EVALUATION OF AN AXIALLY AND RADIALLY VIEWED INDUCTIVELY-COUPLED PLASMA USING AN ECHELLE SPECTROMETER WITH WAVELENGTH MODULATION AND 2ND-DERIVATIVE DETECTION

A high-dispersion echelle spectrometer which incorporates wavelength m odulation and second-derivative signal detection is used to view analy te emission from an inductively coupled plasma in both the axial (end- on) and radial (side-on) configurations. Movement of the plasma torch assembly between the viewing positions is computer controlled. Perform ance characteristics such as background intensity, repeatability, back ground equivalent concentration, limit of detection, dynamic range and interference effects are reported for 24 elements and in general, mea surement in the end-on position produces an improvement in sensitivity . Using end-on measurement, the system is applied to the multi-element analysis of a certified reference water.