On the problem of sulfur losses during PIXE analysis

Abstract

Investigations of laboratory aerosols of H 2SO 4, (NH 4) 2SO 4, and NH 4HSO 4, which are important compounds of ambient aerosol, show that there are experimental conditions allowing the complete determination of sulfate sulfur using the PIXE method, but that there are also such experimental parameters, yielding high sulfur losses ( > 50%). Both experimental regimes can well be involved in PIXE analytical routine. No sulfur losses are observed with proton current densities below ∼ 150 nA/cm 2 for target backings of cellulosic acetate membrane filters of 5 mg/cm 2 thickness at proton energies E p = 2 MeV and a reaction chamber vacuum of approximately 0.01 mbar. The dependence of sulfur losses on proton current density is discussed for several useful experimental conditions and aerosol filter materials. Preliminary results on the influence of varying chamber pressure are outlined.