Portable optical spectroscopy for accurate analysis of ethane in exhaled breath

Abstract

We report on a maintenance-free, ward-portable, tunable diode laser spectroscopy system for the ultra-sensitive detection of ethane gas. Ethane is produced when cellular lipids are oxidized by free radicals. As a breath biomarker, ethane offers a unique measure of such oxidative stress. The ability to measure real-time breath ethane fluctuations will open up new areas in non-invasive healthcare. Instrumentation for such a purpose must be highly sensitive and specific to the target gas. Our technology has a sensitivity of 70 parts per trillion and a 1 s sampling rate. Based on a cryogenically cooled lead-salt laser, the instrument has a thermally managed closed-loop refrigeration system, eliminating the need for liquid coolants. Custom LabVIEW software allows automatic control by a laptop PC. We have field tested the instrument to ensure that target performance is sustained in a range of environments. We outline the novel applications underway with the instrument based on an in vivo clinical assessment of oxidative stress.

Cavity-enhanced optical frequency comb spectroscopy: application to human breath analysis

“…13 As a first-order correction for laser intensity drift between acquisitions of the absorption and reference frames, an area of low absorption in the absorption fringe array is compared to the reference fringe array, and the absorption fringe intensity is equalized to the reference fringe intensity. The absorption fringe array is then subtracted from the reference fringe array, before being divided by the reference fringe array.…”

“…3 These lasers are also used to detect nitric oxide for diagnosing asthma 4 . Finally, both quantum cascade and lead salt lasers have been used to detect ethane which is produced in lipid peroxidation and by some forms of cancer 12,13,14 . While all of these systems provide robust and highly sensitive detections of their analyte molecules, many operate in relatively narrow spectral regions.…”

ICL-based TDLAS sensor for real-time breath gas analysis of carbon monoxide isotopes

“…In particular, laser absorption spectroscopy has had considerable impact on BGA owing to its inherent selectivity and accuracy [15]. While cavity-enhanced techniques are often employed to reach the required sensitivities [16], many important biomarkers can today be accessed with mid-infrared tunable diode laser absorption spectroscopy (TDLAS) [15,17]. The combination of quantum cascade lasers (QCLs) or interband cascade lasers (ICLs) with multipass cells (MPCs) and modulation techniques opens up for sensitive, yet robust and portable instrumentation useful for clinical applications [18].…”

Cavity-enhanced optical frequency comb spectroscopy in the mid-infrared application to trace detection of hydrogen peroxide

“…It has been successfully applied to issues of fundamental scientific importance and serves as the backbone for numerous applications in physics, chemistry, and biology. These applications include control of manufacturing processes [1][2][3], detection of poisonous gasses or explosives [4,5], human breath analysis for medical applications [6][7][8][9], environmental monitoring [10][11][12][13], and optical methods of 14 C dating [14]. Laser spectroscopy also provides high-resolution and precision laboratory data essential for satellite remote sensing of planetary atmospheres and for monitoring of climate changes in the Earth's atmosphere [15].…”

“…The frequencies of single comb lines are shifted from integer multiples of f rep by the carrier envelope offset frequency (f ceo ), caused by different average group and phase velocities in the laser cavity. As a result, the frequency of the mth comb mode is given by ν m = mf rep + f ceo , where m usually is in the order of 10 5 -10 6 . By controlling the radio frequencies f rep and f ceo , it is possible to precisely control the frequency of each comb line [24].…”