Pesticides in Dietary Supplements:
Advantages of QuEChERS vs. PAM 303
- Simple, cost-effective QuEChERS approach saves time and uses 20x less solvent.
- GMP-friendly—prepackaged extraction salts and snap-and-shoot standards reduce human error.
- Cartridge SPE cleanup removes matrix interferences, assuring accurate pesticide determination.
Due to safety and efficacy concerns, the FDA now requires the dietary supplement industry to adhere to current Good Manufacturing Practices (cGMPs). To meet these regulations, dietary supplements must be tested for pesticide contaminants, since the products are largely derived from botanical sources. As a result, labs are working to develop and validate methods, an endeavor which is complicated by the wide range of pesticides and matrices to be tested. Many labs begin method development with the FDA's Pesticide Analytical Manual (PAM), which includes procedures for plant materials. While PAM Method 303 is an appropriate starting point, it has several disadvantages, including high solvent consumption, manual procedures that contribute to analytical variation, and the inability to extract polar pesticides. As an alternative, we developed a QuEChERS-based method for analyzing pesticides in dietary supplements that has several advantages, including decreased costs and less variation among technicians (Table I).
Table I Decrease costs and increase reproducibility with a GMP-friendly QuEChERS approach to analyzing pesticides in dietary supplements.
|PAM 303 Method||QuEChERS + cSPE||Benefits of QuEChERS + cSPE|
|Solvent used (mL)||1,850||92||20x less solvent; cleaner, greener, & cost-effective|
|# of Solvents||4||3|
|Salt and sorbent used (g)||35||6.6||5x less salt/sorbent|
|Glassware/lab equipment||Fast, easy batch processing|
|Manual preparation||None–prepackaged salts, standards, and cSPE cartridges are ready to use.||Highly reproducible; less manual prep means less human error.|
To demonstrate the performance of a QuEChERS-based method, we fortified prepared dandelion root with 46 pesticides of varying classes that had been reported in dietary supplements. Samples were extracted using a QuEChERS procedure, and then two possible cleanup methods, dispersive solid phase extraction (dSPE) and cartridge solid phase extraction (cSPE), were compared. We determined that dSPE did not have the sorbent capacity to adequately clean up sample extracts (Figure 1), so cSPE was used for recovery determinations. Samples were analyzed using an Rxi-5Sil MS column and a LECO Pegasus III GC-TOFMS with ChromaTOF software. The method produced very good recoveries for a wide variety of pesticide chemistries, with slightly lower recoveries for some volatile and/or planar compounds. Representative recoveries are shown in Table II; all results and complete analytical details are available in application note PHAN1242A (5.4 mb pdf).
Overall, the chromatography and recovery results seen for a broad range of pesticides in dandelion root powder demonstrate the benefit of the QuEChERS approach for dietary supplement testing. Adopting a QuEChERS method, such as the procedure used here, can be especially advantageous to labs operating under FDA GMPs, as it is highly amenable to batch processing. Analytical benefits include reduced interferences and good recoveries, even of polar pesticides. Other benefits include an overall savings of both materials and prep time compared to the PAM 303 method, and better expected reproducibility due to the straight-forward procedure with fewer manual preparations.
Figure 1 QuEChERS extracts of pesticides in dietary supplements benefit from cSPE cleanup, which minimizes matrix interferences by removing more sugars and fatty acids than dSPE.
Table II This QuEChERS-based method provides good recoveries for a variety of pesticides found in dietary supplements.
|Compound||RT (sec)||Recovery (%)||Class||Type|
*Average recovery based on recoveries for individually quantified isomers.