What is that graph with peaks on a COA?
Updated: 2026-09-09 · Buying, quality and COA
Short answer
It is a chromatogram: a record of how a sample's components separate as they pass through a column. Each peak is something that came out at a given time, and its area is used to calculate proportions. It shows separation, not identity: on its own it does not confirm which molecule each peak is.
In plain English
- The horizontal axis is retention time; the vertical axis is detector signal.
- Purity percentage is usually main peak area divided by total peak area.
- Identity is confirmed by other testing, typically mass spectrometry.
- A chromatogram with no scales, no method and no lot identification tells you little.
What we know
- HPLC and mass spectrometry are complementary tests with different purposes.
- Serious analytical reports include method, conditions, date and lot.
What we don't know yet
- A standalone image of a chromatogram cannot be traced to its source.
- Anything eluting outside the analysis window never appears on the graph.