Every spectrophotometer is customized for a specific wavelength range. Here is everything you need to know about wavelength range.
Wavelength range can vary from less than a nanometer up to kilometers.
Nanometer (nm) is the most common unit to express the wavelength:
The range of electromagnetic waves, which include Gamma rays, ultraviolet (UV), visible light (VIS), infrared (IR), microwaves and radio waves, creates an electromagnetic spectrum.
In UV/Vis/NIR spectroscopy the ultraviolet (170 nm to 380 nm), visible (380 nm to 780 nm), and near infrared (780 nm to 3300 nm) are used (see Fig. 2). Most spectrophotometers are configured either as UV/Vis instruments that cover the 190 nm - 1100 nm wavelength range or UV/Vis/NIR instruments that cover the 175 nm to 3300 nm wavelength range.
Fig. 2 Electromagnetic wave spectrum.
Most of the spectrophotometers use UV and VIS light to measure the properties of the sample. Usually, most of the measured samples are dissolved substances which are placed inside the cuvette. In spectrophotometry, the light with the accurate wavelengths is emitted on the sample in the cuvette. Some part of light is absorbed, transmitted, scattered or reflected by the sample. The spectrophotometer measures the amount of light that has been absorbed by the sample and it can use this information to determine the concentration of solutes in solution and also the reflection and transmission of the sample.
A spectrophotometer detect the light intensity as a function of wavelength using an appropriate detector. Before the detection, the light beam needs to be diffracted into the spectrum of wavelengths using a diffraction grating or a prism in the monochromator.