Methodology for gas chromatographic-mass spectral analysis of volatile organic compounds emerging from a low-pressure, flow-through reaction cell

A methodology has been developed for the analysis of volatile organic compo unds (VOCs) emerging from a plasma discharge cell operating at a constant f low-rate under subatmospheric pressure (0.266 to 2.66 kPa). The analytical system consisted of a gas reservoir for trapping a portion of the VOC-rare gas mixture, a sampling loop for cryogenically concentrating the VOC produc ts, and either gas chromatography-mass spectrometry (GC-MS) or gas chromato graphy-flame ionization detection (GC-FID). The methodology was evaluated f or the analysis of methylene chloride, benzene and tetrachloroethylene, usi ng n-octane as the internal standard. Calibration curves were constructed b y plotting the pressure ratios of the gas standard relative to the internal standard versus the corresponding peak area ratios. Over a pressure range of 1.133 to 5.32 kPa, the linearity of the calibration curve for each gas s tandard was determined with correlation coefficients ranging from 0.96 to 0 .98. The relative standard deviation for a minimum of triplicate analyses v aried from 1.1 to 18.3% for most VOCs. The calibration curves were used to measure the concentration of premixed VOC-rare gas mixtures as a function o f energy input of the plasma reactor. (C) 1999 Elsevier Science B.V. All ri ghts reserved.