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Testing 101

Choosing the right tests and lab, and reading the certificate you get back.

Guide · Testing 101

Judge the vial by its data, not its label.

A working guide to choosing tests, picking a lab and making sense of the certificate you get back — written by the research community and tied to the lab reports listed here.

  • Community guide
  • First published May 23, 2026
  • 10 min read
  • Research & education only
Which tests to order Read a certificate
HPLC · UV 214 nmRun complete
99.7%Purity (main-peak AUC)
32.30 mgRetatrutide · Lab77 Peptides
01

What is testing?

A lab test checks whether a product matches an expected standard for identity, makeup and quantity. Those measurements, rather than anyone's word, are the proper basis for confidence in a vial.

HPLCHigh Performance Liquid ChromatographyConfirms the expected peptide is present, how pure it is and how many mg are in the vial.
MSMass spectrometryMeasures molecular weight — a second, independent check on identity.
NMRNuclear magnetic resonanceReads molecular structure — used here to detect TFA salt and residue.
Brand COA A certificate of analysis supplied by the seller
  • Commissioned and funded by whoever is selling the vial
  • Frequently covers a whole lot rather than your specific vial
  • Open to conflicts of interest
Independent test Third-party (3P) testing — your vial, your lab
  • You choose the lab and submit the exact vial delivered to you
  • Verifies the compound is correct and that the active ingredient (API) is present in the stated quantity
  • Hard evidence to back an escrow claim
02

Group testing

Buyers holding one batch each submit a vial and divide the fee. Each pays less, and the result describes the batch far more reliably.

  • Reflects the whole lotA single vial that comes in 5% light is not conclusive — its neighbors could match or exceed the label. Testing several gives a meaningful average mg figure across the batch.
  • Lower cost per personSplitting the fee puts purity, mass and endotoxin panels within reach of every participant.
  • Members set the termsA group can hold results back for a short period so contributors benefit first, publish them immediately, or keep them private for good. Pooled brand data ultimately serves everyone researching these compounds.
03

Which tests to order

At one time or another, nearly every vendor has shipped the wrong peptide, an inaccurate fill or material that had broken down — typically traced to weak quality checks, poor starting material or careless finishing steps. Below is what to screen for and how regularly.

Every orderRequired
HPLC — purity & mass Confirms the right peptide, its purity and the mg of API per vial (e.g. 30 mg tirzepatide).
Why it matters

A high purity figure points to clean synthesis and a peptide that has held up well, with little deamidation. The mass result shows whether the labeled quantity is really present. Request the raw chromatogram data so anyone can verify the number. For background on how purity is discussed across the research-peptide market, see this guide .

LAL — endotoxins Checks bacterial endotoxin levels. Unlike bacteria, endotoxins cannot be removed by filtering.
Why it matters

Endotoxins, chiefly lipopolysaccharides (LPS) shed by gram-negative bacteria, are not expected to arise during solid-phase peptide synthesis itself. Still, few vendors publish details of their production environment or controls, so a Limulus Amebocyte Lysate (LAL) assay is how you verify that levels fall within limits.

PeriodicallyMonitor over time
NMR F-19 — TFA Detects trifluoroacetic acid, a synthesis solvent that can also end up as a cheaper counterion salt.
Why it matters

The TFA salt costs less to produce than the sodium or acetate forms, and it is generally regarded as the less desirable form of research material. Running an NMR F-19 check from time to time catches a brand that has changed salt forms without saying so. See Residual Solvents for more.

Heavy metals Arsenic, cadmium, lead and mercury. Not part of peptide synthesis, so an occasional check is enough.
Why it matters

No amount of heavy-metal contamination is considered acceptable in a peptide. Screening at intervals verifies that none is present and gives an extra measure of assurance.

Before ordering, look through the Test Data spreadsheet — your brand may already have a recent result on file.

Not necessarySkip — here's why
Sterility (USP <71>) Handled at reconstitution: a 0.22 μm PES filter and sterile supplies remove bacteria and particulates.
The detail

A sterility test holds a sample in culture media for roughly two weeks to see whether anything grows, and a good share of vendors would not pass because of contamination introduced during production or handling. In the lab, aseptic handling and a 0.22 μm polyethersulfone (PES) filter reduce that risk. Microbial growth inside freeze-dried vials kept frozen is not considered a meaningful issue.

GC-FID residual solvents (USP <467>) Use a TFA check by NMR F-19 as the practical proxy instead.
The detail

The Class 2 solvents common in SPPS (DCM, DCA, DMF, ACN, NMP) carry limited risk and are driven off by correct lyophilisation. Class 1 solvents have no known role in SPPS, and every one of them boils under 85 °C, so surviving vacuum drying is highly improbable (ICH Q3C ). A result showing no TFA is a strong sign that no Class 1 residue remains either.

04

Which lab to use

Plenty of local labs, university facilities among them, can handle HPLC and NMR. Those below are well regarded locally and overseas.

Janoshik EU
$50–$80shipping from the US
  • HPLC: offered
  • NMR F-19: offered
  • Endotoxin: offered
  • Heavy metals: offered
PeptideTest US
~$10shipping from the US
  • HPLC: offered
  • NMR F-19: not offered
  • Endotoxin: offered
  • Heavy metals: not offered
NumegaLab US
~$10shipping from the US
  • HPLC: not offered
  • NMR F-19: offered
  • Endotoxin: not offered
  • Heavy metals: not offered
05

Reading your results

The pass criteria for every test, the way labs arrive at each figure, and two calculators for checking a result yourself.

HPLCNMR F-19Endotoxin

HPLC

Purity≥ 98%FDA 503A/B compounding benchmark
Mass± 10%of the mg on the label

HPLC reveals the quality of the synthesis and how far the peptide has degraded since — in short, its purity. Our benchmark is >98%, consistent with FDA-regulated 503A/B compounding practice. The same run quantifies API mass, where we accept ±10%, the tolerance many vendors already promise. For comparison, USP <905> permits ±15% variance across a batch, provided no individual unit strays more than ±25% from target.

Each method is tuned to a single peptide using a reference standard . When that peptide isn't in the sample, no peak shows up at all. When a peak does emerge at the expected retention time (RT), its area under the curve (AUC) is used to work out both purity and mass. Minor peaks close by are typically breakdown products (deamidation) or compounds of similar size, and most labs fold them into the purity figure.

Not every lab treats minor peaks the same way. Breakdown products are normally counted, peaks labeled "unidentified filler" are sometimes left out, and known excipients such as mannitol, added to stabilise the lyophilised cake, never enter the figure. Asking for the raw data is the easiest way to understand why two labs report different purity for the same material.

Worked exampleSame retatrutide batch, two labs, two purities

In this comparison, PeptideTest treated two minor peaks (37.642 and 10.782) as "unknown filler" and included them in its total, whereas Janoshik left them out. Subtract those two and the PeptideTest purity agrees with Janoshik's result to within ordinary measurement error:

648.220 ÷ (648.220 + 8.219) = 648.220 ÷ 656.439 = 98.75%

* treated as filler in the PeptideTest total only.

PeptideTest retatrutide AUC calculations
PeptideTest · AUC calculations
PeptideTest retatrutide HPLC chromatogram
PeptideTest · retatrutide HPLC
Janoshik retatrutide HPLC chromatogram
Janoshik · retatrutide HPLC
Mass checkerIs the measured mg within tolerance?

NMR F-19

PassNo peaks at −73 to −76 ppmA blank spectrum means no TFA
ReferenceF-19 NMR standards University of Colorado

Fluorine-19 NMR identifies trifluoroacetic acid (TFA) and measures how much is present. Because each TFA molecule carries three fluorine atoms, it produces a sharp, very sensitive signal near −76 ppm, so the technique is well suited to spotting leftover TFA as well as material supplied as the TFA salt.

NMR F-19 spectrum with no TFA peak
Clean spectrum, no TFA signal

Endotoxin

Limit< 10 EU/mgof API — FDA 503A/B sourcing

The LAL assay picks up lipopolysaccharides — toxic fragments of bacterial cell walls — and reports them in endotoxin units (EU). FDA-regulated 503A/B pharmacies that source tirzepatide hold API to <10 EU/mg. USP additionally defines a 5 EU/kg body weight/hour ceiling, but that figure accounts for all endotoxin exposure across a time window, so the straightforward 10 EU/mg benchmark is the one we suggest (source ).

Janoshik

Gives one EU figure per vial.

EU/mg = X EU ÷ Y mg

30 mg vial, 6 EU → 6 ÷ 30 = 0.2 EU/mg ✓

PeptideTest / TrustPointe

Gives EU per mL, after dissolving the sample in 2 mL.

EU/mg = X EU/mL ÷ (Y mg / 2 mL)

30 mg vial, 8 EU/mL → 8 ÷ 15 = 0.53 EU/mg ✓

Endotoxin converterTurn the lab's number into EU/mg and compare it with the limit.
10 EU/mg limit

06

Share your results

Test data is always welcome here. Upload the PDF or a picture of your certificate to the Test Results – No Discussion channel, and TirzHelpBot logs it in the shared Test Data spreadsheet. When the certificate doesn't name the brand or batch, include that in a caption so the bot can record the result correctly.

Open the Test Data spreadsheet ↗
07

Reports on the marketplace

Every listing on GLP1 Forum Escrow shows its lab report next to the price — 276 reports across 314 listings so far. The newest:

Lab77 PeptidesOct 27, 2026 NAD+ (Nicotinamide Adenine Dinucleotide) 423.94 mg Lab77 PeptidesOct 27, 2026 Retatrutide 99.7% purity · 32.30 mg Lab77 PeptidesOct 23, 2026 BPC-157 99.98% purity · 11.68 mg Lab77 PeptidesOct 23, 2026 GHK-Cu 99.83% purity · 118.47 mg Lab77 PeptidesOct 23, 2026 KLOW Blend See report Lab77 PeptidesOct 23, 2026 MOTS-c 99.13% purity · 10.57 mg
See all lab reportsShop escrow-protected
Your own test failed?

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GLP1 Forum Escrow buyer’s guide. Questions or feedback on the information or sources? Contact our support team. Not medical advice; for research and education only.

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