Simultaneous analysis of cotinine and 8-OHdG in urine: A biomarker approach for smoking exposure and oxidative stress.

This study developed and validated a simultaneous LC-MS/MS method to quantify cotinine and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in urine, biomarkers for smoking exposure and oxidative DNA damage. The method demonstrated high specificity, sensitivity, and reproducibility, with detection limits of 0.23 ng/mL for cotinine and 0.5 ng/mL for 8-OHdG. Cross-laboratory validation showed strong agreement between institutions, with Pearson correlation coefficients and intraclass correlation coefficients exceeding 0.9. Analysis of urine samples from children and adults revealed that cotinine and 8-OHdG levels were significantly higher in smokers, and also influenced by age, gender, and alcohol consumption. The findings underscore the potential of these biomarkers for assessing smoking-related oxidative stress and health risks.