Harnessing the potential of sniffing dogs and GC–MS in analyzing human urine: A comprehensive review of sample preparation and extraction techniques

Pathologies such as cancers or infectious diseases can induce modifications in the concentrations of urinary volatile metabolites. Indeed, urine is a large source of Volatile Organic Compounds (VOCs) from the human body. Canine olfaction and Gas Chromatography coupled to Mass Spectrometry (GC–MS) systems are promising tools for the development of non-invasive diagnosis methods based on the analysis of urine. This review paper aims to provide an overview of materials and methods found in the literature for urinary VOCs analysis by detection dogs and GC–MS instruments. It highlights the impact of urine collection procedures and storage conditions. Then, sample preparation protocols for canine olfaction are discussed, as well as for GC–MS analysis, focusing on headspace-based extraction techniques. In the case of instrumental analysis, a significant variability of volatile profiles can be observed depending on the sample preparation (urine pH, extraction methods), and analytical parameters. Lastly, limitations of urinary VOCs analysis for medical diagnosis purposes are considered.