Thin layer chromato-graphy (TLC) is a chromatographic technique that is used in many (phyto) pharmaceutical and analytical research laboratories for the separation and identification by colouring (chroma =Greek for color) of organic compounds in a mixture of hundreds of compounds, like our cannabinoid drop in this figure.
TLC is a simple, rapid and inexpensive technique that uses adsorbtion and capillary action to separate complex mixtures into discrete zones. TLC gives a quick answer as to how many components there are in a mixture. TLC is also used to support the identity of a compound in a mixture when the Rf of a compound is compared with the Rf from the literature (see table 1). In our case, the cannabinoids can be identified by their specific color, specific location (Rf value) and order of appearance on the TLC plate, if carried out with the solvent system from the Kit.
A TLC plate is basically a sheet of glass which is coated with a thin layer of a solid adsorbent silica. A small amount of the mixture to be analysed is spotted near the bottom of this plate. The TLC plate is then placed in a shallow pool of a solvent in a developing chamber so that only the very bottom of the plate is in the liquid. This liquid (or fluent or ‘carrier fluid’) is the mobile phase which slowly rises up the TLC plate by capillary action.
As the solvent moves, it will pass the little spot of cannabinoid oil micro droplet of 2 ul that was applied on the bottom of the plate. An equilibrium is established for each component of the mixture between the component’s molecules which are absorbed on the solid and the molecules which are in solution. In principle, the components will differ in solubility and in strength of their adsorption to the adsorbent. Other components will be carried farther up to the plate than the others.
When the solvent has reached the top of the plate, the plate is removed from the developing chamber and dried by ventilation for only three minutes. After drying, the now separated components (cannabinoids) in the silica layer will be visualized by spraying the plate with a dye. The dye is highly specific for cannabinoids. Every principal cannabinoid will display its own color! THC will appear in wine red, CBG will show in bright yellow, CBD in orange, CBC in violet…etc.
