Methods of sampling trace substances in air

Trace gases are commonly collected via accumulative sampling, employing sorbents and cryotraps that utilize passive (diffusive) or active sampling principles. For semivolatile substances such as ammonium salts as well as oxygenated and halogenated organics, the particulate and gas phases must be collected separately—either side by side or in a sample train. Aerosol particles are collected using a broad spectrum of samplers that rely on physical principles such as inertia-based particle sampling, diffusive particle transport and adsorption to surfaces, particle migration and deposition in external fields, and filter sampling. Dedicated inlet systems with minimized particle losses must be used to ensure that sampling gives representative results, particularly for the particle size distribution. Note that artifact-free sampling is not yet available for a number of target compounds