A K-edge P XANES study of phosphorus compounds in solution

The K-edge X-ray absorption near-edge structure (XANES) spectra of 19 phosphorus-containing compounds have been measured in solution. The energy at maximum intensity of the primary phosphate peak, regardless of chemical species, is 2154.5 ± 0.4 eV. A few of the compounds studied feature XANES spectra which are conceivably characteristic enough to be used as positive identifiers in solution, including O,O-diethyldithiophosphate, (C2H5O)2PS(SH), triphenylphosphine oxide, (C6H5)3PO, and triphenylphosphite (C6H5O)3P. However, most spectra are near-identical or similar enough to another compound to prohibit any useful quantification analysis. The narrow range of absorption edge energy, and all phosphorus compounds studied have an absorption edge at higher energy than elemental phosphorus (red phosphorus). This shows that the electron density of phosphorus in these compounds is lower than in elemental phosphorus, and the conventional use of oxidation numbers cannot be applied.