Ok, I want to get some feedback on this one since I'm not as up on the lab side of things. I have a supplier of a product who provides a CoA for that products lot prior to our accepting it. My main concern in this instance is iron. Our supplier shows CoA's in the 3-7ppm typically. We had some iron issues in our final product so one of the things I did was send out this product to a third party for analysis. Of the 17 samples sent, I have an average of 64.88ppm iron (some spiking 110,133,145) which is way different from what the CoA is showing. Contacted the supplier, explained this is a big deal, they pretty much said "no way" and pulled 3 samples, one to be sent to their independent third party lab, to our independent third party lab, and to our in house global R&D team. So far, from MY third party lab I have an iron result of 62.7ppm , from THEIR third party lab they show an iron of 6ppm.
The methods are different but they are comparable ITSM methods.
Has anyone else run into completely off the wall analysis like this? I almost wonder if they are screwing up in their dilution factor at my third party lab and the decimal should be 1 to the left.
A few questions.
What is the specific item ?.
What is ITSM ? (Google failed).
Are all results for iron expressed as ppm of "Fe" ?
What methods are being used ?
How do you know if samples being distributed are the "same" ?
A typical way to compare labs is to send a well defined "dummy" sample within the samples of specific interest.
PS - reason for queries -
(1) Some Products demand specific methods for accuracy ? (from bitter experiences).
(2) Different methods can give different results (eg due ). The method should ideally be validated. Laboratories sometimes develop short-cut procedures which may fail for atypical samples.
(3) Different samples can obviously give different results.
JFI, one common method for measuring ppm levels of Fe in food is atomic absorption (AA). This can readily distinguish between 5 and 50ppm for appropriate samples. However foods typically require "ashing" prior to AA analysis. The former can cause some variations.
Nonetheless, for similar samples, validated methods should not give variations of magnitude such as you describe.
Edited by Charles.C, 05 January 2021 - 06:26 AM.