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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

Current postings:

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 Q&A's, 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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