P23 Discrimination of oral‐halitosis substance under humidity‐rich environment by using QCM sensor array and a preconcentrator

Abstract

Objectives A halitosis test for objective evaluation is required. Halitosis is due to Volatile Sulfur Compounds (VSCs) produced by bacterial metabolism. In this study, we proposed a method for discriminating among sulfur compounds using a Quartz Crystal Microbalance (QCM) sensor array combined with a preconcentrator. The adjustment of the temperature profile, the optimization of the flow path sequence and the use of a dehumidification filter enabled VSC measurement under a high‐humidity condition. Moreover, the result of principal component analysis indicated that three types of VSCs were separated using the sensor‐array output pattern.Methods Multiple QCMs with different coating films were used as a sensor array and the pattern recognition of eight different sensor responses enabled the odor identification. The preconcentrator was used not only for improving limit of detection but for eliminating the influence of humidity by adjusting the desorption temperature. The headspace over the liquid (water or ODO) where VSC was dissolved with the concentration of 0.1% (w/w) was used as the samples.Results and conclusion An experiment on the discrimination among VSCs was performed. The headspace vapor of each sample was supplied to the preconcentrator for 30 s, followed by an exposure of the vapor thermally desorbed at 170°C to the QCM sensor array. The sensing films suitable for VSCs were selected among the various candidates and the peaks of the sensor responses to VSCs were analyzed using principal component analysis. Each sample was measured 10 times at the intervals of 30 min. As a result, it was found that three kinds of VSCs were successfully discriminated. Furthermore, it was found that the sensor responses increased in case of longer accumulation time. Thus, it is possible to detect the sample with lower concentration. This measurement method will be effective to diagnose halitosis objectively.