Application of adaptive filters to improve online detection sensitivity of ¹³CO₂ in a mixture with ¹²CO₂ in expiratory air

Abstract

The use of adaptive Kalman and Wiener filters and the empirical mode decomposition algorithm for processing the experimental signal obtained by the tunable diode laser absorption spectroscopy method has been reported to improve the sensitivity of the measurement of 13 CO 2 content in human expiratory air. A laser diode, tunable in the range 4860-4880 cm −1 near the wavelength of 2 µm, is used as a source. It has shown that the application of these filters ensures a detection sensitivity of 13 CO 2 at the level of 10 15 cm −3 , while the minimum detectable fraction of 13 CO 2 in a mixture with the 12 CO 2 is 3.8 • 10 −5 .

Application of the Wiener filtering algorithm for processing the signal obtained by the TDLAS method using the synchronous detection technique for the measurement problem of 13CO2 concentration in exhaled air

“…As noted in a series of publications, the tunable diode laser absorption spectroscopy (TDLAS) method, using a tunable diode laser (TDL) emitting near to the wavelength of 2 μm, is one of the most promising for solving a highly sensitive and highly accurate online measurement of 13 CO 2 mixed with 12 CO 2 in human expiratory air [1][2][3][4][5][6][7].…”

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

“…The cell windows were made of potassium bromide, which is optically transparent in the studied spectral range. R (18), R(20), R(22), R(24), R(26), R(28), R(30), R(32), R(34) and R(36) vibration-rotation radiation curves of the 12 Figure 1 shows two sections of the transmission spectrum of a 12 C 16 O 2 and 13 C 16 O 2 mixture at pressures of 210.5 mbar and 15 mbar containing absorption lines of 12 C 16 O 2 and 13 C 16 O 2 ; along the horizontal axis there is the time scan of the signal recorded by the photodetector, which passed through the cuvette.…”

“…Earlier, this method was used to measure the content of 13 C 16 O 2 (636) in a mixture with 12 C 16 O 2 (626) in exhaled air. Performed studies have shown that one of the most promising ranges for measurements is the region near a wavelength of 2 µm (frequency range: 4860-4880 sm −1 ), which contains a number of absorption curves of these molecules, to a minimum extent overlapping, and the experimental arrangement does not require complex and expensive equipment [18][19][20]. To accurately measure the content of 13 C 16 O 2 and 12 C 16 O 2 in the analyzed mixture, knowledge of the absorption constantvalues and their pressure dependence, since the measurements can be carried out at different pressures, are necessary.…”

The H2S online detection in gaseous media using diode laser absorption spectroscopy in the range of 4860–4880 cm−1

“…One of the promising high-sensitive H 2 S detection methods may become the tunable diode laser absorption spectroscopy (TDLAS) based on the phenomenon of direct absorption of laser radiation by gas, previously implemented for some other substances, for instance, 13 CO 2 [20][21][22][23][24][25][26][27][28]. This method is characterized by high selective ability, making it possible to resolve vibrational-rotational absorption spectra of various substances mixed together.…”