Determination of trace amounts of Cu, Ni, Ti and B in Fe-based alloys by radio-frequency-powered glow discharge optical emission spectrometry associated with bias-current conduction method

In an r.f. glow-discharge plasma, a d.c. bias current can be introduced by connecting an electric circuit comprising a low-pass filter and a variable resistor. The bias current promotes the emission excitations in the plasma, leading to an improvement of the detection power in the optical emission spectrometry. By conducting a bias current of 27 mA, the emission intensities of atomic resonance lines were several times larger than those obtained with conventional r.f.-powered plasmas. The detection limits for determination of alloyed elements in Fe-based low alloyed standard samples were estimated to be 3 ppm Cu for Cu I 324.75 nm, 10 ppm Ni for Ni I 352.45nm, 6 ppm Ti for Ti I 364.267 nm, and 7 ppm B for B I 208.96 nm.