The odour laboratory has extensive analytical capacity for olfactory and chemical analysis of odours, odorants, and atmospheric contaminants that includes a dynamic olfactometry laboratory and analytical instrumentation (TD-GC-MS/O, TD-GC-MS/FPD, air server-TD-GC-SCD/NCD) for the chemical characterisation of odours. The laboratory also has specialist capability to undertaken field sampling from area and point source emissions using both flux chamber and wind tunnels.
Olfactory-gas chromatography analysis
The TD-GC-MS/O is used for identification and quantification of non-methane volatile organic compounds (NMVOC’s) with the additional functionality of odorant identification and prioritisation within a gas phase sample. Thermal desorption (TD) provides analyte pre-concentration; gas chromatography (GC) allow analyte separation; mass spectrometry (MS) provided analyte identification and quantification; olfactory detection (O) allows for odorant identification and prioritisation.
Gas chromatography mass spectrometry
The TD-GC-MS(/FPD) is used for comprehensive NMVOC quantification, with enhanced sulphur detection by flame photometric detection (FPD). As with the TD-GC-MS/O the NMVOC analyte pre-concentration, separation, identification and quantification is performed by the TD-GC-MS; whilst the flame photometric detector (FPD) allows superior sulphur detection capabilities. Sulphur species are particularly important in potential odour investigations owing to their low odour detection threshold and unpleasant odour characteristics.
Sulfur and nitrogen analysis
The AS-TD-GC-SCD/NCD is used for assessment of highly volatile sulphur and nitrogen containing samples. Whole air sampling is achieved using canisters of gas bags are introduced to the system via a mass flow controlled air server (AS-TD), this eliminates potential sample degradation and analyte selectivity from thermal desorption tubes. Gas chromatography allows analyte separation, whilst parallel chemiluminescence (sulphur and nitrogen) detectors give high selectivity and sensitivity to volatile nitrogen (VONC) and volatile sulphur (VOSC) species. VONCs and VOSCs often contribute to malodour as many of these compounds have unpleasant odour characteristic and very low odour detection thresholds.
Flux Chamber sampling
US-EPA Flux hoods can be used to measure the emissions from different sources (solid or liquid). The flux hood is purged with high purity nitrogen to generate a flux from the surface which is drawn from the hood and captured for analysis. The availability of standard methods makes the results of flux hood sampling more comparable. The flux hoods are reasonably compact and offer greater logistical advantages over more cumbersome wind tunnels.
Wind tunnel sampling
Wind tunnels can also be used on a variety of area emission sources, however they are generally much larger than flux hoods and require a greater air supply to sweep across the surface being sampled. There is a number of wind tunnel designs in use internationally.
Dilution olfactometry is used to quantify an odour. A panel of people is used to generate a value for a particular strength of odour, the panelists are selected based upon their sensitivity to n-butanol. A standard protocol (AS4323.3.2001) is used to ensure that results obtained from dilution olfactometry are comparable between laboratories.