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General Spectroscopy - Certified concentration of a standard

 
I purchased an arsenic (As) standard for ICP and had a question regarding the certificate of analysis. I noticed that you report two independent assay methods, but you report the certified concentration as the lower of the two. Why don't you average the two together?
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admin Total posts: 529

We used to take the average of both methods. When we applied for our ISO Guide 34 accreditation, we posed this question to our accrediting organization. Their response requested us to do the following:

  1. Validate all methods and only use validated methods for assay purposes.
  2. Compare the two methods for agreement statistically.
  3. Then, if there is agreement, to use the method giving the lowest uncertainty.

The key is the validation and statistical comparison that allows for certification using the most precise data. Otherwise it is just "putting your best foot forward" with no scientific basis.

Posted: 09/04/18 20:09:56

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