QuEChERS: Providing extra-easy cannabis analysis
The best results come from the right sample preparation in all areas of analysis. Many analytical chemists use QuEChERS, which stands for quick, easy, cheap, effective, rugged and safe. What more could you want? Plus, as Theresa Creasey, head of Applied Solutions Strategy, Marketing and Innovation at MilliporeSigma, explains, “QuEChERS methodology was designed primarily for the analysis of pesticide residues.” She adds, “The majority of cannabis testing labs in the United States already use QuEChERS methodology for their pesticide testing requirements.”
QuEChERS also boasts a long history of use in various industries, such as testing fruits for pesticides. As explained by Bob Clifford, General Manager for Marketing at Shimadzu Scientific Instruments: “QuEChERS sample preparation, or a modified version, can be applied to cannabis for the analysis of pesticides just like any other food or consumable product.”
Cannabis, though, makes a pretty tricky sample to test. “There are more than 500 compounds in cannabis, which makes it a difficult analyse,” Clifford points out. “Increasing the difficulty is trying to measure pesticides in the low parts-per-billion range around interfering compounds that are millions of times more concentrated.”
Luckily, QuEChERS can be modified to handle the challenges of cannabis testing.
In brief, QuEChERS removes pesticides from a sample. Traditionally, it just takes mixing a cannabis sample with some reagents, agitating it, doing an easy separation plus pH adjusting, more reagent plus centrifuging, some clean-up and another round of centrifuging. Many places online provide the precise reagents needed. The resulting extract can go into common analytical methods, such as gas or liquid chromatography (GC or LC, respectively), followed by mass spectrometry (MS).
At Shimadzu, Clifford and his colleagues have applied QuEChERS to the analysis of cannabis. As he says, “The method uses less solvents, consumables and time,” when compared with other methods of sample preparation.
Nonetheless, it takes some adjustments to apply this to cannabis. “There are a few modifications,” Clifford explains. “For example, QuEChERS was designed for fruits and vegetables with lots of water.” Consequently, dried cannabis must be hydrated before preparing it with QuEChERS. In addition, Clifford notes, “The original QuEChERS utilized specific salts in specific ratios and concentrations, which get changed during the extraction portion, and since these salts have changed, the method is modified from the original.”
Various companies are working on applying QuEChERS to cannabis. “MilliporeSigma provides all of the necessary products to complete the QuEChERS workflow for both official QuEChERS methods—AOAC 2007.01 and EN15662:2008—as well as specialized QuEChERS cleanup products for problematic matrices and analytes,” Creasey says.
Restek developed a QuEChERS method of sample preparation that works with a Shimadzu LC-MS platform. This takes the simplicity of QuEChERS and combines it with the selectivity and specificity of LC-MS.
At MilliporeSigma, scientists have used QuEChERS to extract cannabis flower material in the analysis of pesticide residues. “During the extraction process, chlorophyll, which produces a green color, is co-extracted with the pesticides,” Creasey explains. “Chlorophyll is problematic in analytical chemistry.” With GC-MS, chlorophyll reduces a GC column’s performance, and with LC-MS, chlorophyll contaminates the MS source. “Therefore, chlorophyll must be removed before the sample is analyzed,” Creasey says. “A novel adsorbent mixture containing carbon and zirconia-coated silica was used to remove the chlorophyll from the cannabis flower material,” without removing the pesticides.
That’s just a mini-selection of the options. As more companies and countries enter this industry, more platforms will surely benefit from QuEChERS preparation, because its speed and simplicity cannot be ignored.