Calibration Curve for ICP-MS Analysis

Theresa writes...
I have been wondering if you have a general recommendation for creating the calibration curve for ICP-MS analysis. We do a 4 or 5 point cal curve forced through zero with a very low standard. For example we would run a 2, 10, 20, 50 and 100 ppb standard and force through zero. I don't understand why simple linear with instrument blank subtraction wouldn't be better? What are your thoughts on this?

Dear Theresa,

Excellent question. In general I do not trust calibration curves. For ICP-MS, I do standard additions and I do not force 0 through 0, but rather I subtract the blank from the sample and sample + spike signals. However, there are different types of blanks:

  • Reagent blank, where the blank signal shows in all samples and standard solutions.
  • Preparation blank, where the blank is from the sample preparation process only and not present in the calibration solution/standards.
  • Background interference that may appear to be a blank; mass scans are generally required along with some investigative work to identify.
  • Random contamination blanks that appear for elements like Ca, Fe, Na, Mg and Zn (the most troubling elements in my case).

I, like you and many analysts, find the blank issue to be more than a little complicated. If you would like to discuss this further, please feel free to reach me through our toll-free number: 1-800-669-6799.

Serving you in chemistry,

Paul R. Gaines, Ph.D.
CEO of Inorganic Ventures & Fellow Chemist

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