Collection of Semi Volatile Organic Material

To address the issues of both 'positive' and 'negative' artifacts in the sampling of particulate phase organic compounds, several groups have constructed and tested sampling systems employing diffusion denuders, filters and sorbent filters. The data obtained to date with these sampling systems show that particulate

Figure 1 Temperature-programmed volatilization analysis of quartz filters (A) not preceded and (B) preceded by a denuder with charcoal impregnated filter surfaces. The large initial peak seen in (A) but not in (B) is due to the absorption of gas phase organic material by the quartz filter not preceded by a diffusion denuder to remove gas phase organic compounds.

Figure 1 Temperature-programmed volatilization analysis of quartz filters (A) not preceded and (B) preceded by a denuder with charcoal impregnated filter surfaces. The large initial peak seen in (A) but not in (B) is due to the absorption of gas phase organic material by the quartz filter not preceded by a diffusion denuder to remove gas phase organic compounds.

phase organic compounds have been significantly underestimated by the collection of particles with only a filter. The collection of gas phase compounds by a quartz filter may produce a significant 'positive' artifact (Figure 1), but a much larger negative error usually results from the loss of 20-80% of the particulate phase semi-volatile organic material during sampling. This sampling artifact must be considered in the collection of semi-volatile particulate organic compounds. Accurate collection procedures for semi-volatile organic compounds must meet the following two criteria:

1. Organic compounds initially present in the gas phase which can be adsorbed onto particles or the filter must be distinguished from semi-volatile organic compounds lost from particles during sampling.

2. Organic compounds initially present in the parti-culate phase and lost from particles during sampling must be captured during sampling separate from compounds which are present in the gas phase in the atmosphere.

These two criteria cannot be met by any sampling procedure in which the particulate phase organic compounds are collected before the collection or separation of gas phase organic compounds because the gas phase organic compounds and organic compounds volatilized from particles become indistinguishable. Thus, it is necessary first to remove the gas phase organic compounds and then to collect the particulate phase organic compounds with a sampler which will collect all organic material, gas and particle. This can be accomplished using diffusion denuder sampling technology.

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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