Development of a compact and simple gas chromatography for oral malodor measurement

Background: Volatile sulfur compounds (VSCs) in oral air are the only type of gases correlated with the strength of oral malodor. We developed a compact and simple gas chromatograph (GC) equipped with a newly invented indium oxide semiconductor gas sensor (SCS) for measuring the concentrations of VSCs in mouth air. We have assessed the correlation between measurements with a GC-SCS and those with a regular GC. Methods: Oral air samples from randomly selected volunteers were analyzed with both a GC-SCS and a GC with a flame photometric detector (FPD), which is specific to VSCs, and GC-SCS measurements were compared to those obtained by GC-FPD. Subsequently, oral air samples before and after mouthrinsing with 5% ethanol mouthwash were analyzed to determine the effect of ethanol on VSC measurements by GC-SCS. Results: There were strong correlations between VSC concentrations determined using these two gas chromatography methods (hydrogen sulfide, R = 0.821, P < 0.0001; methyl mercaptan, R = 0.870, P < 0.0001; and dimethyl sulfide, R = 0.770, P < 0.0001). Although GC-SCS can differentiate ethanol and VSCs in oral air samples after mouthrinsing, GC-SCS measurements demonstrated higher values than those obtained by GC-FPD; however, this discrepancy improved over time due to the reduced effect of ethanol. Conclusion: The results suggest that GC-SCS may be useful for the diagnosis of halitosis.