Monitoring pesticide residues in food — particularly spices and teas — is an important component of public health, but global trade has introduced variations in pesticide applications, the types of native and invasive pest populations, and the definitions of maximum residues. Even deliberate adulteration of food has become more prevalent. These trends have underscored the necessity for accurate and regular testing for pesticides.
A number of analytical methods to detect pesticides are based on liquid-liquid extraction and GC/MS or LC/MS. QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation helps monitor pesticides in spices, teas, and other foods, but this technique oftenintroduces matrix interference that masks or inhibits proper compound identification. Dilution has proven able to bypass this interference, but results in quantitation limits that are too high. Further, dispersive solid phase extraction (dSPE) may clean up extracts, but can leave co-extractants that interfere with your results.
Stir bar sorptive extraction (SBSE) based on GERSTEL Twister polydimethylsiloxane (PDMS) coated stir bars has been shown to extract and concentrate polycyclic aromatic hydrocarbons from QuEChERS extracts while eliminating matrix interference. Based on this successful application, researchers at GERSTEL and General Mills/Medallion Laboratories presented a poster at the North American Chemical Residue Workshop demonstrating the effectiveness of SBSE techniques for detecting pesticide residues in spices while simultaneously eliminating matrix interference.
The researchers spiked samples of ground organic ginger and turmeric with 10 common pesticides. Following QuEChERS extraction, Twister stir bars from GERSTEL and dispersive SPE blends were prepared for comparison. Samples were analyzed with HPLC and Mass Spectrometry. A GERSTEL MPS 2XL autosampler configured with an active wash station performed all injections, and automated the evaporation and sample reconstitution during extraction.
The research showed that Twister SBSE is a superior alternative to dSPE for QuEChERS extraction of these pesticides in these difficult matrices. Automation of sample injection, liquid handling and evaporation are also possible, reducing labor, time and errors that can occur with manual processes.
Most significantly, the researchers found that the Twister SBSE alone resulted in significant cleanup of the QuEChERS extract, eliminating the need to do dSPE cleanup.
Learn more about this procedure, including comparison charts of background matrix interferences and recoveries for pesticides in our poster, “Cleanup of QuEChERS extracts using SBSE for LC/MS/MS determination of pesticides in food products.”
After reading the details of this experiment, we invite you to reach out to us for an in-depth conversation about reducing matrix interference, improving efficiency, and saving labor and time in your analyte and residue detection studies.