NOVEL SORBENTS FAR SAMPLING ORGANIC VAPORS

Sorbent sampling methods are used for obtaining time-weighted average samples to determine the concentrations of gases and vapours in workpl ace air. As knowledge of the toxicity of chemicals improves, lower exp osure limits are often set, and this requires sorbents with lower leve ls of interferences, and improved analyte recovery. Industry sometimes responds to stricter regulations by changing the types of chemicals u sed, for example from hydrocarbon Solvents to alcohols and ketones. Tr aditional sorbents, such as active coconut charcoal and silica gel, ar e poor sorbents for many volatile, polar and reactive compounds becaus e of capacity, desorption and stability problems. New sorbents are req uired for these chemicals. Sorbents are used in tubes coupled with a p ump (active sampling) or in tubes or badge 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 po lymer 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 w hich exhibits the best recoveries and storage stabilities for most com pounds. It has been validated for sampling propene oxide and a wide va riety of ketones and acrylates. It has also been used for dichlorometh ane, acetone and methanol, although sample migration can occur on stor age with these compounds. Anasorb CMS is a carbon molecular sieve that has enhanced capacity for the smallest molecules. It hag been used fo r 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).