Inorganic phosphate quantitative analysis spectroscopy

Phosphorus in starch is found in different forms, mainly starch phosphate monoester, phospholipids, and inorganic phosphate. 31P NMR spectroscopy was used to identify each of these forms in alpha-dextrins prepared from starches of different sources.128 Quantitative analysis was possible in DMSO solution. 

Card JK, Card DR, and Callis CF (1992) Quantitative analysis of inorganic phosphates using NMR spectroscopy. In Walsh EN, Griffith EJ, Parry RW, and Quin ED (eds.) Phosphorus Chemistry, Developments in American Science. Washington, DC American Chemical Society. 

The analysis of phosphates and phosphonates is a considerably complex task due to the great variety of possible molecular structures. Phosphorus-containing anionics are nearly always available as mixtures dependent on the kind of synthesis carried out. For analytical separation the total amount of phosphorus in the molecule has to be ascertained. Thus, the organic and inorganic phosphorus is transformed to orthophosphoric acid by oxidation. The fusion of the substance is performed by the addition of 2 ml of concentrated sulfuric acid to — 100 mg of the substance. The black residue is then oxidized by a mixture of nitric acid and perchloric acid. The resulting orthophosphate can be determined at 8000 K by atom emission spectroscopy. The thermally excited phosphorus atoms emit a characteristic line at a wavelength of 178.23 nm. The extensity of the radiation is used for quantitative determination of the phosphorus content. 

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