In this work, the investigation of degradation of organic compounds by sulphate radicals formed by photolysis of peroxodisulphate anions under the influence of UV radiation was carried out. The degradation of 14 organic compounds selected from the group of aliphatic acids, aromatics, heterocyclic compounds, amino acids, organic colours and highly condensed compounds such as fulvic and humic acids was studied. The experiments were conducted under the flow-through conditions that resemble the real working conditions of on-line TOC analyzers. It was shown that the rate of degradation of organic compounds by sulphate radicals is significantly faster than the rate of degradation due to the UV photolysis only. By using the flow-through UV-persoxodisulphate method, a degradation efficiency of approximately 95% was achieved for the samples with the TOC value of approximately 10 mg/L, with a residence time of samples of only 120 s. These results suggest that the studied method has a great potential for applications, not only in the analysis of TOC, but also in other analytical methods, which require the destruction of organic matter in the sample (e.g. to release analyte).