Quality
Every production lot is tested by a laboratory that has no stake in the result. This page explains exactly what is measured, how, and what the numbers on a certificate mean.
Purity by RP-HPLC
A sample from each lot is analysed by reverse-phase high-performance liquid chromatography with UV detection at 220 nm, the wavelength at which the peptide bond absorbs. The chromatogram separates the target compound from synthesis-related impurities, and purity is reported as the target peak area as a percentage of total peak area.
Brant’s specification is a minimum of 99 %. A lot that assays below specification is not released for sale.
What the figure does not tell you: peak-area purity is a measure of chromatographic homogeneity, not of absolute mass content. It does not account for residual water, counter-ion or solvent, which is why net peptide content and purity are different numbers.
Identity by ESI-MS
Electrospray ionization mass spectrometry measures the mass-to-charge ratio of the compound and confirms the observed mass against the nominal molecular weight calculated from the sequence. This is what distinguishes the correct compound from a different one of similar retention time.
The observed mass on the certificate and the nominal molecular weight on the product page are reported independently and should agree within the instrument’s tolerance.
Endotoxin
Where reported, bacterial endotoxin is measured by Limulus amebocyte lysate assay and expressed in endotoxin units per milligram. It is a measure of Gram-negative bacterial contamination introduced during synthesis, handling or fill.
Traceability
Each lot carries a number in the format BR-YYMM-NNNN, printed on the vial label beneath the compound name. That number is the key to the certificate: enter it on the certificates page and the record for that exact vial comes up. The packing slip in every order lists the lot number of each vial shipped.
What third-party testing is not
An independent purity and identity result says the vial contains what the label says it contains, at the stated purity, on the stated date. It is not a safety assessment, not an approval by any regulatory authority, and not evidence of suitability for any particular use. These are laboratory reagents for in-vitro research; determining fitness for a given experiment is the researcher’s responsibility.