HPLC, UV and gravimetric: what your certificate of analysis is really telling you
By PuraVida Natural · 25 September 2026
HPLC separates and measures individual compounds, UV measures the total of everything that absorbs light at a wavelength, and gravimetric methods weigh an extracted fraction. The same herbal extract can show different percentages by each method, so always compare grades measured by the same method.
HPLC (high-performance liquid chromatography)
HPLC separates an extract into its individual compounds and measures each against a reference standard. It is the most specific of the three: if a specification says "guggulsterones 2.5% by HPLC", that figure refers to identified compounds.
UV spectrophotometry
UV measures how much light the sample absorbs at a chosen wavelength. It is quick and inexpensive, but it reports everything that absorbs there, so it can give a higher figure than HPLC for the same material. Anthocyanins and total flavonoids are often reported this way.
Gravimetric and titration methods
Gravimetric methods weigh a fraction after extraction or drying, for example total saponins or loss on drying. Titration is used for acids and similar assays. These give a total, not a breakdown.
Why it matters when you compare quotes
A 40% by UV and a 30% by HPLC can be the same material. When two suppliers quote different strengths, compare like with like: ask for the method on each specification, and for the batch certificate of analysis rather than a typical value.
- Check the method named next to every percentage.
- Ask for the reference standard used.
- Compare the batch COA, not the brochure.