Analytical Sciences

Improvement of Analytical Sensitivity by Ar-N₂ Inductively Coupled Plasma in Axially Viewing Optical Emission Spectrometry

Masaki OHATA,* Yuichi TAKAKU,** Kazumi INAGAKI,* Akiharu HIOKI,* and Koichi CHIBA*

*National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan
**Institute for Environmental Sciences, 1-7 Ienomae, Obuchi, Rokkasho-mura, Kamikita-gun, Aomori 039-3212, Japan

The analytical sensitivities of elements were improved by Ar-N₂ inductively coupled plasma (Ar-N₂ ICP) in axially viewing optical emission spectrometry (OES). A commercially available ICP-OES instrument was used, and only N₂ gas was added at flow rates of up to 1.0 L min^-1 into Ar plasma gas. A stable Ar-N₂ ICP was obtained, and the net signal intensities of elements were enhanced by factors of up to 25 compared to those observed for Ar ICP-OES. The detection limits evaluated were also improved by factors from 5 to 10, especially for elements with relatively higher ionization energies. Moreover, the analytical sensitivities for these elements observed in axially viewing Ar-N₂ ICP-OES were superior to those in radially viewing Ar-N₂ ICP-OES reported previously. The Ar-N₂ ICP is expected to be a useful alternative source for excitation and ionization in axially viewing ICP-OES.

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