--- title: "Peptide Glossary: Lab and Handling Terms | Primara Labs" url: https://www.primaralabs.com/resources/peptide-glossary source: Primara Labs, markdown mirror of the HTML page --- # Peptide glossary The laboratory and handling terms that appear on peptide product pages, labels and lab reports, each defined in a sentence or two and linked to the guide that covers it in full. By Primara Labs team ยท Updated 24 September 2026 Bacteriostatic water (BAC water) Sterile water for injection with benzyl alcohol added as a preservative that holds back bacterial growth. It comes in a multiple-dose container, so it can be drawn from more than once.\[2\]See: [Bacteriostatic water vs sterile water](https://www.primaralabs.com/resources/bacteriostatic-water-vs-sterile-water) Batch One production run of a compound, identified by the batch number printed on the vial label. A laboratory report names the batch it covers and says nothing about any other batch.See: [Reading your vial label](https://www.primaralabs.com/blog/reading-your-vial-label) COA (certificate of analysis) A document listing the tests run on a sample and the results. It is only as useful as its scope: read which tests it covers, which batch, and whether the laboratory's own record matches it.See: [How to read a Janoshik report](https://www.primaralabs.com/resources/reading-a-janoshik-report) Concentration How much compound each millilitre of solution holds after reconstitution: milligrams in the vial divided by millilitres of water added. 5 mg in 2 mL gives 2.5 mg/mL.See: [Reconstitution calculator](https://www.primaralabs.com/tools/peptide-calculator) Endotoxin A fragment of the outer wall of certain bacteria, measured with the bacterial endotoxins test and reported in endotoxin units (EU). An endotoxin result says nothing about identity, amount or purity.\[5\]See: [Reading an endotoxin result](https://www.primaralabs.com/coa#endotoxin) HPLC (high performance liquid chromatography) A method that pushes a dissolved sample through a packed column so its components separate. The time a peak emerges identifies it against a reference standard, and the peak's area gives the quantity. Purity figures on peptide reports usually come from HPLC.\[6\] Identity test A test that checks the substance in the vial is the compound named, most directly by measuring the molecule's mass with mass spectrometry.\[6\]See: [Purity versus identity testing](https://www.primaralabs.com/answers/purity-vs-identity-testing) Lyophilized Freeze-dried. The solution is frozen and put under vacuum so the ice turns straight to vapour, leaving a dry powder or cake. Products are made this way because they are unstable in solution.\[1\] MS (mass spectrometry) A method that measures the mass of molecules. Used as a detector after HPLC (LC-MS), it gives mass information that identifies the compound, which a retention time alone does not.\[6\] Reconstitution Returning a lyophilized powder to solution by adding a measured volume of diluent, usually bacteriostatic water. The volume added sets the concentration.See: [How to reconstitute a peptide vial](https://www.primaralabs.com/resources/how-to-reconstitute-a-peptide-vial) Sterile water for injection Water for injection with no preservative, packaged in single-dose vials. The label says to discard what is left after the first withdrawal.\[3\] U-100 The scale on a standard insulin syringe: 100 units to 1 mL, so one unit is 0.01 mL. It describes volume on the barrel, not an amount of any compound.\[4\]See: [How to read a U-100 insulin syringe](https://www.primaralabs.com/resources/how-to-read-a-u-100-insulin-syringe) Supplied for laboratory research use only. Not for human consumption. Nothing on this page is medical advice, and nothing here suggests an amount, a frequency or a protocol for any compound. ## Go deeper - [Lyophilized peptides: what to look for, on philippinespeptides.com](https://www.philippinespeptides.com/faq/lyophilized-peptides) ## Related products - [BAC Water 3ml](https://www.primaralabs.com/marketplace/bac-water-3ml) - [Retatrutide 15mg](https://www.primaralabs.com/marketplace/retatrutide) ## Sources 1. [Lyophilization of Parenteral (7/93), inspection guide](https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/inspection-guides/lyophilization-parenteral-793). US Food and Drug Administration. Cited for what freeze-drying is and why products are made that way. Checked 24 September 2026. 2. [Bacteriostatic Water for Injection, USP: prescribing information (Hospira)](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=87d6e9dc-fe3b-4593-ac9a-d7493d1959c7). DailyMed, US National Library of Medicine. Cited for benzyl alcohol content, multiple-dose container, label storage and warnings. Checked 24 September 2026. 3. [Sterile Water for Injection, USP: prescribing information (American Regent)](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=78b35864-4bbc-4759-a5c1-7e4f25e22932). DailyMed, US National Library of Medicine. Cited for single-dose vial, no preservative, discard the unused portion. Checked 24 September 2026. 4. [Giving an insulin injection](https://medlineplus.gov/ency/patientinstructions/000660.htm). MedlinePlus, US National Library of Medicine. Cited for U-100 means 100 units in 1 mL; some 1 mL barrels mark every unit. Checked 24 September 2026. 5. [Pyrogen and Endotoxins Testing: Questions and Answers, guidance for industry](https://www.fda.gov/regulatory-information/search-fda-guidance-documents/pyrogen-and-endotoxins-testing-questions-and-answers). US Food and Drug Administration. Cited for the bacterial endotoxins test and its gel clot, photometric and kinetic methods. Checked 24 September 2026. 6. [High Performance Liquid Chromatography (HPLC) Basics](https://www.ssi.shimadzu.com/service-support/faq/liquid-chromatography/knowledge-base/hplc-basics/index.html). Shimadzu Scientific Instruments (instrument manufacturer). Cited for how HPLC separates, identifies against a standard and quantifies; mass spectrometric detection. Checked 24 September 2026.