Apparatus for performing photochemical measurements on a liquid or liquid-containing sample

An apparatus for performing photochemical measurements on a liquid or liquid-containing sample (LS) comprising:

• a light generating system (LGS), an optical system (OS,OS′) configured for directing light from the light generating system towards the sample, a processor (PR) configured or programmed for controlling the light generating system by modulating the light intensity values for illuminating the sample according to a predetermined illumination sequence and a sensing system (SS, SS′) for measuring at least one optical property of the sample, wherein:
• the light generating system is configured for generating light at at least one wavelength with an intensity level adjustable within a range spanning at least three and preferably at least five orders of magnitude;
• and
• the optical system is configured for directing light from the light generating system towards the sample so as to generate a uniform light intensity level, with a tolerance of plus or minus 30%, preferably plus or minus 20% and even more preferably plus or minus 10%, within a cylindrical region of the sample having a height larger than or equal to five times its radius, said radius being of at least 3 μm.