Method 200.7 Interference Check Standards

We have just bought a ICP instrument and trying to get it certified.

My question for you is regarding your Method 200.7 Interference Check standards. If you would to compare EPA Method 200.7, section 7.13.1, where the interference check standard is specified, with your 200.7 Interference Checks, you will see two major differences:

  1. There concentrations are all different with or without dilutions. E.g., Al 200ppm (200.7) vs. 3,000ppm (IV 2007ICS-4), Fe 300ppm (200.7) vs.  12,500ppm (IV 2007ICS-4)
  2. You deleted Ce, but added B, Sb, Ag, As, K, Pb, Se, Zn, CA, Mg, and Na.

I am pretty sure you have good reasons to do so, but would like to hear about them. One of your chemists said this was based on a USP method, but the standards are listed as method 200.7 standards.

Thank you for your attention!

Thank you for your business and congratulations on the acquisition of your new ICP.

There are several versions of 200.7 where different approaches to IEC are discussed. I believe you are referring to “Methods for the Determination of Metals in Environmental Samples Supplement I”. I suggest that you follow Section 7.13.1 as directed. IV can prepare these solutions for you. Please be assured that the confirmation of freedom from interference can accomplished in a variety of ways.

Serving you in chemistry,

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

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