Abstract

Comparisons between direct-current (dc) and radio-frequency (rf) gas jet-boosted glow discharge atomic emission spectrometry (GDAES) have been made with regard to fundamental characteristics and analytical performance. The study of fundamental characteristics includes the voltage-current relationship; a gas flow rate of 0 mL/min to 800 mL/min and pressures ranging from 3 Torr to 5 Torr on dc bias potential; the sample weight loss; and the emission intensity. The dc-powered glow discharge at 90 mA/450 V and 60 mA/710 V at 5 Torr shows 3 X more sample weight loss than the rf discharge at 40 W. Radio-frequency glow discharge shows a shortterm precision of < 1% relative standard deviation (RSD) and a long-term stability of < 5% RSD for both major and trace element lines. Both rf and dc show calibration curves that are linear over 2-3 orders of magnitude, with a general improvement in linearity from ratioing the signal to an internal standard of the matrix. Further improvement of linearity was possible by correcting the bias potential in the rf glow discharge. Limits of detection (LODs) for rf are tens of parts per billion from many trace elements in lowalloy steel, which is one order of magnitude improvement over those for dc.

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