These instruments employ UV/VIS/NIR spectroscopy, a detection and characterization method, in order to obtain these distinct optical properties, providing both qualitative and quantitative data of the sample.  

Combined, these three wavelengths allow the spectrometer to operate in an optical range from 100 to above 3000 nanometers (nm).

Ultraviolet (UV) light typically has a wavelength range of 100 to 400 nm, and visible light ranges from 400 to 800 nm. Where the range truly extends is in the near-infrared, where wavelengths range from 800 to 3200 nm.

UV-VIS and NIR spectroscopic techniques are useful in a number of ways, and can be used separately or in combination.

On it’s own, UV-VIS spectroscopy only uses the UV and visible portion of the electromagnetic spectrum to look at properties of a substance, observing how matter interacts with either UV or visible light, whether it is through absorption or reflection.

Interactions in this portion of the spectrum result in organic molecules undergoing molecular electronic transition. This is to say that these interactions result in electrons in the molecules becoming energized or excited.

For visible light specifically, the reflection of light results in humans ability to see color. An important law that is used in the application of UV/Vis spectroscopy is the Beer-Lambert law which states that the higher the concentration of a molecule, the more UV/Vis radiation it will absorb.

The structural component responsible for this absorption is called a chromophore. Due to the linear relationship of this law, UV-Vis spectroscopy is an important tool in chemistry for the quantitative determination of analytes in a compound.

Near-infrared spectroscopy (NIRS), when used on its own, is a non-destructive analytical technique that measures how samples absorb NIR light to observe their properties. While UV-Vis observes energy transitions, NIRS is generally used to look at vibrational transitions.

In principle, NIRS shoots a sample with a broad-spectrum of NIR light and analyzes what wavelengths are absorbed, reflected, or scattered by the material. This data can then be used to determine properties about the bonds of the molecules that are in the object of interest.

Bond vibrations between hydrogen and other elements such as oxygen (OH), carbon (CH), and nitrogen (NH) are seen as NIR absorbance bands.

The spectral bands that NIRS gathers are wide which can make their interpretation more complex than other spectroscopy methods, however, their ability to penetrate deep into samples makes them a useful tool.