AWWA WQTC65829

There are many methods used to monitor drinking water to detect odorouscompounds 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. Alsoquick human senses enable the utilities to take precautions earlier. The flavor profileanalysis (FPA, Standard Method 2170) is a commonly used method. The food industrystarted using FPA early 1950s (Caircross and Sjostrom, 1950) and later the waterindustry adopted the method (Suffet et al., 1988).For FPA, samples are presented in cups or standard flasks. After tasting and/orsmelling, panelists rate the samples (descriptor(s) and intensity(ies)). Then the paneldiscusses 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 (Krasneret al., 1985; Suffet et al., 1999). FPA requires a well-trained panel and although tastestandards are well established, FPA training doesn't have an odor standard. Intensity ofan odor is reported based on the learned taste intensities. This step is not very precise. Ifthere was an odor standard, the panel would be trained better and the results would bemore precise.Finding an odor standard is not easy. The ideal odor standard should have a pleasantsmell, 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 alinear Weber-Fechner plot. The Weber-Fechner plots present the relationship betweenthe log concentration of the odorant and the odor intensity. When a straight line isobtained, it means that the odor intensity increases with increasing concentration in alog-linear fashion. Hexanal having a grassy odor and being commonly found in drinkingwater is a good candidate to be an odor standard. This study investigated the suitabilityof hexanal to being an odor standard. For the sensory experiments 500 mL wide mouth Erlenmeyer flasks with stoppers wereused. 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 wereused. Solid phase micro-extraction (SPME) and gas chromatography with massspectrometer was used to measure the headspace concentration of hexanal in the flasksover time and after a few sniffs. Includes 10 references, figure.

Product Details

Edition:

Vol. - No.

Published:

11/01/2007

Number of Pages:

5

File Size:

1 file , 130 KB