COMPARISON BETWEEN DIRECT-CURRENT AND RADIOFREQUENCY GAS-JET-BOOSTED GLOW-DISCHARGE ATOMIC-EMISSION SPECTROMETRY FOR THE ANALYSIS OF STEEL

Comparisons between direct-current (dc) and radio-frequency (rf) gas j et-boosted glow discharge atomic emission spectrometry (GDAES) have be en made with regard to fundamental characteristics and analytical perf ormance, The study of fundamental characteristics includes the voltage -current relationship; a gas flow rate of 0 mL/min to 800 mL/min and p ressures ranging from 3 Torr to 5 Torr on de bias potential; the sampl e weight loss; and the emission intensity, The dc-powered glow dischar ge at 90 mA/450 V and 60 mA/710 V at 5 Torr shows 3x more sample weigh t loss than the rf discharge at 40 W, Radio-frequency glow discharge s hows a short-term precision of <1% relative standard deviation (RSD) a nd a long-term stability of <5% RSD for both major and trace element l ines. Both rf and de show calibration curves that are linear over 2-3 orders of magnitude, with a general improvement in linearity from rati oing the signal to an internal standard of the matrix. Further improve ment of linearity was possible by correcting the bias potential in the rf glow discharge, Limits of detection (LODs) for rf are tens of part s per billion from many trace elements in low-alloy steel, which is on e order of magnitude improvement over those for dc.