Characterization of bidentate phosphoryl compounds on soil particulates using SIMS

The presence of organic compounds as surface contaminants on particles can provide valuable data about the particles environment, but identification can be analytically challenging. This is true particularly for compounds that have the potential for strong surface binding, such as compounds capable of multidentate attachment. Direct analysis using time‐of‐flight secondary ion mass spectrometry was evaluated for characterization of soil particles contaminated with low concentrations of two bidentate organophosphoryl compounds, diphenyl‐N,N‐di‐ n ‐butylcarbamoylmethylphosphine oxide and tetraphenylmethylene diphosphine dioxide. Molecular ions were formed by cationization with H + and alkali elements Na + and K + that are indigenous to the particle surface chemistry. Spectra generated from a contaminated calcareous soil were dominated by K + ‐containing ions, whereas spectra from a sandy loam had more abundant Na + ‐species. Cation‐bound dimers were also formed which favored incorporation of K + , and a unique aluminosilicate‐phosphoryl conjugate cation was also formed when the diphosphoryl ligand was present on the surface. The phosphoryl ligands also underwent fragmentation reactions, the course of which varied depending on the cation that was bound. Minimum detectable surface concentrations were evaluated and were in the 0.04–0.2 monolayer range, depending on the compound and soil particle matrix they was bound to. The ion signature was detected on soil particle surfaces for time periods exceeding six months, suggesting that the characterization approach could be used for environmental exposure history at times well beyond initial exposure. Copyright © 2009 John Wiley & Sons, Ltd.