[RobertM]

I am trying to find the concentration of lead in copper(II) nitrate solution, roughly about 2-3 mg per L , using spectrophotometry (the copper interferes with the lead tests in concentrations greater than roughly 5mg per L so is a big issue). The only way I could find to possibly do so is adding diluted edta solution in the hope of forming insoluble Cu2EDTA.4H2O , but the reaction is slow and non complete . I was wondering if anyone could suggest a better way to do so.

[Arkcon]

Well, I know copper forms a soluble complex with ammonia, after first forming an insoluble hydroxide.  I don't recall lead forming a soluble complex.    But selectively precipitating your analyte and hoping to reconstitute for a spectrophotometric test, that seems too difficult.

[RobertM]

That was my first plan as well, but I lose pretty much all the lead in filtration, ending up with results well below the actual concentration. I'm beginning to think it might not actually be possible :/

[Borek]

Are you required to use spectrophotometry? Perhaps you can use some other method?

Not that I have any suggestions, just asking.