The ability to non-invasively monitor DNA oxidation and its repair has significant utility in large-scale, population-based studies. Such studies could include assessments of the efficacy of antioxidant intervention strategies, pathological roles of DNA oxidation in various disease states and population or inter-individual differences in antioxidant defence and DNA repair. The analysis of urine, or indeed any extracellular matrix, for 8-oxo-7,8-dihydro-2ʹ-deoxyguanosine (8-oxodG), using chromatographic or immunoassay procedures, is by far the most popular method to non-invasively assess oxidative insult to the genome. The actual biological significance of the presence of extracellular 8-oxodG is still a subject for debate however. Studies are slowly ruling out confounding factors such as diet and cell turnover, which would leave endogenous processes, notably repair, as the sole source of extracellular 8-oxodG. The method described herein exploits the non-invasive properties of urine sampling, coupled with efficient extraction of 8-oxodG by a validated solid-phase extraction procedure. Subsequent analysis by liquid chromatography–tandem mass spectrometry has the advantages of sensitivity, internal standardisation and robust peak identification.
