Protocol for UVC uridine actinometry

Uridine contains the chromophore uracil, a base forming part of RNA. In the range 240-290 nm, the absorption spectra of uridine and DNA are very similar and correspond to the spectral inactivation sensitivity of almost all microorganisms. This makes the uridine (absorption maximum 262 nm) an ideal actinometer for determining the germicidal photon flux in the range of 240 to 290 nm. Uridine actinometry is a simple, environmental-friendly, and easy-to-operate actinometry. Thanks to the uridine absorbance spectrum, it was found to be a perfect fit for the photon flux validation of UVC systems. Conventional UV disinfection systems are generally based on low-pressure (LP) mercury lamps which emit at 254 nm. On the other hand, UV light-emitting diodes (UV-LEDs) are a relatively new source of UV light for water treatment, emitting at various wavelengths. This protocol suggests an accurate, simple, easy to operate and straightforward way to determine the photon flux of UVC systems. •Because of the uridine absorbance spectrum, it is an ideal actinometer for photon flux validation of UVC systems.•Initial uridine concentration and photoproduct absorbance impact the kinetic order and quantum yield.•The protocol for UVC uridine actinometry is appropriate for UV-LP and UV-LED sources for water disinfection.