Detection of low levels of genotoxic compounds in food contact materials using an alternative HPTLC-SOS-Umu-C assay

Food contact materials (FCMs) are perceived as major sources of chemical food contamination, bringing signif­icant safety uncertainties into the food chain. Consequently, there has been an increasing demand to improve hazard and risk assessment of FCMs. High-performance thin-layer chromatography (HPTLC) coupled to a genotoxicity bio­assay has been promoted as an alternative approach to assess food packaging migrates. To investigate the value of such a testing approach, a sensitive planar SOS-Umu-C assay has been developed using the Salmonella strain. The new conditions established based on HPTLC were verified by comparison with microtiter plate assays, the Ames and Salmonella-SOS-Umu-C assays. The lowest effective concentration of the genotoxin 4-nitroquinoline-1-oxide (0.53 nM; 20 pg/band) in the SOS-Umu-C assay was 176 times lower than in the microtiter plate counterpart. This was achieved by the developed chromatographic setup, including a fluorogenic instead of chromogenic substrate. As proof-of-principle, FCM extracts and migrates from differently coated tin cans were analyzed. The performance data highlighted reliable dose-response curves, good mean reproducibility, no quenching or other matrix effects, no solvent exposure limitations, and no need for a solid phase extraction or concentration step due to high sensitivity in the picomolar range. Although further performance developments of the assay are still needed, the developed planar assay was successfully proven to work quantitatively in the food packaging field.