Understanding Peptides
What a peptide actually is, how sequence and molecular weight define identity, and why laboratory materials are described so differently from medicines.
Independent educational resource
Read the evidence behind research peptides
The Peptide Progress teaches analytical literacy: what a purity figure means, what a certificate of analysis can and cannot prove, and how batch documentation is supposed to fit together. No products, no protocols, no medical advice — just the skills to interrogate a document properly.
Our purpose
Analytical documents are only useful if you can read them
Research peptides circulate with a paper trail: certificates of analysis, chromatograms, mass spectra, batch codes and test dates. That paperwork is often treated as a badge rather than as evidence. A percentage is quoted without a method. A chromatogram is shown without axes. A batch code on a label matches nothing in the report attached to it.
This site exists to close that gap. Every page here is written to make one specific document, method or claim legible to a non-specialist reader — so that the next time you see “99% purity, third-party tested”, you know exactly which questions remain unanswered.
What this site is
An independently operated, non-commercial library of explanatory articles about peptide science, analytical chemistry methods and documentation standards.
What this site is not
Not a seller, clinic, pharmacy or medical service. We publish no dosing, protocol, reconstitution or administration guidance, make no treatment claims, and recommend no supplier.
Featured learning paths
Four guides, in the order they make sense
Start at the beginning or jump to the document in front of you. Each guide is self-contained, dated and referenced.
Testing & Verification
Identity testing versus purity testing, what HPLC and LC-MS each measure, and the limits that every method carries with it.
How to Read a COA
A field-by-field walkthrough of a certificate of analysis — and the warning signs that tell you a document is decorative rather than analytical.
Batch Traceability
How batch codes, labels, reports and retained records are meant to line up, and what a broken chain of custody actually means.
Research literacy
Four questions that separate evidence from decoration
Analytical literacy is mostly a habit of asking the same small set of questions every time. None of them require a chemistry degree, and together they filter out most unverifiable claims.
- What exactly was tested? A named compound, a batch code and a sample identity — or an unnamed “sample” that cannot be tied to anything you can hold.
- By what method? A purity number without a technique, column, mobile phase and detection wavelength is an assertion, not a measurement.
- Measured how, and against what? Peak area percentage, mass confirmation and quantitative content are different results with different meanings.
- Who performed it, and when? A named laboratory, a report date and a batch date that plausibly relate to each other. Undated reports describe nothing in particular.
If a document cannot answer those four questions, the honest conclusion is not that the material is bad — it is that the document does not tell you. That distinction is the whole subject of this site.
Also useful
The research
glossary defines every term used across these guides, from retention time to
chain of custody.
Latest resources
Recently published
-
Identity and purity are two different questions
A high purity figure says nothing about whether the material is the compound named on the label. Why both tests are needed, and in what order.
-
What mass spectrometry can and cannot tell you
Molecular weight confirmation, isotope patterns, charge states and the common mistake of treating a matching mass as proof of a correct sequence.
-
Peak purity, net peptide content and water content
Three numbers that are routinely confused. What each one measures, and why a chromatographic percentage is not a measure of how much peptide is in the container.
-
How to evaluate an analytical claim
A short, repeatable checklist for deciding whether a testing claim is verifiable, partially verifiable or simply unsupported.
External educational references
Reading beyond this site
We cite primary literature and standards bodies throughout the guides. We also reference a small number of external educational pages where they cover a topic in a complementary way. These are editorial references only — see our ownership disclosure for the connection we are required to declare.
Selected external educational pages:
- Peptide testing and verification overviewexternal
- Batch traceability explainedexternal
- Third-party peptide testingexternal