Phosphate phosphorus, determination

B. Phosphovanadomolybdate method Discussion. This second method is considered to be slightly less sensitive than the previous molybdenum blue method, but it has been particularly useful for phosphorus determinations carried out by means of the Schoniger oxygen flask method (Section 3.31). The phosphovanadomolybdate complex formed between the phosphate, ammonium vanadate, and ammonium molybdate is bright yellow in colour and its absorbance can be measured between 460 and 480 nm. 

Phosphorus, in biological samples, determination by monochromatic x-ray absorption-edge method, 299-301 in ceramic materials, determination by x-ray emission spectrography, 222 in phosphate rocks, determination by x-ray emission spectrography, 260, 261... 

In the method for extractable phosphorus [62, 64-66] the phosphorus is extracted from the soil at 20 1°C with sodium bicarbonate solution at pH8.5. After filtration and release of carbon dioxide the extracts are introduced into a flow-injection system for the determination of phosphate. Phosphate is determined by reaction with vanadomolybdate and the yellow colour evaluated at 410nm. Between 20 and lOOOmg kg-1 phosphorus in soil has been determined using this method. 

If arsenate and phosphate are present together, the total arsenic and phosphorus is first determined, the arsenic is then removed with hydrogen sulphide and the phosphorus determined alone.7... 

Phosphorus exists mostly in the phosphate form in the general environment. The levels of phosphorus determined in most environmental samples are reported as total phosphorus and do not distinguish between elemental phosphorus and its compounds. However, elemental phosphorus is far more toxic than other oxidized phosphorus states (oxides and acids of phosphorus). This profile reports the level of elemental phosphorus and not total phosphorus in environmental samples. 

Fig. 18. Average environment of calcium ions in amorphous calcium phosphates as determined by X-ray absorption spectroscopy near the K absorption edge of calcium. The diagram shows two bidentate and two monodentate phosphate tetrahedra and two water molecules contributing to the eight oxygens of the first coordination sphere of the calcium ions. A third shell, possibly comprising the two phosphorus atoms of the monodentate phosphate ions, can be seen in some of the preparations. The positions of the protons are not established (Holt et al., 1988, 1989b Holt and Hukins, 1991).

Phosphate Analysis, Determination of Organic Phosphorus Compound by (Lindberg... 

Parenteral phosphorus supplementation is associated with risks of hyperphosphatemia, metastatic soft tissue deposition of calcium-phosphate product, hypomagnesemia, hypocalcemia, and hyperkalemia or hypernatremia (caused by intravenous phosphorus salt) (Table 49-9). Inappropriate administration of large doses of parenteral phosphorus over relatively short time periods has resulted in symptomatic hypocalcemia and soft-tissue calcification. The rate of infusion and choice of initial dosage should therefore be based on severity of hypophosphatemia, presence of symptoms, and coexistent medical conditions. Patients should be closely monitored with frequent (every 6 hours) serum phosphorus determinations for 48 to 72 hours after starting intravenous therapy. It may be necessary to continue administration of intravenous phosphorus for several days in some patients, while other patients may be able to tolerate an... 

The most common approach to phosphorus determination is the assessment of phosphate in wet chemistry. Therefore, the majority of samples should be dissolved before analysis. Solid samples are decomposed by alkali or acid treatment silicate is dissolved by treatment with fluoric acid. Samples of biological material are reduced to ash using an appropriate laboratory oven or are digested with hot oxidative acids. A direct phosphate assessment is advised only in some water samples. The determination of total phosphoms is not used to identify soil fertility due to phosphorus content rather, water extracts are used of various pH and ionic strength. 

The quantitative reliability of inductively coupled plasma high-resolution mass spectrometry for phosphorus determinations was judged by comparing it to the standard total filterable phosphorus method (Gooper et al., 1999). That method includes a persulphate oxidation step to convert all forms of phosphorus to phosphate, which is then suitable for the molybdenum blue reaction. Using the same set of standards, calibration curves for both methods were developed over a range of 0-200 pg P/1. Fig-... 

Extracted phosphorus fraction (phosphate or total phosphorus) recommended for microbial phosphorus determination. 

The concentration of phospholipids in a lipid mixture can be estimated as phosphate after ashing the sample. The ash can be treated with nitric acid, dissolved in hydrochloric acid, and the phosphorus determined by inductively coupled plasma-atomic emission spectrometry at 214.9 nm. Alternatively, the phosphorus can be determined by atomic absorption spectrometry at 213.547nm with a graphite furnace. Traditional methods for phosphorus determination include the precipitation of phosphate as quinoli-nium molybdophosphate and gravimetric determination, or colorimetric methods such as the reaction with ammonium molybdate and acidic ammonium vanadate solution followed by determination of the absorbance at 460 nm. 

The molar absorptivity of the partly reduced heteropoly acid is 22700 at 880 nm, which means that the net absorbance for a l.O/xmol/L phosphate sample is 0.227 measured in a 10 cm cuvette. With a good spectrophotometer an absorbance of 0.002 can be read, and the smallest concentration of phosphate-phosphorus that can be determined directly thus is 0.01 /imol/L. The absorbances are a linear function of the concentrations up to 28 /imol/L, equal to a net absorbance of approximately 0.630 in a 1 cm cell. 

Phenolic Compounds of Interest in Metabolism (Bray and Thorpe)... Phosphate Analysis, Determination of Organic Phosphorus Compounds by (Lindberg and Ernster). 

FLOW INJECTION ANALYSIS METHODOLOGIES FOR PHOSPHORIC ACID, PHOSPHATES, AND TOTAL PHOSPHORUS DETERMINATION... 

Parra, A., M. Ramon, J. Alonso, S. G. Lemos, E. C. Vieira, and A. R. A. Nogueira. 2005. Flow injection potentiometric system for the simultaneous determination of inositol phosphates and phosphate Phosphorus nutritional evaluation on seeds and grains. J. Agric. Food Chem. 53 7644-7648. 

The suspension obtained as described in Part IV.2 is treated with perchloric acid, evaporated, and the residue is heated to oxidize organic matter and liberate phosphorus as inorganic phosphate. The phosphate is determined by the procedure given in Part II.2.I. 

Phosphor-athcr, m. phosphoric ether (ester of phosphoric acid, specif, ethyl phosphate), -basis, phosphorus base, -bestimmung, /. determination of phosphorus, -blei, n. lead phosphide Min.) pyromorphite. -bombe, f. phosphorus bomb. -brandgranate, /. phosphorus incendiary shell, -brei, m. phosphorus paste, -bromid, n. phosphorus bromide, specif, phosphorus pentabromide, phos-phorus(V) bromide, -bromijr, n. phosphorus tribromide, phosphorus(III) bromide, -bronze, /. phosphor bronze, -calcium, n. calcium phosphide, -chlorid, n. phosphorus chloride, specif, phosphorus pcntachloride, phosphorus(V) chloride, -chloriir, n. phosphorous chloride (phosphorus trichloride, phosphorus(III) chloride), -dampf, tn. phosphorus vapor or fume, -eisen, n. ferrophos-phorus iron phosphide, -eisensinter, m. diadochite. 

The method can be applied to the determination of phosphorus in a wide variety of materials, e.g. phosphate rock, phosphatic fertilisers and metals, and is suitable for use in conjunction with the oxygen-flask procedure (Section 3.31). In all cases it is essential to ensure that the material is so treated that the phosphorus is converted to orthophosphate this may usually be done by dissolution in an oxidising medium such as concentrated nitric acid or in 60 per cent perchloric acid. 

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