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

Multi-residue pesticide analysis in dried chili powder is critical for ensuring consumer safety and regulatory compliance. The highly oily and resinous nature of chili powder challenges traditional extraction and cleanup approaches, driving the need for optimized workflows that deliver accurate results and reduce instrument downtime.

Objectives and Study Overview

This study presents optimized cleanup strategies following a modified QuEChERS extraction to enable reliable quantitation of a broad range of pesticides in chili powder by both UPLC–MS/MS and GC–MS/MS using APGC.

• Adapt a QuEChERS protocol for a water-equilibrated, dried chili powder matrix.
• Compare dispersive SPE (dSPE) and cartridge SPE cleanups tailored for LC and GC analysis.
• Assess recovery performance and reproducibility for over 50 pesticide residues against EU maximum residue limits (MRLs).

Methodology

Sample Preparation:

• Hydration: Mix 2 g chili powder with 10 mL water, equilibrate 30 min.
• Extraction: Add 10 mL acetonitrile and QuEChERS salts (DisQuE pouch), shake and centrifuge.

dSPE Cleanup for UPLC–MS/MS:

• Aliquot 1 mL extract into a dSPE tube containing 150 mg MgSO4, 25 mg PSA, 25 mg C18, 7 mg GCB.
• Vortex, centrifuge, dilute supernatant to 1 mL with aqueous ammonium acetate.

SPE Cleanup for APGC–MS/MS:

• Dilute 1 mL extract with 10 mL acetone/toluene (3:1).
• Pass through a PSA/carbon Sep-Pak cartridge loaded with 200 mg MgSO4.
• Rinse, evaporate, exchange toluene to final 0.5 mL for injection.

Used Instrumentation

• ACQUITY UPLC I-Class with BEH C18 column (2.1×100 mm, 1.7 µm).
• Xevo TQ-S Mass Spectrometer for UPLC and APGC operation.
• Atmospheric Pressure Gas Chromatography source.
• Agilent 7890 GC with J&W DB-5 MS column (30 m×0.25 mm×0.25 µm).

Main Results and Discussion

UPLC–MS/MS recoveries ranged from 61 % to 113 % at 10 and 100 ppb, with relative standard deviations below 20 %. APGC–MS/MS recoveries spanned 58 % to 106 % at equivalent levels. The dual cleanup approach effectively removed fatty acids, pigments, and polyphenols, as evidenced by clear extracts and stable chromatography. A 10 ppb pendimethalin spike yielded clean MRM chromatograms, demonstrating method sensitivity.

Comparative cleanup visuals showed significant reduction of colored matrix in both dSPE and SPE protocols, extending column and injection port lifetimes from a few samples to hundreds without maintenance.

Benefits and Practical Applications

• Streamlined sample prep with rapid QuEChERS extraction and targeted cleanups.
• One mass spectrometer configured for fast switching between LC and GC reduces capital and downtime.
• Robust performance across diverse pesticide chemistries supports routine QA/QC in food safety labs.

Future Trends and Opportunities

Emerging directions include integration of automated QuEChERS-dSPE workflows, exploration of novel sorbents for enhanced matrix removal, and application of this dual-cleanup strategy to other high-resin spices and dried botanicals. Data-driven optimization and miniaturized extraction platforms may further increase throughput and sustainability.

Conclusion

The presented protocols deliver effective multi-residue pesticide analysis in dried chili powder, achieving high recoveries, low variability, and clean extracts suitable for both UPLC–MS/MS and APGC–MS/MS. These workflows enhance laboratory efficiency and support stringent regulatory monitoring.

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.
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.