Simultaneous determination of 74 kinds of pesticides in Chinese herbal medicine listed in Chinese pharmacopoeia (2015) by GPC-GC-MS/MS

Importance of the Topic

The analysis of pesticide residues in Chinese herbal medicines is critical for ensuring product safety and compliance with regulatory standards. Herbal extracts often contain complex matrices that can interfere with detection of low-level contaminants. Developing robust methods to screen multiple pesticide residues simultaneously supports quality control and consumer protection.

Objectives and Study Overview

This study aimed to implement and validate a method for the simultaneous determination of 74 pesticide residues in Chinese herbal medicine samples based on the 2015 edition of the Chinese Pharmacopoeia. An online gel permeation chromatography (GPC) coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) system was applied to improve cleanup efficiency and detection sensitivity compared to conventional GC-MS/MS.

Methodology and Instrumentation

Sample Preparation:

• Herbal materials were finely ground and extracted with 1% acetic acid in water.
• Acetonitrile and isotope-labeled internal standard (Fenthion-d6) were added for target analyte extraction.
• Extracts underwent dispersive solid-phase extraction using PSA, MgSO4, C18, graphitized carbon black, and silica to remove matrix interferences.

GPC-GC-MS/MS Setup:

• GPC system: Shimadzu LC-20A with a CLNpack EV-200 (2.0 mm i.d. × 150 mm) column.
• GC-MS/MS: Shimadzu GCMS-TQ 8040 equipped with a splitless PTV injector.
• GC configuration: empty inlet column (5 m × 0.53 mm), precolumn and main column both InertCap 5MS/NP with dimensions 5 m × 0.25 mm × 0.25 μm and 25 m × 0.25 mm × 0.25 μm, respectively.
• Analytical conditions: temperature gradient from 82 °C to 300 °C, carrier pressure program, injector and interface temperatures set to optimize transfer, electron ionization MRM acquisition.

Main Results and Discussion

Online GPC cleanup effectively reduced matrix background, allowing injection volumes up to 20 μL and enhancing method sensitivity. Calibration curves for all pesticides showed excellent linearity (r > 0.995) over 1–50 ng/mL. Limits of detection for most analytes were below 0.5 ng/mL. Repeatability tests (n=6) yielded relative standard deviations under 10%. Recoveries ranged between 60% and 120%, meeting pharmacopeial requirements. Representative compounds such as dichlorvos, chlorpyrifos, and parathion demonstrated robust performance in terms of low LODs and consistent recoveries.

Benefits and Practical Applications

This GPC-GC-MS/MS approach offers:

• Efficient online matrix cleanup that minimizes manual sample handling.
• Large-volume injection capability to achieve lower detection limits.
• High-throughput screening of a broad pesticide panel in complex herbal matrices.
• Compliance with stringent regulatory criteria for herbal medicine quality control.

Future Trends and Potential Applications

Advancements may include:

• Expansion of target analyte lists to cover emerging pesticide classes.
• Integration with high-resolution mass spectrometry for non-targeted screening.
• Automation of sample preparation workflows to increase throughput.
• Coupling with data analytics and IoT-based monitoring for real-time quality assurance in herbal production.

Conclusion

The implemented online GPC-GC-MS/MS method provides a powerful tool for comprehensive determination of pesticide residues in Chinese herbal medicines. The combination of efficient matrix removal and sensitive detection meets regulatory standards and supports stringent quality control. This methodology can be further adapted to evolving analytical needs and broader residue monitoring programs.

Reference

No specific literature references were provided in the original text beyond compliance with the Chinese Pharmacopoeia (2015) guidelines.