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Is there a way to quantitatively measure the interference of different metal ions in solution? I plan to measure concentration of Pb(II), Fe(II), and Cu(II) in solution together using a spectrophotometer.

I know that I can put multiple samples of two ions together to test for the interference trends/effects, but can I do this for all three? e.g. measure interference effects of both iron/copper on lead? Or are there too many variables to measure concentrations?

If not feasible, are there other accessible ways (besides mass-spec) to measure multiple concentrations of all three at once?

EDIT: I already plan to measure concentrations using reagents, specifically Hach TnTplus 850 and 858, and Hach CuVer 1, as they seem easy to get and use. My purpose is to accurately measure concentrations of one ion when in the presence of two other interfering ions.

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  • $\begingroup$ Do you want to measure the concentration of each or measure how much one type of ion causes an erroneous measure of the concentration of another type ? $\endgroup$ – porphyrin May 28 '18 at 7:43
  • $\begingroup$ It doesn't satisfy your criteria perfectly, but atomic absorption spectroscopy will do it one element at a time: using flame ionization for the iron and copper, and a graphite furnace for the lead. $\endgroup$ – pentavalentcarbon May 28 '18 at 18:40
  • $\begingroup$ I want to measure the concentration of each in the presence of the other ions, i.e. measure Pb when the solution also has both Cu and Fe in it. I listed my probable reagents above in the edit. I think calculating interference curves would be helpful for this too. I was thinking that it would be easy to calculate one ion's interference on the other, but calculating interference of two ions at once would be harder. Sorry for any confusions $\endgroup$ – Phoenix91 May 28 '18 at 18:54
  • $\begingroup$ Also AAS is out of my budget, so simpler reagents/methods work better for me. $\endgroup$ – Phoenix91 May 28 '18 at 18:55
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What you can do is to add a reagent which forms a highly coloured complex with one of the metals, this will allow you to make a measurement which is good for one of the metals. You may need to do three different experiments on three seporate aliquats from the same solution.

For example for the iron, I would suggest that you use 2,2'-bipyridine, or 2,2'-bipy as it is sometimes known. This forms a very deep red complex with ferrous iron. This would allow you to measure the iron.

You would need a series of calibration samples with different amounts of iron, please do be aware that the matrix can sometimes interfere with this measurement. I have found that oxalic acid does inhibit the formation of the iron tris bipy complex.

Maybe you should read this paper which is about 2,9-dimethyl-4,7-diphenyl phenanthroline. This is a reagent which has been reported to be good for copper determination.

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  • $\begingroup$ Thanks. I forgot to mention that I plan on using Hach TnTplus 850 and 858, and Hach CuVer 1 already, for Pb, Fe, and Cu. They measure using PAR, 1, 10 phenanthroline, and Bathocuproin, respectively. I already know the basic process behind using reagents and spectrophotometers, but is there a way to calculate the effect of multiple ions on one ion's concentration? i.e. put a concentration of Pb into solution with Cu and Fe, and measure just the concentration of Pb using the TnT 850 PAR? $\endgroup$ – Phoenix91 May 28 '18 at 18:50
  • $\begingroup$ Can't you simply run standard curves for Fe in the absence and presence of either or both of the other metals? Of course, the concentration of the other metals may make a difference, and it certainly isn't feasible to run standard curves for all possible combinations and permutations. $\endgroup$ – Dr. J. May 28 '18 at 19:03

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