coa peptide FAQ

Yes, but adjust your dosing. A 96.8% pure peptide means 3.2% of the powder is impurities or inactive material. If you ordered 5mg and dose based on 100% purity, you're actually administering 4.84mg of active peptide per vial. For single-dose protocols, this difference is negligible. For multi-week studies where cumulative dose matters, recalculate based on the actual purity. Multiply your target dose by 0.968 to determine the correct administration amount. Research-grade protocols prefer ≥98% specifically to avoid this math.

Walk away or request it before using the peptide. HPLC without MS is insufficient for sequence confirmation. You have no way to know if the primary peak is the correct peptide or a closely related compound with similar hydrophobicity. Some suppliers provide HPLC-only COAs for cost reasons, but this is a red flag for research applications. Real Peptides includes both HPLC and MS verification on every COA because sequence accuracy is non-negotiable for reproducible experiments.

Verify your peptide's pH stability range. Some peptides tolerate 5.0–7.0 (the full BAC water specification), while others require tighter control. If your protocol specifies 6.0–7.0 and the COA shows 5.2, the water is out of spec for your application even though it meets general BAC water standards. In this scenario, source water with confirmed pH ≥6.0 or contact the peptide manufacturer for pH compatibility clarification. Tirzepatide and semaglutide both tolerate 5.0–7.0. But CJC-1295 and certain acetate-salt peptides degrade rapidly below pH 6.0.

Request a detailed impurity analysis from the supplier. High purity with multiple secondary peaks suggests incomplete purification where several low-abundance byproducts remain. If the supplier cannot identify the impurities or confirm they are inert (e.g., residual TFA, salts), reject the batch. Structurally similar deletion sequences or oxidized variants can compete for receptor binding and confound dose-response curves.

A 25% deviation in lysine content suggests either a deletion sequence (one lysine removed during synthesis) or incomplete hydrolysis during AAA. Request the supplier re-run the AAA or provide an independent third-party analysis. If the lysine deficiency is confirmed, the peptide sequence is incorrect and the batch cannot be used. Lysine residues are often critical for solubility and receptor interaction.

You're looking at oxidation, most likely of methionine or cysteine residues. Add 16 Da per oxidized residue. This is common if the peptide wasn't stored under nitrogen or argon during lyophilization, or if it was exposed to air during reconstitution. Oxidized peptides lose biological activity. Methionine oxidation can reduce receptor binding affinity by 50–90% depending on the residue's position in the sequence. If oxidation exceeds 5% of total peptide mass (check the HPLC for secondary peaks at slightly later retention times), request a replacement batch or use a reducing agent during reconstitution to reverse some oxidation.

Request a re-analysis with a fresh column or a different solvent gradient. A drifting baseline means the purity calculation is unreliable. Impurities may be hidden under the drift, artificially inflating the target peak percentage. If the supplier cannot or will not rerun the analysis, consider the peptide suspect and do not use it in experiments where purity directly affects the outcome (dose-response curves, receptor binding assays, mechanistic studies). Baseline drift of more than 5 mAU (milliabsorbance units) over the chromatogram duration is a red flag.

Reject the vial. A 2-Dalton discrepancy suggests either a synthesis error (wrong amino acid incorporated) or contamination with a structurally similar peptide. Mass spec tolerance for research-grade peptides is ±1 Da maximum. Beyond that, you're not using the compound you think you are. This isn't a purity issue (HPLC might still show 99%). It's an identity failure. Contact the supplier for a replacement batch with correct MS confirmation before proceeding.

This indicates methionine oxidation, which is reversible under some conditions but may affect peptide stability and bioactivity. Contact the supplier to confirm whether the peptide was synthesized with oxidation or if it occurred during storage. Methionine-containing peptides should be stored under argon or nitrogen to prevent further oxidation. If the oxidation occurred before shipping, request a replacement batch synthesized and stored under inert atmosphere.

Trust the COA, not the label. Labels are printed in advance and applied during packaging. The COA is generated after testing the actual batch. If there's a mismatch, the COA value is correct. This happens when production lots are split into different fill sizes but the wrong labels are applied. Reconstitute based on the COA concentration to avoid 2× overdosing. We've seen this exact error cause researchers to double their intended dose for an entire study phase.

The peptide identity is correct, but impurity levels are too high for reliable research. MS confirms you received survodutide, not a different compound, but 8% impurities mean nearly one in twelve molecules is something else. Enough to skew receptor activation studies, particularly at low concentrations where impurities represent a larger fraction of the active dose. Use this batch only for preliminary method development, not for data collection. Order a higher-purity replacement for actual experimental work.

Do not use it until you obtain endotoxin data. Contact the supplier and request LAL (Limulus Amebocyte Lysate) testing for your specific batch. If they cannot provide it, either send a sample to a third-party testing lab for independent LAL analysis (cost: approximately 150–300 USD per sample, turnaround 5–7 days) or accept that the peptide is unsuitable for cell-based work. Endotoxin contamination as low as 0.5 EU/mg can alter cytokine expression, immune cell activation, and apoptosis rates. Rendering your results uninterpretable.

Reject the batch. The purity percentage is calculated from peak areas, but if multiple peaks exceed 10% relative intensity, you're working with a mixture where the 'impurities' represent significant contamination with structurally similar peptides. Likely deletion sequences or oxidized variants. These won't separate cleanly in your assay and will produce inconsistent dose-response data. Request a replacement batch with a chromatogram showing one dominant peak above 95% and all other peaks below 3%.

Temperature excursions during shipping can denature lyophilized peptides, especially those with disulfide bonds or oxidation-prone residues. If the vial wasn't shipped on dry ice or with cold packs and the shipping time exceeded 48 hours, the peptide may have partially degraded. Run your own HPLC or request the supplier provide post-shipping stability data. Some peptides tolerate brief temperature excursions (24–48 hours at 25°C), but others. Particularly those with multiple cysteine residues or unprotected methionine. Show measurable purity loss after just 72 hours above 8°C.

The peptide is correctly synthesised but incompletely purified. The 8% impurity consists of structurally similar peptides (deletion sequences, protected amino acids, or truncated forms) that don't affect molecular weight enough to shift the MS base peak but do appear as separate HPLC peaks. For some applications (screening assays, preliminary dose-finding), 92% is acceptable. For quantitative work (IC50 determination, structural studies, pharmacokinetics), it's not. The impurities introduce variability you can't correct for. Use it only if you can verify the impurities are biologically inert in your specific assay.

Request the chromatogram and examine the peak shape. If the 96% purity reflects a single dominant peak with minimal shoulders, it's usable for non-critical applications. If the chromatogram shows multiple large secondary peaks, the remaining 4% is a mixture of deletion sequences or aggregates that could interfere with receptor binding assays or dose-response studies. For competitive binding studies or structure-activity work, 96% purity introduces too much uncertainty. Request a re-synthesis or choose a supplier with ≥98% purity standards.

A 3 Da shift indicates a synthesis error. Likely an amino acid substitution or an extra acetyl group from incomplete deprotection during synthesis. This is not AOD-9604. The peptide may have similar chromatographic behaviour (explaining why HPLC purity looks acceptable), but the biological activity will differ from the published literature on AOD-9604. Reject the batch and request mass spectrometry confirmation before accepting a replacement.

You're working with 22% excipients. Likely residual acetate salts or TFA (trifluoroacetic acid) from synthesis. If the vial is labelled as 5mg AOD-9604, the actual peptide mass is approximately 3.9mg. Reconstituting as if the full 5mg is active peptide will underdose every experiment by roughly 20%. Recalculate all reconstitution volumes based on the reported peptide content percentage, or request a batch with ≥85% content to simplify dosing math.

Do not use the water. Pending results mean testing is incomplete. Endotoxin testing via LAL assay takes 24–48 hours under standard protocols, so 'pending' status indicates either the batch was released prematurely or testing hasn't been performed. Contact the supplier for completed results before reconstituting any peptide. Our team has seen researchers use 'pending' water assuming it would retroactively pass. In three documented cases, final results exceeded 0.5 EU/mL, meaning all reconstituted peptides from those batches were contaminated.

Bacteriostatic water has a shelf life. Typically 28 days after opening and up to 24 months unopened when stored at 20–25°C. If the COA is more than 12 months old, verify the vial's expiration date printed on the label. An old COA with a current expiration date is acceptable. The COA documents the batch at manufacturing, not at your purchase date. If the expiration date is missing or illegible, contact the supplier for confirmation. Expired bacteriostatic water loses preservative efficacy. Benzyl alcohol concentration drops below 0.9% w/v, which allows microbial growth even in a previously sterile vial.