For female mammals, communicating the timing of ovulation is essential for successful reproduction. Urinary volatile organic compounds (VOCs) play a key role in intraspecific communication among many mammals. Using laboratory mice as a model species, we investigated urinary VOCs across the oestrous cycle. We monitored the oestrous stage through daily vaginal cytology assessment and analysed urinary VOCs using headspace gas chromatography-mass spectrometry (GC-MS), testing the utility of portable GC-MS against the more robust benchtop device. We detected 65 VOCs from 40 samples stored in VOC traps and analysed on a benchtop GC-MS and 15 VOCs from 90 samples extracted by solid-phase microextraction (SPME) and analysed on a portable GC-MS. Only three of the identified compounds were found in common between the two techniques. Urine collected from the fertile stages of the oestrous cycle had increased quantities of a few notable VOCs (3,4-dehydro-exo-brevicomin, butanoic acid, pent-1-ene/cyclopentane, 1,2,3-/1,2,4-trimethylbenzene, heptadecane, dioctyl ether, dodecan-1-ol and 2-ethylhexyl salicylate), compared to urine collected from non-fertile stages. However, we did not find differences in the Bray-Curtis chemical dissimilarity indices among oestrous stages. It is possible that the variation in urine VOCs concentration at play during the oestrous cycle was too subtle to be detected by our analytical methods. Overall, the use of the VOC traps combined with benchtop GC-MS was more successful than SPME combined with portable GC-MS in capturing and identifying murine urinary VOCs. Nonetheless, portable GC-MS systems have the potential for some in situ applications since they allow for the immediate interpretation of results, especially at remote field sites.

Using laboratory mice as a model species, we investigated urinary VOCs across the oestrous cycle. We monitored the oestrous stage through daily vaginal cytology assessment and analysed urinary VOCs using headspace gas chromatography-mass spectrometry (GC-MS), testing the utility of portable GC-MS against the more robust benchtop device.