Advantages and effects of nitrogen doping into the central channel of plasma in axially viewed-inductively coupled plasma optical emission spectrometry

Abstract

The effects and benefits of N2 addition to the central channel of the ICP through the nebulizer gas used in ICP OES with axial view configuration were investigated in the present study. The N2 flow rate, nebulizer gas flow rate, RF power and sample uptake rate were evaluated and compared for two sample introduction systems (pneumatic nebulization/aerosol desolvation and conventional pneumatic nebulization). It was observed that N2 did not affect solution nebulization and aerosol transport but affects the ICP characteristics. The higher thermal conductivity of N2 (in comparison with Ar) changes energy distribution in the ICP, observed by monitoring the signals of Ar emission lines and sodium emission. The ratio Mg(II)-280.270nm/Mg(I)-285.213nm was utilized as a diagnostic tool for plasma robustness. The addition of N2 (20mLmin−1) increased plasma robustness significantly and mitigated effects caused by Na, K and Ca. For 40 spectral lines evaluated, it was observed that the emission signals of ionic spectral lines were in general more affected by N2 than those of atomic spectral lines. Detection limits, precision, sensitivity and linearity of calibration curves obtained using N2-Ar-ICP were almost similar to those obtained using Ar-ICP. The analysis of 5 different reference materials revealed that accuracy was not degraded by adding N2 to the Ar-ICP.