Research notes.
How we test. Why thresholds matter. What UK researchers should look for in their supplier.
Written by the Alphex team for laboratories buying research peptides in the UK: peptide purity and how HPLC measures it, how to read a Certificate of Analysis, storage and reconstitution, UK compliance, and how to compare suppliers. Every note is dated, updated when the method or the law changes, and links to the compounds it applies to. All content concerns laboratory and in-vitro research only.
101 notes, newest first. Every note is dated and reviewed when the method, the catalogue or UK guidance changes.
How Alphex tests every batch: synthesis, RP-HPLC and the COA
The verification pipeline every Alphex research peptide batch passes before vialling: SPPS, RP-HPLC at 220 nm, then the batch-matched COA.
Read the note220 nm or 280 nm: peptide detection wavelengths
Why purity is measured at 220 nm, what 280 nm is actually good for, and how to read a COA reported at an unusual wavelength.
Read the noteBacteriostatic water for peptide reconstitution: when to use it and how
What 0.9% benzyl alcohol bacteriostatic water does, when sterile water or buffer is better, the step-by-step reconstitution method.
Read the noteThe Human Medicines Regulations 2012 and research peptides
The two-limb definition of a medicinal product applied to research peptides, what it means for suppliers and researchers, and common misconceptions.
Read the noteAliquoting peptide stock solutions
Why aliquot, how to size aliquots, which tubes to use, how to label and thaw, and why batch numbers belong on every tube.
Read the noteThymosin beta-4 versus TB-500: protein and fragment
A 43-residue protein and a 7-residue fragment of it, routinely confused. The relationship, the practical differences, and how to tell which you have.
Read the noteThe Alphex purity guarantee and refunds, explained
What is guaranteed, how a purity claim works step by step, what is not covered, and how damaged or compromised vials are handled.
Read the noteBulk and repeat orders for laboratories
Single-batch supply, scheduled dispatch, purchase-order invoicing and documentation packs, how to arrange them, and what we cannot do.
Read the noteRetatrutide, tirzepatide and semaglutide: receptor targets
One, two and three receptors: the shared design, what differs, why the naming confuses, and the analytical and handling consequences.
Read the noteReference standards in peptide HPLC
What a reference standard is, how it is used in a batch test, why it matters for D-amino-acid peptides, and what to look for on a certificate.
Read the notePeptide purity versus potency
Two words used interchangeably that measure different things, why they come apart, what a supplier can honestly promise, and how to diagnose a poor result.
Read the noteHow to calculate peptide concentration: mg/mL and molar
The arithmetic for mg/mL and molar stocks, the two corrections most people forget, worked examples for each catalogue compound, and common mistakes.
Read the noteInternational orders: research peptides from the UK
Where we ship, transit times, customs and import charges, the legal position at the destination, and documentation for institutions abroad.
Read the noteResearch peptide supplier red flags
Twenty red flags grouped by where you meet them: product page, certificate, stock and shipping, company, and guarantee.
Read the noteThe peptide vial: septum, crimp and vacuum seal explained
What the stopper, crimp and internal vacuum do, how to open a vial correctly, and how to spot one whose seal has been compromised.
Read the noteHPLC or UHPLC for peptide analysis?
Same technique, smaller particles: what changes on the chromatogram, what does not, and how to compare purity figures from each.
Read the noteFake peptide COA red flags
Seventeen tells that recur in borrowed, recycled and fabricated certificates, grouped by document, chromatogram, mass spectrum and context.
Read the noteWhat a chromatogram is and how to read one
The features of a genuine HPLC trace, how to read the main and minor peaks, and the tells of a fabricated or borrowed chromatogram.
Read the noteFreeze-thaw cycles and peptide stocks
What each freeze-thaw cycle does to a peptide in solution, how many are tolerable, and the aliquot habit that makes the question go away.
Read the notePeptide molecular weight and molar calculations
Average versus monoisotopic mass, free peptide versus salt, theoretical versus observed, and worked molar calculations for the catalogue.
Read the noteDo research peptides need to be shipped cold?
Why sealed lyophilised peptides ship fine at ambient temperature, why ice packs can make things worse, and what actually matters in transit.
Read the noteChoosing a UK research peptide supplier: the 12-point checklist
Twelve checks UK researchers should run before ordering research peptides from any supplier: stock location, COA policy, lab independence.
Read the noteIpamorelin, GHRP-6 and GHRP-2 compared
Three growth hormone secretagogue receptor ligands: sequences, what the literature reports as differing, and the practical bench differences.
Read the note98% or 99+% purity: what actually changes
Read as impurity fraction the gap is a halving. What sits in that fraction, why 99+% costs more to reach, and when it matters enough to pay for.
Read the notePeptide solubility: water, buffer or a co-solvent?
How to read a sequence for solubility, which solvent to try first, when a buffer or DMSO is justified, and how each catalogue compound behaves.
Read the noteHow Alphex chooses which compounds to list
The five hurdles a compound must clear before listing, why the current six, why some requested compounds are not stocked, and how to influence the list.
Read the noteResearch use only: what it means legally
The phrase is the legal basis of the sale. What it says about the product, what it commits supplier and purchaser to, and how it differs from related labels.
Read the noteNet peptide content versus gross vial weight
A 10 mg vial does not hold 10 mg of peptide. The difference between gross weight, purity and net content, and how to handle it in concentration-critical work.
Read the noteCopper peptides in cosmetic science research
GHK-Cu as a formulation-science model compound: chelation and pH problems, redox and light constraints, and the analytical questions that follow.
Read the noteUK, US or China: research peptide suppliers compared
Where research peptides actually come from and how the three buying routes compare on verification, transit, customs, accountability and landed cost.
Read the noteHow to make a buffer for peptide reconstitution
When water is not enough, which buffers suit which peptides, how to prepare one cleanly, and what to avoid with copper peptides.
Read the noteAre research peptides legal in the UK?
Yes, for laboratory research. Why they are not controlled substances, why they are not medicines, what research use only means.
Read the noteRecord keeping for research peptide purchases
What to record at purchase and at use, why it matters for reproducibility and audit, and a simple system keyed on batch numbers.
Read the noteBPC-157 research peptide UK: sequence, purity, storage and COA
BPC-157 for UK laboratories: sequence, molecular weight and CAS, where it appears in the research literature, storage and reconstitution.
Read the noteWhy UK stock matters: shipping, customs and certificates
What UK-held stock changes about transit, customs, certificates and accountability, and five ways to tell whether a supplier really holds it.
Read the noteWater content and Karl Fischer titration, explained
Why lyophilised peptides are not dry, how Karl Fischer measures the water, when the figure matters, and how to work without it.
Read the noteResearch peptide storage, reconstitution and shelf life: protecting integrity in the lab
How to store lyophilised research peptides, reconstitute them for assay work with bacteriostatic water, and recognise degradation: temperatures.
Read the noteWhat next-day delivery really means
Alphex's cut-off, courier and weekend handling, how to read other suppliers' delivery promises, and why transit time matters for peptides.
Read the noteDeamidation and oxidation in stored peptides
The two reactions behind most slow peptide degradation: the chemistry, which sequences are vulnerable, what accelerates them and how to slow them.
Read the noteResearch peptides and UK advertising rules
Medicines advertising law, the CAP code and platform policies applied to research reagents, and how to read a supplier's marketing as a signal.
Read the noteThe ghrelin receptor GHS-R1a: research background
The receptor behind the growth hormone secretagogue literature: its unusual discovery history, the 1a and 1b variants, and practical points for in-vitro work.
Read the noteThe MHRA and research peptides: what suppliers must not do
What the MHRA does and does not regulate here, the six behaviours that attract enforcement, and what compliant supply looks like.
Read the noteWhat does "99+% HPLC-verified purity" actually tell you?
What an HPLC purity percentage measures, what it leaves out (identity, net peptide content), why 98% and 99+% differ more than they look.
Read the noteSterile water, bacteriostatic water or saline?
Three near-identical vials with different consequences: how they compare as peptide diluents and a decision rule for each situation.
Read the noteCan you freeze reconstituted peptides?
Yes, and for anything not used within weeks you should. What freezing costs, the aliquot routine that avoids freeze-thaw damage, and compound-specific notes.
Read the noteWhat does lyophilised mean for a research peptide?
Freeze-drying explained: why peptides are supplied this way, what else is in the vial besides peptide, and how to handle a lyophilised cake.
Read the noteLipidated peptides: why they behave differently
What a fatty acid chain does to solubility, aggregation, adsorption, chromatography and purification, plus a working protocol for GLP-3 (RT).
Read the noteReading preclinical peptide literature critically
Ten questions to ask of any preclinical paper, where secondary sources go wrong, and what it implies for how you characterise your own material.
Read the noteThird-party versus in-house peptide testing
Three arrangements that all get called tested, why independence matters, and the six questions that separate the real thing from the phrase.
Read the noteAmino acid analysis versus HPLC purity
What AAA measures that HPLC cannot, what it cannot tell you, why it is not on most research peptide COAs, and when to commission it.
Read the noteCan universities and labs buy research peptides in the UK?
Who can purchase, what institutions need from a supplier, purchase orders and VAT, and which approvals apply to the research itself.
Read the noteHow HPLC purity is calculated
From injection to percentage: integration, baseline, thresholds and co-elution, plus the two ways a purity figure can be quietly inflated.
Read the noteHow to reconstitute research peptides: the step-by-step method
The laboratory method for reconstituting lyophilised peptides: choosing the diluent, adding it slowly, why not to shake.
Read the noteVial sizes: 5 mg or 10 mg, and per-mg cost
Why larger vials cost less per mg, how to choose a size for the work in hand, and the trade-off with reconstituted shelf life and batch consistency.
Read the noteAcetate versus TFA salt: why the counter-ion matters
Where the counter-ion comes from, how TFA and acetate differ in net content, pH and cell toxicity, and which salt form Alphex supplies.
Read the noteResearch peptide glossary
A working glossary of the terms on peptide specifications, certificates and listings, from acetate salt to 220 nm, each linked to a fuller note.
Read the noteHow research peptide pricing works
What goes into the price of a vial, how to compare suppliers per mg on landed cost, and what a suspiciously low price usually means.
Read the noteWhy COA batch matching matters
A certificate describes one batch. What matching means in practice, why it is the basis of traceability and any guarantee, and how to check it.
Read the noteHow to read a research peptide COA (and how to spot a fake one)
Most COAs supplied with UK research peptides fail one of four checks. What a genuine Certificate of Analysis contains, and the tells of a fabricated one.
Read the noteSolid-phase peptide synthesis, explained
The SPPS cycle in plain terms, why purity falls with length, and what the method explains about the counter-ions and impurities in your vial.
Read the notePeptide naming: INNs, development codes and trade names
Five naming layers for one molecule, how to move between them with a CAS number, where naming causes real problems, and how to write it in a methods section.
Read the noteActin-binding peptides: cell biology background
The actin cytoskeleton, the beta-thymosins and the LKKTETQ motif, the other proteins in the system, and the in-vitro readouts used to study them.
Read the noteLight-sensitive peptides: which ones and how to handle them
Which residues and structures make a peptide photolabile, where each catalogue compound sits, and the habits that remove the risk.
Read the noteHow Alphex packs and ships research peptides
The picking, checking and packing sequence behind every order, what is in the box, what is deliberately not, and what to check on arrival.
Read the noteUK research peptide compliance: what suppliers and researchers can and cannot do
A plain-English summary of the UK legal position on research peptides: unlicensed substances, the Human Medicines Regulations.
Read the noteWhere to buy research peptides in the UK (2026): how to compare suppliers
A 2026 guide to buying research peptides in the UK: the types of supplier, what separates them, a comparison scorecard.
Read the noteWhat a 1 Da mass tolerance means
Why identity criteria are set at 1 Da, what sits inside that window and what falls outside it, and how to read the numbers on a certificate.
Read the noteAlphex testing partner independence
Who tests Alphex batches, what stake they have, why each element of independence matters, how to check it, and the limits stated plainly.
Read the noteTB-500 research peptide UK: the thymosin beta-4 fragment explained
TB-500 is the Ac-LKKTETQ fragment of thymosin beta-4, not the full protein. Its chemistry, literature, storage.
Read the noteCAS numbers for research peptides
What a CAS number is, the numbers for the Alphex catalogue, what to use them for, their limits, and how to use one as a supplier check.
Read the noteBenzyl alcohol in bacteriostatic water, explained
What the 0.9% preservative does and does not do, when it interferes with assays or HPLC, and why the vial is discarded 28 days after opening.
Read the noteHow to verify a peptide COA with the laboratory
What you need from a certificate, how to contact the issuing laboratory, what it will and will not confirm, and what to do when verification is impossible.
Read the noteHow to store research peptides long term at -20 C
Why -20 C for lyophilised powder, the frost-free freezer problem, how to organise storage, and what to do with a vial stored longer than intended.
Read the noteCommon mistakes first-time peptide buyers make
Twenty mistakes from procurement to first reconstitution, each with the fix, and the short version at the end.
Read the noteHow to recognise peptide degradation
The visual signs worth acting on, the invisible degradation only analysis reveals, and a practical rule for when to discard a peptide stock.
Read the noteStability testing of peptides, explained
How a stability study is structured, what is measured at each time point, what results typically show, and how to run a cut-down version in house.
Read the noteWhat a compliant peptide listing looks like
The seven things a compliant listing contains, the six it leaves out and why, and how to use it as a checklist when reviewing a supplier.
Read the noteControls for peptide experiments
The vehicle, scrambled and concentration controls that make a peptide result interpretable, plus compound-specific controls for copper and lipidated peptides.
Read the noteTen questions to ask a peptide supplier before ordering
The questions that reveal more than any website, what a good answer sounds like, and Alphex's own answers so you can hold us to the same test.
Read the noteHow to spot a drop-shipped peptide supplier
The signals on the website, in the answers to your questions and in the parcel itself that distinguish a stockholder from a storefront.
Read the noteThe Alphex batch numbering system
What a batch is, where the number appears, what it lets you do, and what changes and does not change between batches.
Read the noteMass spectrometry identity for peptides: ESI-MS explained
What electrospray mass spectrometry measures, what agreement proves and does not, how to read a mass discrepancy, and larger-peptide spectra.
Read the notePeptide adsorption and low-binding tubes
Why dilute peptide solutions lose material to tube walls, which compounds are worst affected, and the precautions that prevent it.
Read the noteGHK versus GHK-Cu: free tripeptide and copper complex
Two different reagents sold side by side. What the copper changes about weight, colour, handling and chemistry, and how to be sure which is in the vial.
Read the noteCommon peptide impurities and where they come from
The synthesis, cleavage and storage impurities that appear on a chromatogram, their masses and retention behaviour, and how they are controlled.
Read the noteWhy the Alphex catalogue is small
What it takes to list a compound, why these six, why some requested compounds are not listed, and what a short catalogue gives a laboratory.
Read the notePeptide sequence notation, explained
One-letter and three-letter codes, direction, Ac- and -NH2, D-residues and Aib, fragment ranges, and worked readings from the catalogue.
Read the noteWhat happens when a batch fails
Where failures are caught, what happens to the batch, what it costs, and why a supplier that never fails a batch is telling you something.
Read the noteGHK-Cu copper peptide UK: chemistry, research uses, handling and COA
GHK-Cu for UK laboratories: the copper complex versus free GHK, molecular weight and CAS, the gene-expression literature, light-sensitive storage.
Read the noteIpamorelin research peptide UK: a selective GHS-R ligand for the laboratory
Ipamorelin (NNC 26-0161) for UK researchers: its Aib and D-amino-acid chemistry, receptor pharmacology literature, solubility.
Read the noteBPC-157 versus TB-500: the differences
Two compounds constantly discussed together and rarely distinguished: origin, chemistry, handling, and where each appears in the research literature.
Read the noteGLP-3 (RT) / retatrutide research peptide UK: chemistry, purity and handling
Research-grade retatrutide, listed by Alphex as GLP-3 (RT): the 39-residue lipidated peptide's chemistry, why 99+% purity is hard at this size.
Read the noteHow often should research peptides be retested?
Retest intervals for supplier stock and laboratory stock, what a retest involves, and how ageing batches are handled.
Read the noteHow to request a COA before ordering
How to ask, what you receive, how quickly, what happens if the batch turns over, and how to verify the certificate with the laboratory.
Read the noteD-amino acids and unnatural residues in peptides
Why D-residues, Aib and naphthylalanine are used, what they change, and the verification problem they create for mass spectrometry.
Read the noteEndotoxin testing and research peptides
What endotoxin is, how LAL measures it, when it matters for laboratory work, and why Alphex does not put an endotoxin line on its COA.
Read the noteHow long do reconstituted peptides last in the fridge?
Working shelf lives for peptide stocks: lyophilised, refrigerated in bacteriostatic water, frozen aliquots, and how to tell when a stock is past use.
Read the noteDisposal of research peptides as laboratory waste
How peptides, stocks, sharps and empty vials leave the laboratory, what to record, and the two things not to do with unused material.
Read the noteReference standard or certified reference material?
Two terms used interchangeably that are not the same. What each involves, why the distinction matters on a COA, and which applies to peptide testing.
Read the noteWhy Alphex runs out of stock
What sold out means here, why we accept running out rather than drop-shipping, how long the batch pipeline takes, and how notifications work.
Read the noteImporting research peptides into the UK: customs explained
The legal position on import, what happens at the border, import VAT and courier fees, the transit problem, and how to reduce the risk.
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