Non‐invasive sorptive extraction for the separation of human skin surface chemicals using comprehensive gas chromatography coupled to time‐of‐flight mass spectrometry: A mosquito‐host biting site investigation

Abstract

Variation in inter-human attractiveness to mosquitoes, and the preference of mosquitoes to bite certain regions on the human host, are possible avenues for identifying lead compounds as potential mosquito attractants or repellents. We report a practical, non-invasive method for the separation and detection of skin surface chemical compounds and comparison of skin chemical profiles between the ankle and wrist skin surface area sampled over a 5-day period of a human volunteer using comprehensive gas chromatography coupled to time-of-flight mass spectrometry. An in-house made polydimethylsiloxane passive mini-sampler, worn as an anklet or a bracelet, was used to concentrate skin volatiles and semi-volatiles prior to thermal desorption directly in the gas chromatography. A novel method for the addition of an internal standard to sorptive samplers was introduced through solvent modification. This approach enabled a more reliable comparison of human skin surface chemical profiles. Compounds that were closely associated with the wrist included 6-methyl-1-heptanol, 3-(4-isopropylphenyl)-2-methylpropionaldehyde, 2-phenoxyethyl isobutyrate, and 2,4,6-trimethyl-pyridine. Conversely, compounds only detected on the ankle region included 2-butoxyethanol phosphate, 2-heptanone, and p-menthan-8-ol. In addition to known human skin compounds we report two compounds, carvone and (E)-2-decenal, not previously reported. Limits of detection ranged from 1 pg (carvone) to 362 pg (indole).

A headspace collection chamber for whole body volatilomics

“…Although less commonly the subject of metabolomics investigations, skin VOCs can provide insight into the human metabolome and be utilized across numerous fields of research. The study of skin emanations has been conducted to develop analytical techniques for the detection of human scent during search and rescue operations, [24][25][26][27][28] explore individual differences in human odor, [29][30][31] evaluate the attraction of mosquitoes to human odor, [32][33][34] and to fundamentally understand the biological basis of human scent. [35][36][37][38] Skin VOCs are typically collected using sorbent materials placed in direct contact with the skin.…”

A headspace collection chamber for whole body volatilomics

“…Although less commonly the subject of metabolomics investigations, skin VOCs can provide insight into the human metabolome and be utilized across numerous fields of research. The study of skin emanations has been conducted to develop analytical techniques for the detection of human scent during search and rescue operations, [24][25][26][27][28] explore individual differences in human odor [29][30][31] , evaluate the attraction of mosquitoes to human odor, [32][33][34] and to fundamentally understand the biological basis of human scent. [35][36][37][38] Skin VOCs are typically collected using sorbent materials placed in direct contact with the skin.…”

“…33,[39][40][41] This form of sample collection has similarly been achieved using SPME fibers, 42 and polydimethylsiloxane (PDMS), including coated stir bars, 43 patches, 44,45 and wearable wrist bands. 34,46 Aside from contact-based sampling methods, skin emanations have been explored using sampling devices and bags to collect headspace from isolated body parts, namely the hands and feet, onto SPME fibers or thermal desorption tubes. 37,38,42 Most human volatilomics studies to date focus on the detection of volatiles in a particular medium, such as exhaled breath, a bodily fluid, or from an isolated part of the body.…”

A headspace collection chamber for whole body volatilomics

“…The study of skin emanations has been conducted to develop analytical techniques for the detection of human scent during search and rescue operations, [21][22][23][24][25] explore individual differences in human odor [26][27][28] , evaluate the attraction of mosquitoes to human odor, [29][30][31] and to fundamentally understand the biological basis of human scent. [32][33][34][35] Skin VOCs are typically collected using sorbent materials placed in direct contact with the skin.…”

“…30,[36][37][38] This form of sample collection has similarly been achieved using SPME fibers, 39 and polydimethylsiloxane (PDMS), including coated stir bars, 40 patches, 41,42 and wearable wrist bands. 31,43 Aside from contact-based sampling methods, skin emanations have been explored using sampling devices and bags to collect headspace from isolated body parts, namely the hands and feet, onto SPME fibers or thermal desorption tubes. 34,35,39 Most human volatilomics studies to date focus on the detection of volatiles in a particular medium, such as exhaled breath, a bodily fluid, or from an isolated part of the body.…”