The molecule we identify.
The assays we run on Tirzepatide.
The failure modes we see most.
- 01Methionine oxidation. Tirzepatide contains methionine, which oxidizes during storage. The +16 Da variant co-elutes near the main peak; LC-MS will catch it, HPLC purity alone may not.
- 02Sequence truncations. A 39-residue peptide has many more opportunities for incomplete coupling than a shorter sequence. Look for related-impurity peaks at RT - 0.4 to RT - 1.2 min of the main peak.
- 03NPC drift across vials. Tirzepatide formulations vary by lyophilization protocol. Two vials from the same labeled batch can vary 8-12 % in NPC if water-of-hydration isn't controlled.
- 04TFA above 3 %. Specific to Tirzepatide because the longer sequence requires more synthesis cycles, leaving more counter-ion to clean up post-synthesis.
- 05Endotoxin contamination during reconstitution. The bacteriostatic water used to reconstitute frequently fails its own LAL spec. Test the reconstituted vial when possible.
Transparent panels for Tirzepatide.
Identity (LC-MS) + HPLC purity % + Net Peptide Content. Baseline COA — public + accession #.
- Identity (LC-MS/MS)
- HPLC purity % + impurity peaks
- Net Peptide Content
- Public COA + accession #
- 5-7 day turnaround
COA Essentials plus USP <85> endotoxin (LAL) and USP <71> sterility. The injectable-grade package.
- Everything in COA Essentials
- Endotoxin (LAL) USP <85>
- Sterility USP <71>
- Conformity Testing +1
- 5-7 day turnaround
Plus heavy metals (ICP-MS, USP <232>) and USP <61> bioburden. The full vendor / compounding COA.
- Everything in Injectable Safety
- Heavy metals (ICP-MS) USP <232>
- Bioburden (USP <61>)
- Conformity Testing +1
- 5-7 day turnaround
Tirzepatide testing — the common questions.
Why does Tirzepatide need methionine-oxidation screening?+
Tirzepatide contains a methionine residue that oxidizes during storage, especially after reconstitution. The oxidized variant differs by +16 Da and co-elutes near the main peak in HPLC, so it inflates apparent purity if you don't run MS alongside. Every peptide panel includes LC-MS identity — COA Essentials ($289), Injectable Safety ($599), and Vendor Full QC ($849) all catch it. If you're verifying long-term stability or post-reconstitution material, LC-MS is the assay that flags the oxidized variant.
What's a reasonable Net Peptide Content for Tirzepatide?+
Industry-typical NPC for lyophilized Tirzepatide runs 78-88 %. Below 75 % usually indicates excessive counter-ion or residual water. Above 90 % is rare for TFA-salt material and may indicate the vendor is reporting gross peptide salt rather than true active mass. Net Peptide Content is what tells you whether a vial labeled '10 mg' contains 8.5 mg of active or 6.8 mg.
Do you confirm the dual GIP / GLP-1 agonism by assay?+
No — we don't run receptor-binding bioassays. We confirm identity by LC-MS (matching the published Tirzepatide monoisotopic mass of 4813.45 Da) and purity by HPLC. Receptor-binding bioassays are a separate workflow that requires cell-based platforms; we don't currently offer them. For research-use applications, the analytical identity + purity + NPC stack is what brands and clinicians ask for.
Is testing different for Mounjaro / Zepbound vs research material?+
Pharmaceutical-grade Mounjaro and Zepbound are produced under Eli Lilly's regulated supply chain and we test them on the same bench using the same methods. The COA looks identical — same HPLC purity %, same LC-MS m/z verification, same NPC. Research-grade material from compounding pharmacies or research peptide vendors typically has wider variability in purity and NPC, which is why an independent third-party test matters more for that material.
How long does the full Tirzepatide panel take?+
COA Essentials ($289): 5-7 business days. Injectable Safety ($599): 5-7 days. Vendor Full QC ($849): 5-7 days — the added safety assays run in parallel with the base workup, so the full panel still lands in the same window. Expedited turnaround (48-72 hours) on the COA Essentials panel is available at +50 %.
Can you test Tirzepatide compounded combinations (e.g. with cyanocobalamin)?+
Yes. Compounded Tirzepatide + B12 (cyanocobalamin) is a common research formulation. We can quantify both actives on the same HPLC run with appropriate wavelength switching (Tirzepatide at 214 nm, B12 at 361 nm). Add 'Karl Fischer water content' if the formulation includes preservatives — preservative breakdown is the most common stability issue for combo products.
Other dual gip / glp-1 receptor agonist testing —
Single-agonist GLP-1 (Ozempic / Wegovy active). Same HPLC + MS + NPC + TFA panel.
Triple GLP-1 / GIP / glucagon agonist in clinical development. Same instrument stack.
Full peptide menu — all bundles, panels, and compounds we cover beyond GLP-1.
Verify the vial. Sign the COA.
HPLC purity, LC-MS identity, NPC, TFA, endotoxin, sterility — Houston bench, public COA, transparent pricing.