Application of the method of absorption diode laser spectroscopy for measuring the content of $^{13}$С and $^{12}$С in exhaled air

The paper reports on experimental studies of the absorption of $^{13}$С$^{16}$О$_2$ in a mixture with $^{12}$С$^{16}$О$_2$ in exhaled air by laser absorption spectroscopy using a diode laser tunable in the frequency range 4860–4880 cm$^{-1}$. The results of the studies showed that the minimum detectable concentration of $^{13}$С$^{16}$О$_2$ is at a level of less than 20 ppm, and this approach is promising for measuring the content of $^{13}$С$^{16}$О$_2$ in exhaled air for non-invasive online diagnosis of oncological diseases of the gastrointestinal tract at early stages.