Odor concentration prediction by gas chromatography and mass spectrometry (GC-MS): importance of VOCs quantification and odor detection threshold accuracy

Overview & Synopsis

Odor annoyance is the second most important nuisance in Europe. So, the knowledge of the odor concentration is very important to assess the odor impact on the environment. In Europe, EN 13725 regulates the method to measure the odor concentration. If olfactometry is the only normalized method to measure odor concentration, it is nevertheless often interesting to be able to assess it on the basis of a physico-chemical analysis. To reach this goal, the odor concentration can be obtained by the following equation: ܸΣ n (i=1) 0AVi = Σ n (i=1) Ci/(ODTi) In this equation, ܸ0AVi is the odor activity value that corresponds to the ratio of the chemical concentration to the odor detection threshold of compound݅ . Ci corresponds to the concentration of compound in the gaseous mixture and ODTi to the odor detection threshold of this compound. These two parameters affect odor activity value and therefore odor concentration assessment accuracy. In this context, the main goal of our experiment was to determine what conditions are suitable to obtain the most precise prediction. Our study consisted in the first step to generate a calibrated gaseous mixture of odorous compounds and to analyze it by GC-MS and olfactometry (EN 13725). The reproducibility of the gaseous mixture generation was tested. Physico-chemical results were analyzed using a global quantification (mg/m3 toluene eq.) on one side and individual quantification of each compound on the other side. In the same way, we used odor detection thresholds from the literature on one side and odor detection thresholds measured in our lab, according to EN 13725, on the other side. This study allowed us to emphasize the weight of quantification and odor thresholds accuracies on odor concentration prediction.