Quantitation of pesticide residues in garlic and cumin using an Orbitrap Exploris 120 high-resolution mass spectrometer

Importance of Topic

Accurate quantitation of pesticide residues in spices such as garlic and cumin is critical for food safety and regulatory compliance. High‐resolution mass spectrometry methods offer improved confidence in detection at trace levels, addressing the need for reliable screening of diverse agricultural products. This application note explores a robust multi‐residue approach using the Thermo Scientific™ Orbitrap Exploris™ 120 mass spectrometer, capable of meeting or exceeding EU maximum residue level requirements and enabling both targeted quantitation and non‐targeted screening.

Objectives and Study Overview

The primary goal was to develop and pre‐validate a high‐throughput method for simultaneous quantitation of a broad list of pesticides in garlic and cumin, achieving limits of quantification at or below current legislative thresholds. Two complementary acquisition workflows were implemented:

• Full‐scan data‐independent acquisition (FS‐DIA) for targeted quantitation and confirmation
• AcquireX™ intelligent data acquisition for enhanced unknown screening via automated background exclusion

The method was evaluated against SANTE/12682/2019 guidelines for selectivity, sensitivity, linearity, precision, and recovery, with potential for extension to additional analytes.

Methodology and Instrumentation

Sample preparation followed a modified QuEChERS protocol:

• 2 g spice powder extracted with water (1% acetic acid) and acetonitrile
• Dispersive cleanup using MgSO₄ and sodium acetate salts
• Centrifugation, filtration (0.45 µm), and matrix‐matched spiking at six levels (0.5–100 ng/mL)
• Injection volume: 1 µL

Chromatographic separation was performed on an Accucore aQ column (100 × 2.1 mm, 2.6 µm) using a 15 min gradient from aqueous ammonium formate/formic acid to methanolic mobile phase.

Used Instrumentation

Instrumentation details:

• UHPLC: Thermo Scientific™ Vanquish™ Flex Binary UHPLC system
• Mass spectrometer: Thermo Scientific™ Orbitrap Exploris™ 120
• Acquisition software: Thermo Scientific™ TraceFinder™ for automated data processing and reporting

MS parameters:

• Full‐scan range m/z 100–1100 at 60 000 resolution
• DIA MS2 at 15 000 resolution, stepped HCD (nCE 18, 35, 60)
• Spray voltage: 3.5 kV; capillary temperature: 290 °C; vaporizer temperature: 350 °C

Main Results and Discussion

Targeted quantitation of over 100 pesticides yielded:

• Linearity: R² > 0.99 for > 95% of compounds across 0.5–100 ng/mL
• LOQs: 0.5–10 µg/kg depending on compound, all meeting EU MRL criteria
• Precision: RSD ≤ 15% at LOQ levels
• Recoveries: 70–120% at three concentration levels (1.3, 6.6, 13.3 µg/kg) in both matrices

FS‐DIA quantitation based on accurate‐mass precursor ions was complemented by fragment ion confirmation and library matching. AcquireX workflows used blank matrix subtraction to generate exclusion lists and focused MS2 acquisition on sample‐specific features. This strategy increased confidence in detection and freed capacity for non‐targeted analysis.

Unknown screening identified several unexpected compounds in garlic and cumin, including benzylpiperazine, elaidolinolenic acid, 1‐dodecyl‐2‐pyrrolidinone, octhilinone, and Proxan, illustrating the power of integrated high‐resolution screening with online database searching (e.g., ChemSpider, mzCloud).

Benefits and Practical Applications

Key advantages of this workflow include:

• Simultaneous targeted quantitation and retrospective non‐targeted screening in one run
• High mass accuracy (< 5 ppm) and resolution reduce false positives/negatives
• Automated data processing streamlines laboratory throughput and ensures regulatory compliance
• Flexible software configuration allows rapid transition between quantitative and unknown workflows

This approach supports QA/QC laboratories, regulatory monitoring, and research applications requiring comprehensive pesticide surveillance in complex spice matrices.

Future Trends and Opportunities

Advancements in intelligent data acquisition and spectral libraries will further enhance non‐targeted screening capabilities. Potential developments include:

• Expanded compound databases and in‐silico fragmentation tools for faster unknown identification
• Integration of machine learning to predict sample‐specific background features and optimize exclusion lists
• Higher throughput platforms enabling larger sample sets with minimal user intervention
• Coupling with orthogonal techniques (e.g., NMR) for definitive structural confirmation of novel contaminants

These trends will improve monitoring of emerging residues, environmental pollutants, and novel contaminants in food and agricultural products.

Conclusion

The Orbitrap Exploris 120 combined with QuEChERS extraction and TraceFinder software offers a robust, sensitive, and efficient multi‐residue method for garlic and cumin. It meets stringent EU MRL requirements, provides high confidence in both targeted and non‐targeted analysis, and supports rapid data review. The integration of AcquireX intelligent workflows further streamlines unknown compound discovery, making this approach valuable for regulatory, industrial, and research laboratories.

Reference

• SANTE/12682/2019. Guidance on analytical quality control and method validation procedures for pesticide residues analysis in food and feed. European Commission, 2019.
• SANTE/11813/2017. Guidance document on analytical quality control and validation procedures for pesticide residues analysis in food and feed. European Commission, 2017.