Identification by cryofocusing–gas chromatography–mass spectrometry of odorous cyclic acetals emitted from a polyester resin plant

Abstract

A simple and inexpensive cryofocusing device was developed ad hoc in order to analyse at sub-ppb levels airborne organics, sampled by Tenax tubes and recovered by thermal desorption. By means of this device and of gas chromatography-mass spectrometry, the odorous compounds in the air around a polyester resin factory were identified as 2-ethyl-4-methyl-I ,3-dioxolane (EMD), 5,5-dimethyl-l,3-dioxane (DMD), 2,5,5trimethyl-l,3-dioxane (TMD), 2-ethyl-5,5-dimethyl-1,3-dioxane (EDMD) and 2-isopropyl-5,5-dimethyl-1,3-dioxane (IDMD). These compounds are produced during the synthesis of polyester resins by cyclic acetalization of vicinal diols under acid catalysis. Their structures were confirmed by laboratory syntheses. The Odour Index of these organics was evaluated by means of dynamic olfactometry, and the results were 22 100 for IDMD, 27 200 for DMD, 98 100 for EMD, 1 003 000 for TMD and 2 094000 for EDMD. Their odour changes dramatically from a pleasant mint scent at higher concentrations to a very unpleasant smell at ppb level con cent rat ions.

Organic compounds in office environments - sensory irritation, odor, measurements and the role of reactive chemistry

“…A fraction of the population may perceive a given odor at least one order lower than the majority of the population according to the definition of an odor threshold (50% median response fraction). Sensory irritation and odor perception may be confused. Information, experience and habituation may alter the association of perceived health effects (Devries et al., 2004; Opiekun et al., 2003; Van den Bergh et al., 2002; Winters et al., 2003), and reported odor intensity in some cases (Distel et al., 1999). Concentration may not be the best indicator of the impact of an odor, partly because persistence and hedonic value influence its impact (Nicell, 2003), and the relationship between concentration and pleasantness or intensity may be inverse for some compounds (Cocheo et al., 1991; Whelton and Dietrich, 2004). Short‐term evaluation of the perceived air quality is probably not relevant for the evaluation of symptoms built up during the working day (Bluyssen et al., 1996; Wolkoff et al., 1991b).…”

“…Concentration may not be the best indicator of the impact of an odor, partly because persistence and hedonic value influence its impact (Nicell, 2003), and the relationship between concentration and pleasantness or intensity may be inverse for some compounds (Cocheo et al., 1991; Whelton and Dietrich, 2004).…”

Identification of 1,3-Dioxanes and 1,3-Dioxolanes as Malodorous Compounds at Trace Levels in River Water, Groundwater, and Tap Water

“…Preliminary analytical data showed the presence of antioxidants, aromatic solvents, and chlorinated solvents that due to their low concentration levels were discarded as the potential origin of the odor event as were a large number of unidentified compounds with no equivalents in mass spectral libraries. These compounds were further identified as 2-alkyl-5,5-dimethyl-1,3-dioxanes and 2-alkyl-4-methyl-1,3-dioxolanes (see acronyms in Table 1) after comparison of their mass spectra with the products published by Cocheo et al (24) in the air around a polyester resin plant and by Preti et al (25), who identified 2-ethyl-5,5-dimethyl-1,3-dioxane (2EDD) as the malodorous compound in the treated water of Philadelphia.…”

On-column cryofocusing and analyte enrichment device for gas chromatography systems

“…Cryofocusing devices are mostly based on three different designs: electrical cooling (Peltier element [6]) is the simplest method [7,8], but it is limited in its cooling capacity; cooled gas is more well-known and can be used to cool the whole GC oven or just part of the column [9]; a liquid gas system [10] can achieve very low temperatures in a short amount of time, but requires a liquid coolant (He or N 2 ). The cryofocusing device described in this paper is based on the liquid gas system.…”