Effect of adding oxygen gas to a high power nitrogen microwave-induced plasma for atomic emission spectrometry

In order to investigate the effect of adding oxygen gas (O-2) to a high power nitrogen microwave-induced plasma (N-2-MIP:2.45 GHz, surface wave mode) for atomic emission spectrometry, the signal intensities for atom and ion lines of Ca, V, Ti, Mg, and Cd were observed by adding O-2 gas into N-2 outer gas in a range from 0 to 20%. From the observation of the background spectrum in a wavelength range of 200-400 nm, it was found that NO band spectra were enhanced largely with an increase in the addition of O-2 gas. The excitation temperatures (T-ex) observed decreased from 5500 to 4800 K with an increase in the percentage of adding O-2 gas from 0 to 20%. The relatively large signal enhancement was observed for all atom lines of Ca, V, Ti, Mg, and Cd when O-2 gas was added to N-2 outer gas. The emission signals for some of ion lines of Ca, V, Ti, and Mg also showed a signal enhancement when a small amount of O-2 gas was added. It was considered that the reason for the enhancement phenomena of the ion lines of these elements was attributed to the mechanism of the charge transfer reaction. (C) 2000 Elsevier Science B.V. All rights reserved.