Reading and understanding HPLC purity
HPLC (high-performance liquid chromatography) separates a sample's components and measures their relative amounts. Purity is expressed as a percentage of the total peak area. When a published report states a purity value, RetaEU shows that value. Some reports state only identity and amount.
- Unit
- % peak area
- Purity value
- If reported
- Complementary method
- MS
How HPLC measures purity
In HPLC a sample passes through a column where components elute at different times (retention time). The detector records each component as a peak.
Purity is the area of the main peak divided by the total area of all peaks, expressed as a percentage.
What the percentage means
A measured value of 99.3% means 0.7% of the signal is attributed to other peaks. The higher the percentage, the fewer secondary components were detected.
Look at the reported value itself, not a marketing rounding like “99%+”.
HPLC versus mass spectrometry
HPLC quantifies purity; mass spectrometry (MS) confirms identity by measuring mass. The two methods complement each other: purity and identity.
- USP — <621> Chromatography
- IUPAC — Nomenclature for Chromatography
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