Solvent interactions with test compounds and recommendations for testing to avoid artifacts.

Reports in the literature describing artifactual results owing to interactions of test materials with solvents are becoming more frequent. The present study was initiated to examine possible interactions of 1,1,3-trichloro-, 1,1,3,3-tetrachloro-, pentachloro- and hexachloroacetones with different solvents, since certain solvent effects with the last compound have been shown previously. Quantitative differences in levels of mutagenic potency were found for tri-, tetra-, and pentachloroacetone, dissolved in acetone or dimethyl sulfoxide (DMSO). On the other hand, hexachloroacetone without solvent was mutagenic, and this activity was enhanced when it was dissolved in DMSO; in acetone it was not mutagenic. A time-dependent reaction of hexachloroacetone with DMSO was the only test material-solvent interaction found in this study. The results show clearly that DMSO is not an appropriate solvent for hexachloroacetone. On the basis of these and previous results, we recommend consideration of the following strategy to help prevent reporting of artifactual results owing to interaction with solvents: Results from initial screening experiments should be confirmed in repeat experiments using a different solvent; and a different solvent should be used in confirming the findings of other investigators. Differences in results would indicate a need for further study.