Outdoor Air Quality
The inherent sensitivity of chromatography and mass spectrometry makes the combined techniques ideal for the analysis of odours and/or non odorous volatile organic compounds (VOC) found in the outdoor environment. Traditional areas for outdoor surveys include boundary fence surveys usually performed to determine the odor impact of an industrial site on its neighbours, stack gas analysis of compounds discharged through factory chimneys and ‘on-plant’ analysis used to determine the exposure of plant operatives to potentially hazardous vapors.
In a year long programme, VOCs were monitored around the boundary fence of a large petrochemical facility to determine the background levels of odours prior to the construction of a new plant. The requirement of the survey was to collect samples 24 hour/day. Compounds of interest included methyl mercaptan, ethyl mercaptan, and propyl mercaptan and hydrogen sulphide with a requirement to measure to sub part per billion levels, which is well below their odour thresholds. To automate the sample collection process SGS M-Scan designed and constructed a number of static air sampling stations which were distributed around two sites, each programmed to collect a known volume of air per day. Once collected, samples were returned to SGS M-Scan’s laboratory for analysis by Thermal Desorption GC-MS (TD GC-MS).
A company manufacturing gases was concerned about impurity levels in their product. The inherent sensitivity of the Thermal Desorption GC/MS technique makes it an ideal technique for this analysis. Samples can be collected in gas bags or preferably directly onto thermal desorption tubes depending on the gas pressure at the sampling point.
A chemical manufacturer discovered that its stack emissions were having toxic effects on the bird population. In addition to the effects on wildlife there was concern over the toxicity for plant operatives. Stack samples and additional air samples were collected from around the plant and analysed by Thermal Desorption GC/MS. The analysis showed that an unexpected by-product not previously seen from this process was being released. Subsequent investigations showed that the by-product was being created due to an impurity in a raw material supplied to the plant.