Spectrophotometry Detection and Recording

Earlier work involved measurements at a single wavelength while recent spectrophotometric detection involves full spectral scans covering the whole chromatographic retention time scale. The results are obtained in three dimensions - wavelength, absorb-ance and retention time. Such a result is shown in Figure 4, where the wavelength scale follows the x-axis, the absorbance values the yy-axis and the retention time goes along the z-axis. This particular sample is cigarette smoke injected by means of a loop injector (200 |L) on the micro gas chromatograph shown in Figure 3. UV spectra of compounds in the cigarette smoke are measured by means of an array of 1024 diodes, which cover a wavelength range from 168 to 330 nm. The spectrometer employed has a band width 1.7 nm or less in order to record the finer spectral details. The diode array detectors usually have a minimum exposure time of 0.02 s. The measuring exposure time must be below a level where a saturation of the diodes occurs. Typically, the exposure time is & 0.1 s. A number of these exposure values are measured and their average is calculated. The absorbance values at any retention time are then calculated for every diode representing a wavelength. The number of the exposure values are chosen according to the desirable chromatographic resolution.

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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