Quantitation of Over 300 Pesticide Residues in Three Processed Cocoa Matrices

Summary: Quantitation of Over 300 Pesticide Residues in Processed Cocoa Matrices

Importance of the topic

Routine, high-throughput screening for pesticide residues in processed cocoa (powder, liquor, and butter) is critical for food safety, export compliance, and sustainable processing. Cocoa matrices are complex (high pigment and lipid content) and pose analytical challenges that require robust extraction, selective cleanup, and sensitive LC/MS/MS measurement to ensure reliable detection at low ng/mL levels.

Objectives and overview of the study

This application study aimed to develop and validate a comprehensive workflow to quantify 308 pesticide residues across three processed cocoa matrices. The goals were to achieve low limits of quantitation, high recoveries, good precision, minimal matrix interference and carryover, and a practical sample-preparation method suitable for routine laboratory testing in support of expanded cocoa processing capacity.

Methodology

Sample preparation and cleanup

• Sample mass: 1.5 g of matrix (powder, liquor, butter).
• Spiking for recovery studies: 150 µL of 1 or 5 µg/mL solutions (evaluated at 2 and 10 ng/mL final).
• Extraction: addition of 4 mL 0.1% formic acid then 15 mL acidified acetonitrile (1% acetic acid), agitation (Geno/Grinder), and centrifugation.
• Cleanup: Agilent Captiva EMR–GPD 6 mL pass-through cartridges containing Carbon S (pigment removal), PSA (fatty acid removal), and C18 (hydrophobic matrix removal). Eluate dried over anhydrous MgSO4, then diluted 1:5 with water prior to LC/MS.
• Calibration: matrix-matched calibration in blank matrix at 0.5, 2, 5, 10, and 50 ng/mL; LOQ defined at 0.5 ng/mL (S/N > 10).

Used instrumentation

• LC: Agilent 1290 Infinity III platform (High-Speed Pump G7120A, Multisampler G7167B, Multicolumn Thermostat G7116B, InfinityLab Assist Hub G7180A).
• Column: Agilent ZORBAX RRHD Eclipse Plus C18, 2.1 × 150 mm, 1.8 µm.
• MS: Agilent 6475 Triple Quadrupole LC/MS with Agilent Jet Stream (AJS) ion source operating in dMRM mode with positive and negative polarity.
• Key LC conditions: 40 °C column temperature, mobile phases with 5 mM ammonium formate + 0.1% formic acid (A) and + 0.1% methanol (B), 0.4 mL/min flow, gradient from 5% to 100% B, 2 µL injection volume.
• Key MS source parameters: drying gas 200 °C/9 L/min, sheath gas 400 °C/12 L/min, nebulizer 35 psi, capillary voltage +2,500 V / -3,000 V. dMRM transitions optimized for 308 analytes.

Main results and discussion

• Analytes and sensitivity: All 308 pesticides detected down to 0.5 ng/mL with S/N > 10; LOQ set at 0.5 ng/mL for the method.
• Linearity: Excellent linearity across matrices. R2 ≥ 0.990 for all compounds. Cocoa powder showed strongest linearity (≈88% of analytes R2 ≥ 0.995), liquor and butter slightly lower but acceptable.
• Recovery: At 2 and 10 ng/mL, >90% of pesticides met 70–120% recovery in cocoa powder and liquor (289 compounds, 93.8%). Cocoa butter performed slightly less well (90% within 70–120% recovery), with a modest increase in low recoveries attributed to higher lipid content.
• Precision: High repeatability observed. At 2 ng/mL, >93% of pesticides exhibited RSD < 10% across matrices (96.1% powder, 94.5% liquor, 93.2% butter).
• Matrix effects and carryover: No significant carryover or MRM interference detected after cleanup; the Captiva EMR–GPD passthrough approach effectively reduced pigment and lipid interferences.

Benefits and practical applications

Combined use of the Bond Elut QuEChERS AOAC extraction kit and Captiva EMR–GPD passthrough cartridges delivers a streamlined, scalable workflow for routine pesticide screening in processed cocoa. Practical advantages include:

• Comprehensive multi-residue capability (308 targets) in a single LC/MS/MS run using dMRM.
• Low LOQ (0.5 ng/mL) suitable for regulatory monitoring and export control.
• High throughput sample preparation compatible with positive pressure manifolds (PPM-48) and common bench equipment.
• Effective pigment and lipid removal enabling robust quantitative performance across different processed cocoa forms.

Future trends and potential uses

The workflow supports several opportunities for future development and broader application:

• Extension to other high-pigment, high-lipid commodity matrices (e.g., spices, nuts, chocolate products) using similar passthrough EMR cleanup strategies.
• Integration with automated sample-prep platforms to increase throughput for commercial testing laboratories and regulatory agencies.
• Expansion of target lists and incorporation of HRMS screening for non-targeted or emerging contaminants while retaining the validated targeted dMRM quantitation for routine monitoring.
• Adoption of isotopically labelled internal standards to further improve quantitation in high-lipid matrices such as cocoa butter.

Conclusion

The described method provides a validated, high-performance approach to quantify over 300 pesticides in processed cocoa powder, liquor, and butter. The combination of QuEChERS AOAC extraction and Captiva EMR–GPD cleanup, paired with Agilent 6475 triple quadrupole LC/MS in dMRM mode, achieved low LOQs, strong linearity, high recoveries for the majority of targets, and excellent precision—demonstrating suitability for routine food-safety screening in the cocoa processing industry.

Appendix: scope of analytes

The study includes an explicit appendix listing the 308 pesticide residues evaluated, spanning a broad range of chemical classes (organophosphates, carbamates, neonicotinoids, pyrethroids, triazoles, strobilurins, herbicides, fungicides, and others). The full compound list is provided in the original appendix of the application note.

References

1. Zhao, L.; Andrianova, A. Determination of Over 300 Pesticides in Cinnamon Using Captiva EMR–GPD Passthrough Cleanup and LC/MS/MS and GC/MS/MS Detection. Agilent Technologies Application Note, publication 5994-5671EN, 2023.
2. Zou, A.; Pillai, S.; Kornas, P.; Schober, M.; Zhao, L.; Zanotti, M.; Gan, C. S. Comprehensive LC/MS/MS Workflow of Pesticide Residues in Food Using the Agilent 6470 Triple Quadrupole LC/MS System. Agilent Technologies Application Note, publication 5994-2370EN, 2020.