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Solvent effect on absorption spectroscopy and Difference between UV and Visible Spectroscopy

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Solvent Effect
Solvents play an important role in UV spectra. Compound peak could be obscured by the solvent peak. So a most suitable solvent is one that does not itself get absorbed in the region under investigation. A solvent should be transparent in a particular region. A dilute solution of sample is always prepared for analysis. Most commonly used solvents are as follows.

Solvent λ of absorption
Water 191 nm
Ether 215 nm
Methanol 203 nm
Ethanol 204 nm
Chloroform 237 nm
Carbon tetrachloride 265 nm
Benzene 280 nm 
Tetrahydrofuran 220 nm

Difference between UV and visible

Wavelength of UV radiation is 200 nm to 400 nm while wavelength of visible radiation n is 400 nm to 800 nm.

 The order of frequencies and their energy is visible < ultraviolet.

 Ultraviolet & infrared are invisible to our eyes whereas visible rays [VIBGYOR] are only radiation that is visible to us.

 Ultraviolet rays are both useful & harmful. These are used in various biological experiments & researches. UV radiation is needed for synthesis if Vit. D in our body but its excess is harmful. Other types of UV radiations such as UV- B & UV- C are harmful because they cause skin cancer, DNA damage, cataracts, etc. while; visible rays are needed to see various colours of our surroundings. Some part of light get reflected and absorbed by various objects and we can see only the colours which are reflected by any object.


Types of Transition EMR Spectra
Beer-Lambert's Law Instrumentation
Effect of Solvent Applications