Hexavalent Chromium in Trivalent Chrome Bath: Smart Method

Summary for hexavalent chromium in trivalent chrome bath Discussion

Hexavalent chromium in trivalent chrome plating bath is the focus of this thread, where Simone Pasquali asks for an analysis method using UV/VIS, ICP-OES, or HPLC-UV and requests step-by-step guidance. Derek Hutter replies that EPA Method 7196a, a UV/Vis procedure for hexavalent chromium versus total chromium in soil, has also worked for plating baths, but he warns that very precise dilutions are needed for consistent results. He also suggests that, depending on the ICP model, it may be possible to measure total chromium and trivalent chromium separately and then infer hexavalent chromium by difference. The discussion is practical rather than definitive: it points to workable lab approaches, but emphasizes dilution control and instrument capability as key limitations.

Electrodeposition of some metals can be done from alternate solutions in different valence states ⇦ huh?. Chrome plating has traditionally been done (and largely still is) from a strong solution of toxic & carcinogenic hexavalent chromium (valence +6) — the stuff that made Erin Brockovich famous.
But it has also been possible for several decades now to do chrome plating from a solution of trivalent chrome (valence +3), which doesn’t pose similar environmental and safety issues.
So, for operational and/or regulatory reasons it can be necessary to know how much hexavalent chrome is in a trivalent plating bath, and vice versa.

Q. Good morning,

First of all I wanted to thank you for the opportunity to write here. I wanted to ask you if anyone knows an analysis method for the determination of hexavalent chromium in a trivalent chromium sulfate bath. In the laboratory where I work, we have a UV/VIS spectrometer, ICP-OES and HPLC-UV. I ask you, if it is not too much trouble, to describe all the steps of the method.
Thanks to everyone for the help.

Simone Pasquali
– Italy
June 14, 2025

A. EPA method 7196a is a UV/Vis method for testing hex chrome compared to total chrome in soil samples. I have used it successfully for plating baths but you need to have very precise dilutions to get consistent results.

Depending on the model of the ICP you may be able to create methods for total Cr and Cr3 separately and then use the difference of the two tests to get a good idea.

Derek Hutter
– Buffalo, NY
June 16, 2025