Purity, identity and certificates of analysis — how to tell what you are actually working with.
Reproducible research depends on knowing exactly what you are working with. Two batches that look identical can differ in purity and identity — and those differences show up in results. That is why analytical documentation matters as much as the compound itself.
Two things tell you the most: a purity figure and a certificate of analysis (COA) for the specific batch.
High-Performance Liquid Chromatography separates the sample and measures what fraction is the target compound. A figure such as ≥ 99% indicates high purity with minimal impurities.
MS confirms the compound’s molecular weight — evidence that the peptide is the correct identity, not just pure.
Together, HPLC answers “how pure?” and MS answers “is it the right molecule?” — both are needed for confidence.
A Certificate of Analysis is a per-batch report from analytical testing. Typically it lists:
Match the batch. Check the lot number on the COA matches the vial you received.
Check purity. Look for the HPLC figure — higher is better; ≥ 99% is a strong result.
Confirm identity. The MS-reported mass should match the compound’s expected molecular weight.
Keep it on file. Store the COA reference with your research notes for reproducibility.
It means chromatographic testing found the target compound makes up at least 99% of the sample, with impurities below 1% — an indicator of high purity.
No. Purity (HPLC) tells you how clean the sample is; identity (mass spectrometry) confirms it is actually the intended molecule. Both matter.
A COA is only meaningful for the specific batch it was generated from. Matching the lot number ensures the documentation applies to the vial in your hand.
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