Peptide Laboratory Testing
A transparent guide to analytical testing methods, ensuring researchers have complete confidence in the integrity of their materials.
High-Performance Liquid Chromatography (HPLC)
HPLC is the gold standard for determining the purity of synthesized peptides. During solid-phase peptide synthesis (SPPS), amino acids are added one by one. Occasionally, an amino acid might be missed (creating a deletion sequence) or added twice.
HPLC separates the components of a sample based on their interactions with a stationary phase (the column) and a mobile phase (the solvent).
- The main peptide peak represents the pure compound.
- Smaller surrounding peaks represent synthesis impurities.
The area under the main peak relative to the total area of all peaks gives the purity percentage (e.g., 99.2%).
Mass Spectrometry (LC-MS)
While HPLC tells you how pure a sample is, it cannot definitively tell you what the substance is. That is the role of Mass Spectrometry.
Mass Spectrometry measures the mass-to-charge ratio of ions. By ionizing the peptide, the instrument can determine the precise molecular weight of the compound in the main HPLC peak.
If the measured molecular weight matches the theoretical molecular weight of the target sequence (e.g., Retatrutide), the identity of the peptide is confirmed. Without Mass Spec data, an HPLC report is essentially meaningless, as you could have a 99.9% pure sample of the wrong substance.
Reading a Certificate of Analysis (COA)
A genuine COA should contain both HPLC and MS data. When interpreting a Reta Pharma COA, look for:
- Batch Number: Must match the physical vial.
- Testing Date: Ensures the test is recent and relevant.
- Target Mass vs. Observed Mass: These should be nearly identical (within acceptable instrument variance, usually ±1.0 Da).
- Purity Area %: We target >99% purity for all research peptides.