FAQ · Research peptides
What does 99% HPLC purity actually mean?
A 99 percent HPLC purity claim means that when a sample of the peptide is run through high-performance liquid chromatography, at least 99 percent of the detectable peptide content is the named molecule. It is the standard purity benchmark for UK research peptide retailers. HPLC does not prove biological activity, sterility, or correct labelled dose; those are separate analytical tests. Mass spectrometry alongside HPLC strengthens identity confirmation. A 99 percent dead peptide is still 99 percent pure.
What HPLC proves
- · The proportion of the named molecule in the sample, relative to other detectable peptide content.
- · The absence of major synthesis by-products above the stated purity threshold.
- · Repeatability when the same sample is tested again.
What HPLC does not prove
- · Biological activity. A 99 percent pure dead peptide is still 99 percent pure.
- · Sterility. Sterility is a separate analytical test using direct culture or rapid microbial detection.
- · Correct labelled dose. Dose accuracy requires a separate quantitative analytical test.
- · Endotoxin content. Endotoxin uses LAL or recombinant Factor C, not HPLC.
- · The molecule is what the label says it is, by itself. HPLC reports proportions; mass spectrometry confirms identity.
Why mass spectrometry strengthens the certificate
HPLC alone can tell you that 99 percent of the peptide in your sample is one consistent compound. It cannot tell you whether that compound is BPC-157 or a different 15-amino-acid peptide of similar HPLC behaviour. Mass spectrometry measures the molecular mass directly, which lets the lab confirm that the named peptide is what is in the vial. A CoA that pairs HPLC purity with MS identity is meaningfully stronger than HPLC alone.
What 99 percent really competes with
In practice, the difference between 98 percent and 99 percent purity matters less than whether the CoA is real and dated correctly. UK retailers publishing CoAs with batch numbers tied to physical vials and full HPLC-plus-MS documentation are more trustworthy than retailers claiming higher percentages without traceable certificates. The headline number alone is not the signal.
Related: HPLC purity deep-dive · Certificate of Analysis · UK retailer comparison.