Static secondary ionization mass spectrometry analysis of tributyl phosphate on mineral surfaces: Effect of Fe(II)

The static secondary ionization mass spectrometry (SIMS) spectrum of tri-n-butyl phosphate (TBP) on a variety of basalt and quartz samples is affected by the chemical composition of the mineral surface. When TBP is adsorbed on Fe(II)-bearing surfaces, the compound undergoes concomitant H^? abstraction and reduction, followed by the elimination of two C₄H₈ molecules to form an ion at m/z 137⁺. When TBP is adsorbed to quartz or other nonreducing surfaces, it merely undergoes protonation and elimination of three C₄H₈ molecules to form H₄PO ₄ ⁺ . When TBP is adsorbed to Fe(III)-bearing surfaces, it undergoes H^? abstraction and elimination of two C₄H₈ molecules, to form an ion at m/z 153⁺. These conclusions are supported by model studies that employed FeO, Fe₂0₃, TBP, and tributyl phosphite. The results show that the SIMS spectrum is very sensitive to the mode of TBP adsorption on the mineral surface.