The UV cutoff wavelength is the minimum effective wavelength for the measurement. The mobile phase composition affects its UV cutoff wavelength.

In general, mobile phases are solvents, such as, water, acetonitrile, methanol, or other substances. They may also contain salts, such as sodium hydroxide (NaOH).

Most solvents have a UV cutoff wavelength within the spectral range of the device. For optimum measurement results, perform quantitative measurements at a wavelength that is sufficiently above the UV cutoff wavelength. The UV cutoff wavelength also depends on the quality of the solvent. For information about the UV cutoff wavelength for a solvent, contact the manufacturer of the solvent.

The refractive index of different solvents can differ. Therefore, changing the mobile phase composition can lead to baseline fluctuations.