Chromatography is the most commonly used method for analyzing chemical compounds. Gas Chromatography (GC) is the analytical procedure used to separate and identify individual chemical substances from a mixture of substances by heating and turning the sample to a gas. GC is accomplished with the sample being heated to a gas (volatilization). The gas is passed through a separating column and as the separated materials leave the column they are measured by a detector. At Green Leaf Lab, we use a flame ionization detector (FID). GC is the generally preferred chromatography method because it is extremely sensitive, does not generate a waste stream, is robust and is one of the most used analytical methods for laboratory testing.
If the analytes do not become volatile, they can usually be separated and detected as a liquid using HPLC. HPLC requires the use of chemical solvents to push the sample through the separating column at the end of which the separated materials are detected optically and measured. However, there is a constant waste stream which must be collected and properly disposed of in an environmentally responsible manner. HPLC is not as sensitive when doing trace level analysis (ppb levels) as a GC, so is usually used for samples not amenable to GC analysis.
Gas Chromatography is more efficient and sensitive of these two methods. It is also more environmentally friendly and green conscious than HPLC. We believe it is the better equipment for measuring potency and most pesticides. Because of this, Green Leaf Lab utilizes the gas chromatography systems for potency and pesticide analysis.
OUR STANDARD OF EXCELLENCE
Medical Cannabis potency is determined by calibrating the GC equipment using standards (known amounts) of the three major potency components (THC, CBD and CBN). Once the GC is calibrated, samples can be run to determine the concentration (%) of the potency components in the sample. Similarly, standards are used for pesticide analysis. Standards are available commercially, have a certificate of analysis and are traceable back to the prepared batch of material. A reputable lab should be able to provide the client with their source of standards including the batch number of the standard. At Green Leaf Lab, we maintain our records and run our laboratory utilizing traditional standards for cannabis testing.
During a run of samples, a fortified sample (known amounts of the analyte added to a sample), may be run to cross check the calibration of the equipment. Any out of compliance sample batches are rerun after recalibration of the instrument. This assures an accurate and economical analysis. We are committed to cross checking the calibration of our equipment to maintain a reliable and consistent analysis.
A note about HPLC potency measurement: Potency can be measured with both HPLC and GC. Some labs claim there are other potency components (in edible products) that can be measured by HPLC over GC. These are usually potency components that are intermediate metabolites or have been converted to other forms through chemical interaction and conversion. To our knowledge there are no commercially available standards for these “converted” compounds. Thus, it is unclear how labs using HPLC can measure and quantitate these compounds reliably. Knowing that there are other components in a sample may be useful, but without knowing the quantities of these, effective use of that information would seem limited.