Procurement comparison
Peptide COA Guide: Comparison Table
Understanding what different COA parameters mean and how they impact research outcomes requires comparing the testing methods, what they detect, and what they miss. The table below maps each major COA data point to its practical research implications. HPLC Pur
Review the documented criteria directly; this page does not generate a winner or rating.
- Understanding what different COA parameters mean and how they impact research outcomes requires comparing the testing methods, what they detect, and what they miss. The table below maps each major COA data point to its practical research implications.
- HPLC Purity
- High-Performance Liquid Chromatography
- Percentage of sample eluting at target retention time vs. impurities
- Structural isomers, co-eluting peptides, bioactivity
- 95–99% depending on application
- Essential first-pass filter. Not sufficient alone for identity confirmation
- Molecular Weight (MS)
- Mass Spectrometry (ESI or MALDI)
- Confirms peptide mass matches theoretical value
- Post-translational errors (misfolding, aggregation), bioactivity
- Observed mass within ±0.5–2 Da of calculated mass
- Non-negotiable for sequence confirmation. Should match expected mass exactly
- Peptide Content (%)
- Amino acid analysis or quantitative HPLC
- Actual peptide as percentage of total lyophilized powder weight
- Nothing. This is the most accurate content measure
- 70–85% for most peptides (higher is better)
- Critical for accurate dosing. Must be used to calculate reconstitution volume
- Endotoxin Level (EU/mg)
- Limulus Amebocyte Lysate (LAL) assay
- Bacterial endotoxin contamination from synthesis or handling
- Viral contamination, non-endotoxin pyrogens
- <1.0 EU/mg for in vitro, <0.1 EU/mg for in vivo
- Required for any cell culture or in vivo work. Skipping this risks immune activation artifacts
- Residual TFA (%)
- Ion chromatography or NMR
- Trifluoroacetic acid remaining from peptide cleavage
- Other acidic impurities
- <0.1% for most applications
- TFA can interfere with some assays and cause cytotoxicity. Check if using sensitive cell lines
- Acetate Content (%)
- Ion chromatography
- Counterion from purification (acetate salts)
- Other counterions (chloride, formate)
- Variable. Not a quality issue but affects net peptide content
- Acetate itself is benign but contributes to total powder weight. Impacts concentration calculations