A radio frequency plasma detector for element specific detection in gas chromatography is described. The detector is comprised of a radio frequency (300 kHz) discharge between electrodes in helium, and utilizes a low‐resolution emission spectrometer to monitor selected spectral emission lines produced when the helium discharge decomposes and excites the atomic constituents in the chromatographic column effluent. The spectrometer is tuned to an atomic emission line in the near‐infrared portion of the spectrum, and the emission intensity from the discharge region of a selected line is used to monitor the concentration of the element producing that line. Acceptable detector sensitivity was achieved by the use of a high‐throughput optical system. Selectivity was achieved by a combination of correct line selection, plasma and carrier gas purification, and plasma gas doping.

A radio-frequency plasma source has been characterized for use as an element-selective detector with capillary gas chromatography using atomic emission in the near-infrared region of the spectrum. With selected compounds introduced at rates similar to those encountered during a chromatographic run, the performance of the plasma has been characterized as a function of several interdependent variables, including plasma makeup gas flow, electrode spacing, and applied power. These settings have been optimized, and detection limits for several nonmetallic elements determined. Detection limits range from 0.2 to 50 pg/s.

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This work was funded by the Center for Advanced Technology Development (formerly the Center for New Industrial Materials) which is operated for the U.S. Department of Commerce by Iowa State University under Grant No. ITA 87-02.

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