Glossary
Counter-ion
A small ion, such as acetate or trifluoroacetate, that balances the charge on a peptide. It contributes to vial weight but is not peptide.
Further reading
- HPLC vs mass spectrometry: what each test tells you about a peptide
HPLC measures purity, mass spectrometry confirms identity. Why a CoA needs both, what each cannot detect and how to read the results.
- TFA vs acetate peptide salts: why the counter-ion matters
Synthetic peptides are supplied as salts. What trifluoroacetate and acetate counter-ions are, why they change net content and when the choice matters.
- How to read a peptide Certificate of Analysis
What each line of a peptide CoA means, which checks matter most, and the red flags that suggest a document is decoration rather than evidence.
- Purity versus net peptide content: why 99% is not 99%
HPLC purity and net peptide content measure different things. Understand the gap, why vials contain counter-ions and water, and how it affects solution concentrations.
- How research peptides are made and tested
From solid-phase synthesis to preparative HPLC, freeze-drying and quality control: what happens between an amino acid sequence and a vial.