Reading a Certificate of Analysis
What each section of a certificate of analysis is asserting, and how to tell a document that reports measurements from one that reports adjectives.
6 min read
What the document is
A certificate of analysis reports the results of testing performed on a sample of a specific lot. It is a record of measurements, issued by whoever performed them, describing the material identified on it.
The document reports only what was measured on the sample tested. It does not certify a production process or describe material outside the lot it names.
Identification
The header establishes what the document refers to. It should name the compound, the lot number, and where applicable the batch number, and it should carry a date of analysis and a date of issue.
Every other field depends on the lot number. Without it, a certificate that names only a compound cannot be connected to any particular container, and none of its results can be verified.
Methods and results
Each result should be accompanied by the method that produced it. A purity figure should state that it was determined by HPLC. An identity statement should state that it was determined by mass spectrometry. Where conditions materially affect interpretation, those should be available as well.
The most common weakness in a certificate is a result with no method. A percentage with no stated method cannot be interpreted, because you have no way to know what was measured or what the figure is a proportion of. Two documents reporting the same number from different methods are reporting different things.
Supporting data makes a certificate easier to check. A chromatogram lets you see peak shape and resolution instead of taking an integrated number on trust. A mass spectrum lets you compare the observed mass against the expected value directly. With summary figures alone, you have to trust numbers you cannot check.
Attribution
The document should identify who performed the analysis. Testing may be conducted by the manufacturer or by an independent laboratory, and you are entitled to know which.
Where a laboratory is named, the name should be specific enough to be checked. An unattributed certificate reports results without anyone standing behind them.
Signals worth weighing
A document reporting a numeric result with its method makes a statement you can check. A document describing material as high quality or premium grade is not reporting an analysis, because no measurement corresponds to those terms.
Also check whether the lot number on the document matches the container, whether dates are present and internally consistent, whether supporting data is available alongside the summary values, and whether fields with no verified value are marked as pending rather than filled with something plausible.
Pay most attention to the last one. A visible gap shows where no verified result exists, while a document with no gaps at all may be one where someone filled them in.
This article is general reference material describing methods and records. It does not describe any particular material and is not medical advice.
