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

Abstract

A class of compounds which are byproducts of the resin manufacturing process, has been responsible for three different taste and odor episodes in drinking water around the world. One such episode which occurred on the Ohio River, 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 formation of 2-EMD were examined specifically under the conditions which were present 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 synthesized and purified in order to determine odor characteristics and odor thresholds using the method of flavor profile analysis (FPA). The distinctive 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 levels of 2-EMD found in drinking water samples from the taste and odor event of the Ohio River were above this odor threshold.