Home Blog Reading the paperwork
Reading the paperwork
What each line on a certificate measures, and what a weak one leaves out.
Reading the paperworkGSH, GSSG and total glutathione: what the number on a certificate meansAn aqueous glutathione sample is a two-component redox mixture. Reduced GSH and oxidised GSSG side by side, the chemistry that shifts the balance, and what the common assays count.
Reading the paperworkWhy two laboratories get different numbers on the same lotAn HPLC purity figure is a method-dependent number. Where the differences between two reports on one lot come from, what measurement uncertainty is, and how to tell an expected gap from a real discrepancy.
Reading the paperworkSterility, metals and solvents: tests a purity certificate omitsWhat third-party tested actually covers. Purity, identity, sterility, endotoxin, elemental impurities, residual solvents and water are seven separate assays with seven separate standards, and a research certificate carries two or three of them.
Reading the paperworkSeven ways a certificate of analysis misleadsRepresentative certificates, lot numbers that match nothing, in-house tests dressed as independent, purity without identity, stale dates and purity without net content: each pattern, and what a good certificate shows instead.
Reading the paperworkIs the vial actually 5 mg? Fill weight, overfill and label accuracyHow a lyophilized vial gets its label mass, why that number is a target rather than a measurement, how a fill is checked, and how it interacts with net peptide content.
Reading the paperworkA peptide paperwork glossaryThirty-six entries for the terms that appear on peptide certificates, labels and regulatory pages, each defined in one to three sentences from a primary source and linked to the piece that explains it.
Reading the paperworkMass spectrometry identity: what a one-dalton match provesESI and MALDI in plain terms, why a peptide shows up at several m/z values at once, monoisotopic against average mass, and a worked example on a stocked fifteen-residue peptide from its PubChem entry.
Reading the paperworkHow to verify a peptide certificate of analysisHow to check that a peptide lab report is genuine, is about the lot in your hand, and comes from a lab whose accreditation you can confirm, with worked examples for TP-RTA-3, GHK-Cu and kisspeptin-10.
Reading the paperworkEndotoxin: what EU/mg means on a certificateWhat bacterial endotoxin is, how the LAL and recombinant Factor C methods detect it, why FDA's limit is a ratio rather than a figure in EU/mg, and why a research certificate usually stops short of it.
Reading the paperworkReading a chromatogramOne peak is the answer everyone wants. What the shoulders, the late cluster and the flat stretch before it are telling you.
Reading the paperworkWhy an independent laboratory mattersA manufacturer tests its own material at release. That is normal, necessary, and the one party with an interest in the answer. What an independent certificate adds, and what it does not.
Reading the paperworkHow to read a certificate of analysisWhat each line on a COA is actually measuring, in the order it matters, and the four things a weak certificate leaves out.
Reading the paperworkWhat a blend is, and what its certificate should saySeveral peptides co-lyophilized into one vial is one lot number and several different purity questions.
Reading the paperworkNet peptide content, and the 18% error nobody catchesWhy the milligrams on the label are not the milligrams of peptide, and what that does to a concentration you already wrote down.
Reading the paperworkWhat a lot number is forThe FDA has documented batch numbers being rewritten a tier upstream. Here is what that means for the document in your hand.
Reading the paperworkPurity is not potencyHPLC, mass spectrometry and Karl Fischer each answer a different question. Three suppliers quoting "99%" may be quoting three different things.
Other shelves
- How it is madeSynthesis, freeze-drying, formulation and format: how a peptide becomes the vial, spray or strip on the shelf, and where the cost goes.4 pieces
- HandlingStorage, stability and the arithmetic of a stock solution.7 pieces
- Where the line isWhat this site will and will not say about the material it sells, and why.13 pieces
- Sourcing and provenanceWhere research peptides come from, how to check a vendor with documents, and what an importer and a buyer are actually responsible for.5 pieces
- The moleculesWhat each peptide is: sequence, class, salt form, naming, and its regulatory status on a given date. Never what it does in a person.14 pieces
Nothing here is medical advice. Everything on this site is supplied for laboratory research use only.