What do HPLC, mass spec and endotoxin tests actually show?
HPLC estimates purity, mass spectrometry checks identity by molecular mass, and endotoxin testing measures bacterial endotoxin; each answers a different question, and none answers all of them alone.
What does third-party lab testing mean?
Testing done by a lab that is separate from the seller. It is only useful if you can tell which lot was tested and can confirm the report on the lab's own site.
What does an HPLC purity result mean?
High-performance liquid chromatography separates a sample into components. Purity is usually reported as the main peak's share of the detected peak area under the method's conditions. It does not confirm identity by itself.
What does mass spectrometry (MS) show?
Mass spectrometry measures the mass of molecules in the sample. Matching the expected molecular mass supports identity. Pairing it with HPLC (often written LC-MS) covers both identity and purity.
What is endotoxin testing?
It measures bacterial endotoxins, commonly with a LAL-based assay, and reports results in endotoxin units (EU). An endotoxin result is not a sterility test.
What does ISO/IEC 17025 accreditation mean?
ISO/IEC 17025 is the international standard for the competence, impartiality and consistent operation of testing and calibration labs. Accreditation bodies use it to assess labs.
Why does accreditation scope matter?
A lab is accredited for a specific list of tests and methods, its scope. Look the lab up in its accreditation body's directory and check the method on your report is in scope.
What can't these tests tell you?
They report on the sample tested. They don't show your vial came from that lot unless the lot IDs match, and they make no claim about fitness for any use.
What is a chromatogram?
A chart of the detector's signal over time as the sample passes through the HPLC column. Each peak is a separated component. The purity figure comes from comparing the main peak's area with the total area of detected peaks.
Why can two labs report different purity for the same lot?
Methods differ: column, solvent gradient, detection wavelength, integration settings and sample handling all affect the number. Compare methods before comparing figures, and treat small differences between labs as normal.
What does "not detected" mean on a lab report?
The amount was below the method's limit of detection. It does not prove the amount is zero.
What is a limit of detection?
The lowest amount a method can reliably tell apart from no signal. It should be stated, or available from the lab, for any "not detected" result.
What is a content or assay test?
A test of how much of the target material is in the sample, often compared with the amount stated on the label. It answers a different question from purity.
Which tests should a COA show?
At minimum, a result for identity and one for purity, each with the method named. Anything else is only meaningful if the lab actually ran it and reported it.
Does a high purity number mean the material is what the label says?
Not by itself. HPLC purity says how much of the detected material is the main component, not what that component is. Identity needs a method such as mass spectrometry.
Sources
- ISO/IEC 17025:2017, General requirements for the competence of testing and calibration laboratories
- FDA: Pyrogen and Endotoxins Testing: Questions and Answers