Components of UV:

There are five essential components of UV-visible instruments. These are: radiation source, wavelength selector, sample holder, detector and a signal processing and output device. For UV region a deuterium lamp is used as the source whereas for visible range a tungsten filament lamp is employed. The wavelength selection is achieved by absorption filters in low cost instruments for visible region. In the modern instruments this is done by using suitable monochromators. The sample is taken in quartz cuvettes, though for visible region even glass cells can be used. The detection of the transmitted radiation is done generally by a phototube or a photomultiplier tube. Nowadays, the modern machines employ diode arrays for detection purposes. These components  are  assembled  into  single  beam,  double  beam  and  diode  array spectrometers.

UV-VIS spectrometry can be used to detect one or more components in a solution and measure the concentration of these species. Further, it may also used for acquiring structural information of substances; particularly the organic compounds and it may as well help in establishing the identity of a molecule. The most important qualitative application of UV-VIS spectrometry is to detect the presence of unsaturation in the molecule. Further, the changes in spectra due to the changes in the pH of the solution or the solvent can provide useful information about the nature of the analyte. Instead, because of its versatility, sensitivity and accuracy UV-VIS spectrometry can be used for direct determination of a large number of organic, biochemical and inorganic species accurately at fairly low concentrations of the order of 10^-4 to 10^-5 M or even lower. A quantitative determination follow a common methodology including four steps as, identifying or creating an absorbing species, selection of the measurement wavelength, controlling factors that influence absorbance and validation of Beer and Lambert's law.