High precision measurements of the 13CO2/12CO2 isotope ratio at atmospheric pressure in human breath using a 2 μm diode laser

Monitoring CO2 concentration and δ13C in an underground cavity using a commercial isotope ratio infrared spectrometer

“…(5) and (6), CO 2 concentration in exhaled air is found to be around 15,000 ppm and the volume fraction of contamination by human breathing to be of 2 %. This value of C breath is lower than the few % measured directly in the exhaled air [24], which is explained by the rapid dilution of exhaled air by the low CO 2 concentration tunnel air.…”

“…is similar to the one obtained from other tracers ( 222 Rn and SF 6 ) for the same area of the tunnel [24]. A modified box model can then be applied to obtain the evolution of δ 13 C in the tunnel during the decay of the CO 2 concentration: where δ i and δ ∞ are, respectively, the peak and background carbon isotope compositions of CO 2 .…”

“…6). Human breath has δ 13 C values between −20 and −23 ‰, with CO 2 concentration of several percent [23][24][25]. As the isotope signature of human breathing is lower than that of the background in the tunnel (δ 13 C ≈ −8 to −15 ‰), the resulting δ 13 C decreases during CO 2 peaks.…”

Fundamentals of spectral detection

“…Online in situ gas analysis fi nds increasing application in such as combustion (Chao et al , 2012) and plasma diagnostics (R ö pcke et al , 2008), reaction rate measurements (Kasyutich et al , 2013), exhaust gas analysis (Yamamoto et al , 2011), explosives detection (Bauer et al , 2008), plant physiology (Hunsmann et al , 2008) and life sciences (Cristescu et al , 2008). Other challenges are clinical breath analysis (Risby and Tittel, 2010), medical diagnostics (Andreev et al , 2011;Brandstetter et al , 2013;Gianella and Sigrist, 2012;Svanberg, 2008) and the analysis of stable isotope ratios (Kerstel, 2004;Nelson et al , 2008;Tuzson et al , 2008). The need to meet environmental and legislative requirements has led to the development of commercial analysers (FLAIR, 2011) to measure a variety of gases based on near-and mid-infrared absorption spectroscopy (Werle et al , 2002.…”

Precise13CO2/12CO2isotopic ratio measurements for breath diagnosis with a 2-μm diode laser

“…In addition, the water absorption lines are weak and even could be avoided. By using a 2.0 μm tunable diode laser, S. N. Andreev et al [4] obtained 0.07‰ measurement precision of 13 CO 2 / 12 CO 2 isotope ratio in human breath.…”