablets prepared with either lactose. The dicalcium phosphate dihydrate/rice starch combination is influenced very strongly by the three factors studied. This combination is not suitable for use in tropical countries. Neither is the combination of B-lactose and crospovidone. 

From the SIR of disintegration time calculations no general conclusions can be drawn. It is merely possible to detect which specific combination is influenced strongly by the storage conditions. In this respect the dicalcium phosphate dihydrate/rice starch and the B-lactose/crospovidone combinations were conspicuous. These combinations should be avoided in formulations for use in tropical countries. 

Landln M, Martinez-Pacheco R, Gomez-Amoza JL, Souto C, Concheiro A, Rowe RC. The effect of country of origin on the properties of dicalcium phosphate dihydrate powder. Int J Pharm 1994 103 9-18. 

Landin M, Rowe RC, York P. Particle size effects on the dehydration of dicalcium phosphate dihydrate powders. Int J Pharma 1994 104 271-275. 

Beevers, C. A. The crystal structure of dicalcium phosphate dihydrate, CaHPC>4 2 H2O. Acta Cryst. 11, 273-277 (1958). 

FIGURE 19 (a) 3D data plot with fitted plane twisted at t = tmax and (b) 3D parameter plot of ( ) DCPD dicalcium phosphate dihydrate, (O) spray-dried lactose, ( ) MCC. microcrystalline cellulose, (0) theophylline monohydrate, and ( ) HPMC hydroxypropyl methylcel-lulose for data gained with an eccentric table ting machine [47]. 

Schmidt, P. C., and Leitritz, M. (1997), Compression force/time-profiles of microcrystalline cellulose, dicalcium phosphate dihydrate and their binary mixtures—A critical consideration of experiments and parameters, Eur. J. Pharm. Biopharm., 44, 303-313. 

Rodriguez, L., Caputo, O., Cini, M., Cavallari, C., and Greechi, R. (1993), In vitro release of theophylline from directly-compressed matrixes containing methacrylic acid copolymers and/or dicalcium phosphate dihydrate, Farmaco, 48,1597-1604. 

Dicalcium phosphate dihydrate (DCPD) CaHP04-2H20 6.59... 

Moreno, E.C, Brown, W.E, and Osborn, G. Stability of dicalcium phosphate dihydrate in aqueous solutions and solubility of octacalcium phosphate. Soil Sci. 24, 99-102 (1960). ... 

Marshall, R.W. and Nancollas, G.H. The kinetics of crystal growth of dicalcium phosphate dihydrate. J. Phys. Chem. 73, 3838-3844 (1969). 

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