Research notes
What a purity percentage actually measures
Sep 2, 2026 · 4 min read
The number is method-bound
When a certificate of analysis states a purity of 99.2%, that figure is not a universal property of the material. It is the area of the main peak relative to all detected peaks in a chromatogram, produced under one specific method: a particular column, mobile phase, gradient, flow rate and detection wavelength.
Change the method and the number can move. A detection wavelength that misses an impurity class will overstate purity; a shallow gradient that co-elutes two compounds will understate it. This is why a purity figure quoted without its method is marketing, not measurement.
What to look for on a certificate
A usable certificate prints the analytical conditions alongside the result: the column type and dimensions, the gradient programme, the detection wavelength, and the integration window. It also names the laboratory and dates the analysis to a specific batch.
Our certificates carry the column, gradient and detection wavelength next to every result, and each report is tied to the batch number printed on the vial label. The figure and the method travel together or not at all.
Why this matters for research material
In-vitro work depends on knowing what is actually in the vial. A purity claim that cannot be traced to a method and a batch cannot be relied on when interpreting results, and it cannot be compared across suppliers.
The practical rule is simple: treat any purity figure without a stated method and batch reference as unverified, whatever its size.
This note describes analytical documentation only. Materials supplied by Basic Tides are for in-vitro laboratory research only — nothing here is guidance for use in humans or animals. For the underlying framework, see our research standards.