CHARACTERIZATION OF AN ELEMENT-SELECTIVE GC PLASMA DETECTOR BASED ON DIODE-LASER ATOMIC-ABSORPTION SPECTROMETRY

An element-selective GC-plasma detector consisting of a modulated low- pressure microwave-induced plasma and a laser detection system based o n Wavelength Modulation Diode Laser Atomic Absorption Spectroscopy (WM -DLAAS) was investigated. The influence on the plasma conditions and t he fragmentation capability of different types of organic compounds, s uch as alkanes, alkenes, alkynes and aromatics, was studied by measure ments of the element ratios of C, H and Cl, and the population density of the metastable 1s(5) level of Kr added as a trace to the plasma ga s (He or Ar). Deviations from the expected stoichiometrical ratios wer e found to be insignificant. Therefore, calibration and determination of the sum formula of analyte species is possible if an internal stand ard is used. Furthermore, the correlation between the metastable densi ty in the microwave-induced plasma and the total dissociation energy o f the analytes was studied. (C) 1998 Elsevier Science B.V.