Testing School
A free course on peptide testing, in order. Start with what a test can and cannot tell you, finish able to read a chromatogram, check a mass and verify any certificate in two minutes. Progress is saved in this browser.
What a test measures
- Lesson 1What a peptide test can and cannot tell youLesson 1 of Testing School. Every result is a question, a method, an output and a limit. Learn to sort any line on a report into those four parts.
- Lesson 2Identity: why it comes firstLesson 2 of Testing School. Why identity is settled before purity or amount, which identity methods are orthogonal, and how to judge an identity line.
- Lesson 3Purity: what HPLC measuresLesson 3 of Testing School. How reversed-phase HPLC separates a peptide sample, how area percent is calculated, and what reporting thresholds hide.
- Lesson 4Amount: content vs labelLesson 4 of Testing School. How a lab turns a peak area into milligrams, how to check the arithmetic, and why the reference standard's basis matters.
- Lesson 5Net peptide content and counterionsLesson 5 of Testing School. Estimate how much of a peptide salt is counter-ion, why short peptides lose more weight to salt, and which tests measure it.
Reading the outputs
- Lesson 6Reading a chromatogramLesson 6 of Testing School. A seven-step routine for reading an HPLC trace and peak table: axes, baseline, main peak, small peaks, shape and arithmetic.
- Lesson 7Reading a mass spectrumLesson 7 of Testing School. Read m/z, charge states, monoisotopic and average mass, and ppm error, and calculate where a peptide's peaks should appear.
- Lesson 8Endotoxin and sterilityLesson 8 of Testing School. How to read an endotoxin line and a spike recovery, why results say "less than", and why one vial cannot prove sterility.
- Lesson 9Heavy metals and residual solvents in peptidesHow ICH Q3D, ICH Q3C and USP <232>/<233> set limits for elemental impurities and leftover solvents, and why most peptide COAs never report either.
- Lesson 10Water content and stability of peptide powdersWhy freeze-dried peptides pull water from the air, how Karl Fischer titration measures it, and what ICH Q1A stability terms mean on a certificate.
Samples, labs and certificates
- Lesson 11Batches, lots and why one vial is not the batchWhat batch and lot mean in GMP rules, how a batch code traces a vial's history, and what one tested vial can and cannot say about the rest of its batch.
- Lesson 12Blind testing and why it matters for peptidesBlind testing has two halves: the seller does not pick the vial, and the analyst does not know the seller. Why each matters and how to tell which you have.
- Lesson 13How labs get peptide results wrongHonest labs still make errors: unvalidated methods, weak reference standards, integration choices, co-elution and typos. How each happens and looks.
- Lesson 14How peptide COAs get faked, and how to spot itThe common ways a certificate of analysis is altered, reused or invented, from edited PDFs to lookalike verify pages, and the check that catches each one.
- Lesson 15How to verify any COA in 2 minutesA five-step, two-minute routine for any peptide certificate: match the vial, read the scope, verify with the issuer, check the signer, check the numbers.
- Lesson 16How the Tested Index scores peptide vendorsThe exact Tested Index formula: which batches count, purity, amount, consistency and transparency scores, recency weighting and grades, worked through.
Prefer a quick answer? The guides answer single questions; the lessons build the full picture.
Browse the guidesCOA School: read a certificate field by field