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Recommended UV/Vis instruments for plating bath analysis?

I am a chemist for a small research company, and I finally got the go ahead to purchase a UV/Vis instrument. Could someone recommend a good model? We do have an Iron/Nickel bath and are thinking of bringing in a ternary bath as well, will a UV/Vis be able to handle the more complex solutions, or will the peaks tend to overlap and obscure each other? Also how critical is the range, I have found some inexpensive instruments but their range is 200 to 1000 nm's, and if I wanted 190 to 1100 nm's it would cost more, is the slight increase in range worth it? Finally does a dual beam help, I seem to recall it was mainly a means of eliminating background and stabilizing the baseline? Thanks for any help or suggestions it is greatly appreciated.

Richard Caldwell
chemist in a small plating research company. - Seattle, Washington
April 6, 2009

Ed. note: Readers, please recommend types and specifications, but not brand names. Thanks.

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My first question is why do you want to use UV/vis spectroscopy? As with all analytical techniques, it has its place, but for analysis of cations it is not ideal. If you want to measure iron and nickel, try either atomic adsorption spectroscopy (AAS) ⇦ this on eBay or Amazon [affil links] or ICP. The former is cheaper than the latter, but ICP is faster and can do multiple elements in one go. These techniques are much more sensitive to Fe and Ni than UV spectroscopy and are easier to interpret.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
April 9, 2009

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I have worked in many plating labs and visited many more so I can confidently say that UV/Vis is a rarity and of very limited use. Saccharin and coumarin are possible uses but the former has a relatively simple titration and neither are routinely analysed. Most proprietary additives are not declared composition so no help there.
Most labs go for AAS as the first instrument, labs with plenty of funding (very few) may have an ion chromatgraph or an autotitrator. Even research labs do very well with titration and a pH meter.
My preferred instrument is a polarograph. If a species is electroactive it can be determined. If it is not electroactive it is unlikely to affect a plating solution.

The answer to your original question is - Decide what analysis you are going to do and the instrument will select itself.

Geoff Smith
Hampshire, England
April 9, 2009

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April 14, 2009

We have a AAS but it is time consuming, and I would love an ICP but the cost is prohibitive. UV-Vis instruments are pretty cheap right now and I was under the impression they would simplify my analysis.

I have seen articles in metal finishing where they used it for Saccharin, and I thought you could use UV-Vis for metal analysis as well? I had envisioned using this to analyze for nickel, iron and saccharin simultaneously.

I used it in college for confirmation but never for determining specific concentrations. Can you run calibration curves of pure standards of the metals and saccharin and then use the peak height and location to pick out the concentrations of the individual analytes in a solution with multiple anayltes? We have multiple metal cations in most of our baths and I am worried about the overlap of the peaks on UV-Vis.

The setup and calibration would be time consuming, but if it worked it would dramatically speed up my analysis while reducing the cost. We currently do have the AAS and use titrations for nickel so I would shift these to more of a QC control of the UV-Vis process in the hopes of saving time and chemicals.

Richard Caldwell
- Seattle, Washington, USA