A dual-channel gas chromatography method for the quantitation of low and high concentrations of NF3 and CF4 to study membrane separation of the two compounds

Abstract A dual-channel gas chromatographic method is described in this paper that can be conveniently used for quantitation of NF 3 /CF 4 mixtures with a thermal conductivity detector (TCD) on one channel for the quantitation of high-concentrations, and a pulsed discharge helium ionization detector (PDHID) on a second channel for the quantitation of low concentrations. It is shown that adequate separation is achieved on both channels with this dual single-column setup in which column switching as used for NF 3 /CF 4 analysis in industrial chromatographic methods are not required, thus yielding an effective analysis method for laboratory-scale investigations. In addition, the use of packed columns with purified divinylbenzene–styrene co-polymers as the sole stationary phase yields satisfactory resolution between NF 3 and CF 4 at isothermal conditions of 30 °C, with elution times of less than 8 min on the TCD channel and less than 4 min on the PDHID channel. Consequently, this method allows for reliable, straight-forward quantitation of NF 3 /CF 4 mixtures, which is necessary when studying the commercially important problem of NF 3 and CF 4 separation by different methods. Therefore, the applicability of the method to studying membrane separation of NF 3 and CF 4 is briefly discussed and illustrated, for which the dual-channel setup is especially beneficial.