Collection of Gas Phase Organic Material

A well validated technique for the collection of gas phase organic material for subsequent analysis is the use of SUMMA stainless steel canisters. If the canisters are properly cleaned before use and analysed within a few weeks of sample collection, valid results can be obtained for most gas phase compounds.

A second method which has frequently been used to collect gas phase organic materials consists of the use of a filter to remove particulate material, followed by a sorbent bed to collect the gas phase organic compounds. This approach is not valid if (1) the gas phase organic material is oxygenated or polar and therefore capable of being absorbed by a quartz filter or by organic material colleted by the particle removing filter, or (2) the gas phase organic material is semi-volatile and therefore, may be present on and lost from particles during sampling (see following section). The absorption of organic material by various types of filters has been reviewed. Teflon has been suggested to be relatively inert to absorption artifacts, but this filter is not amenable to the determination of total carbon. Glass fibre and cellulose membrane filters both absorb significant quantities of gas phase organic material. Quartz membrane filters are suitable for the determination of total carbon, but they also can absorb significant quantities of gas phase organic material. This is illustrated in Figure 1 which shows the analysis of total carbon for a filter which was preceded and not preceded by a charcoal based diffusion denuder to remove gas phase material. The large peak seen in the absence of a diffusion denuder is gas phase organic material collected by the quartz filter. A similar peak (plus some higher temperature material) is seen on a second quartz filter which is not preceded by a denuder.

Materials which have been validated as sorbents for the removal of gas phase organic compounds include polyurethane foam (PUF), poly(oxy-m-ter-phenyl-2',5'-ylene), Tenax, copolymers of styrene and divinylbenzene (XAD), Chromosorb and charcoal. Of these sorbents, Tenax is best suited for the collection of very low molecular weight organic material and Chromosorb or XAD are effective for collection over a wide range of molecular weights. A caution is that many of the sorbents can produce spurious results due to reactions during sample collection and each of the sorbents can be difficult to clean for the detection of trace substances. Thus, for example, a PUF cartridge produces mutagenic compounds upon extraction with methanol and Tenax forms decomposition products during sampling.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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