Calcium phosphate stability

Nzihou, A. Sharrock, P. 2002. Calcium phosphate stabilization of fly ash with chloride extraction. Waste Management, 22, 235-239. 

Many modifications of stabilized phosphate technology now exist (for example, zinc is often included) and new, further improved calcium phosphate stabilizers have emerged. 

Reynolds, E.C. 1998. Anticariogenic complexes of amorphous calcium phosphate stabilized by casein phosphopeptides a review. Spec. Care Dent. 18, 8—16. 

Acumer. [Rohm Haas] Polyacrylic acids or their sodium salts dispersant, thickener, anti-scale dqx)8ition agent for NR, SR latexes, for water treatment calcium phosphate stabilizer. 

In particular, where polyphosphate is added either to the MU waterline (say, as a stabilizer against the risks of after-precipitation) or to the FW line or FW tank (as a precipitating treatment for residual hardness), there is some risk of FW line phosphate deposits developing. Such deposits are likely to be primarily composed of hard, intractable calcium phosphate [tricalcium phosphate Ca3(P04)2] scale, but they may include magnesium phosphate [Mg3(P04)2] and other insoluble phosphates and hydroxides. The risk of precipitation and subsequent deposition is increased where the pH is below 8.3, if the FW line is particularly long, or when the FW temperature is high. 

Some acrylic acid copolymers are promoted as having a very wide range of functions that permit them to act as calcium phosphate DCAs, barium sulfate antiprecipitants, particulate iron oxides dispersants, and colloidal iron stabilizers. One such popular copolymer is acrylic acid/sulfonic acid (or acrylic acid/ 2-acrylamido-methylpropane sulfonic acid, AA/SA, AA/AMPS). Examples of this chemistry include Acumer 2000 (4,500 MW) 2100 (11,000 MW) Belclene 400, Acrysol QR-1086, TRC -233, and Polycol 43. 

SS/MA may be structured in different ratios of sulfonated styrene to maleic anhydride. Typically, it is 3 1 (20,000 MW) or 1 1 (15,000 MW). The application rates of all calcium phosphate scale/sludge inhibitors or stabilizers vary, based on the amount of calcium present in the cooling system, with increased calcium hardness leading to higher levels of polymer required. 

Stabilization of amorphous calcium phosphate by Mg and ATP Calcified Tissue Research 23 245-250. 

Foam cement is a special class of lightweight cement. The gas content of foamed cement can be up to 75% by volume. The stability of the foam is achieved by the addition of surfactants, as shown in Table 10-9. A typical foamed cement composition is made from a hydraulic cement, an aqueous rubber latex in an amount up to 45% by weight of the hydraulic cement, a latex stabilizer, a defoaming agent, a gas, a foaming agent, and a foam stabilizer [359,362]. Foamed high-temperature applications are based on calcium phosphate cement [257]. 

Most of this section will be devoted to summarizing information relating to the stability constants reported for complexes of this group of Ca2+-binding ligands. However, we shall precede this main part with a short mention of a few relevant structures. Other properties of calcium phosphates and phosphonates will be mentioned in Sections VIII.B.4 and VIII.D below. An overall view of complexes of nucleosides, nucleotides, and nucleic acids is available (670). 

Solubilities and stabilities of calcium phosphates in natural waters have been described (735), as have the nucleation and growth of calcium phosphate from solution (736). Several species have long been known to inhibit the precipitation of calcium phosphates, for example carbohydrates (646) and statherin, the tyrosine-rich peptide which occurs in saliva (737). The role of... 

Calcium Phosphates And Calcified Tissues. Precipitation in the system Ca(0H)2 - H3PO4 - H2O can lead to the formation of several calcium phosphates (shown in Table IV), of which hydroxy-apatite 0HA is the most stable above a pH of about 4.1. The relative stabilities are illustrated in Figure 12. 

Monobasic calcium phosphate is primarily used in fertilizers. It also is used in baking powders as a mineral supplement in food as a buffer for pH control and as a stabilizer for plastics. 

C.P.A.T. Klein, J.G.C. Wolke, J.M.A. de Blieck-Hogervorst, K. de Groot, Calcium phosphate plasma-sprayed coatings and their stability An in vivo study, J. Biomed. Mater. Res. 28 (1994) 909-917. 

Sodium fatty acid ester sulfonates are known to be highly attractive as surfactants. These have good wetting ability and excellent calcium ion stability as well as high detergency without phosphates, and are used in powders or liquids. They can also be used in the textile industry, emulsion polymerization, cosmetics, and metal surface fields. Moreover, they are attractive because they are produced from renewable natural resources and their bio degradability is almost as good as alkyl sulfates (134—137). 

The stability of excipients is almost always taken for granted. Obviously, there is the potential for a phase change with certain lower melting excipients, e.g., semisolid materials, however, this is not a chemical phenomenon although it may enhance the potential for interaction by increasing the effective interface available at which the interaction can take place. However, some materials are not stable under conditions encountered in excipient compatibility screening or accelerated stability testing. A notable example is dibasic calcium phosphate dihydrate. At temperatures as low as 37°C, under certain conditions, the dihydrate can dehydrate to form the anhydrous material with the concomitant loss of water of crystallization (25), and at 25°C, it is a stable solid with a shelf life, when stored correctly, of more than two years. 

The dibasic calcium phosphate dihydrate example discussed above is probably an extreme example of the instability of an excipient relating to the release of water. But many excipients exist in a hydrated state, and heating them for the purposes of compatibility studies, or accelerated stability testing, can cause any free water, and sometimes other types of water, to be released, which can then influence any potential interaction, or even interact itself with the drug. 

Although CCP represents only about 6% of the dry weight of the casein micelle, it plays an essential role in its structure and properties and hence has major effects on the properties of milk it is the integrating factor in the casein micelle without it, milk is not coagulable by rennet and its heat and calcium stability properties are significantly altered. In fact, milk would be a totally different fluid without colloidal calcium phosphate. 

On heating at temperatures above 100°C, lactose is degraded to acids with a concomitant increase in titratable acidity (Figures 9.5, 9.6). Formic acid is the principal acid formed lactic acid represents only about 5% of the acids formed. Acid production is significant in the heat stability of milk, e.g. when assayed at 130°C, the pH falls to about 5.8 at the point of coagulation (after about 20 min) (Figure 9.7). About half of this decrease is due to the formation of organic acids from lactose the remainder is due to the precipitation of calcium phosphate and dephosphorylation of casein, as discussed in section 9.4. 

Reducing the level of colloidal calcium phosphate increases stability in the region of the HCT maximum. 

---