I would recommend a sample preparation step in the form of 0.45um filter and subsequent solid phase extraction (SPE), for example IST Env+. The free cations will be retained on the solid phase, and can then be eluted using dilute acid, and analyzed using ICP-MS.

hi Jesper

thanks for the answer

I will check on it :)

You mentioned that other than complexation of the ions with suitable completing agent and then by using UV-Vis spectroscopy you can quantitate ionic concentration on developing calib curve. If not you can precipitate the ions and by using equivalence relations you can estimate the concentration.

You may also try to use ion-selective electrodes.

You have the possibility to use ion-selective electrodes? If not, Ag(I) ions can be analysed by a turbidimetric method, while for Cu(II) ions determination can be used a spectrophotometric method. If you are interested in these alternatives, please let me know and I will send you all the technical details.

Laura Bulgariu I don't have ion-selective on hand at the moment. I am aware also that ion selective might have interference due to other ions but not sure which!

If you can send me data over turbidimetric method & spectrophotometric method, I would appreciate it.

For Cu(II) determination, please see the paper: Article SPECTROPHOTOMETRIC DETERMINATION OF Cu(II), Co(II) AND Ni(II...

The turbidimetric method for Ag (I) ion analysis will be sent later, after the English translation.

Dear Mona, maybe a bit exotic..but NMR based chelatometry does also work (see enclosed poster-pdf)...good luck

Alfred

Do you want to measure this in the same solution ?

What complexes do you have in solution ?

Do you have other metals tin there ? what pH ?

This is not an easy question !

The easiest approach is to compare analyses of total element (ICP-MS) with colorimetric measurements of the complexe(s). But this works only in case where you have only one complex, or non overlaping ones.

ISE have known selectivities towards other ions, ie you can take their selectivity into account when choosing the type of ISE. But more important: "free ions" per se do not exist in solution. The theoretical description by the Nernst equation is strictly valid only for highly diluted solutions (10-6M), the more ions there are the more Dipole-Dipole interactions become relevant. I want to rephrase your question: you are interested in the binding constant of ions in a specific system. The specific binding energy is a function of the type and amount of the counterions.