Platform-wide defaults.
Across the Cresten catalog, the same baseline specification applies unless explicitly noted on the individual product page. Catalog peptides are released at ≥99.0 percent HPLC purity as the platform specification, with batch-by-batch results reported to two decimal places on the certificate. The default salt form is acetate, selected over the industry-standard TFA (trifluoroacetic acid) for compatibility with cell culture and biological assays where TFA exposure is a confounding variable. Net peptide content is quantified per batch via CLND (chemiluminescent nitrogen detector), with the result reported on the COA alongside HPLC purity and total mass. The weight basis is gross weight per industry standard, including the peptide, water of hydration, counter-ion, and trace residual solvents; net peptide content is the separate quantity that buyers running stoichiometrically-precise work should reference.
Variations from these defaults are available on quote: alternate salt forms (TFA, chloride, ammonium), extended-scope analytical panels (endotoxin LAL, full bioburden including TAMC and TYMC, heavy metals classes 1 and 2 per Ph. Eur. 2.4.20, residual solvents, FTIR identity confirmation), and custom vial sizes including bulk packaging up to gram-scale. The bulk-inquiry channel handles all of these.
Salt forms and counter-ion content.
The salt form of a peptide is the counter-ion paired with the peptide’s charged residues during purification. It does not change the peptide sequence. It does change the peptide’s solubility, the percentage of vial mass that is peptide versus counter-ion, and in some cases the compound’s behaviour in cell culture. Most catalog peptide suppliers default to TFA salt because TFA is the standard mobile phase modifier in reverse-phase HPLC purification; TFA-salt peptides are what comes out the bottom of the prep column without further processing. The TFA stays bound to basic residues (lysine, arginine, histidine, free N-terminal amine) at proportions roughly equal to the number of basic residues in the sequence.
For research applications where TFA is itself a known cell-biology variable, salt exchange to acetate, chloride, or ammonium is performed as an additional purification step. Cresten ships acetate-form peptides as the default. The counter-ion content is reported per-batch on the COA. For BPC-157 specifically, the acetate salt-form means roughly 90 to 92 percent of vial mass is peptide; the remainder is acetate counter-ion plus water of hydration. The CLND quantification gives the exact figure for each batch.
Chemistry FAQ.
Pyroglutamyl (pGlu) formation.
When a peptide’s N-terminal residue is glutamine (Gln, Q) or glutamic acid (Glu, E), the residue can spontaneously cyclize to form pyroglutamate (pGlu). The reaction proceeds without enzymatic catalysis, particularly during synthesis, lyophilization, and storage in solution. The resulting pGlu form is structurally distinct from the parent peptide but is biologically active in many cases and is included in HPLC purity reporting rather than treated as an impurity. Eurogentec and other CDMO references describe pGlu as “a normal subset of such peptides.” For BPC-157, the N-terminal residue is glycine, so pGlu formation is not applicable. For peptides where pGlu is a possibility, the LC-MS spectrum on the COA will show the pGlu and parent peptide masses if both are present.
Gross weight versus net peptide content.
A vial labelled “5 mg BPC-157” contains 5 mg of total mass: peptide plus counter-ion plus water of hydration. The peptide-only mass is less, typically 90 to 92 percent of total for acetate-salt peptides with multiple basic residues. The HPLC purity figure reported on the COA (the reported purity figure on a certificate) is the percentage of the peptide fraction that is the target compound versus structurally-related impurities; it does not tell you how much of vial mass is peptide. The CLND figure does. Researchers running quantitative work, particularly receptor-binding assays where molar concentration matters, should reference the net peptide content figure from the COA rather than assume nominal vial mass.
Salt exchange.
Salt exchange is performed by ion-exchange chromatography or by lyophilization in the presence of the desired counter-ion. Cresten can supply alternate salt forms (TFA, chloride, ammonium) on quote. The lead time for salt-exchanged batches is approximately four weeks longer than catalog batches, and the per-vial price reflects the additional purification step. Submit requests through the bulk-inquiry channel.
Cyclization and disulfide bridges.
Some peptides contain intramolecular disulfide bridges between cysteine residues, or are cyclized head-to-tail. For Cresten’s current catalog, no compound contains cysteine residues, so disulfide-bridge formation is not a synthesis or storage concern. For peptides that do contain disulfide bridges, the COA includes a confirmation of bridge formation via HPLC retention-time shift and MALDI-TOF mass spectrum (the disulfide-bridged form has a mass two atomic units lower than the reduced form due to loss of two hydrogen atoms).
The lab check, step by step.
Every batch Cresten releases passes through a five-step lab check before stock is released for shipment. The same chain runs across all compounds. The same chain runs across all batches. The same chain runs across all years. Consistency at the method level is what makes batch-to-batch comparison meaningful.
The five steps are: manufacturing at a partner facility inside the European Union, an internal final lab check by the partner, an third-party check at an accredited lab, certificate publication on a public verification page before stock listing, and stock release. Each step produces a document. Each document is referenced in the certificate of analysis. Each certificate is published on this site before any vial of that batch leaves the EU.
"A certificate of analysis is only as strong as the chain it comes from. The chain is what gives the certificate meaning."
This page walks through each step. The level of detail is set on purpose at what a serious buyer or auditor would expect. The same level of detail is offered to any qualified institutional buyer or regulator on request.