Olfactory Experiments with Cotton or Viscose Pads: Major Chemical Confounders Detected by GCxGC-Q-TOF

The release of volatile organic compounds (VOCs) from sweat pads is modulated by both material composition and conditions of use, particularly moisture content and thermal treatment. In this study, we investigated the impact of water addition and heat exposure on VOC emissions from cotton and viscose–polyester sweat pads using dynamic headspace sampling coupled with two-dimensional gas chromatography–high-resolution time-of-flight mass spectrometry (DHS-GCxGC-QTOF-MS). Water addition led to a pronounced increase in VOC release — including key VOCs with low ppbv odor thresholds like acetic acid, 2,4-nonadienal and 2,3-butanedione — with at least a five-fold increase observed for 110 compounds extracted from cotton pads at ambient temperature. Extraction at elevated temperature (60 °C) resulted in even higher fold changes in VOC release. The emission patterns differed markedly between materials: VOC release from cotton pads followed an exponential trend, while viscose–polyester pads showed a biphasic response — initially exponential, then more linear at higher moisture levels. Heat treatment at 150 °C prior to water dosing further amplified VOC emissions, particularly in cotton pads, where over two-thirds of detected compounds exhibited increased release. These observations suggest that cellulose–water interactions play a fundamental role in mediating VOC emission dynamics. Our findings highlight the material- and condition-dependent variability in VOC release from sweat pads and underscore the need for rigorous control of hydration and thermal effects in chemical and psychophysical studies involving olfactory stimuli. Given the widespread use of cotton pads in psychological and chemosensory research, these methodological considerations are critical for ensuring reliable chemical analysis and reproducible perceptual outcomes.