Introduction
Pesticides have been used for over 4500 years, and pesticide residues in foods are often stipulated by regulatory bodies in many countries. Based on the types of pests, pesticides could be classified into herbicides, rodenticides, bactericides, fungicides, and larvicides. However, according to chemical structure, pesticides could be classified into organophosphate, carbamate, organochlorine, pyrethroid, triazines, triazoles, and neonicotinoids. This paper targeted to develop a fast, sensitive and comprehensive method to quantify 112 pesticide residues (see Table 1) in botanical and non-botanical dietary supplements with GC/MS/MS and LC/MS/MS coupling with “QuEChERS” (Quick, Easy, Cheap, Effective, Rugged, and Safe) and dSPE (dispersive solid phase extraction) method.
Methodology
Sample Preparation and Extraction:
About 3.00 grams of sample and internal standards (IS) were extracted by the “QuEChERS” extraction method using H2O, HOAc, MeCN, MgSO4, NaOAc, and ceramic homogenizer, followed by the dSPE method.
GC-MS/MS Conditions
GC system: Agilent 7890B GC system including 7693 auto-sampler (see Table 2 for parameters)
Column: HP-5MS (15m x 250 um x 0.25 um) (Agilent)
Oven Temperature Program: see Table 3.
MS detector: Agilent Triple Quadrupole 7000 D
Results and Discussions
Sample Extractions
For sample extraction, we started using USP extraction solvent, which is proper for botanical matrix but not for non-botanical matrix. The AOAC extraction solvent was then tried, but it was not proper for dry powder samples like dietary supplements (Table 5). More extraction solvents were further investigated, and Dyad Labs’ solvent can efficiently extract pesticides from both matrix (Figure 1). Different dSPEs were also compared for sample clean-up, and Agilent Fatty Sample dSPE (part#5982-5122) was selected for both matrices. During the sample extraction, some pesticides have hydrogen bonding with the active sites on the container surface. To prevent this bonding issue, the analyte protectant solvent (sorbitol and gulonolactone in H2O) was used (Table 6). The final optimized extraction procedure is shown in Figure 2.
Specificity
The specificity results indicated that there is no interference between the analyte and IS. The blank diluent and matrix extracts have no interference at the analyte and IS expected retention time. Thus, the method is specific. The representative chromatograms are shown in Figures 3-4.
Linearity
The curve range of 2.00-1,000 ng/mL, covering nine points at 2.00, 5.00, 10.0, 20.0, 50.0, 100, 200, 500, and 1,000 ng/mL, was successfully validated. Each pesticide has its own specific range between 2.00 and 1,000 ng/mL based on USP 561. The regression is quadratic with 1/x as the weighing factor (Figure 5). The correlation coefficient R2 is > 0.995 (Figure 5). The representative chromatograms for ULOQ are in Figure 6.
Accuracy and Precision
The accuracy and precision were investigated with post-spiking pesticides in blank botanical and nonbotanical matrices at lower, medium, and high regions of the established range of the calibration curve (Tables 7-8).
Conclusion
This fast, specific, sensitive, and comprehensive method was first published to simultaneously quantify 112 pesticides in botanical and non‐botanical dietary supplements.
