The key difference between IR and UV and visible spectroscopy is that IR spectroscopy uses the low-energy infrared part of the spectrum, whereas UV and visible spectroscopy use UV and visible regions of the electromagnetic spectrum.
There are different spectroscopic techniques according to the wavelength range that is being measured. IR and UV and visible spectroscopy are two such spectroscopic techniques.
What is IR Spectroscopy?
IR spectroscopy or infrared spectroscopy (also known as vibrational spectroscopy) is the measurement of the interaction of IR radiation with the matter by absorption, emission, or reflection. This method is useful in studying and identifying chemical substances or functional groups in solid, liquid, or gaseous forms. Moreover, we can use IR spectroscopy to characterize new materials and identify and verify known and unknown samples.
IR spectroscopy involves the absorption frequencies by molecules that are characteristic of the structure. Typically, these absorptions occur at resonant frequencies (it is the frequency of the absorbed radiation that matches the vibrational frequency). Particularly, in the Born-Oppenheimer and harmonic approximations, resonant frequencies are associated with the normal modes of vibration that correspond to the molecular electronic ground state potential energy surface. Moreover, resonant frequencies are related to the strength of the bond and the mass of the atoms at each end. Therefore, the frequency of these vibrations is associated with a particularly normal mode of motion and a particular bond type.
What is UV and Visible Spectroscopy?
UV and visible spectroscopy or UV-vis spectroscopy is an analytical instrument that analyzes liquid samples by measuring its capability to absorb radiation in ultraviolet and visible spectral regions. This means this absorption spectroscopic technique uses light waves in visible and adjacent regions in the electromagnetic spectrum. Absorption spectroscopy deals with the excitation of electrons (movement of an electron from the ground state to the excited state) when the atoms in a sample absorb light energy.
Electronic excitations take place in molecules containing pi electrons or non-bonding electrons. If electrons of molecules in the sample can easily be excited, the sample can absorb longer wavelengths. As a result, the electrons in pi bonds or non-bonding orbitals can absorb energy from light waves in the UV or visible range.
The major advantages of UV-Visible spectrophotometer include simple operation, high reproducibility, cost-effective analysis, etc. In addition, it can use a wide range of wavelengths to measure analytes. The basic components of UV-visible spectroscopy include a light source, a sample holder, diffraction gratings in the monochromator, and a detector.
A UV-visible spectrophotometer can be used to quantify the solutes in a solution. This instrument can be used to quantify analytes such as transition metals and conjugated organic compounds (molecules containing alternating pi bonds). We can use this instrument to study solutions, but sometimes scientists use this technique to analyze solids and gases as well.
What is the Difference Between IR and UV and Visible Spectroscopy?
Spectroscopy is the study of the absorption and emission of light and other radiation by matter. There are different types, such as IR spectroscopy and UV-visible spectroscopy. The key difference between IR and UV and visible spectroscopy is that IR spectroscopy uses the low-energy infrared part of the spectrum, whereas UV and visible spectroscopy use UV and visible regions of the electromagnetic spectrum.
Below is a summary of the difference between IR and UV and visible spectroscopy in tabular form.
Summary – IR and UV vs Visible Spectroscopy
Spectroscopy is an important analytical technique useful in studying different chemical substances. IR spectroscopy and UV-visible spectroscopy are two types of this analytical technique. The key difference between IR and UV and visible spectroscopy is that IR spectroscopy uses the low-energy infrared part of the spectrum, whereas UV and visible spectroscopy use UV and visible regions of the electromagnetic spectrum.
1. “Understanding Spectrometry and Spectroscopy.” ATA Scientific.
1. “Portable Screening Devices (1435) (8225044148)” By The U.S. Food and Drug Administration – (Public Domain) via Commons Wikimedia
2. “GENESYS™ 10S UV-Vis Spectrophotometer – Thermo Fisher Scientific” By PhotoLanda (CC BY-NC-SA 2.0) via Flickr