After a small amount of H2O2 has been added to the sample as radical initiator, the sample is irradiated with UV light with wavelengths of 200 to 400 nm, producing OH radicals that spontaneously react with the organic molecules.
In the resulting radical chain reaction, all the organic molecules are broken down to low-molecular-weight compounds such as CO2, H2O, N2, or NH3, which do not interfere with VA analysis.