The ideal solvent for UV-Visible spectroscopy should fulfill the following requirements:
- It must be transparent in the region of interest (i.e., it should not absorb radiation where the sample absorbs).
- It should not chemically react or interact adversely with the solute molecules.
A commonly used solvent is 95% ethanol. It is cost-effective, possesses good solvating power, and is transparent above 210 nm.
Other examples of solvents transparent above 210 nm include n-hexane, cyclohexane, methanol, water, and ether. Conversely, solvents like benzene, chloroform, and carbon tetrachloride are restricted in lower UV regions because they absorb significantly in the 240–280 nm range.
While non-polar solvents (like hydrocarbons) are preferred to minimize solvent-solute interactions, polar solvents are frequently chosen when dealing with polar or ionic analytes.
Common UV Solvents and Their Cut-off Wavelengths
| Solvent | Cut-off Wavelength |
|---|---|
| Water | 205 nm |
| Methanol | 210 nm |
| Ethanol | 210 nm |
| Ether | 210 nm |
| Cyclohexane | 210 nm |
| Dichloroethane | 220 nm |
| Chloroform | 245 nm |
| Carbon tetrachloride | 265 nm |