A dc Microplasma on a Chip Employed as an Optical Emission Detector for Gas Chromatography

Abstract

A micromachined plasma chip is coupled to a conventional gas chromatograph to investigate its performance as an optical emission detector. The device employs a 180-nL plasma chamber in which an atmospheric pressure dc glow discharge is generated in helium. Applied power is 9 mW (770 V, 12 μA) and helium flow rate 320 nL s^-1. A number of carbon-containing compounds are detected in the column effluent by recording the emission at 519 nm. For hexane, the detector has a linear dynamic range of over two decades and a minimum detectability of 10^-12 g s^-1 (800 ppb). The detector signal shows a marked peak broadening and tailing when compared with the signal of a flame ionization detector. This is mainly attributed to dead volumes and chromatographic processes introduced by the connecting tubing and the chip glass channels. The device was operated for more than 24 h without a significant change in performance. Operation is stable and instrumental requirements are simple. Future use of the detector chip in conventional gas chromatography or as an integrated detector in on-chip gas chromatography is discussed.