Abstract
Optimum analytical lines as well as the discharge conditions for lead determination in steel samples were investigated in direct-current and radio-frequency glow discharge optical emission spectrometry (d.c. and r.f. GD-OES). Two emission lines: Pb I 405.784 nm and Pb II 220.356 nm, were compared on their analytical performance in d.c. GD-OES, indicating that the Pb II 220.356-nm line should be selected as the analytical line because the emission intensity is much larger than that of the Pb I 405.784-nm line. Several iron lines were also measured for correcting variations in the sampling amounts so that the emission intensities of Pb II 220.356 nm can be estimated more accurately. Atomic and ionic iron lines, such as Fe I 344.374 nm and Fe II 254.874 nm, having similar excitation energies to Pb II 220.356 nm, were suitable for the internal standard line, because their emission intensities well follow the intensity of the Pb II line when the sampling rate and the excitation conditions are changed. In r.f. GD-OES, a bias-current introduction method was employed for enhancing the emission intensity of the Pb I 405.784-nm line. By conducting of the bias-current of 33 mA at the r.f. power of 80 W, the emission intensities were 12 times larger than those obtained with the conventional plasma. This effect contributes to Pb determination with a higher detection ability in r.f. GD-OES.
