The formation, stability, and odor characterization of 2-ethyl-4-methyl-1,3-dioxolane (2-EMD)

A class of compounds which are byproducts of the resin manufacturing proces s, has been responsible for three different taste and odor episodes in drin king water around the world. One such episode which occurred on the Ohio Ri ver, Pennsylvania, USA in 1989 was linked to the chemical, 2-ethyl-4-methyl -1,3-dioxolane (2-EMD). In this study, the mechanism and kinetics of format ion of 2-EMD were examined specifically under the conditions which were pre sent in the waste water of a resin manufacturer during the Ohio River event . The stability (fate) of 2-EMD was studied at aqueous pHs of 3, 5, 7, and 9. Hydrolysis occurred on the order of hours at pH 3 and its stability was questionable even at pH 7, but appeared to be stable at pH 9. 2-EMD was syn thesized and purified in order to determine odor characteristics and odor t hresholds using the method of flavor profile analysis (FPA). The distinctiv e sweet odor described as "sickening sweet" or "medicinal sweet" was found to have an odor threshold concentration of between 5 and 10 ng/l. The level s of 2-EMD found in drinking water samples from the taste and odor event of the Ohio River were above this odor threshold. (C) 1999 Published by Elsev ier Science Ltd on behalf of the IAWQ. All rights reserved.