Multiresidue determination of more than 90 pesticides by gas chromatography tandem mass spectrometry in red chili powder

Importance of the Topic

Red chili powder is one of the most widely used spices worldwide, particularly in Asia. Extensive application of pesticides in chili cultivation raises concerns about consumer exposure to harmful residues. Reliable multi-residue analysis is essential to ensure food safety, maintain export quality and comply with international regulations.

Objectives and Study Overview

This work aimed to develop and validate a robust gas chromatography tandem mass spectrometry method for simultaneous determination of over 90 pesticides in red chili powder. Key goals included minimizing pigment co-extraction, optimizing cleanup to protect instrument performance, and achieving high analytical throughput.

Methodology

Sample preparation followed a modified QuEChERS protocol:

• Weigh 2 g ground chili powder, hydrate with 10 mL water, shake and equilibrate.
• Add 10 mL acetonitrile with 1 % acetic acid, agitate, then salt out with magnesium sulfate and sodium acetate.
• Centrifuge and transfer 1 mL extract into a dispersive cleanup tube containing PSA, C18, graphitized carbon black and MgSO4.
• Shake, centrifuge and transfer supernatant for GC-MS/MS analysis.

GC-MS/MS analysis was performed on an Agilent 7890A GC coupled to a 7000B Triple Quadrupole in MRM mode using back-flush and optimized temperature programs.

Used Instrumentation

• Agilent 7890A gas chromatograph
• Agilent 7000B Triple Quadrupole GC/MS system
• HP-5MS columns with retention gap and back-flush capability
• MassHunter software for MRM optimization and data acquisition

Main Results and Discussion

Graphitized carbon black combined with PSA and C18 achieved the most efficient pigment removal, reducing beta-carotene by over 40 %. Clean extracts maintained low injector liner fouling and stable MS response across repeated injections. Method performance:

• Recoveries of 90 % of target pesticides ranged 70–120 %
• Intra-laboratory precision (RSD) below 20 %
• Linear calibration over 0.19–200 ng/mL with correlation coefficients above 0.99

Analysis of market chili samples detected multiple residues above 10 ng/g, demonstrating method applicability.

Benefits and Practical Applications

This approach enables high-throughput screening of diverse pesticide classes with minimal maintenance downtime. Simplified cleanup prolongs injector liner and column lifetimes, improving laboratory productivity. The method supports quality control in food processing, regulatory monitoring and export compliance.

Future Trends and Potential Applications

• Extension to other spice and food matrices through tailored cleanup sorbents
• Integration with automation and online sample preparation systems
• Application of high-resolution MS and data-driven algorithms for non-targeted screening
• Enhanced mobile and field-deployable platforms for rapid on-site testing

Conclusion

A streamlined QuEChERS-GC-MS/MS method was established for reliable multi-residue analysis of over 90 pesticides in red chili powder. Optimized cleanup effectively reduces pigment interference, ensuring robust performance and high laboratory throughput.

References

• Mathew Attokaran PhD Natural Food Flavors Colorant ISBN 9780813821108
• Pesticides and Environmental Pollutants MRM Database Agilent part G9250AA
• QuEChERS Sample Preparation Manual Agilent publication 5991-1057EN
• User Guide to Pressure Control Back-Flush Agilent publication 5990-5484EN