Residual Pesticides Analysis of Botanical Ingredients Using Gas Chromatography Triple Quadrupole Mass Spectrometry

Importance of the Topic

Botanical dietary supplements derived from dried plant ingredients are widely consumed around the world. Ensuring their safety requires accurate monitoring of residual pesticides. Conventional sample preparation methods face challenges due to heavy interferences from dried botanical matrices. A robust analytical approach combining a modified QuEChERS extraction with gas chromatography–triple quadrupole mass spectrometry (GC-MS/MS) addresses these challenges and enables reliable trace-level pesticide analysis.

Study Objectives and Overview

This study aimed to develop and validate a high-throughput method for simultaneous determination of over 200 pesticide residues in botanical ingredients. The approach involved a modified QuEChERS extraction, solid-phase cleanup, toluene dilution, and GC-MS/MS analysis employing a Smart MRM library and automatic retention time adjustment. Key performance metrics included detection capability, linearity, accuracy, recovery, and ion ratio consistency.

Methodology and Instrumentation

• Sample Preparation: 1 g ground ginseng powder hydrated with water, extracted with acetonitrile containing internal standard, followed by salt partitioning (MgSO4, NaCl).
• Cleanup: Dispersive SPE using graphitized carbon black and PSA, followed by toluene elution and evaporation to near dryness. Final extracts spiked with quality control standards and anhydrous MgSO4.
• Instrumental Setup: Shimadzu GCMS-TQ8040 with AOC-20i autosampler, SH-Rxi-5MS capillary column with guard. GC conditions: splitless injection at 250 °C, temperature program from 90 °C to 330 °C in 24.3 minutes. MS in EI mode at 70 eV, MRM acquisition with two transitions per compound, loop time 0.4 seconds.
• Smart MRM and AART: Database-driven automatic creation of optimized MRM methods and retention time alignment using an n-alkane standard mixture.

Main Results and Discussion

• Matrix-Matched Calibration: Of 232 target compounds, 230 were detected within ±0.1 minute of predicted retention times. Calibration curves showed excellent linearity (r2 > 0.99) across 1 to 200 ng/mL, with back-calculated concentrations within ±20% of theoretical values.
• Method Sensitivity: Even with a four-fold dilution inherent to cleanup, the method quantified pesticides at 2 ng/g equivalent levels with acceptable accuracy.
• Recovery and Ion Ratio: Fortified ginseng samples at 10 and 50 ng/g exhibited 85% of compounds within 70–120% recovery. Relative ion ratios met ±30% criteria for over 76% of compounds at 10 ng/g and 83% at 50 ng/g. A combination map identified compound groups requiring further optimization due to low recovery or ion ratio deviations.

Benefits and Practical Applications

• High Throughput: Total analysis cycle of about 30 minutes covers over 200 pesticides in a single run.
• Robustness: Modified QuEChERS and SPE cleanup effectively suppress matrix interferences from dried botanicals.
• Sensitivity and Accuracy: GC-MS/MS with optimized MRM transitions yields reliable quantification at trace levels.
• Laboratory Efficiency: Automated method creation and retention time adjustment streamline routine pesticide monitoring workflows.

Future Trends and Potential Applications

• Expansion of Compound Coverage: Incorporation of additional pesticides and emerging contaminants into Smart MRM databases.
• Enhanced Automation: Integration of sample preparation robotics and real-time data review for further throughput gains.
• Green Chemistry: Development of solvent-minimized or solvent-free extraction alternatives for botanical matrices.
• Advanced Detection: Application of high-resolution MS or ion mobility separations to further reduce background noise and improve selectivity.

Conclusion

The combination of a modified QuEChERS extraction, SPE cleanup, and GC-MS/MS with Smart MRM and AART provides a rapid, sensitive, and reliable method for routine monitoring of over 200 pesticide residues in botanical ingredients. This workflow overcomes challenges posed by dried sample matrices and offers high throughput for quality control and safety assurance in dietary supplement analysis.

Reference

• Anastassiades M, Lehotay SJ, Štajnbaher D, Schenck FJ. Fast and Easy Multiresidue Method Employing Acetonitrile Extraction/Partitioning and Dispersive Solid-Phase Extraction for the Determination of Pesticide Residues in Produce. J AOAC Int. 2003;86(2):412-431.
• European Commission, Health & Consumer Protection Directorate-General. Guidance Document on Analytical Quality Control and Validation Procedures for Pesticide Residues Analysis in Food and Feed (SANCO/12571/2013). 2013.