Rapid determination of methyl tert-butyl ether using dynamic headspace/ion mobility spectrometry

Using an original, experimental set-up named dynamic headspace/IMS (DHS/IMS), ppb levels of methyl tert-butyl ether (MTBE), a gasoline additive and environmental pollutant, were determined in drinking and ground water. A portable IMS (Bruker, Raid-1 model) was connected to the outlet of a Drechsel bottle containing 100 ml of water-based sample. Automatically activated to sample air, the IMS built-in pump was used to produce a continuous and gentle air flow bubbling through the water-based sample. This allowed volatile MTBE to be isolated and transferred into the Drechsel headspace and then into the IMS. Analyses of reference solutions and real samples resulted in MTBE detection limits of 20 ppb, calibration curves in the 20-200 ppb range, and relative standard deviations of 4.7 and 8.4%, respectively, for inter- and intra-day reproducibility tests. Detection limits were further improved to 0.5 ppb by means of a Tenax trap cooled with liquid nitrogen, placed between the sample bottle and the IMS. Overall, DHS/IMS could well become a simple and cost-effective tool for rapid and on-line analysis of volatile organic compounds in water.