UV Vis spectrophotometers can be classified into two categories according to the geometry of the components building up the optical system for the recording of spectra: Scanning spectrophotometer Array spectrophotometer The spectrum of a scanning UV Vis device is obtained by continuously changing the wavelength of the light (i.e. scanning), which separately passes through the sample by rotating a reflection grating, as shown in the figure below. In an array spectrophotometer, the light of a full wavelength passing through a sample is diffracted by a reflection grating located after the cuvette, it is then received by an array detector (e.g. CCD sensor).This allows for the simultaneous measurement of all wavelengths of the light in a short amount of time. As a result, array spectrophotometer can deliver the spectrum of a full scan (e.g. 200 – 800 nm) within several seconds, whereas a scanning spectrophotometer needs a minimum of several minutes to complete the same task. The mechanically rotating elements of a scanning spectroscopy instrument can impact the accuracy and reproducibility of a wavelength. In order to avoid that, it requires a regular re-calibration and the involved maintenance costs. An array spectrophotometer does not have any moving optical parts, which means wavelength deviations due to mechanical imprecisions do not occur. An additional advantage of an array spectroscopy instrument is its immunity to ambient light due to its optical design, which means it does not require a closed sample compartment, rendering sample changing easier.