Effect of O2 in plasma gas on parameters of nitrogen MIP-OES†
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 Esum values from 2.1 to 15.4 eV) of 12 elements has been studied. The intensity of atomic lines with Esum 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.