Nitrous oxide is a significant greenhouse gas that is produced by many human activities, including fertilizer applications and fossil fuel combustion. Precise nitrous oxide measurements are critical for understanding anthropogenic effects on the climate and for complying with global greenhouse gas emissions regulations.
Several different nitrous oxide analyzer exist to measure N2O, each with its own advantages and drawbacks. Electrochemical amperometric sensors quantitatively determine N2O concentrations by measuring the current produced from the reduction of N2O to N2. Alternatively, optical-fiber instruments can detect N2O directly using the absorbance of the gas on a dimethylpolysiloxane surface. This technique requires no chemical transformation of the sample and can be much faster than SPME-GC-MS measurements, with response times reported to be as low as 240 s [76].
The most common approach for measuring atmospheric N2O is by gas flux chambers that collect a known volume of air over a soil surface and then analyze the gases in the trapped volume. This allows for measurement of point-source N2O fluxes and line-averaged N2O concentrations in a defined area, making it a suitable method for measuring agri-gases in treated fields or intensive animal-production systems.
Nitrous Oxide Analyzers: Precise Measurement for Industrial Use
Optical techniques can also be used to measure N2O, including FTIR and laser-induced fluorescence. Lead-salt diode lasers can be tuned to the infrared absorption band of N2O, but require cryogenic cooling with liquid nitrogen or closed-cycle helium refrigerators and have relatively slow response times. More recently, quantum-cascade laser (QCL) spectroscopy has been employed to measure N2O in the field, with detection sensitivities in the range of ppmv. Commercially-available instruments have been developed that use high-finesse optical cavities to achieve long path-lengths and ultra-sensitive N2O detection in a compact, portable package. These instrumentation systems can also simultaneously detect a variety of other gases, such as CH4, CO2 and N2 in a single analysis.
