[ehchandler]

Quick question:

I am preparing a procedure for the determination of the Bismuth concentration in a standard OTC bottle of Pepto Bismol. Given the matrix of that, I would much prefer to use Standard Addition rather than Calibration Curves. One of the techniques we will be using is Atomic Absorption, but as the analyte is consumed in the analysis, I cannot find a good, descriptive way to account for the change in concentration of the analyte solution when the instrument sucks up solution until it gets a reading, indiscriminate of Volume. Though it seems that the general consensus online is that standard addition is done regularly in this context.

Any thoughts on how to do standard addition under these conditions on Flame AA?

Thanks in advance.

[marquis]

Do you have any choices other than flame aa?

The bismuth level is very high in pepto.  This means
you would have to use an insensitive
line of bismuth or dilute heavily. Or both.

[ehchandler]

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.

[marquis]

There are a number of references to standard addition.
Wikipedia is a good starting place, although there are
many others with some variations.

It sounds like you will be using a pharmaceutical reference
of some kind.  The best place to start is with the pharmacopeia
you will be referencing.  For example, if you are trying to compare
to the USP, then pull the standard addition reference out of the
USP.