AWWA WQTC65829

There are many methods used to monitor drinking water to detect odorous compounds before the water is distributed (Mallevialle and Suffet, 1987; Dietrich et al., 2004). The sensory methods are more effective as the human nose is very sensitive. Also quick human senses enable the utilities to take precautions earlier. The flavor profile analysis (FPA, Standard Method 2170) is a commonly used method. The food industry started using FPA early 1950s (Caircross and Sjostrom, 1950) and later the water industry adopted the method (Suffet et al., 1988). For FPA, samples are presented in cups or standard flasks. After tasting and/or smelling, panelists rate the samples (descriptor(s) and intensity(ies)). Then the panel discusses and comes to a consensus about the ratings. A seven-point scale is used: 1 = threshold value and the even numbers up to 12 are used as the intensity ratings (Krasner et al., 1985; Suffet et al., 1999). FPA requires a well-trained panel and although taste standards are well established, FPA training doesn't have an odor standard. Intensity of an odor is reported based on the learned taste intensities. This step is not very precise. If there was an odor standard, the panel would be trained better and the results would be more precise. Finding an odor standard is not easy. The ideal odor standard should have a pleasant smell, should be detected by most of the population, would be stable during sampling, would be reproducible for every panel, would not cause anosmia, and should have a linear Weber-Fechner plot. The Weber-Fechner plots present the relationship between the log concentration of the odorant and the odor intensity. When a straight line is obtained, it means that the odor intensity increases with increasing concentration in a log-linear fashion. Hexanal having a grassy odor and being commonly found in drinking water is a good candidate to be an odor standard. This study investigated the suitability of hexanal to being an odor standard. For the sensory experiments 500 mL wide mouth Erlenmeyer flasks with stoppers were used. Hexanal solutions were prepared in Nanopure® water at 1, 5, 10, 25, 50, 100, 500, and 1000 µg/L concentrations. All of the flasks were washed and rinsed until odor free. For analytical analyses, similar flasks with a septum port attachment on the side were used. Solid phase micro-extraction (SPME) and gas chromatography with mass spectrometer was used to measure the headspace concentration of hexanal in the flasks over time and after a few sniffs. Includes 10 references, figure.