Reduction of spectral interferences in inductively-coupled plasma emission spectrometry by selective spectral-line modulation

Spectral interferences in inductively-coupled plasma (i.c.p.) emission spectrometry can be significantly reduced through the use of selective spectral-line modulation. In this method, a mirrored, rotating chopper directs the emission from an i.e.p. alternately through and past a flame; selective modulation is achieved when the flame contains absorbing atoms identical to emitting atoms in the i.c.p. The ability of selective spectral-line modulation to minimize broadband, narrow line, and scattered light spectral interferences is demonstrated. Signal-to-background ratios for detection with spectral-line modulation are shown to be higher than those obtained by conventional detection. The effect of modulating conditions on working curve slope and linearity is discussed and the limitations of the proposed method are critically evaluated.