UV–Vis Spectrometers

A UV–Visible spectrometer consists of a light source, such as a deuterium lamp for the UV region and a tungsten lamp for the visible region, a monochromator, a sample holder,  and a detector.

Visible spectroscopy uses sample cells of glass or plastic, while UV spectroscopy uses cells of quartz.

The prism splits the beam of light into its component wavelengths, and a system of slits and filters focuses the desired wavelength on the sample cell.

The photodiode detector measures the intensity of light passing through the sample cell.

In single beam instruments, the monochromator placed between the source and the sample allows analysis of one wavelength at a time.

Alternatively, in a double beam instrument the monochromator is equipped with splitters and mirrors, which split the light into two beams. The sample beam passes through the sample cell, and the reference beam passes through the reference sample.

The two spectra are subtracted to remove contributions from the reference sample from the acquired raw spectrum.