Determination of phosphorus

Alkyl and alkylether phosphates are most conveniently analysed by NMR spectroscopy, but if this technique is not available phosphorus can be identified and determined after destruction of the organic matter, by one of the many versions of the molybdenum blue test, as in the following method [8]. 

Place a sample containing 0.0025-0.0035 g phosphorus and transfer it to a micro-Kjeldahl flask. Clamp the flask so that the neck is inclined at about 45 and points towards the rear of a well-ventilated fume cupboard. 

Add 5 ml concentrated sulphuric acid and 5 ml concentrated nitric acid (caution both are corrosive) and heat slowly over a micro-burner until white fumes appear above the liquid. 

Add dropwise by Pasteur pipette about 1ml concentrated nitric acid and continue heating until the brown fumes disppear. Continue heating and adding nitric acid in 1 ml portions until the solution is clear and colourless. Allow to cool. 

Cautiously add 25 ml water and two glass beads and boil gently over the micro-burner for 30 min to hydrolyse the condensed phosphates. Add more water if necessary to maintain the volume. Allow to cool. 

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Hobbins, W. B. Direct Determination of Phosphorus in Aqueous Matrices by Atomic Absorption Varian Instruments at Work, Number AA-19, Eebruary 1982. 

THE SOLID-PHASE REAGENTS FOR THE DETERMINATION OF PHOSPHORUS AND ORGANIC REDUCTANTS... 

A reaction of mixed molybdenum polyoxometalates (POMs) with cyanine dye has been used for highly selective and sensitive spectrophotometric determination of phosphorus(V) and arsenic(V). Color of the solution is considerably changed by reaction of Keggin POMs with styrene cyanine dyes. Derivatives of l,3,3-threemethyl-3//-indol - astrazone violet (AV 3R), astrazone rose, astrazone yellow, astrazone red were investigated. 

Phosphorus and Silicon in Waters, Effluents and Sludges [e.g. Phosphorus in Waters, Effluents and Sludges by Spectrophotometry-phosphomolybdenum blue method. Phosphorus in Waters and Acidic Digests by Spectrophotometry-phosphovanadomolybdate method. Ion Chromatographic Methods for the Determination of Phosphorus Compound, Pretreatment Methods for Phosphorus Determinations, Determination of silicon by Spectrophotometric Determination of Molybdate Reactive Silicon-1 -amino-2-naphthol-4, sulphonic acid (ANSA) or Metol reduction methods or ascorbic acid reduction method. Pretreatment Methods to Convert Other Eorms of Silicon to Soluble Molybdate Reactive Silicon, Determination of Phosphorus and Silicon Emission Spectrophotometry], 1992... 

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. 

Bowden M., Geschke O., Kutter J.P., Diamond D., C02 laser microfabrication of an integrated polymer microfluidic manifold for the determination of phosphorus, Lab On a Chip 2003 3 221-223. 

Of course, not all dissolved ions produce colored solutions, and therefore not all ions in solution can be quantified by colorimetry. Noncolored solutions can sometimes, however, be converted to colored solutions by introducing chromophore species which complex with (i.e., attach themselves to) the target ion to produce a colored solution, which may then be measured by UV/visible colorimetry. An important archaeological example of this is the determination of phosphorus in solution (which is colorless) by com-plexation with a molybdenum compound, which gives a blue solution (see below). The term colorimetry applies strictly only to analytical techniques which use the visible region of the spectrum, whereas spectrophotometry may be applied over a wider range of the electromagnetic spectrum. 

Dobolyi and Bidlo [76] have described methods for the determination of phosphorus in lake sediments. Shulka et al. [75] investigated the interference by arsenic in the perchloric acid digestion procedure of Murphy and Riley [85] for the determination of phosphorus in sediments. Arsenite concentrations up to 20pg did not interfere but arsenate interfered. Between 1 and 45 pg arsenic g"1 was extracted from a lake sediment and in all cases the error in the determination of phosphorus due to the presence of arsenic was less than 1%. 

A British standard method [93] has been published for the determination of phosphorus and silicon in sludges. 

Solyom has conducted an intercalibration of methods used for the determination of phosphorus in sludges [37]. The methods used to determine phosphorus were that of Koroleff [83] in which the sample is digested with potassium peroxydisulphate and phosphate determined spectro-photometrically. Alternatively a reducing Kjeldahl digestion was used followed by determination of phosphate using molybdate and ascorbic acid. The former method gives somewhat low results. The reducing Kjeldahl method is therefore recommended. 

Allen, R. J. L. (1940). Micro-determination of phosphorus. (Colorimetric estimation molybdate blue.) Biochem. J. 34, 858. Bellamy, L. J. (1954). Infra-red Spectra of Complex Molecules. Methuen and Co. 

Simmons, W. R. and Robertson, J. H. (1950). Spectrophotometric determination of phosphorus in organic phosphates. Analyt. Chem. 22, 1177. 

Fiske CH, Subbarow Y. The colorimetric determination of phosphorus. J Biol Chem 1925 66 375. 

Fig. 5.3. Manifold for the automated determination of phosphorus in soil extracts.

Fig. 7.4. Flow diagram for determination of phosphorus in plant digest solutions... 

Craven, P. and Schwer, E.W. (1950) The determination of phosphorus. In Joint Symposium on Fertiliser Analysis. Proceedings No. 52, The Fertiliser Society, London, pp. 139-175. Discussion, pp. 175-183. 

Story WC, Caruso JA. 1993. Gas chromatographic determination of phosphorus, sulfur and halogens using a water-cooled torch with reduced-pressure helium microwave-induced plasma mass spectrometry. J Anal Atomic Spectrometry 8 571-575. 

A. P. Krushevska, K. Klimash, J. F. Smith, E. A. Williams, P. J. McCloskey and V. Ravikumar, Determination of phosphorus in polymeric systems using an ashing procedure and inductively coupled plasma atomic emission spectrometry, J. Anal. At. Spectrom., 19(9), 2004, 1186-1191. 

More recent flame photometric methods rely on direct measurement of the phosphorus emission. If organophosphorus compounds are injected into a hydrogen flame, a continuous emission is obtained in the 490-650 nm region. A broad band system, with an intensity maximum at 526 nm, is superimposed on this background139 it is attributed to the HPO species formed in the flame. An early determination of phosphorus at 0.01-0.04 m concentrations was based on examination of the continuous emission standard and sample solutions were injected into the burner and the intensities were measured at 540 nm the calibration graph was linear down to the detection limit of 10 4 M phosphorus sodium or calcium, if present in the sample, interfered with the results140. 

SiMouO ]4-.134 The structure of the heteropoly blue species (four-electron-reduced PM012O40]3-) formed in the molybdenum blue determination of phosphorus has been reported135 and a review of molybdate heteropoly blues has appeared.130 A stability index of polyanion structures has been discussed.137 The presence of two PMo, anions in aqueous solutions of molybdate and phosphate has been demonstrated by 31P NMR.138 Solid state NMR (nonspinning and MAS techniques) has been used for characterization of heteropolyanions.139 Molybdenum-95 NMR spectra of some polymolybdates have been reported.140... 

S. F. Boulyga, C. Pickhardt, J. Becker. S. Buddrus, and M. Przybylski, Determination of Phosphorus In Small Amounts of Protein Samples by ICP-MS," Anal. 

Although we must not underestimate the importance of coordination compounds such as ammonium phosphomolybdate (for the determination of phosphorus and more recently as an inor-... 

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