Reading a certificate of analysis: what each field tells you

A certificate of analysis (CoA) answers one question: which tests did this one batch pass, by which method, and with what result? Check five places to see whether a certificate does that. Does the batch number match? Are the methods named? Is there a specification next to each result? Which dates does it carry? And who tested and released the batch?

The reference: ICH Q7

For active ingredients used to make medicines, the GMP guideline ICH Q7 sets out in section 11.4 what a certificate of analysis should contain. The guideline applies to the manufacture of medicines, not to research material. Its list still works as a checklist, because it asks the same questions a laboratory has about any delivery.

The fields and what they tell you

Specification and result: two columns, two statements

The specification says what was required. The result says what was measured. Only the two together show whether the batch meets the requirement and how far it sits from the limit. When a test that gives a number reports only "conforms", that distance is exactly what you cannot see.

The method belongs with the specification. A purity value depends on how it was measured: column, mobile phase, detector wavelength. What an HPLC purity measures and what it leaves out is covered in HPLC purity explained. Why purity and identity are two separate tests is covered in Identity by mass spectrometry.

The dates on the certificate

A CoA carries several dates with different meanings:

• Release date: the day the quality unit released the batch.
• Expiry date: the material may be used until this day.
• Retest date: under ICH Q7, the day the material should be examined again to confirm it is still suitable.
• Date of signature: when someone signed the document and took responsibility for it.

A retest date is not an expiry date. It says when to measure again. How to store material until then is covered in Storing lyophilised peptides.

Red flags

• The batch number is missing, or it does not match your delivery.
• Results appear without a specification or without a method.
• A test that gives a number reports only "conforms".
• The certificate states a purity but no identity test.
• There is no date, no signature, or no laboratory responsible for the analysis.
• A newly issued certificate does not refer to the manufacturer's original.

If the batch's chromatogram and mass spectrum are attached to a certificate, you can see what its figures rest on.

Why a second look pays off

A research group at Ghent University ordered 98 synthetic peptides for research from two suppliers, with a required minimum purity of 95.0% (Verbeke and others, 2015). Each came with a certificate of analysis stating that purity. The group's own incoming inspection found it for 43 of the 98 peptides. In one sample the main peak was not the ordered sequence. For one peptide the supplier reported at least 95.0%, while the group measured 80.6% with a different separation system; in their assessment, the supplier's method did not separate well enough.

The authors therefore advise researchers to run their own incoming quality control. A complete CoA with method, specification and numerical result makes that control easier, because you know which measurement you are repeating.

The CoA at Novo Labo

Novo Labo provides the certificate of analysis for a batch on request. To ask for it, write to hello@novolabo.com. All products are sold strictly for laboratory and research use.