Effect of O2 in plasma gas on parameters of nitrogen MIP-OES

Abstract

We studied the effect of O₂ content in the range of 0.1–1.2% in plasma gas on the plasma characteristics, the analytical signal and the intensity of the molecular species in nitrogen MIP. The plasma temperature decreases from 4.50 × 10³ to 4.39 × 10³ K with increasing O₂ content. The Mg(II)/Mg(I) intensity ratio decreases from 1.14 to 0.90, and the electron density decreases from 1.16 × 10¹⁴ to 0.85 × 10¹⁴. The intensities of N₂, N₂⁺ and NH decrease, and the NO and OH intensities increase when O₂ is added. The influence of O₂ content on the intensity of several atomic and ionic emission lines (covering E_sum values from 2.1 to 15.4 eV) of 12 elements has been studied. The intensity of atomic lines with E_sum values lower than 6 eV was enhanced in the presence of O₂ but it was suppressed for the ionic lines tested. It was shown that the O₂ addition leads to a decrease in the LOD calculated from atomic lines and to an increase in the LOD calculated from ionic lines.