What is a system suitability failure and what happens to the batch?

I am comparing a supplier certificate against an independent result on the same lot.

I have read the primary source rather than the summary, which has left me with more questions.

I understand the headline. I do not understand the footnotes, and the footnotes look important.

What would I need in addition before this supported a decision?

Most research work uses in-house standards of unknown provenance, which is exactly the situation where a mistake in the standard produces systematic error in every sample measured against it.

Purity of the standard is not the same as traceability of the standard — purity tells you the composition, traceability tells you the standard came from a credible source.

On the detail: comparing your quantitation result to a standard certificate requires that the sample purity be accounted for — if you measure a 95 per cent pure sample against a 99 per cent pure standard, the content result is biased.

I would not accept a standard that does not come with a certificate stating its purity.

Do not use an in-house standard without independent verification of its purity.

Certified reference materials from national metrology institutes carry a purity statement and a statement of traceability, and both matter.

A reference standard that has been opened and used many times is more exposed to contamination and moisture than a fresh standard is.

Concretely, a standard purchased from a supplier carries a certificate stating its purity, and that purity is your starting point for understanding your result.

The practical summary: use a standard of declared purity and verified traceability, and check that the certificate is current.

Mechanically, using a standard of unknown or undeclared purity is like building on sand — every number downstream inherits that uncertainty and amplifies it.

A standard of uncertain purity used to measure an unknown sample produces a result whose uncertainty is larger than you will have estimated.

The caveat is that a standard certificate is only as good as the issuing laboratory is reliable, and not all certificates are equally credible.

Ask for the standard's purity when you buy it.

In practice, comparing results from different laboratories requires knowing that both used standards of declared purity and traceability, and often they did not.

System suitability for a standard includes that replicate measurements of the same standard give consistent results, and if they do not, something in the method or the instrument is wrong.

Certified reference materials are available from national metrology institutes and carry full documentation of their purity and traceability.

Do not use an in-house standard without independent verification of its purity.

edited 14 Jun 2025 by klara_novotna — added the placebo-arm figures