Laser-based systems for trace gas detection in life sciences

Infrared gas phase spectroscopy is becoming very common in many life science applications. Here we present three types of trace gas detection systems based on CO2 laser and continuous wave (cw) optical parametric oscillator (OPO) in combination with photoacoustic spectroscopy and cw quantum cascade laser (QCL) in combination with wavelength modulation spectroscopy. Examples are included to illustrate the suitability of CO2 laser system to monitor in real time ethylene emission from various dynamic processes in plants and microorganisms as well as from car exhausts. The versatility of an OPO-based detector is demonstrated by simultaneous detection of 13C-methane and 12C-methane (at 3240 nm) at similar detection limits of 0.1 parts per billion by volume. Recent progress on a QCL-based spectrometer using a continuous wave QCL (output power 25 mW, tuning range of 1891–1908 cm-1) is presented and a comparison is made to a standard chemiluminescence instrument for analysis of NO in exhaled breath.