Metaphosphates analysis

SatnpCe Preparation. Seventy grams of sample, previously calcined at 538°C, was dispersed in about 125 mL of sodium metaphosphate solution and "wet screened" using a sieve stack of 250, 270 and 325 mesh, 8-inch diameter sieves. The sieves were washed with water until the effluent was free of any particulate and then rinsed with acetone to de-water. After air drying, the contents of each sieve were transferred to a porcelain dish and the material was recalcined at 538°C. Appropriate weights taken during this procedure allowed for the determination of percent moisture in the starting material and sieve analysis relative to the appropriate sieve fractions. The total +325 mesh material was recombined and mixed for the test. 

As cyclophosphates and the catenaphosphate anion (together termed metaphosphates) share the basic composition (PO3 ) , crystal-structure analysis is often the only way to determine which species is present, although IR spectroscopy may be useful (see Section 3.2.1). Different isomers of the same metaphosphate composition are often found. Six crystal forms (A-F) of M(P03)3 (M = Al, Cr, Mn, Fe, Ga) have been identified, three of which have been structurally characterized and found to contain cyclotetraphosphate (form A), cyclohexaphosphate (B), and catenaphosphate (C) anions. 

As was the case with other phosphotransfer reactions, the hydrolysis reaction catalyzed by PTPs lies along a mechanistic continuum between the limiting cases of associative and dissociative mechanisms. In the case of Yersina PTP, a crystal structure was solved with nitrate, a mimic of the transition state similar to the use of AIF3 with protein kinase A. In this case, analysis of the structure is proposed to be more consistent with a -1 charged metaphosphate, dissociative mechanism (11). 

In physical and theoretical methods there has been a notable increase in the use of recently developed techniques - most of which have trendy acronyms. Thus DRAMA P NMR has been used to determine internuclear P-P distance in a phosphine sulfide 4,8-residue substituted decapeptide, and XANES has been applied to structural studies of phosphine selenides. In the mass spectral field MALDI-TOF has been found to be better than FAB for the determination of the mass spectra of nucleotide triphosphates, LA-FTICR has been used to study tris(cyanoethyl)phosphine and metaphosphates have been detected for the first time by laser photoionisation MS. ERMS was shown to be a powerful technique for the analysis of structurally similar organophosphate insecticides (OPs) and trace quantities of OPs can be determined by Cl using water as the ionising agent. 

Buchwald, Friedman and Knowles succeeded in preparing 2,4-dinitrophenyl phosphate in which the three free oxygen atoms on phosphate were labeled stereospecifically with different isotopes of oxygen. Solvolysis of this compound in methanol and analysis of the methyl phosphate product showed that the reaction had proceeded with inversion of configuration at phosphorus (79). This remarkable experiment supports a concerted bimolecular displacement mechanism, with no metaphosphate intermediate, for the solvolysis of 2,4-dinitrophenyl phosphate in methanol. However, it does not rigorously exclude a stepwise mechanism in which a metaphosphate intermediate with a very short lifetime is formed and reacts with methanol faster than it rotates, and it does not provide direct evidence for a bimolecular, concerted reaction with solvent water. 

As noted previously, studies of the mechanisms of phosphate monoester solvolysis have been extended to the mechanisms of the analogous phosphorothioate ester solvolysis because the thiometaphosphate anion is believed to be more stable than the metaphosphate anion. Thus, a general method based upon P NMR spectroscopy for the configurational analysis of chiral thiophosphate monoesters (see Fig. 10) was described recently by Cullis and co-workers (38). 

The expulsion of monomeric metaphosphate ester in EtCN at -78 °C can be followed by P NMR spectroscopy, and this allowed the detection of a species formed in competition with the elimination process. The second product from 42 (R - 1-adamantoxy, R = Me, R = H) was shown, by single-crystal X-ray analysis, to have the structure 47, additionally... 

Tyner, E.H. 1939. The use of sodium metaphosphate for dispersion of soil for mechanical analysis. Proceedings of the Soil Science Society of America Journal, 4 106-113. 

Even if the instrumental techniques gain ever more ground, some of them in automated form, evaluated and documented by computer, the simple, manual methods such as paper and thin-layer chromatography still have their role to play. One need only think of the separation of the various forms of phosphate such as orthophosphate, pyrophosphate, metaphosphate, polymeric phosphates and condensed phosphates, or the separation of polycyclic aromatic hydrocarbons (specifically with thin-layer chromatography) in water analysis. 

In subsequent schemes of qualitative analysis, orthophosphates, obtained in Group III separations, were distinguished from pyro and the so-called metaphosphates by the ammonium molybdate test. 

The detailed chemistry of these films is stiU controversial older works based on elemental analysis with SEM-EDX showed that the film contained Zn, S, P, C and O [14]. XPS [15] and AES [16,17] have also been used to provide chemical differentiation for the different elements P was claimed to be present as a phosphate and S as a sulfide, the corresponding cation being zinc or iron. XANES spectroscopy revealed that the chemical nature of P and S in the tribofikns was different from that of the pure ZnDTP substances and depends on the alkyl group used in ZnDTP [18]. With isopropyl ZnDTP, phosphorus is found to correspond closely to metaphosphate (polyphosphate with a cyclic structure) whereas with u-butyl ZnDTP pyrophosphates are found. This is important when discussing the results obtained from commercial ZnDTP, which often consist of a blend of ZnDTP molecules containing different alkyl groups [3]. 

Anderson et al. have presented solid-state NMR analysis of local structural environments in phosphate glasses for educational purposes. " In particular, the solid-state NMR wide-line spectra of a series of sodium phosphate glasses have been considered, which can also be simulated by spectral addition of reference solid-state spectra obtained for pure pyrophosphate and metaphosphate salts. The example chosen introduces the principles of solid-state NMR and allows interpretation of the spectrum in terms of the composition and localised phosphate environment. 

The normal catalytic process involves addition of TPP to pyruvate and subsequent loss of carbon dioxide. It was proposed that 14 would not undergo a reaction analogous to the decarboxylation in the normal catalytic process because the necessary leaving species would be methyl metaphosphate. This process certainly involved a large energy barrier [58]. This analysis suggested the enzyme was responsible for catalyzing the formation of a-lactyl-TPP as a reactive intermediate. 

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