High Performance Liquid Chromatography coupled with UV diode array detector is a technique used to detect molecules with chromophoric groups capable of absorbing the energy of ultraviolet radiation.
The radiation emitted by a lamp consists of a multitude of wavelengths (= polychromatic light). This is broken down using a monochromator and each diode in the strip will receive radiation with a specific wavelength λ.
This light radiation is split in two allowing a part to pass through the sample and to undergo absorption of certain wavelengths. While the second will not undergo any modification. Subtracting the intensity of the two signals detected on the diode arrays will give the value of the absorption of the sample.
The diode array detector has advantages such as the possibility of simultaneously analyzing molecules over a wide range of wavelengths often ranging from 190 to 400 nm, unlike the conventional UV detector which can only analyze one wavelength at a time. It is possible to obtain the chromatogram at each λ.
Another interesting advantage is that for each chromatographic peak, it is possible to have the corresponding spectrum. This constitutes information on the structure but also on the purity of this peak.
This system allows the acquisition of three-dimensional chromatograms comprising time on the abscissa, wavelength on the ordinate and the intensity of the signal on the depth (z-axis).