B.14.4 Wavelength selection
The tables in this section provide UV cutoff values for these items:
• Common solvents
• Common mixed mobile phases
B.14.4.1 UV cutoffs for common solvents
The table below shows the UV cutoff (the wavelength at which the absorbance of the solvent
equals 1 AU) for some common chromatographic solvents. Operating at a wavelength near or
below the cutoff increases baseline noise because of solvent absorbance.
Table B–3: UV cutoff wavelengths for common chromatographic solvents
Solvent
UV cutoff (nm)
Acetone
330
Acetonitrile
190
Diethyl amine
275
Ethanol
210
Isopropanol
205
Isopropyl ether
220
Methanol
205
n-Propanol
210
Tetrahydrofuran (THF)
230
B.14.4.2 Mixed mobile phases
The following table provides approximate wavelength cutoffs for some other solvents, buffers,
detergents, and mobile phases. The solvent concentrations represented are those most
commonly used. If you want to use a different concentration, you can determine approximate
absorbance using Beer’s law, because absorbance is proportional to concentration.
Note:
λ cutoff is the wavelength at which the absorbance of the solvent equals 1 AU.
Table B–4: Wavelength cutoffs for different mobile phases
Mobile phase
UV cutoff (nm)
Acetic acid, 1%
230
Ammonium acetate, 10 mM
205
Ammonium bicarbonate, 10 mM
190
August 8, 2016, 715005049 Rev. C
Page 96
