Organic condensed phosphates

Sugar phosphates and organic condensed phosphates form complexes with many cations. Stability constants for Ca2+ and Mg are on the order of 103-104. 

The ionizable phosphate group present in organic phosphorus species provides the basis for separation by anion exchange chromatography. This approach has been applied to the separation of phosphate, inositol phosphates, organic condensed phosphates, nucleic acids, nucleoside phosphonates, phospholipids and other organic phosphorus species. 

FOP fraction is composed of compounds such as nucleic acids, phospholipids, inositol phosphates, phosphoamides, phosphoproteins, sugar phosphates, aminophosphonic acids, phosphorus-containing pesticides, and organic condensed phosphates. 

Dispersant materials include condensed phosphates, organic polymeric dispersants. poly(meth)aerylatcs. polymaleates. condensed phosphates, poly-sulfonates. sulfonated polycondcnsatcs. and tannins, lignins, glucosides, and alginates. 

Orthophosphate and condensed phosphate are a measure of inorganic phosphoms. The latter is also termed as acid-hydrolyzable phosphate. However, during mild acid hydrolysis, a small amount of phosphoms from organic phosphoms compounds may be released. To determine suspended and dissolved forms of phosphoms, the sample should be filtered through a 0.45 pm membrane filter, and the filtrate and the residue analyzed separately. 

For a proper understanding of the processes which take place in living organisms, a precise knowledge of the chemical structures of the compounds that participate in these processes is required. It is therefore deemed essential to present, even if only briefly, an account of present-day ideas of the chemical structures of condensed phosphates, hitherto often known by the long-obsolete terms metaphosphates and hexametaphosphates . 

The earlier work on the isolation of PolyPs from the cells of living organisms usually employed the same methods as those used for the extraction of nucleic acids. It was not until 1936 that MacFarlane (MacFarlane, 1936) proposed a specific method for the extraction and fractionation of condensed phosphates present in cells. It was found that these phosphates could be divided into two main fractions, i.e. one soluble in 5 % trichloroacetic acid (TCA) and the other insoluble, and ever since then cellular condensed polyphosphates have been divided into acid-soluble and acid-insoluble fractions. 

The oldest and most extensively used method for determination of PolyPs in biological materials, although of course the least accurate, is based on the staining of cells and tissues by certain basic dyes such as toluidine blue, neutral red and methylene blue. The presence of condensed phosphates in the organisms is judged by the appearance in the cells of metachromatically stained granules, or volutin granules. 

Beveridge, T. J., Meloche, J. D., Fyfe, W. S., and Murray, R. G. E. (1983). Diagenesis of metals chemically complexed to bacteria laboratory formation of metal phosphates, sulfides and organic condensates in artificial sediments. Appl. Environ. Microbiol. 45, 1094-1108. 

The condensed phosphates or polyphosphates are another important class of inorganic phosphates. In these compounds, two or more phosphate groups bond together via P - O - P bonds to form chains or in some cases cyclic species. In soils and waters polyphosphates generally account for only a small part of the total P content. However, these species are very reactive and in many places they are responsible for anthropogenic pollution of natural water, for instance, by detergents. The polyphosphates are formed also in reactions between orthophosphates of mineral fertilizers and soil organic matter and can be leached to surface waters (Kudeyarova and Bashkin, 1984 Kudeyarova, 1996). 

Soils and sediments Digest organic matter pyrosulfate fusion dissolve condensed phosphates p-GPC No data No data EMMI 2000c, 2000d... 

Phosphorus compounds occur in wastewater under various forms, among which the reduced ones are predominant. The phosphorus compounds of wastewater concern not only some organic forms (natural or anthropic) but also orthophosphate ion and acid hydrolysable phosphate (condensed phosphate) (Fig. 10). 

As previously mentioned, phosphorus compounds are commonly classified into orthophosphates (PO ), acid-hydrolysable (condensed) phosphates and organic phosphates. It must be noticed that acid-hydrolysable phosphates (as pyrophosphates) are negligible in sewage [30], The general procedure illustrated in Fig. 11 includes two main steps an indirect UV-visible measurement (PO -) and a photo-oxidation step followed by a UV-visible measurement (Pgl)- First, orthophosphates are determined by spectrophotometric measurement of a phosphomolybdate complex (formed with addition of ammonium molybdate 40 gL-1) using the spectrum deconvolution method. 

Total Soluble Phosphorus. Total soluble phosphorus includes soluble orthophosphate (soluble condensed phosphate if present) and soluble organic phosphorus. A membrane-filtered sample is treated to release phosphorus as orthophosphate from combination with organic matter and condensed phosphates by some form of oxidation (and hydrolysis). 

Typical concentrations of phosphates found in various waters are given in Table 6-4. In fresh raw domestic wastewater the phosphate is distributed approximately as follows orthophosphate, 5 mg/liter as phosphorus, tripolyphosphate, 3 mg/liter as phosphorus, pyrophosphate, 1 mg/liter as phosphorus and organic phosphates < 1 mg/liter as phosphorus. Secondary biological treatment, and indeed prolonged contact with the microorganisms in raw sewage, ensures the hydrolysis, ("reversion") of condensed phosphates to orthophosphate. Tripolyphosphate, for example, hydrolyzes as follows ... 

The organic phosphorus content of solutions is generally determined by the difference between total phosphorus and molybdate-reactive phosphorus. As this fraction may also contain condensed phosphates (Ron Vaz etal., 1993), the operational term molybdate-unreactive phosphorus is used throughout the chapter, rather than organic phosphorus, which is used in a generic sense. 

Using P-labelled bacterial extracts, Mack-Ion et al. (1997) showed that dissolved organic phosphorus and condensed phosphates accounted for 87% and 6%, respectively, of microbial phosphorus and that... 

Traditionally, phosphorus research in the water column has been limited to measuring concentrations of operationally defined, but not chemically well-characterized, phosphorus fractions. Aquatic phosphorus is traditionally divided into particulate and dissolved fractions by filtration, with further division into phosphate, inorganic condensed, organic condensed, organic, mineral, and mixed-phase phosphorus species (Holtan et al., 1988 Maher and Woo, 1998, and references therein see also McKelvie, Chapter 1 Cade-Menun, Chapter 2 Cooper et al.. Chapter 3, this volume). 

This appendix provides a list of some of the most common organic phosphorus compounds found in the environment, ft also includes complex inorganic phosphates (condensed phosphates) and synthetic organic phosphates commonly used in assays of phosphatase activity. It is not an exhaustive list, but rather provides a handy... 

Waters and wastewaters may contain orthophosphates, condensed phosphates (poly- and metaphosphates) and organic phosphorus compounds. Under natural conditions free from human influence, concentrations of phosphorus... 

The determination of TP, condensed and organic phosphorus all require predigestion and/or hydrolysis of the water sample prior to detection of the orthophosphate produced. Complete conversion of particulate and filterable components requires conditions that are conducive to dissolution of phosphate mineral phases, hydrolysis of condensed phosphates, and oxidation of organic phosphorus species. Niunerous methods have been proposed, but whichever procedure is selected for the determination of TP or FTP, the digestion efficiency should be assessed using appropriate certified reference materials and a range of organic or condensed phosphorus model compounds. The latter should include compoiuids such as tripolyphosphate, inositol hexakisphosphate, and 2-aminoethylphosphonic acid that contain P-O-P, C-O-P, or C-P chemical bonds, respectively, and that are known to be more refractory. 

A great variety of condensed phosphates are known, mostly as anionic species, but molecular oxides such as P40,o (Chapter 4.2) are also included. Orthophosphate anions PO may also condense with other tetrahedral oxyanions XOJ (X = Al, Si, S, As, Fe, Co, Ni, Mn, etc.) to produce numerous anionic species (5.6c). Both organic esters of type (5.3) and the corresponding condensed varieties also exist in great variety. 

Other values for this ratio correspond to condensed phosphates (Section 5.4). Orthophosphoric acid readily forms esters in which the hydrogen atoms are replaced by organic groups (Section 5.6). 

The first and most critical analytical step for the determination of total phosphorus is the acid hydrolysis and the digestion of condensed phosphates and organic phosphoms for their conversion into orthophosphate and subsequent determination of this ion by a multitude of different flow analytical techniques [110]. 

In order to avoid laborious and time-consuming procedures for converting the phosphoms to measurable phosphate ions some improved methods have been reported that may be effective for online monitoring, e.g. thermal induced digestion, ultraviolet photooxidation [110], and microwave-assisted digestion [81,97,105]. Whatever the choice, it is important to ensure that quantitative oxidation of relatively refractory organic phosphoms compounds, i.e. condensed phosphates, and further hydrolysis and release of P from polyphosphates occurs prior to the detection step. 

It was observed that organically bound phosphorus is completely decomposed to phosphate when oxidized with persulphate in an alkaline medium. Furthermore, more than 60 % of condensed phosphates are hydrolyzed. As concentrations of polyphosphates are negligible in most natural waters, a simultaneous oxidation procedure for organic phosphorus and nitrogen compounds has been developed by Korolejf (1977). Valderrama (1981) compared the procedure with former methods using separate determinations. In the simultaneous oxidation, the pH of the reaction starts at ca. 9.7 and ends at 4-5. These conditions are obtained by a boric acid-NaOH system. In seawater samples no precipitation is formed when the oxidation mixture is added. At elevated temperatures a precipitation is formed, which, however, dissolves as oxidation proceeds. 

It was observed that the organic phosphorus digestion ability decreased with time (days) as the hydrogen peroxide formed imderwent decomposition, but that the thermal condensed phosphate digestion efficiency did not show any decrease with time because of the stability of the sulfuric acid. Since H2O2 decomposes slowly, Aminot and Kerouel recommended that the stock solution be assayed about twice a year, and working solutions prepared accordingly [70]. 

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