Gas Chromatography Infrared Spectrometry

"To data system for further processing Figure 1 Schematic of typical light-pipe-based GC-FTIR interface (based on Hewlett Packard IRD).

performed. For light-pipe-based GC-IR systems, it is rarely necessary to measure spectra at high resolution, as the spectral bands are quite broad. Since most bands in the spectra of molecules in the vapour phase have a width of at least 10-cm"1, the typical resolution at which GC-IR spectra are measured is 8 cm-1.

When operated at their highest scan speeds, FT-IR spectrometers can measure between 5 and 20 inter-ferograms per second that would yield spectra of this resolution. During a chromatographic analysis, inter-ferograms are measured continuously. Thus for a 30-min-long chromatogram, it would be possible to measure tens of thousands of interferograms, giving rise to an amount of data that could exceed 100/MB and hence could exceed the capacity of the disk on a typical personal computer (PC). Fortunately, most GC peaks have a full-width at half-height (FWHH) of several seconds. Thus it is common practice to average blocks of interferograms for a period of time that is slightly less than the FWHH of the narrowest peak in the chromatogram (usually 1-2 s). The single-beam spectrum is then computed from this signal-averaged interferogram and ratioed against an appropriate background spectrum; finally, the resulting transmittance spectrum is converted to a linear ab-sorbance format. On many fast PCs this entire sequence of operations is performed while the next block of interferograms is being acquired.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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