32P-postlabeling of DNA adducts arising from complex mixtures: HPLC versus TLC separation applied to adducts from petroleum products

The carcinogenicity of petroleum products is mainly due to their content of polycyclic aromatic compounds (PACs). These compounds may be activated metabolically and react with DNA to form DNA adducts, which is a critical event in the initiation of cancer. One of the most common techniques for analyzing DNA adducts is 32P-postlabeling. The chromatographic method often used has been 32P-TLC (thin-layer chromatography), but the more recently developed 32P-HPLC (high-performance liquid chromatography) method has shown advantages. The aim of this study was to test the hypothesis that the 32P-HPLC method has a better ability of detecting DNA adducts derived from petroleum products than 32P-TLC. It was found that some DNA adducts migrated from the application point in 32P-TLC in such a way that it is doubtful if they could be detected and quantified properly. It was also found that, when using 32P-HPLC, it is possible to use the same protocol for substances with a wide variety of DNA adduct forming potential, whereas 32P-TLC needs to be optimized regarding time of exposure and/or the amount of DNA applied. Further, a pattern of recognition in 32P-HPLC enables a selective assessment of DNA adducts derived from complex mixtures whereas 32P-TLC is very limited when analyzing complex mixtures due to poor resolution. With more knowledge about the properties of the most mutagenic DNA adducts in HPLC, it could be possible to know also which pattern corresponds to a mutagenic or carcinogenic oil. Consequently, 32P-HPLC is a good alternative when assessing the genotoxicity of petroleum products.