Tripolyphosphate complexes

Mi FL, Shyu SS, Lee ST et al (1999) Kinetic study of chitosan-tripolyphosphate complex reaction and acid-resistive properties of the chitosan-tripolyphosphate gel beads prepared by in-liquid curing method. J Polym Sci Pol Phys 37 1551—1564... 

The pH of a 1% solution of pure sodium tripolyphosphate is 9.9 and that of commercial samples may vary between 9.5 and 10.1. The pH of a given sample of solid STP drops slowly with age because of water adsorption and partial reversion to orthophosphate and pyrophosphate. The pH of solutions varies with concentration because the sodium ion is bound in the complex form NaP O o higher concentrations maximum pH is reached at between 1—2% solution. 

Sequestration forms the basis for detergent and water-treatment appHcations of polyphosphates. Sequestration of hardness ions by sodium tripolyphosphate used in detergent formulations prevents the precipitation of surfactants by the hardness ions. Sodium polyphosphate glass (SHMP) may be added to water system to prevent the formation of calcium or magnesium scales by reducing the activity of the hardness ions. However, if the ratio of cation to polyphosphate is too high at a given pH, insoluble precipitates such as may result instead of the soluble polyphosphate complexes. The... 

A simple example of gel formation is provided by chitosan tripolyphosphate and chitosan polyphosphate gel beads the pH-responsive swelling abihty, drug-release characteristics, and morphology of the gel bead depend on polyelectrolyte complexation mechanism and the molecular weight. The chitosan beads gelled in pentasodium tripolyphosphate or polyphosphoric acid solution by ionotropic cross-hnking or interpolymer complexation, respectively. 

In aq soln HgjfNOjfj reacts with Na4P207 (Na4L) to form complex ions with the formulas [Hg2(OH)L] and [Hg2L2r. The tripolyphosphate [PjO,)] " and tetrapolyphosphate [P40 3] ions form similar complex ions. The stability of these complex phosphates decreases as the chain length increases. The dicarboxylic acids oxalic, dimethylmalonic and succinic, H2L, form complexes with Hg2 ions ... 

Various polyphosphates are effective sequestering agents under appropriate conditions. The best known of these is sodium hexametaphosphate (10.14), the cyclic hexamer of sodium orthophosphate. Further examples are the cyclic trimer sodium trimetaphosphate (10.15), as well as the dimeric pyrophosphate (10.16), the trimeric tripolyphosphate (10.17) and other linear polyphosphates (10.18). All of these polyanions function by withdrawing the troublesome metal cation into an innocuous and water-soluble complex anion by a process of ion exchange as shown in Scheme 10.7 for sodium hexametaphosphate. Hence these compounds are sometimes referred to as ion-exchange agents. 

Sodium tripolyphosphate, Na5P3O10, is the most important salt of the polyphosphoric acids. It is used in sulfonate detergents, in which it functions to complex with Ca2+ and Mg2+ (known as sequestering) to prevent the formation of insoluble soaps in hard water. 

Another strong complexing agent sodium tripolyphosphate, NasPsOio, was employed during the electrolysis of Am(III) inadilute (2 mM) H2SO4 solution to attempt stabilization of Am(IV) [142]. The concentration of NasPsOio was 0.17-0.8 M at pH 1-3 with 0.9 mM Am(III). The reported results indicate that a mixture of Am(IV) and Am(VI) was produced in solution during the electrolysis at 1.9 V versus SHE. 

The determination of phosphate concentration in a washing powder requires first the hydrolysis of the tripolyphosphate components into the phosphate ion or its protonated forms. Then a quantitative colorimetric method based upon the absorption of the yellow complex of phosphate and ammonium vanado-molybdate can be used. A series of standard solutions was prepared. The complex was then developed in 10 ml aliquots of these solutions by adding a 5.0 ml aliquot of an ammonium vanadomolybdate solution. 

A chemical compound added into detergent formulations to aid oil emulsification (by raising pH and to complex and solubilize hardness ions). Example sodium tripolyphosphate. 

Another approach to reach delayed release from chitosan matrices are ionic interactions with polyanions. The formation of a polyelectrolyte complex membrane prevents early drug release. Via this method microcapsules can be formed between chitosan and alignate or even nanoparticles can be derived upon the complexation of chitosan with the polyanion tripolyphosphate. 

Some representative linear polyphosphates are the alkali salts M PjO, (pyrophosphates) and M5P3Oi0 (tripolyphosphates). Many detergents contain Na5P3Oi0, and it has other industrial uses. In detergents the triphosphate serves to sequester Ca2+ and Mg2+ ions. Using Ln3+ ions as models, the mode of complexation was shown by nmr to involve attachment of two tetradentate P3Ofo ions. 

Sodium tripolyphosphate (STP) was commercially available in the mid-1940s and had replaced TSPP because of its superior detergent processing, solubility, and hardness ion-sequestering characteristics. Sequestration is defined as the reaction of a cation with an anion to form a soluble complex. The sequestration of Ca and Mg " ions leads to softened water and is the most important function of any detergent builder [3, 4]. 

The proportion of a Tc bone agent which is taken up by bone after intravenous injection will be affected by its binding to proteins in the blood serum. The proportions of the plasma Tc which were protein bound two hours after administration were found to be 16, 31, 54 and 85% with HEDP, MDP, PYP and tripolyphosphate respectively. In addition, the proportion of the administered dose of Tc which was taken up in bone was found to increase linearly with the fraction of Tc in the plasma which was not protein bound. Cox has reported a linear decrease in bone uptake with molecular weight for this series of bone agents, an observation which appears to reflect differences in their plasma protein binding behaviour. Thus the blood serum proteins may compete with bone for the Tc complexes and reduce the bone labelling efficiency of the radiopharmaceutical. The "Tc-diphosphonate formulations showed better performance in this respect than "Tc-PYP or Tc-tripolyphosphate. 

In sequestration (chelation) the hardness ions are bound to the builder in the form of soluble complexes. Phosphates, citrates, and nitrilotriacetic acid (NTA) are examples of this class of builder compound. Table 8.3 lists the calcium binding capacities of various builders. Other strongly chelating compounds exist, such as phosphonates and EDTA, but they are generally not extensively used in HDLDs. The most efficient builder is sodium tripolyphosphate (STPP). Unfortunately, tripolyphosphate has been identified as a possible cause of eutrophication in lakes and rivers. It is severely controlled and even banned in several countries. As a result, most countries in North America and Europe have converted to nonphosphate formulations. Other regions are also gradually imposing restrictions on the use of phosphates. 

Because complexation with Ca2+ results in insoluble CaCC>3, which deposits on items being washed, carbonate alone is not an effective builder system. In contrast, tripolyphosphate forms a soluble calcium salt, preventing deposition of insoluble salts. Sodium sesquicarbonate (Na2CC>3 NaHC03 -2 0) and sodium bicarbonate (NaHCCb) have not been used in LADD formulations, except where buffering action is needed. 

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