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Cobalt & nickel analysis -- A.A., ICAP/MS, or colorimetric


A.A. = atomic absorption spectrometry
ICAP/MS = Inductively Coupled Plasma / Mass Spectrometry
CBN = cubic boron nitride

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May 26, 2022

Q. We have a small plating shop having anodizing as one of the processes. We are doing black electrolytic coloring using cobalt acetate, nickel sulphate, boric acid and 5 sulpho salicylic acid.

We are not able to analyze cobalt and nickel metal content separately in solution for replenishment purpose. Please suggest suitable analytical method.

U Vaishali
- Gujarat India

Closely related historical posts, oldest first ...


Q. Hey Everybody,

Wendt Dunnington makes Diamond and CBN tooling and we electroplate nickel (from Watts and Sulfamate baths) to hold the super abrasives in place. In a R&D mode we are adding Cobalt (1000 to 3000 ppm range)to the nickel chemistry. A low cost analysis for Cobalt in the presence of Nickel would be very helpful. Any ideas?


Fred Mueller, CEF
Wendt Dunnington - Royersford, Pennsylvania

"Atomic Absorption Spectrophotometry"
by Hasna Ait Bouh
from Abe Books

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A. Nickel and cobalt are so close to identical That a cheap method is probably not possible. Atomic Absorption and possibly ICAP/MS may be necessary.

James Watts
- Navarre, Florida


A. As long as the Ni/Co ratio is not more than a few hundreds, you should be able to do a colorimetric analysis based on formation of cobalt thiocyanate and its extraction into an organic phase. You will need a simple spectrophotometer (2K) and, preferably, a simple centrifuge (about 0.5K).

Another option I am aware of is potentiometric titration with potassium ferricyanide in the presence of ammonia. Worth trying if you have the equipment.

Emanuel I. Cooper
IBM - Yorktown Heights, New York


Q. I am working on a method to Analyze Cobalt in a nickel sulfamate bath I have tried linear, nonlinear, and matrix addition calibrations. I have also try matrix matching I have gotten good result however I am getting about 200 to 300 ppm less than the outside lab analysis. Can I get any suggestion on what to try next.

David Morrison
QC chemist - Titusville, Pennsylvania, USA


"Atomic-Absorption Spectrophotometry"
by Elwell & Gidley
from Abe Books

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A. Are you using the same type of AA? Flame, Graphite Furnace or ICP-MS? It will make a difference. You might try using a standard from the same lot number as your outside contract lab does. All certified standards are not equal, despite certification.

James Watts
- Navarre, Florida


A. David,

You may have to face the possibility that you're right! One error would be not diluting the sample & standard to the linear range for Cobalt, in which case any readings below the concentration of the standard (SOP) would read too high. Another error would be to choose a frequency for Cobalt measurement at which Nickel also has minor absorbance, again resulting in a high reading. Create a test sample of Nickel Sulfamate bath with a known measured quantity of Cobalt, have both machines test it.

Craig Haseltine
C&L Equipment Inc - St Charles, Illinois, USA


Q. I am using nonlinear Direct addition on an AAnalist 200 with a wavelength of 240.73 nm I use a diluted Standard Nickel Sulfamate solution for the Blank and standards trying hard to eliminate any matrix effect. A have done a solution multiple times and had close numbers. I have even changed my dilutions and still came up pretty good. The only thing that I noticed is the higher the cobalt level the closer I get to them. I use a 1 ppm, 2.5 ppm, 5 ppm, and a 10 ppm. standards the Absorption of the 10 ppm is about .35 and 1 ppm is about .049 ppm I try to keep the sample as close to 5 ppm as possible. I guess I will track my number versus theirs and see what changes.

David Morrison [returning]
- Titusville, Pennsylvania, USA

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