Chemical analysis of exhaled human breath using a terahertz spectroscopic approach

Abstract

As many as 3500 chemicals are reported in exhaled human breath. Many of these chemicals are linked to certain health conditions and environmental exposures. This experiment demonstrated a method of breath analysis utilizing a high resolution spectroscopic technique for the detection of ethanol, methanol, and acetone in the exhaled breath of a person who consumed alcohol. This technique is applicable to a wide range of polar molecules. For select species, unambiguous detection in a part per trillion dilution range with a total sample size in a femtomol range is feasible. It compares favorably with other methods of breath analysis.

Terahertz volatile gas sensing by using polymer microporous membranes

“…One method is to radiate THz waves directly on the gaseous analytes and acquire their spectral information, such as the fingerprint feature or decay signals of a pulse [9] as response signals for sensing purposes. As reported in literature, the systems include photo-mixing [10], heterodyne detection [1,11], and chirped-pulse THz spectroscopy [12]. The spectroscopic approach has been used to analyze the gas mixtures of more than 30 chemicals [1] and distinguish gases that possess similar compositions by fingerprint spectra information.…”

“…As reported in literature, the systems include photo-mixing [10], heterodyne detection [1,11], and chirped-pulse THz spectroscopy [12]. The spectroscopic approach has been used to analyze the gas mixtures of more than 30 chemicals [1] and distinguish gases that possess similar compositions by fingerprint spectra information. This recognition system provides high selectivity based on the rotational/vibrational transition of gas molecules.…”

“…Various types of gas sensors based on different detection principles have been developed, such as gas chromatography-mass spectroscopy [1], electrochemical [2], and optical sensors. The electrochemical sensors, like metal oxide semiconductors [3,4], are often operated at a raised temperature for high sensitivity, causing high power consumption and sparking risks in explosive gas detection.…”

“…This recognition system provides high selectivity based on the rotational/vibrational transition of gas molecules. Nevertheless, the THz spectroscopic system should be equipped with a long folded multipass gas cell [1,9,12], a cryo/sorbent preconcentration system, and a heating apparatus [1,11] to improve the sensing limit from the ppm concentration to the ppb level. The overall configuration is complicated, bulky, expensive, and consumes high power.…”

245 GHz SiGe Transmitter Array for Gas Spectroscopy

“…Recently, sensor systems for mm-wave gas spectroscopy, which are based on commercially available components using frequency multiplication to 210-270 GHz have been reported [1]. These sensor systems may become the technique of choice for detection of a broad range of chemicals [2]. The implementation of integrated mm-wave TX and receiver (RX), [3] - [6], offer a path towards a compact and low-cost system for gas spectroscopy.…”