Pesticide Extraction Using QuEChERs and SPE Method

Are You Meeting Pesticide Regulations?

Extracting pesticide from the cannabis flower for analysis.

As the legalization of medical and recreational cannabis continues to expand in the states, regulations to protect patients and consumers are also increasing. While the level and type of allowable pesticides differ from state to state, pesticide regulations are in place where ever cannabis is legal. In order to test the levels of the pesticide, you need to extract the pesticide from the cannabis flower to analyze it. There are several ways to do this.

Extraction of pesticides from the flower is typically done using QuEChERS extraction. The extract can then be analyzed with liquid or gas chromatography to determine the types of pesticides and the concentration levels of individual pesticides. This data allows the researcher to determine if the level of pesticides present in the cannabis is within the regulations required by the state and United States Environmental Protection Agency (EPA). The QuEChERS extraction method poses its own limitations, and more laboratories are adopting techniques such as solid-phase extraction (SPE) and other dilution methods to test for the complete range of possible detectable pesticides, as regulations and laws rapidly change in this quickly growing industry. QuEChERS and SPE methods are two of the most popular methods for the cleanup phase when analyzing pesticides in cannabis.

Extraction using QuEChERS

Kinesis TELOS QuEChERS and Cleanup Kit

QuEChERS extraction has been used in the agriculture industry and, more specifically, in the cannabis industry, for years.1 The initial extraction and separation step uses organic solvents and salt solutions to extract the required analytes into solution. This step extracts a range of chemical interferences that are removed during the subsequent cleanup stage of the QuEChERS extraction.

Kinesis® TELOS® QuEChERS are appropriate for this type of extraction. TELOS QuEChERS
extraction
and cleanup kits provide effective sample preparation for solid sample matrices. Developed to conform with documented AOAC 2007.1 and EN 15662 protocols, TELOS QuEChERS offer a complete solution for both salt-assisted sample extraction and dispersive SPE. A user-friendly salt pack makes the transfer of the salt to the required centrifuge tube rapid and easy, while generating minimal waste. Six different TELOS QuEChERS extraction kits support all AOAC 2007.1 and EN 15662 methodologies. The kits are supplied with or without 50-mL centrifuge tubes, with the latter also available with homogenizer beads for the breakup of more complex samples.

QuEChERS extraction protocols outlined by the Association of Official Agricultural Chemists (AOAC) and European (EN) legislation are similar, but they have a few distinct differences. It is very important for any lab that handles a consumable product to use a kit that covers either protocol. Failure to do this can lead to harmful results to the consumer as well as substantial fines for businesses not adhering to regulations.

quenchers extraction method protocols

For many pesticides, TELOS QuEChERS extraction is suitable for preparing the sample for spectroscopy; however, there are some limitations to this method.2 Additions of the necessary salts and water will lead to pH changes that can cause reactions that degrade certain pesticides. This is why it is important to know if TELOS QuEChERS extraction will provide accurate results for a certain pesticide before analysis of solution with liquid or gas chromatography.

SPE extraction method: A better solution for polar pesticides

For pesticides that are more polar in nature, Kinesis TELOS C18 nonpolar SPE column extraction is a better solution for the separation process. In less robust polar pesticides, QuEChERS cleanup can create reactions that destroy the pesticides and render them undetectable for analysis.3 SPE extraction involves running the solution through a column with a resin bed or sorbent to essentially allow for the catch and release of what the scientist wants to extract versus certain contaminants. When a solution is first placed on a conditioned column, the desired analyte isKinesis TELOS C18 Nonpolar SPE Columns trapped to the resin bed. This allows for the contaminants to be filtered out using a series of washes aimed at removing just the contaminants, as the desired analytes continue to be bound by the bed. After the washes, a final elution wash is run to release the chemicals of interest, providing a cleaner sample before liquid or gas chromatography techniques are applied.

Large batch solution

For large batches, TELOS® neo PAX MicroPlate SPE microplate and columns can be used for a high-throughput column wash. The modular design of TELOS microplates allows matching of the sample numbers to be processed. Sample evaporation is minimized using the optimized sorbent mass geometry. Moreover, SPE plate and collection plate compatibility prevent cross-contamination.

The importance of cleanup steps

Kinesis TELOS neo PAX MicroPlate SPE Microplate, loose wells

Cleanup steps using QuEChERS or SPE methods are important before running the solution through a liquid or gas chromatograph to ensure elimination of as much noise as possible in the pesticide analysis. Samples that have been cleared of unwanted contaminants enable researchers to more effectively determine if the pesticide is present and at the levels acceptable for national or regional standards. Cleanup also facilitates repeatability and reduces risk of contamination to the chromatograph.

Summary

As standards for acceptable pesticide levels in cannabis become more established, it is crucial for labs to be able to quickly adapt. Most state regulating both the types of pesticides to be tested for and acceptable limits are rarely the same, underscoring the importance of sample cleanup prior to chromatographic analysis. It is a waste of time and money to test a sample only to realize that QuEChERS cleanup may not be appropriate for certain pesticides. The ability to switch from QuEChERS extraction to SPE extraction and finding the correct balance between the two cleanup techniques will play a significant role in how the industry is legalized. The more accepted and regulated the research, the more cumbersome it can become. However, when a standard of conformity is eventually set, researchers will have a better idea of how to carry out testing. Until then, familiarity with both QuEChERS extraction and SPE extraction is necessary to ensure efficient use of time and precious sample.

References

  1. CEN–EN 15662. Foods of plant origin—multimethod for the determination of pesticide residues using GC- and LC-based analysis following acetonitrile extraction/partitioning and clean-up by dispersive SPE–Modular QuEChERS-method; https://standards.globalspec.com/std/10387667/EN 15662.
  2. Lehotay, S. and Mastovska, K. Evaluation of two fast and easy methods for pesticide residue analysis in fatty food matrices. J. AOAC Int. 2005, 88(2), 630–7.
  3. Chen, Y.; Al-Taher, F. et al. Multiresidue pesticide analysis of dried botanical dietary supplements using an automated dispersive SPE cleanup for QuEChERS and high-performance liquid chromatography-tandem mass spectrometry. J. Agric. Food Chem. Oct 10, 2012, 60(40), 9991–9; doi: 10.1021/jf301723g; Epub 2012 Oct 1.