Comparison of Instrumental (Gas Chromatography) and Organoleptic Measures of Malodour

Methods: 20 healthy volunteers between the ages of 20-60 were recruited and provided breath samples up to eight times in a day. Samples were taken using a disposable 20 ml syringe and were analysed for VSCs utilising gas chromatography with flame photometric detection. Oral malodour was assessed by judges on a six point intensity scale. The Pearson correlation coefficient was calculated between the oral malodour scores and the VSC concentration.

Results: Hydrogen sulfide concentrations ranged from 5 to 2405 ppb (n=70), methyl mercaptan concentrations ranged from 0 to 632 ppb (n=70). Correlation between VSCs and malodour scores was poor (oral malodour and hydrogen sulfide correlation co-efficient=0.4283, methyl mercaptan correlation co-efficient=0.3850). However, certain trends were observed. Malodour intensity scores between 0 to 3 had corresponding hydrogen sulfide concentrations in the range 0 to 350ppb. Samples with hydrogen sulfide concentration in excess of 300ppb corresponded with malodour scores of 3 to 5. Samples greater than 500ppb hydrogen sulfide corresponded with high malodour scores (4 or 5). Subjects with a malodour score of 5 had hydrogen sulfide concentrations as high as 2405ppb but not all high malodour scores had a corresponding high hydrogen sulfide concentration. This indicated that the components responsible for the malodour in these subjects were not VSCs but other, as yet uncharacterised malodourous compounds.

Conclusion: The GC has a greater range than malodour judges for high levels of VSCs but it cannot discriminate between different levels of low to moderate malodour. Further investigation into non-sulfur derived malodour compounds is required.