Infrared analysis gaseous samples

Photometric Moisture Analysis TTis analyzer reqiiires a light source, a filter wheel rotated by a synchronous motor, a sample cell, a detector to measure the light transmitted, and associated electronics. Water has two absorption bands in the near infrared region at 1400 and 1900 nm. This analyzer can measure moisture in liquid or gaseous samples at levels from 5 ppm up to 100 percent, depending on other chemical species in the sample. Response time is less than 1 s, and samples can be run up to 300°C and 400 psig. 

The sampling loops were replaced by two stainless steel U-tubes of 1.5- and 20-cc. capacity. The expansion bomb is a 1.7-liter stainless steel cylinder. The trap between the helium supply and the Beckman valve is 1/4-inch stainless steel tubing. A null detector is used to measure pressures in the inlet system. Samples are obtained in 10-ml. stainless steel cylinders fitted with a Vg-inch stainless steel Hoke valve with a V-stem and Teflon packing. When the sample is liquid, it is entirely vaporized into the 1.7-liter expansion bomb, and a gaseous sample is taken for infrared, near infrared, and gas chromatographic analysis. 

If the reflectance of a sample is low, as it is with gaseous samples, e(v), is approximately equal to 1 — r(. Thus, for any sample for which a transmittance spectrum with discrete absorption bands can be measured, the emittance spectmm should yield equivalent information. As a result, qualitative analysis of the components of hot gases by infrared emission spectroscopy can be as easy as it is by transmission spectrometry. The problem of obtaining quantitative information by infrared emission spectroscopy is more difficult, since not only must the temperature of the sample be known if the radiant power from the blackbody is to be calculated, but the instrument response function must also be taken into account [1]. 

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