Liquid chromatography-tandem mass spectrometry (LC-MS/MS)
LC-MS/MSLiquid chromatography-tandem mass spectrometry, or LC-MS/MS, pairs liquid chromatography with two stages of mass analysis to identify and measure compounds at very low levels with high selectivity.
After chromatographic separation, the first mass analyzer selects a compound by its mass, a collision cell breaks it into fragments, and the second analyzer measures those fragments. The combination of retention time, parent mass and fragment masses makes misidentification unlikely, and the sensitivity reaches parts-per-billion levels. Because the sample is not heated, acidic cannabinoids survive intact.
On a certificate of analysis the method is most often listed beside pesticide and mycotoxin results, where many compounds must be found at trace levels in a complex oil, and beside some cannabinoid panels. In drug testing it is a confirmatory method that distinguishes THC metabolites from other cannabinoids. Its precision does not remove the need to read the reporting limits; a result still depends on what the laboratory was calibrated to look for.