Nondispersive infrared spectroscopy

Both nondispersive infrared spectroscopy and cavity ring down spectroscopy (employing a near-infrared external cavity diode laser) can be used to determine the ratio in the CO2 of expired... 

GC, preferably with MS coupling and sample preparation (extraction, purge trap, spray trap, solid phase extraction (SPE), solid phase microextraction, headspace, thermodesorption, soil air trap], nondispersive infrared spectroscopy (NDIR). FT-IR, TLC, immunoassays and biosensors (for determination of defined substances)... 

Infrared (IR) spectroscopy offers many unique advantages for measurements within an industrial environment, whether they are for environmental or for production-based applications. Historically, the technique has been used for a broad range of applications ranging from the composition of gas and/or liquid mixtures to the analysis of trace components for gas purity or environmental analysis. The instrumentation used ranges in complexity from simple filter-based photometers to optomechanically complicated devices, such as Fourier transform infrared (FTIR) spectrometers. Simple nondispersive infrared (NDIR) insttuments are in common use for measurements that feature well-defined methods of analysis, such as the analysis of combustion gases for carbon oxides and hydrocarbons. For more complex measurements it is normally necessary to obtain a greater amount of spectral information, and so either Ml-spectrum or multiple wavelength analyzers are required. 

Other infrared absorption techniques are also used in ambient air measurements, including tunable diode laser spectroscopy (TDLS), nondispersive infrared (NDIR) spectroscopy, and matrix isolation spectroscopy. These are discussed in more detail later. 

Organic/elemental carbon speciation is performed on yg-sized samples using a thermal evolution technique (11) in which carbon is evolved in 2 discrete steps at 400°C in He and at 650<>C in 10% 02/He, then measured as OO2 by nondispersive infrared (NDIR) spectroscopy (Beckman Model 865). 13c/12c measurements are made by... 

Note Key CL = chemiluminescent EC = electro-chemical FID = flame ionization detector GC = gas chromatograph HC = hydrocarbons IR = nondispersive infrared LA = line absorption Para. = paramagnetic RS = Raman spectroscopy. 

Infrared spectroscopy is widely used in industry. The applications range from quality control and quality assurance of raw materials to customer complaints (troubleshooting) to quantitative analysis and online process monitoring and control. Most of the instrumentation is based on a Fourier transform infrared (FTIR) spectrometer but specialist applications use instruments as diverse as a nondispersive infrared detector through to mid-infrared diode lasers. 

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