Nitrogen quantification with SNMS

Plasma-based secondary neutral mass spectrometry plasma SNMS.is a powerful analytical method for determining the elemental concentrations of almost any kind of material at low cost by using a cheap quadrupole mass filter. However, a quadrupole-based mass spectrometer is limited to nominal mass resolution. Atomic signals are sometimes superimposed by molecular signals 2 or 3 atomic clusters such as CHq, CHq2 or metal oxide clusters. andror intensities of double-charged species. Especially in the case of nitrogen several interferences can impede the quantification. This article reports on methods to recognize and deconvolute superpositions of Nqwith CHq2, Liq2, and Si2q at mass 14 D Debye.occurring during analysis of organic and inorganic substances. The recognition is based on the signal pattern of Nq, Liq, CHq, and Siq. The latter serve as indicators for a probable interference of molecular or double-charged species with N on mass 14 D. The subsequent deconvolution use different shapes of atomic and cluster kinetic energy distributions kEDs.to determine the quantities of the intensity components by a linear fit of Nq and non-atomic kEDs obtained from several organic and inorganic standards into the measured kED. The atomic intensity fraction yields a much better nitrogen concentration than the total intensity of mass 14 D after correction. q1999 Elsevier Science B.V. All rights reserved.