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Plating bath analysis using XRF

I am working for a company that performs Zinc and Nickel analysis for its plating baths and wants to switch to XRF for these analyses. The XRF is already used to measure the thickness of deposited metal. However, problems arise when I try to measure the bath metal concentrations: I consistently get the same number of hits for all sample solutions and a number of background hits that is roughly the double of the signal hits. The XRF uses a tungsten lamp (1 mA). I have tried to calibrate with 3000, 6000, 9000 and 12000 ppm Zinc samples and always got about 480 hits for the Zinc ROI and 800 for the background ROI. Any suggestions/ideas would be very helpful as to why the signal/background is so bad (and constant): is it the lamp, the ppm amount or the used samples (is there any specific preparation required)? or any XRF settings that would have to be adjusted for these types of measurements?

Thanks for a reply!

Sebastian Gliga
anodizing, plating, painting - Montreal, Quebec, Canada
2004

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XRF is not very good at solution analysis. Wet chemistry or atomic absorption ⇦ this on eBay or Amazon [affil links] methods are really much better.

Jon Barrows, MSF, EHSSC
GOAD Company

Independence, Missouri

2004

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But, Jon! XRF is so much more expensive than beakers that it simply must be better, no? :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August , 2007