Gaseous ensembles of molecules, called the volatilome, are fingerprints [START_REF] Amann | The human volatilome: volatile organic compounds (VOCs) in exhaled breath, skin emanations, urine, feces and saliva[END_REF]- [START_REF] Sohrabi | Volatile Organic Compounds as Novel Markers for the Detection of Bacterial Infections[END_REF] of the metabolism of living organisms, including bacteria and archeobacteria. The submillimetre spectroscopy of these mixtures [START_REF] Fosnight | Chemical analysis of exhaled human breath using a novel sub-millimeter/terahertz spectroscopic approach[END_REF] could provide an interesting analysis alternative to gas chromatography coupled to mass spectroscopy (GC-MS) as there would be less effects (heating, ionization) damaging the integrity of large molecules. The characterization of ensembles would then in medical situations [START_REF] Cornu | Olfactory Detection of Prostate Cancer by Dogs Sniffing Urine: A Step Forward in Early Diagnosis[END_REF], [START_REF] Bashiardes | Non-alcoholic fatty liver and the gut microbiota[END_REF] discriminate pathological situations or possibly identify bacteria resistant to antibiotics, and in food industry [START_REF] Casaburi | Bacterial populations and the volatilome associated to meat spoilage[END_REF], [START_REF] Tavaria | Amino Acid Catabolism and Generation of Volatiles by Lactic Acid Bacteria[END_REF] survey fermentation processes. The realization of an instrument meets several challenges. (a) The optical generation of submillimetre waves promises to attain a large frequency span, thus a large molecule span: we will present results towards such a compact and tuneable source. (b) The detection system should present a large signal to noise ratio, in order to detect molecules at trace levels. (c) The sampling system should take care that a large fraction of volatile biological molecules are actually liquid at ambient temperature and pressure.

Institut de Physique de Rennes, UMR 6251, CNRS/Université de Rennes 1


published or not. The documents may come

Towards a compact instrument to measure the volatile metabolites with submillimeter spectroscopy

٥٥Monitoring

  No heating, no ionization: molecule integrity ٥ Prefers liquid phase sampling for solute molecules at room temperature and pressure ٥ Measurement at low pressure (< 1 mbar) ٥ lots of molecules not in HITRAN/JPL/CDMS databases One laser diode wavelength stabilization Modeling (non-linear) phase and amplitude noise effects in cell transmission: Signal to noise depends on integration time, line strength, cell length… sub-ppm detectability seems achievableConclusion and outlook٥ Robust synthesis of submm wave ٥ in DC-580 GHz range ٥ with photonics components ٥ Step 1 GHz ٥ Linewidth below requirements ٥ Construct continuously tunable synthesizer ٥ Build homodyne detection system ٥ Test on molecules in databases ٥ Test on real case June 2017 Microorganisms: ٥ own metabolism ٥ Volatile molecular output not unique? ٥ environmental growth factors? B. A. Kimball, "Volatile metabolome: problems and prospects", Bioanalysis, 8(19) 2016 M. Sohrabi et al. "Volatile Organic Compounds as Novel Markers for the Detection of Bacterial Infections", Clin. Microbiol. Open Access, 3(3) 2014 A. Casaburi et al. "Bacterial populations and the volatilome associated to meat spoilage", Food Microbiol., 45, 2015 F. K. Tavaria et al. "Amino Acid Catabolism and Generation of Volatiles by Lactic Acid Bacteria", J. Dairy Sci., 85(10) 2002 Output variability, compatible with statistical classification analysis M. Le Corvec et al. (DIAFIR, Rennes), "Mid-infrared fiber evanescent wave spectroscopy of serum allows fingerprinting of the hepatic metabolic status in mice," The Analyst, 2016 . Neese et al., "compact submillimeter/terahertz gas Sensor with efficient gas collection, preconcentration, an ppt sensitivity", IEEE sensors journal, 12 (8) 2012