Updated: Jan 26
Chromatography and Cannabinoid Testing
Chromatography is a process that separates components of a mixture allowing the observer to identify what percentage each component makes up. There are many kinds of chromatography but its originates from a 19th century process used to separate pigments of color in a complex palate mixture. In this procedure the mixture is dissolved into a solvent which is called the “Mobile Phase”, which is carried through a second substance called the “Stationary Phase”
In the 19th century a piece paper or cloth would be placed with its end in a vial containing a mixture of the unknown mixture of pigment dissolved into alcohol. Capillary action soaks up the alcohol and pigment along with it to climb up the paper. The largest molecules would travel slower while the smaller pigments climbed faster. The result the Stationary Phase (paper) developing bands of color corresponding to the components of the Mobile Phase (alcohol solvent). Originally used by artists to perfect industrial dyes for textiles this procedure spawned a new branch of chemistry. Altering the stationary, mobile, or the factors determining the rate of travel a wide range of chromatographic approaches have been created. Liquid Chromatography and Gas Chromatography are the preferred methods for analyzing Cannabis.
Between 2015 and 2018 several different approaches to Liquid Chromatography were identified that accurately quantified the content and stability of cannabis compounds. It can also compare the variance between major compounds to determine the potential antioxidant activity of the plant. High Performance Liquid Chromatography (HPLC) was developed with the addition of a diode array detector as a means of deciphering compounds.
In HPLC the solvent is pumped at a specific flow rate (mobile phase) typically measured in milliliters per minute. The sample in question is then injected into this stream and passes through a column of chromatographic packing material necessary to effect the separation of compounds (stationary phase). The diode array detector then reads the wavelength of light that the compound reflects as it emerges from the column. Wavelengths in most cases that are beyond the visible spectrum of color. These results are expressed as the time it takes from injection to measurable results as Retention Time (RT in Minutes) or Relative Retention Time (RRT), the ratio of RT to the analyte peak relative to the other compounds in the sample. This data is displayed on a chromatograph and translated to a Certificate of analysis expressed as compounds as percentages of total weight in the sample or as milligrams per gram.