UV-visible spectroscopy

What is UV-visible spectroscopy used for?

UV-vis spectroscopy can be used to identify the presence of both organic and inorganic compounds in a solution and quantify their concentrations quickly and efficiently. This gives the method applications in chemical analysis, where it can also be used to monitor the progression of reactions.

DNA and RNA can be effectively quantified using UV-vis, as absorption of UV light at 260 nm is an indicator of their presence. UV-vis is also a popular quality assurance technique in the pharmaceutical and food industries, and can be used to characterize the composition of industrial chemicals according to the REACH regulation.

How does UV-vis spectroscopy work?

A UV-vis spectrophotometer works by shining light onto a sample that is usually in the form of a solution, though solid-state UV-vis is also occasionally used. The light's wavelength is gradually varied across a range of ultraviolet and visible light, and the percentage of light that passes through the solution is monitored. From this, the amount of light absorbed at each wavelength can be presented as a spectrum that can be compared to existing data libraries to identify the sample's components.

When a sample absorbs a certain wavelength of light, its visual appearance will usually be of the color of light on the opposite side of the spectrum. For example, a solution that strongly absorbs blue light will typically appear orange to us. UV-vis makes the most of this quality and gathers important data by analyzing the type of light that a sample will absorb or reflect.

Strengths and limitations of UV-vis

The ability of UV-vis to analyze organic compounds in addition to inorganic ones is a major advantage compared to methods like atomic fluorescence spectroscopy (AFS) and atomic absorption spectroscopy (AAS), which can only detect elements that absorb light in the visible range.

The primary limitation of UV-visible spectroscopy is its inability to analyze compounds that do not interact with light in the UV and visible areas of the spectrum. This includes certain inorganic compounds and organic components that do not have a high level of electron conjugation. The effectiveness of UV-vis will depend mostly on the compound, and whether or not it has the correct properties to interact with UV or visible light.

Furthermore, to determine unknown concentrations using UV-vis, other known concentrations will usually need to be analyzed to produce a calibration curve as a reference. For this, several samples may need to be tested, making the calibration process much more lengthy than the analysis itself.

Sample requirements and preparation

In most cases, UV-vis samples must be dissolved in a suitable solvent before analysis. The solvent should successfully dissolve any solid material without producing any results itself. The resulting solution must be in a concentration that allows light to transmit through. If the concentration is too high, the solution will likely need further dilutions, until accurate results can be obtained.

Solid-state UV-visible spectroscopy is also occasionally used. For this, a solid sample is compacted into a disc, and the light reflected from it is analyzed. The sample must be in a powdered form so that it can be easily analyzed by the spectrophotometer.

Need a UV-vis spectroscopy analysis?

Measurlabs offers UV-visible spectroscopy analyses with fast results and affordable prices. If you have any questions about your sample or its suitability for the method, our experts are always happy to help. You can contact us through the form below or at info@measurlabs.com.