Multi-Residue Pesticide Analysis in Dried Chili Powder: Optimized Cleanup After QuEChERS Extraction for UPLC-MS/MS and GC-MS/MS Analysis

Significance of the Topic

Chili powder is a complex matrix of pigments, oils and resinous compounds that pose challenges for pesticide analysis. Accurate multi-residue testing is critical for food safety, regulatory compliance and quality control in spice production.

Objectives and Overview

This note describes a robust workflow combining QuEChERS extraction with tailored cleanup strategies to enable sensitive, reliable determination of pesticide residues in dried chili powder using both UPLC-MS/MS and GC-MS/MS with APGC.

Instrumentation Used

ACQUITY UPLC I-Class System
Xevo TQ-S Mass Spectrometer
Atmospheric Pressure Gas Chromatography (APGC) interface
ACQUITY UPLC BEH C18 column
DisQuE QuEChERS extraction and dSPE cleanup products
Sep-Pak PSA/Carbon SPE cartridges
MassLynx MS Software with Quanpedia database

Methodology and Sample Preparation

• Equilibrate 2 g chili powder with water, extract with acetonitrile and CEN QuEChERS salts.
• Perform dispersive SPE cleanup (MgSO₄, PSA, C18, GCB) for UPLC-MS/MS.
• Apply PSA/carbon SPE cleanup with acetone/toluene dilution for APGC-MS/MS, including evaporation and reconstitution in toluene.
• LC conditions: ACQUITY UPLC BEH C18 2.1×100 mm, gradient elution with 10 mM ammonium acetate (pH 5.0), 0.45 mL/min, Xevo TQ-S in ESI ± mode.
• GC conditions: DB-5 MS 30 m×0.25 mm×0.25 µm column, 2 µL splitless injection, helium at 2.0 mL/min, temperature ramp 80 °C to 300 °C, APGC with Xevo TQ-S in API+ mode.

Main Results and Discussion

Recoveries for over 50 pesticides ranged from 61% to 113% by UPLC-MS/MS and 57% to 106% by APGC-MS/MS at 10–100 ppb spikes, with RSDs below 20%. Dispersive SPE effectively removed fatty acids and pigments, improving LC performance. PSA/carbon SPE cleanup eliminated colored co-extractives, extending GC column and injection port lifetime from a few to hundreds of injections without maintenance. APGC-MS/MS provided sensitive MRM detection of pendimethalin and other analytes at low ppb levels.

Benefits and Practical Applications

• Integrated two-method workflow on a single Xevo TQ-S platform, reducing LC–GC conversion time to minutes without venting.
• Cleaner extracts lead to reduced instrument downtime and maintenance costs.
• Comprehensive multi-residue capability suitable for regulatory monitoring and routine QA/QC of dried spices.

Future Trends and Potential Applications

Emerging developments may include automated miniaturized sample preparation, high-resolution MS for greater selectivity, and application of APGC-MS/MS to other challenging matrices such as dried herbs, seeds and powders. Method adaptation for non-volatile and thermally labile residues will expand analytical scope.

Conclusion

The optimized QuEChERS extraction and cleanup protocols demonstrated here offer a reliable, high-throughput approach for multi-residue pesticide analysis in dried chili powder. Combining dispersive SPE for LC and SPE cartridge cleanup for GC enables high recoveries, low matrix interference and extended instrument performance on a single mass spectrometer platform.

References

1. Multi-Residue Pesticide Analysis in Tea: Optimized Cleanup After QuEChERS Extraction for UPLC-MS/MS and GC-MS/MS Analysis. Waters Application Note no. 720004819EN, 2019.
2. Multi-Residue Pesticide Analysis in Ginseng Powder: Optimized Cleanup After QuEChERS Extraction for UPLC-MS/MS and GC-MS/MS Analysis. Waters Application Note no. 720005006EN, 2019.