What is HPLC?
HPLC stands for high-performance liquid chromatography. This laboratory method separates the components of a sample and determines how much of each is present. In quality control it is used to measure active-ingredient content precisely.
How does HPLC work?
In HPLC the dissolved sample is pumped with a stream of solvent (the mobile phase) at high pressure through a column packed with fine material, the stationary phase. Each component interacts differently with the column and therefore travels at a different speed, so the substances reach the end of the column one after another.
There a detector, often a UV or diode-array detector (DAD), measures how much light the emerging substances absorb. The result is a chromatogram:
- Retention time: when a peak appears indicates which substance it is, compared with a reference standard.
- Peak area: a measure of the amount. With a calibration using solutions of known concentration, the content can be calculated.
What is HPLC used for in supplements?
HPLC checks whether a product really contains the amount of active ingredient stated on the label. Typical uses are the content of vitamins and plant compounds and the purity of a raw material. Results usually appear in a batch's certificate of analysis.
For curcumin, the three curcuminoids (curcumin, demethoxycurcumin and bisdemethoxycurcumin) can be separated in one run and quantified individually. This is the basis for standardisation to a defined curcuminoid content. Every batch of Curcumin+ is tested by HPLC.
HPLC and other tests
Which method answers which question?
| Question | Typical method |
|---|---|
| Question How much active ingredient (e.g. curcuminoids) is in it? | Typical method HPLC with UV or DAD detection |
| Question How much lead, cadmium, mercury, arsenic? | Typical method Elemental analysis, e.g. ICP-MS |
| Question Which microbes are present? | Typical method Microbiological testing |
HPLC does not answer every quality question. A certificate with an HPLC content says nothing about heavy metals or microbes; separate methods exist for those. Make sure the certificate names the batch, method and date.