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Purity and identity
Two questions get collapsed into the word "tested". They are not the same question, and a certificate answering only one leaves the other open.
- Purity asks: how much of this is one thing?
- High-performance liquid chromatography separates the components of a sample and reports the proportion attributable to the main peak. A 99% figure says the sample is mostly one substance. It does not say which substance.
- Identity asks: is that thing the right thing?
- Mass spectrometry measures molecular weight and compares it against the expected mass for the stated compound. This is what distinguishes the labelled peptide from a different peptide of similar purity.
Why both, every lot
Peptide synthesis fails in ways that produce clean-looking material: truncated sequences, deletion products and counter-ion content can all pass a careless reading. A purity figure with no identity result, or an identity result with no purity figure, is half a certificate. Our Lot Standard requires both, from an independent accredited laboratory, for the lot in the vial.