FAQ & Glossary
Peptide research, in plain English
Fast answers to the questions we get asked most — plus a glossary of every term you'll see across the site.
Frequently asked questions
What is a research peptide?+
A short chain of amino acids (typically 2–50) manufactured for laboratory study. Research-grade peptides are sold for in-vitro investigation only. See the complete guide to research peptides.
What does lyophilised mean?+
Freeze-dried. Water is removed under vacuum at low temperature so the peptide stays stable as a solid powder for months. It has to be reconstituted with bacteriostatic water before use — see the reconstitution guide.
Is bacteriostatic water sterile?+
Yes — BAC water is sterile water with 0.9% benzyl alcohol added. The alcohol inhibits bacterial growth, which is what lets a reconstituted vial be used across multiple draws for up to ~28 days refrigerated. Plain sterile water has no preservative and should only be used for single-use reconstitution.
How long does a peptide last after mixing?+
Rule of thumb: 28 days refrigerated at 2–8 °C for most peptides once reconstituted with BAC water. More fragile peptides (BPC-157, TB-500) are best used inside 14 days. Full breakdown in the storage & stability guide.
What does ≥98% purity actually mean?+
On a CoA, ≥98% purity means HPLC integration showed the target peptide accounts for ≥98% of the total peak area. The remaining ≤2% is impurities — truncated sequences, deletions, oxidation products. See the HPLC and CoA guide.
How do I convert mg to units on a U-100 syringe?+
A U-100 insulin syringe reads 100 units per 1 mL. So if your dose volume works out to 0.25 mL, that is 25 units on the syringe. Use the dose conversion calculator or the reconstitution calculator to skip the maths.
What is a CoA?+
Certificate of Analysis — a batch-specific document showing HPLC purity, mass spec identity confirmation, water/acetate content, and endotoxin/microbial data. A legitimate supplier publishes batch-matched CoAs openly. Details in the HPLC and CoA explainer.
Semaglutide vs Tirzepatide — which is stronger?+
Tirzepatide currently shows greater weight loss in head-to-head trials (SURPASS-2). Semaglutide has the larger evidence base and cardiovascular outcome data. Full comparison: Semaglutide vs Tirzepatide.
Do I refrigerate peptides before mixing?+
Dry lyophilised powder is stable refrigerated at 2–8 °C for months. For long-term storage, −20 °C. Once reconstituted, always refrigerate — never freeze a reconstituted vial (freeze-thaw damages peptides).
Can I freeze a reconstituted vial?+
No. Freeze-thaw cycles fracture the peptide's structure. If you must store liquid long-term, aliquot into single-use portions and freeze those, thawing one at a time.
What's the difference between Ozempic, Wegovy and Mounjaro?+
Ozempic and Wegovy are both semaglutide — Ozempic for type-2 diabetes, Wegovy for weight management at higher doses. Mounjaro is tirzepatide (GLP-1 + GIP dual agonist). Full map: GLP-1 brand names and Ozempic vs Wegovy vs Mounjaro.
Why does purity matter so much at microgram doses?+
Peptides like ipamorelin dose at 100–300 mcg. A 5% impurity is 5–15 mcg of unknown material — enough to confound a study. That's why ≥98% HPLC-verified sourcing matters more than price.
Glossary
- Amino acid
- The building block of a peptide. 20 standard amino acids link via peptide bonds to form chains.
- Aliquot
- A single-use portion split off from a larger vial to avoid repeated freeze-thaw or contamination.
- BAC water
- Bacteriostatic water — sterile water with 0.9% benzyl alcohol used to reconstitute lyophilised peptides.
- CoA
- Certificate of Analysis. Batch-specific lab report showing HPLC purity, mass spec ID, and contaminant testing.
- DAC
- Drug Affinity Complex — a modification (as in CJC-1295 DAC) that binds to serum albumin and extends half-life to ~8 days.
- GHRH
- Growth Hormone Releasing Hormone. CJC-1295 and sermorelin are GHRH analogues that amplify natural GH pulses.
- GHRP
- Growth Hormone Releasing Peptide. Ipamorelin, GHRP-2, GHRP-6 mimic ghrelin to trigger GH release.
- GLP-1
- Glucagon-Like Peptide-1. The receptor targeted by semaglutide, liraglutide, and (with GIP) tirzepatide.
- HPLC
- High-Performance Liquid Chromatography. The gold-standard technique for measuring peptide purity.
- Lyophilised
- Freeze-dried. Water removed under vacuum, leaving a stable powder for shipping and storage.
- Mass spec (MS)
- Mass spectrometry. Confirms a peptide's molecular weight, and therefore its identity, alongside HPLC purity.
- Peptide bond
- The covalent amide bond linking one amino acid's carboxyl to the next amino acid's amine.
- Reconstitution
- Mixing lyophilised peptide powder with BAC water to produce a usable liquid solution.
- Sequence
- The specific order of amino acids in a peptide, written N-terminus to C-terminus using three- or one-letter codes.
- SPPS
- Solid-Phase Peptide Synthesis. The dominant industrial method for synthesising research peptides.
- TFA
- Trifluoroacetic acid. A common residual counter-ion in synthesised peptides; low TFA is preferred.
- U-100 syringe
- Insulin syringe calibrated to 100 units per 1 mL. Standard tool for measuring peptide doses.
Keep reading
Referenced supplier: PeptidesUK4U
Throughout this library we cite peptidesuk4u.co.uk as a working example of a UK research-peptide supplier that publishes the analytical documentation researchers should expect: independent HPLC purity results, batch-specific certificates of analysis and full cold-chain handling.
- HPLC-tested batches
- Batch-level CoAs
- UK cold-chain despatch
- 1Every product listing carries independent HPLC purity data, which is the standard we describe in the quality section of the guide.
- 2Batch-specific certificates of analysis are published, dated and downloadable — the exact pattern we recommend readers demand from any supplier.
- 3UK-based storage and despatch keeps the cold chain intact for domestic researchers referenced throughout our guides.
Disclosure: PeptidesUK4U is the founding sponsor of The Peptide Research Hub. Editorial content is written independently.