peptide quality FAQ

Don't. Once reconstituted with bacteriostatic water, peptides degrade through oxidation, aggregation, and microbial contamination even under refrigeration. Lyophilized peptides stored at −20°C remain stable for 12–24 months, but reconstituted solutions lose potency after 28 days regardless of storage conditions. Prepare only the volume needed for immediate experiments and keep the remaining powder frozen.

Contact the supplier immediately and request a replacement batch or refund. A peptide below 98% purity contains sufficient impurities to compromise experimental reproducibility, and using it means any resulting data will be unreliable. Reputable suppliers replace out-of-spec batches at no cost. Resistance to replacement is a red flag signaling the purity issue isn't isolated to one batch.

Request MS data before using the peptide. HPLC verifies purity but not sequence accuracy. A peptide can show 98% purity on HPLC while containing the wrong amino acid sequence. Mass spectrometry is the only method that confirms molecular weight matches the expected structure. Suppliers who refuse to provide MS data are either not testing it or hiding failed results.

Discard immediately; cloudiness indicates peptide aggregation or bacterial contamination, both of which compromise results. Aggregation occurs when peptides clump into insoluble complexes that cannot bind receptors, effectively removing active compound from solution without changing the measured concentration. Bacterial growth introduces endotoxins that trigger inflammatory responses in cell culture or animal models, confounding metabolic measurements. Never attempt to salvage cloudy peptide solution by filtering or re-dissolving. The molecular damage is done. Prevent cloudiness by using sterile technique during reconstitution, storing at proper temperature, and limiting air exposure by minimizing needle punctures through the vial stopper.

Contact the supplier immediately with photographic documentation and request batch replacement. Lyophilized IGF-1 LR3 can tolerate brief ambient temperature exposure (up to 72 hours at <25°C), but you cannot verify exposure duration during shipping. Request temperature log data if the supplier uses monitored shipping—any excursion above 30°C or total ambient exposure exceeding 96 hours likely compromised peptide stability. Suppliers refusing replacement for documented temperature failures are not operating at research-grade standards.

Refrigerate immediately but do not use for critical experiments until you contact the supplier for guidance. Most peptides tolerate brief temperature excursions (under 2 hours at room temperature) without catastrophic degradation, but extended exposure above 8°C causes progressive loss of bioactivity that cannot be reversed. Request a temperature log if the supplier uses monitored shipping; if the vial spent more than 6 hours above 15°C, request a replacement. The supplier should replace compromised shipments at no charge. If they refuse, that's a signal to source elsewhere. For studies already in progress, consider ordering a fresh vial and running a parallel dose-response comparison to quantify any activity difference; if the warm-shipped vial shows reduced potency, discard it and do not use the data generated from it.

Verify that the supplier maintains retained samples from every batch for minimum two years and can provide comparative purity data across sequential batches. Request a formal quotation covering projected volumes with pricing stability and guaranteed availability. For longitudinal research, you need assurance that peptides purchased in year three match the validated batch from year one. Some suppliers offer custom synthesis runs for large research programs, ensuring that all peptide used throughout the study comes from a single master batch, eliminating batch-to-batch variability entirely.

This is a critical documentation failure. Do not use the peptide until you receive a batch-matched COA. Generic certificates mean the supplier is not testing every batch individually, which creates risk that your specific vial contains deletion sequences, oxidation products, or contamination not reflected in the provided data. A batch-matched COA is not a premium service—it's a minimum standard for research-grade peptides. If the supplier cannot provide it, they're not maintaining pharmaceutical-grade documentation practices.

Request the supplier's business license, 503B registration certificate (if applicable), and liability insurance documentation. Real Peptides maintains a vendor qualification package specifically for institutional procurement departments, including FDA registration verification, CGMP compliance attestation, and product liability coverage confirmation. Most research institutions have formal vendor qualification checklists; share that checklist with your supplier before placing the order to confirm they can provide all required documentation. If the supplier cannot or will not provide regulatory documentation, that's an immediate disqualifier for institutional research use. Alternative vendors exist that meet compliance standards without evasion.

This indicates batch-to-batch variability, which is the most common failure mode for mid-tier suppliers. Request retained sample testing comparing the two batches—a professional supplier can provide comparative HPLC and MS data showing whether purity or sequence fidelity differed. If the supplier cannot provide this data, switch to a vendor offering small-batch synthesis with verified consistency. Batch variability is unacceptable in dose-response research, receptor binding studies, or any protocol requiring reproducibility across multiple experimental runs.