When a laboratory tests a material, it is answering two questions: is this the substance it is claimed to be, and how pure is it? The results are recorded on a certificate of analysis, a one or two page document that travels with the batch.
Identity: is it the right molecule?
Identity is most often confirmed by mass spectrometry. The instrument measures the mass of the molecules in a sample with great precision. Every molecule has a known theoretical mass, so a match between the measured and expected values confirms what the sample is.
Purity: how much of the sample is that molecule?
Purity is usually measured by high-performance liquid chromatography, known as HPLC. The sample is pushed through a column that separates its components, and a detector records each one as a peak. The size of the main peak compared with all the peaks gives the purity as a percentage.
What a certificate of analysis contains
- The name of the material and its batch or lot number
- The tests performed and the method used for each
- The result of each test, with the specification it was measured against
- The date of analysis
- The laboratory that performed the work
Why independent testing matters
A certificate is only as reliable as the laboratory behind it. Testing by a laboratory that is separate from the manufacturer removes the conflict of interest, and many independent laboratories let anyone confirm a report directly with them using a reference number printed on it.
How to check a report
- Match the batch or lot number on the report to the one on the material
- Check that the report is dated and names the laboratory
- Use the verification service of the laboratory where one is offered
- Be cautious of reports with no batch number, no date or no named laboratory
This article is for general educational purposes only and is not medical advice.
Frequently asked questions
What is a certificate of analysis?
A document that records the tests performed on a specific batch of material and the result of each one.
What is HPLC?
High-performance liquid chromatography, a method that separates a sample into its components so the amount of each can be measured.
What does a purity percentage mean?
It is the share of the sample that is the intended substance, based on the size of its peak relative to everything detected.
What is mass spectrometry used for?
Confirming identity. It measures the mass of the molecules in a sample, which is compared with the expected mass.
Why is the batch number important?
It ties the report to one specific batch. A report without a batch number cannot be matched to any material.
Is this medical advice?
No. This article is general educational information only.