Our lab has acquired a brand new ICP-OES 5800, mainly to run weekly analysis on our galvanic baths.
The method development was going well, but we have an issue with our Nickel bath, as the ICP consistently gives results below what's expected.
Previously, this analysis was done with an AA spectroscope, with results around 75.0g/L Ni.
Now, the ICP hardly gives any results above 71g/L Ni.
Worst, those results are not repetable if the same solutions are analyzed twice.
For example I had 2 dilutions from the same bath, E1 and E2. dilution 1/2000 in water with Ni standard 50/25/10/5 ppm.
They were tested in a first sequence with Intelligent rinse set on moderate, and a second sequence on thorough.
I wanted to do a screening of the main emission rays to check if some would give better results so I selected about 30 rays.
The table below is quite representative of what I'm getting every time - it can be worse.
|Ni 230.299 nm|
As you can see, even if it's the same samples that have been run twice, there is a big discrepancy between E1 and E2.
Our first results (70.97 and 71.27 g/L) are way below what our AA gives us (78g/L).
This problem does not occurs when other Ni containing baths are tested, so I was wondering if an interference not listed in the ICP Expert tables could occur.
This bath contains HBO3, does it matter? Can Boron smother the signal and give the flickering results?
If anyone has any idea, please let me know.