MICROWAVE-INDUCED-PLASMA REFLECTED-POWER DETECTOR FOR GAS-CHROMATOGRAPHY

The potential usefulness of the reflective properties of microwave-induced plasma (MIP) as a gas chromatographic detector is reported. The detector operation is based on the measurement of the change in reflected power arising from the interaction of the analyte with an atmospheric pressure argon plasma sustained in the highly efficient TM010 resonant cavity. Microwave forward power and tangential gas flow are optimized for n-pentane. The lowest microwave powers produced the best signal sensitivities. For the particular discharge tube employed, a maximum response is obtained at approximately 1.6 L/min. The nonlinear calibration curve obtained for n-pentane is discussed, and its conversion to a linearized calibration curve is presented. Calculated detection limits for carbon and hydrogen lie in the upper nanograms of element per second range.