LC–MS/MS Method Tackles Complex Challenge of Pesticide Detection in Chili Powder

A study published in the Journal of AOAC International has detailed the development and validation of a method for detecting pesticide residues in chili powder (1). The research looks to address a hurdle in food safety: accurately monitoring contaminants in one of the world's most popular, yet analytically challenging, spices.

The research, conducted by a collaborative team from Devchand College, Pollucon Laboratories, and PerkinElmer, provides a robust, high-throughput solution for quantifying 135 different pesticides in the spice simultaneously, helping to assist global food trade by ensuring that products comply with the stringent maximum residue limits (MRLs) set by regulatory bodies such as the European Commission and the Food Safety and Standards Authority of India (FSSAI).

Chili powder presents a formidable challenge for chemists. Its intense red pigmentation and the presence of natural compounds called capsinoids co-extract with pesticides during testing. These substances can severely interfere with laboratory instruments, suppressing or enhancing the signal of pesticide residues. This matrix effect can lead to inaccurate measurements, making it difficult to achieve the low detection levels required by international law, often as strict as 0.01 mg/kg. Previous attempts to mitigate this have involved costly and time-consuming cleanup procedures. The research team set out to develop a method that was not only sensitive and accurate but also practical for routine use in testing laboratories.

A critical step involved a cleanup procedure using dispersive solid-phase extraction (d-SPE) with a specific combination of sorbents: graphitized carbon black (GCB) to remove pigments, primary secondary amine (PSA) to eliminate fatty acids and sugars, and C18 to target non-polar interferents. The researchers tested this combination and found it reduced the amount of non-volatile matrix components by 63%. To further enhance the method, the cleaned extract was evaporated and reconstituted in a solvent compatible with the mass spectrometer, a step that reduced the matrix effect for most compounds to below 35%.

The analytical method was then put through a rigorous validation process as per the SANTE/11312/2021 v2 guidelines, the international benchmark for pesticide residue analysis. The method achieved a limit of quantification (LOQ) of 0.005 mg/kg for all 135 pesticides, meeting the most stringent default MRLs. Recovery rates for most pesticides fell within the acceptable range of 70–110%, with both intra-day and inter-day precision (measured as relative standard deviation) below 15%, indicating high reliability and repeatability. The method demonstrated consistent performance even after 50 consecutive injections of a spiked chili sample, showing no loss of sensitivity.

To demonstrate its practical application, the team analyzed 50 chili powder samples purchased from local markets in the Kolhapur and Mumbai regions. They detected pesticides, including acetamiprid, azoxystrobin, and chlorantraniliprole, in several samples. Reassuringly, all detected residues were below the legal MRLs. The method also successfully quantified residues in intentionally treated (incurred) samples, confirming its effectiveness for real-world monitoring.

By providing a simple, fast, and robust protocol for a notoriously difficult matrix, the research enables testing laboratories to more effectively monitor compliance and protect consumers. Based on its performance, the authors recommend it for routine regulatory testing.

Reference

(1) Shinde, R. C.; Suraliwala, M.; Kumar, D.; Atugade, S.; Shiragave, P. High-Throughput Quantification of Pesticide Residues in Complex Matrix (Chili Powder) Using Liquid Chromatography Tandem Mass Spectrometry: Inter-and Intra-Day Validation. J. AOAC Int. 2025, qsaf079. DOI: 10.1093/jaoacint/qsaf079