Simultaneous quantification of three alkylated‑purine adducts in human urine using sulfonic acid poly(glycidyl methacrylate‑divinylbenzene)-based microspheres as sorbent combined with LC-MS/MS

Three alkylated DNA adducts, N3‑methyladenine, N3‑ethyladenine and N7‑ethylguanine, have been proved to be potential biomarkers for DNA injury caused by exposure to cigarette smoke. In this study, a highly specific and sensitive method using a new mixed-mode sulfonate-functionalized poly(glycidyl methacrylate-divinylbenzene) as a solid-phase extraction sorbent was developed for the analysis of these three alkylated-purine adducts in human urine. Under optimized conditions, the prepared sorbent interacts strongly with these urinary adducts, demonstrating high clean-up efficiency and extraction recovery. The method detection limits (S/N ≥ 3) of N3-MeA, N3-EtA and N7-EtG were 1.75, 0.20, and 0.15 pg mL−1, respectively, while the method quantitation limits were found to be 5.78, 0.66, and 0.49 pg mL−1 for N3-MeA, N3-EtA and N7-EtG, respectively. The intra-day and inter-day precisions were investigated, of which were in the range of 1.6-3.8% and 3.2-5.6%, respectively. The recovery values of the alkylated DNA adducts in spiked urine sample were ranged 89.7-104.5%. Their concentrations were statistically significantly higher in smokers than in nonsmokers. These results show that the proposed method is suitable for the analysis of alkylated DNA adducts.