Yes, we are trying to replicate the results in a certain paper, and the paper also includes EDTA titrations and UV-vis spectroscopy, so we have multiple methods, and thus a lot of points for statistical comparison, and will see how the calibration curve is for Flame AA, but if there is a relatively simple way to do standard addition for Flame AA, it would be preferable to add that to the data we already will get, given the matrix in peptobismol. If nothing else, we can just assume the matrix in each tablet is roughly equivalent and any difference will produce a negligibly different matrix effect; and then make a series of standard solutions from different tablets to mimic the standard addition in a single tablet, and see the numbers that are generated. Given the flame works in only ppm, and not ppb, any discrepancies will hopefully be negligible at that precision level.
And yes, we were planning on a heavy dilution, based on the concentration indicated by the packaging.
If there isn't another great method other than something like setting up a flow system to flow the pepto bismol solution first into a stream of standard, and then into the flame, and doing that at different ratios of standard spikes to Pepto Bismol solution, that is fine. It just seemed like everywhere online preferred Standard Addition, but didn't have a good explanation for how to do it.