Analysis of Organochlorine Pesticides (OCPs) present in Ayurvedic Churnas using Multi Dimensional Gas Chromatograph Mass Spectrometer (MDGC/GCMS)

Importance of the Topic

Herbal formulations such as Ayurvedic Churnas enjoy widespread use for preventive and therapeutic purposes. However, cultivation and processing of plant materials can lead to contamination by persistent organochlorine pesticides (OCPs). Monitoring these residues is critical to ensure consumer safety and regulatory compliance, particularly under guidelines issued by WHO and the Indian AYUSH authority.

Objectives and Study Overview

This study aimed to develop and validate a single-run multi-dimensional gas chromatographic method coupled to mass spectrometry (MDGC/GC-MS) for the determination of 19 OCPs in three commercial Ayurvedic Churna products. The focus was on minimizing matrix interference while achieving high sensitivity and throughput.

Methodology

The analytical workflow comprised:

• Liquid–liquid extraction of 15 g Churna with acetic-acidified acetonitrile, spiked with OCP standards.
• Clean-up using primary–secondary amine, MgSO4, NaOAc, NaCl and C18 sorbents, followed by centrifugation.
• Concentration under nitrogen to 1 mL and reconstitution in toluene for injection.
• Multi-dimensional separation: unresolved heart-cuts from the first GC column were directed into a second column via a multi-Deans switch.
• Detection in negative chemical ionization (NCI) mode using selective ion monitoring (SIM) for enhanced specificity.

Used Instrumentation

• Shimadzu GC-2010 Plus with 30 m Rtx-5Sil MS column and ECD detector for initial screening.
• Shimadzu GCMS-QP2010 Ultra equipped with a Stx-CLPesticide column and multi-Deans switching system.
• Helium as carrier gas, methane as reagent gas, injector at 280 °C and interface at 300 °C.

Key Results and Discussion

Application of heart-cut MDGC enabled clear separation of 19 OCPs from complex herbal matrices. The NCI-SIM mode delivered limits of detection in the low ppb range and relative standard deviations below 5% for retention time and peak area. Quantitative analysis of Nityam, Sitopaladi and Hingashtaka Churnas showed OCP levels within AYUSH permissible limits. Matrix effects were markedly reduced compared to one-dimensional GC approaches.

Benefits and Practical Applications

The demonstrated method offers:

• Single-run analysis of multiple analytes with high selectivity.
• Reduced false positives/negatives due to matrix removal by heart-cuts.
• Robust performance suitable for routine QA/QC in herbal product testing.
• Compliance with regulatory protocols for traditional medicines.

Future Trends and Potential Applications

Advancements may include coupling MDGC to high-resolution mass spectrometry for accurate mass confirmation, extending the approach to other classes of contaminants (e.g., pyrethroids, organophosphates) and adapting automated sample preparation for higher throughput in industrial quality control environments.

Conclusion

The MDGC/GC-MS method in NCI-SIM mode provides a powerful solution for simultaneous screening and quantification of OCP residues in complex herbal matrices. Its high sensitivity, precision and matrix-cleanup capability support reliable compliance testing of Ayurvedic formulations.

References

• Protocol for testing guideline for Ayurvedic, Siddha and Unani medicines, Department of AYUSH, Government of India, Nov. 2003.
• Shimadzu Application Note SCA-180-017: Introduction of MDGC solution, Shimadzu Europa GmbH.