Every UK Peptides lot is independently tested to 99.99% HPLC-UV purity and confirmed by ESI mass spectrometry at an accredited independent laboratory before release. The signed Certificate of Analysis is linked from the product page. Open it, read it, then decide whether to buy.
RP-HPLC-UV
C18, 0.1% TFA / acetonitrile, 214 nm
ESI-MS
Identity match vs theoretical mass
Two labs
Accredited independent labs
Per-lot CoA
Signed, dated, published in our lab reports library
When an analyst injects a peptide sample into a reverse-phase HPLC column, the detector records a chromatogram, a graph of UV absorbance against retention time. The intended peptide elutes as a single dominant peak. Synthesis impurities (truncated sequences, deletion peptides, oxidation products, capping artefacts) elute as smaller, distinct peaks. The purity figure is the area under the main peak expressed as a percentage of the area under every detected peak.
A figure of 99.99% means that under 2% of the UV-absorbing material in the vial is anything other than the named compound. For most in-vitro research that is enough signal-to-noise to draw clean conclusions. For analytical work where contaminant peaks would interfere with detection, labs typically request a re-test against a higher-resolution method.
For a full walkthrough of the HPLC and mass spectrometry methods, read the guide to verifying peptide purity.
Case study · in-house re-test
In September 2025, a UK in-vitro research group ran two consecutive lots of UK Peptides BPC-157 5mg through their in-house HPLC against a USP reference standard. The first lot returned 99.1% purity, the second 99.4%, against figures of 98.6% and 98.9% printed on the independent certificates. ESI-MS identity matched the theoretical 1,419.55 Da mass on both lots within 0.01%.
"Purity came back slightly above the floor on the CoA. Consistently better than I expect from a sub-£60 vial. Will keep ordering."
Laura H., research scientist, September 2025
View BPC-157 5mg with CoA →Click any product to open the signed third-party Certificate of Analysis for the lot you would receive. No login, no form, no email request.
Metabolic Research
99.99% (HPLC-UV)Retatrutide 20mg
Buy retatrutide peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Skin Health / Anti-Ageing
99.99% HPLCGHK-Cu 100mg
Buy GHK-Cu peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Recovery / Healing
99.99% HPLCBPC-157 5mg
Buy BPC-157 peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Growth Hormone / Recovery
99.99% HPLC (both peptides)CJC-1295 + Ipamorelin 5+5mg
Buy the CJC-1295 + Ipamorelin blend from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Skin / Hormonal Research
99.99% HPLCMT-2 10mg
Buy Melanotan 2 peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Recovery / Healing
99.99% HPLCTB-500 5mg
Buy TB-500 peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Nootropic / Cognitive Research
99.99% HPLCSemax 10mg
Buy Semax peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Mitochondrial / Metabolic Research
99.99% HPLCMOTS-C 10mg
Buy MOTS-C peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Longevity / Metabolic Research
99.99% HPLCNAD+ 500mg
Buy NAD+ from UK stock, sent the same day you order. A freeze-dried coenzyme, 99.99% pure, with the signed lab certificate on this page.
Nootropic / Anxiolytic Research
99.99% HPLCSelank 10mg
Buy Selank peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Skin / Anti-Ageing Blend
99.99% HPLC (all components)GLOW 70mg
Buy GLOW peptide blend from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Skin / Anti-Ageing Blend
99.99% HPLC (all components)KLOW 80mg
Buy KLOW peptide blend from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Antioxidant / Skin Research
99.99% HPLCGlutathione 1500mg
Buy glutathione peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Sleep / Neuropeptide Research
99.99% HPLCDSIP 5mg
Buy DSIP peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Growth Factor Research
99.99% HPLCIGF-1 LR3 1mg
Buy IGF-1 LR3 from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
Anti-Inflammatory Research
99.99% HPLCKPV 10mg
Buy KPV peptide from UK stock, sent the same day you order. 99.99% pure, with the signed lab certificate on this page.
| Criterion | UK Peptides | Typical grey-market UK source |
|---|---|---|
| HPLC purity floor | 99.99%, every lot, before release | Claimed in marketing, rarely verified |
| CoA source | Independent lab | In-house template, often unsigned |
| CoA lot-matching | Lot on vial = lot on CoA = lot on invoice | Generic CoA recycled across batches |
| Identity confirmation | ESI-MS on every lot | Often omitted entirely |
| UK business address | Named UK trader, Manchester despatch | PO box or no address at all |
| Dispatch speed | Same day on every order, no cut-off | 1–3 working day handling |
In the research-peptide market, 'high purity' is generally accepted to mean 99.99% by HPLC-UV at 214 nm against impurity-resolved peaks. UK Peptides applies a strict 99.99% floor on every lot, verified by an independent analytical laboratory before release. Anything below the threshold is rejected and destroyed. Never relabelled, never discounted, never dispatched.
Purity is quantified by reverse-phase High-Performance Liquid Chromatography with UV detection (RP-HPLC-UV). The peptide is separated on a C18 column under a TFA / acetonitrile gradient and the area under the main peak is expressed as a percentage of the total area under all detected peaks. A second method, ESI mass spectrometry, confirms the identity of the main peak matches the theoretical mass of the named peptide.
99.99% is the de facto floor for laboratory-grade research peptides because residual synthesis impurities (truncated sequences, deletion peptides, oxidation products) are extremely difficult to eliminate below 1–2% without further preparative chromatography. Material at ≥99% exists but typically commands a 30–50% price premium without a meaningful effect size in most in-vitro work. 99.99% is the price/quality sweet spot used by serious UK research labs.
Read the CoA. A genuine CoA is signed by a named analyst at a named external laboratory, dated, lot-numbered, and includes the HPLC method (column, mobile phase, gradient) plus a printed chromatogram. If any of those are missing, the purity figure on the front of the document is not verifiable. Every UK Peptides product page links the signed CoA directly.
Yes. Take a small sample of any lot to an external analytical laboratory (an independent laboratory) and request HPLC-UV plus ESI-MS. Multiple UK research labs have done exactly this. See the Retatrutide case study below. Independent re-test figures consistently fall within standard analytical tolerance of the figure on the supplied CoA.
Higher purity reduces analytical noise and improves experimental reproducibility, but it is not the same as potency. A 99% lot and a 98% lot of the same peptide will behave identically in most in-vitro assays. The difference appears in highly sensitive analytical work where contaminant peaks would interfere with detection. Our current lots measure 99.99%.
Next step
Browse the catalogue, open a CoA, or read the full methodology behind every UK Peptides lot.