Development and evaluation of a calibration gas generator for the analysisof volatile organic compounds in air based on the injection method

The development and operational evaluation of a calibration gas generator f or the analysis of volatile organic compounds (VOC) in air is described. De tails of the construction, as well as of the evaluation of the apparatus ar e presented here. The performance of the test gas generator is validated bo th by on-line GC analysis of the calibration gas produced and by off-line a nalysis of adsorptive samples taken from the generated calibration gas. Bot h, active and passive sampling have been used, and the results demonstrate the excellent accuracy and precision of the generated test gas atmosphere: For the I I investigated organic Compounds (aromatic and halogenated compou nds), the found values were in most cases within 5% of the target value wit h a reproducibility of better than 3% RSD (as determined by the analysis of the sampled adsorbent tubes). Custom made adsorbent tubes were used for ac tive and passive sampling and in both cases were analysed by thermal-desorp tion GC. Particularly the combination of passive sampling and thermodesorpt ion-GC analysis offers significant advantages over the commonly used active sampling on activated charcoal, followed by CS2 desorption in terms of avo idance of hazardous solvents, potential for automation and improved detecti on limits. Both sampling techniques are capable for monitoring VOCs at conc entrations and under conditions relevant for workplace monitoring.