A direct-current, chip-based plasma has been used for gas sample injection in gas chromatography. A second identical plasma chip has been used as the excitation source for an optical emission detector. The first plasma is normally continually sustained during operation, causing continuous ionisation/fragmentation of the sample, whilst the second plasma records the optical emission downstream. For injection, the first plasma is briefly interrupted, introducing a â plugâ of unmodified sample into the system. Injection plug sizes of between 5 and 50 µl have been reproducibly obtained, although significantly smaller volumes may be possible with the use of smaller cross-section columns, lower flow rates and/or shorter plasma interruption times.