If your concentration is in the range ppb to ppm non electrochemical techniques such as ICP-MS or ICP-OES work best, above this i.e. ppm and higher XRF is useful. Both techniques enable you to unambiguously determine metal ion concentration. Electrochemical techniques centred mostly around stripping voltammetric techniques can be challenging if the solution contains more than one metal ion and will require much more work for calibration

Julie V Macpherson Thanks for the reply.

I have only one metal in the electrolyte. Not all the the metals together in the same solution. to be precise,

I have a Di Rhodium Tri Sulphate (Rh2(SO4)3) solution with concentration of 2g of Rh in 100 ml of Rh2SO4 solution (Prepared by dissolving Rh in H2SO4).

When I use this solution in electro-deposition, the concentration of Rh will be reduce in the solution.

So can I measure the concentration of the Rh in the solution at frequent intervals during the electro-deposition.

I have considered ICP-MS & ICP-OES. But these are costly tests. I am looking for the cheaper techniques and the in a portable device.

How good id the UV-Vis spectroscopy technique for this?

For this concentration, the best approach is a titration method:

http://pubs.rsc.org/en/content/articlelanding/1984/an/an9840900659/unauth#!divAbstract

It will be the most precise.

But you can also try a spectrometric method:

http://www.biblioteca.uma.es/bbldoc/tesisuma/16613661.pdf

Cornel Radu

Thanks for the prompt reply Sir.

Most of these techniques are based on usage of some reagent to impart colour to the rhodium solution which will be used then to check in the spectrophotometer.

By this, every time I test, some amount of the Rhodium sulfate will be used. So I cannot put back into the electro deposition bath after adding the reagent and measuring the concentration. As this solution is costly, I cannot afford the solution loss.

So can you please suggest any other method, where I can measure the properties like, electrical conductivity/ electrode potential (ORP) which will vary according to the concentration of the Rh3+ in the solution so that solutions can be reused without contamination.

Thanks in advance.

Best method for elemental analysis is Laser induced breakdown spectroscopy. It can provide information about the concentration also.

Virendra Nath Rai

Thanks for the reply sir.

I am looking for a portable device like the one in the link below.

Please let me know if any one like that. The concentration of the Metal salt solutions are in the range of 2 to 5 g / liter.

https://hannainst.in/products/portable-photometers/copper-high-range-portable-photometer-hi96702.html