Novel sorbents for sampling organic vapours

Abstract

Sorbent sampling methods are used for obtaining time-weighted average samples to determine the concentrations of gases and vapours in workplace air. As knowledge of the toxicity of chemicals improves, lower exposure limits are often set, and this requires sorbents with lower levels of interferences, and improved analyte recovery. Industry sometimes responds to stricter regulations by changing the types of chemicals used, for example from hydrocarbon solvents to alcohols and ketones. Traditional sorbents, such as active coconut charcoal and silica gel, are poor sorbents for many volatile, polar and reactive compounds because of capacity, desorption and stability problems. New sorbents are required for these chemicals. Sorbents are used in tubes coupled with a pump (active sampling) or in tubes or badges used in the diffusive mode (passive sampling). Three new sorbents for sampling polar and reactive compounds have been evaluated in sample tubes and diffusive samplers that employ solvent desorption. Anasorb 727 is a hydrophobic porous polymer that can be used for sampling reactive molecules such as methyl methacrylate, cyclohexanone and terpenes. Anasorb 747 is a relatively hydrophobic, synthetic carbon with a broad range of application, and which exhibits the best recoveries and storage stabilities for most compounds. It has been validated for sampling propene oxide and a wide variety of ketones and acrylates. It has also been used for dichloromethane, acetone and methanol, although sample migration can occur on storage with these compounds. Anasorb CMS is a carbon molecular sieve that has enhanced capacity for the smallest molecules. It has been used for methyl chloride, dichloromethane, acetone, butan-2-one, anaesthetic gases, propene and sulfuryl fluoride (vicane). Sample displacement by water vapour, and sample migration during storage, occur only with the most volatile compounds (e. g., methyl chloride).