According to Maron and Ames, 25 the
described method (preincubation technique)
was performed to assay mutagenicity in both
non-metabolic (-S9 mix) and metabolic (+S9
mix) activation of the extract. Briefly, 50 μl
of solvent (negative control), 0.2-5 mg/plate
of the extract, or standard mutagens as
positive control, AF-2 or 2-AA, were added
by 500 μl of phosphate buffer or S9 mix.