Technology
How we measure what is in your sample
Every result on a certificate of analysis comes from an instrument finding one compound among thousands. Pick a method and scroll to follow one molecule from the sample jar to the detector.
In words
LC-MS/MS: Finding one pesticide among thousands of compounds
Colorado regulates 100 pesticides, and each one has to be found and measured in a sample that contains thousands of other compounds. Follow one orange molecule through the instrument to see how.
- The sample. Pesticide residues sit among thousands of other compounds from the plant. While everything is mixed together, nothing can be measured.
- Extraction. A solvent pulls the compounds out of the sample and into liquid, so they are free to travel through the instrument.
- Separation (LC). The liquid is pushed through a packed column. Each compound moves at its own pace, so they leave in groups, one after another.
- Detection (MS). Each compound is given a charge. A filter then lets through only ions with the right mass-to-charge ratio, and every other ion crashes into the rods. What gets through is counted, so it is identified and measured, even at trace levels.
Simplified. A triple-quadrupole instrument filters twice, with a fragmentation step in between, to be certain of each identification. Compounds and amounts shown are illustrative, not sample data.
HPLC-DAD: Measuring one cannabinoid among hundreds of plant compounds
Potency tells a producer how much of each cannabinoid is in a product. Close chemical cousins have to be told apart and each one measured. Follow one orange molecule through the instrument to see how.
- The sample. Cannabinoids sit among hundreds of other compounds from the plant, including cousins that look almost the same. While everything is mixed together, nothing can be measured.
- Extraction. A solvent pulls the cannabinoids out of the sample and into liquid, so they are free to travel through the instrument.
- Separation (LC). The liquid is pushed through a packed column. Each cannabinoid moves at its own pace, so they leave in groups, one after another.
- Detection (UV). Each group passes through a beam of ultraviolet light. Cannabinoids absorb some of the light, and the more there is, the more light is blocked. The dip in light is turned into an amount by comparing it with standards of known strength.
Simplified. Mycotoxin testing uses the same kind of separation with a fluorescence detector in place of the UV one. Compounds and amounts shown are illustrative, not sample data.
qPCR: Finding a few DNA molecules among millions
Microbial testing looks for the DNA of organisms that should not be there. A sample can hold only a handful of target molecules, so the instrument copies them until they can be seen. Follow one orange DNA molecule to see how.
- The sample. Cells from the product, including a few of the organism being tested for, are mixed in with everything else on the plant. The target DNA is locked inside its cell.
- Extraction. The cells are broken open and their DNA is released into liquid. Short matching pieces called primers, and an enzyme, are added. The primers only fit the target.
- Copying (PCR). The tube is heated and cooled again and again. Each cycle splits every target strand and builds a copy, so the number of copies doubles. Other DNA is left alone, because the primers do not fit it.
- Detection. A dye glows as copies build up, and the instrument reads the glow after every cycle. The cycle where the glow crosses a threshold shows how much target the sample began with: the more it had, the sooner it crosses.
Simplified. A real run uses about 40 cycles, and a result is judged against positive and negative controls. Confirmatory plating is not shown. Cycle numbers are illustrative, not sample data.
GC-FID: Measuring terpenes as vapors
Terpenes are the aromatic compounds in cannabis. They evaporate easily, so we measure them as a gas. Follow one orange molecule from the vial to the flame.
- The sample. Terpenes sit among heavier plant material in a sealed vial. While everything is mixed together, nothing can be measured.
- Heating (headspace). The sealed vial is warmed. Volatile compounds escape from the sample into the air above it, while the heavy matrix stays behind in the vial.
- Separation (GC). A stream of carrier gas pushes the vapors through a long, coated column in a hot oven. Compounds that cling to the coating more strongly travel slower, so they leave in groups, one after another.
- Detection (FID). Each group is burned in a small flame. Burning makes charged particles, and a collector measures the tiny current they carry. The more compound, the bigger the current.
Simplified. Compounds and amounts shown are illustrative, not sample data.
ICP-MS: Counting individual metal atoms
Heavy metals such as lead and arsenic matter at very low levels. The instrument turns the sample into charged atoms and counts them by mass. Follow one orange lead atom through it.
- The sample. Trace metals sit inside plant material, mixed in with everything else. While they are locked in a solid, they cannot be measured.
- Digestion. Acid and heat break the sample down into a clear liquid. The metals dissolve and are free to move.
- Plasma. The liquid is turned into a fine mist and carried into a plasma hotter than the surface of the sun. Everything is broken into single atoms, and the atoms pick up an electric charge.
- Detection (MS). A filter steps through the masses of interest many times a second. Only atoms of the mass it is tuned to get through, and every other ion crashes into the rods. What gets through is counted.
Simplified. Real instruments also use a collision cell to remove interferences, and many ions of each mass are counted at once. Elements and amounts shown are illustrative, not sample data.