Preparation of Environmental Air Samples for Organic Analysis

The determination of volatile organic compounds (VOCs) in the atmosphere can be done by trapping them on a solid support material (e.g. Tenax) and then using thermal desorption directly into a gas chromatograph for subsequent analysis. Trapping of VOCs can be done actively or passively. In active trapping, air is drawn through a sorbent (e.g. Tenax) at a fixed flow rate for a period of time; this allows a mass of VOCs per volume of air to be calculated. In passive trapping, a sorbent, for example a filter paper or solid phase microextraction (SPME) fiber, is left exposed to the air for a period of time and the concentration of VOCs on the sorbent calculated. An effective way to desorb the VOCs from the sorbent is via thermal desorption; other approaches include solvent extraction, for example Soxhlet extraction.