UV-Visible Spectroscopy

What is UV-visible spectroscopy?

UV-Visible spectroscopy (also known simply as UV-Vis) is an analytical technique that makes use of light in the visible and ultraviolet sections of the spectrum. 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 wavelength of this light 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/reflected can be quantified, which provides useful insight into the properties of the sample.

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 very 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.

What is UV-visible spectroscopy used for?

For colored solutions, such as those containing metal ions, UV-Vis can be used to determine concentrations based on how much the observed absorbance deviates when compared to solutions with known concentrations. The method can also be used to monitor the movement of electrons within certain substances, allowing for a better understanding of reactions that occur between metal-containing compounds.

UV-Vis is also useful when it comes to analyzing certain organic compounds, particularly those that absorb light within the UV-visible part of the spectrum. This is a major advantage compared to atomic absorption spectroscopy (AAS), which can only detect elements that absorb light in the visible range.

In the case of both organic and inorganic compounds, UV-Visible spectroscopy is an excellent way of determining unknown compounds in a solution. The spectrum produced is representative of how the material interacts with light and can be compared to existing data for identification purposes, making UV-Vis a fast and efficient technique in comparison with other types of analysis.

What are the limitations of UV-visible spectroscopy?

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 itself, 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, the sample 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 will allow light to successfully transmit through. If the concentration is too high, then 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, where the light reflected from it can be 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 by emailing us at info@measurlabs.com.