What does HPLC purity mean for peptides?
Updated October 2026
"99% HPLC purity" is the headline number on every peptide listing. Here's what the test actually measures.
How HPLC works
High-performance liquid chromatography pushes a dissolved sample through a column packed with a material that different molecules travel through at different speeds. As each component exits, a detector records it as a peak. The target peptide is the main peak; impurities show as smaller peaks.
Reading the number
Purity is the area of the target peak as a percentage of all peaks. "99.6% by HPLC" means the target makes up 99.6% of the detected material. For research-grade peptides, 99%+ is the expected standard, and a trustworthy vendor shows the actual chromatogram, not just the number.
Why it matters
In research, impurities are confounds — they can skew assay results. High purity, confirmed per lot, is what makes experiments reproducible. Pair HPLC purity with a mass-spec identity check (see our COA guide) for a complete picture.