Lucidin-3-O-primeveroside (LuP) is a component of madder color (MC), a compound which is carcinogenic in the kidney and liver of rats. Since LuP is metabolized to generate genotoxic compounds such as lucidin (Luc) and rubiadin, it is likely that these play key roles in MC carcinogenesis. In fact, after incubation of Luc with calf thymus DNA, Luc-N(2)-dG and N(6)-dA adducts were reportedly formed, possibly via the sulfotransferase metabolic pathway. However, the precise extent of formation in vivo remains uncertain. In the present study, to quantitatively determine Luc-specific DNA adducts in in vivo samples, we developed an online sample purification method using column-switching and an isotope dilution LC-ESI-MS/MS technique. The limits of quantification were 0.2 and 0.04 fmol on column for Luc-N(2)-dG and N(6)-dA adducts, respectively. Using the new analytical method, we attempted to measure adduct levels in the kidneys and livers of rats treated with 0.06, 0.3, and 1.5% LuP in the diet for one week. Luc-N(2)-dG and N(6)-dA adducts in these organs were detected at ranges from 7.97 to 51.67/10(9) dG and from1.83 to 37.10/10(9) dA, respectively. Dose-dependent increases of each adduct were observed in both organs. These quantitative data obtained with our newly developed analytical method might help to improve our understanding of MC carcinogenesis.