Use of pump current modulation of diode laser for increased sensitivity of detection of¹³СO₂in human exhaled breath

Abstract

This paper reports that the use of a lock-in detection technique, when the pump current modulation of a diode laser is operating near the wavelength of 2 µm, allows the improvement of the sensitivity of the online detection of 13СO2 in expired air by more than three orders of magnitude. The sensitivity of the 13СO2 detected in the paper is 60 ppb with an error of 13СO2 concentration measured in the exhaled breath at the level of 2.9% for an optical path length of 60 cm.

TDLAS second harmonic demodulation based on Hilbert transform

“…Characterized by high sensitivity, high resolution, and fast response, tunable diode laser absorption spectroscopy (TDLAS) is extensively employed in industrial process gas analysis [1,2], environmental monitoring [3,4], and biomedical science [5][6][7]. TDLAS technology can be roughly divided into direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS).…”

Experimental observation of the vibration-rotation radiation curves of 12C16O2 and 13C16O2 absorption constants ranging from 4860 to 4880 sm−1 by the tunable diode laser absorption spectroscopy method

“…Thus, the measurement of the carbon dioxide spectra makes it possible to study the atmospheric composition of Venus, Marsand other planets [1,2], to predict the possibility of changing the Earth's climate due to an increase in carbon dioxide emissions (which is one of the main greenhouse gases) into the atmosphere. One of the important applied problems is a medical challenge-measuring the content of 13 CO 2 in exhaled air makes it possible to diagnose some oncological diseases of the gastrointestinal tract in the early stages [3,4].…”

Experimental measurement of collision broadening of vibrational-rotational spectral lines 12C16O2 and 13C16O2 in the 4860–4880 cm−1 region by diode laser absorption spectroscopy

“…A large number of papers have been devoted to the studying of carbon dioxide isotopologues ( 16 O 12 C 18 O, 16 O 12 C 16 O, 16 O 13 C 16 O, 16 O 13 C 18 O, 16 O 13 C 17 O, etc) infrared absorption spectra by various methods in various spectral ranges [1][2][3][4][5][6][7][8][9]. Among various fundamental and practical tasks that require carbon dioxide isotopologues content data in gas media that is different by component composition, it is necessary to highlight an important practical task of measuring the 13 C 16 O 2 content in the exhaled air, since the exhaled amount of 13 C 16 O 2 allows to diagnose a number of the gastrointestinal tract diseases (including cancer) at early stages [10,11].…”