Reading and interpreting a peptide Certificate of Analysis (COA) is essential for verifying product quality and ensuring experimental reproducibility. The COA provides critical information about peptide identity, purity, and quantity that should be reviewed before use.
Purity (by HPLC) is the most important parameter on the COA. The purity percentage indicates the proportion of the sample that is the target peptide. Higher purity means fewer impurities that could interfere with experiments. The HPLC chromatogram included with the COA shows the impurity profile, with the main peak representing the target peptide.
Molecular weight (by MS) confirms peptide identity. The observed molecular weight should match the expected molecular weight calculated from the sequence. For modified peptides, the observed molecular weight should reflect the modifications. A discrepancy between observed and expected molecular weight indicates a problem with synthesis or modification.
Counterion content indicates the salt form of the peptide. Common counterions include TFA (from HPLC purification) and acetate. The counterion affects the peptide's properties including solubility and activity. The COA should specify the counterion and its content.
Water content indicates the amount of residual water in the lyophilized peptide. Water content affects the peptide's stability and the accuracy of weighing. The COA should specify the water content and the method used for measurement.
At PeptideHub, we provide comprehensive COAs with every shipment, including HPLC chromatograms, mass spectra, and all relevant quality parameters. Our documentation enables you to verify product quality and make informed decisions about your research.