Determination of 366 Pesticides in Cocoa Liquor

Significance of the topic

Cocoa liquor is a complex, high‑fat, and highly pigmented intermediate used to produce chocolate, cocoa butter and powder. Its composition (lipids, pigments and other coextractives) makes pesticide residue analysis analytically demanding because of severe matrix effects, contamination risk and potential degradation of instrument performance. Reliable multi‑residue methods for cocoa liquor are therefore essential to meet regulatory maximum residue limits and to support food safety, quality control and supply‑chain compliance.

Objectives and study overview

This application study aimed to develop and validate a high‑coverage workflow to quantify 366 pesticide residues in cocoa liquor. The approach combines QuEChERS AOAC extraction, passthrough cleanup using Agilent Captiva EMR‑GPD cartridges, and orthogonal detection by GC/MS/MS and LC/MS/MS in dynamic multiple reaction monitoring (dMRM) mode. The goal was to deliver robust matrix removal, high sensitivity and reproducible quantitation across chemically diverse pesticides for routine regulatory testing.

Methodology and sample preparation

• Sample and extraction: 1.5 g cocoa liquor was extracted following the Agilent Bond Elut QuEChERS AOAC protocol. Samples were hydrated with 4 mL water (0.1% formic acid) and extracted with 15 mL acetonitrile containing 1% acetic acid, followed by addition of AOAC salts and ceramic homogenizers. Mechanical agitation (Geno/Grinder) and centrifugation were used to separate phases.
• Passthrough cleanup: 2.7 mL of crude extract was mixed with 0.3 mL water and passed through a 6 mL Captiva EMR‑GPD cartridge placed on a positive‑pressure manifold. The EMR‑GPD sorbent integrates carbon for pigments, PSA for fatty acid removal and EC‑C18 for hydrophobic cleanup. Eluate was dried with anhydrous MgSO4, centrifuged and aliquots prepared for analysis.
• Post‑treatment: A direct aliquot of the cleaned extract was used for GC/MS/MS; a 5× dilution with water was performed for LC/MS/MS to match LC conditions and reduce matrix load.
• Calibration and QC: Matrix‑matched calibrations were prepared (GC: 2.5–100 ng/mL; LC: 0.5–50 ng/mL). Prespiked QC levels were used (typical spikes: 10 µg/kg for GC targets and 2 µg/kg for LC targets) to evaluate recovery and precision.

Matrix‑optimized MRM and data acquisition

• dMRM acquisition was used on both platforms to maximize sensitivity and selectivity while efficiently using instrument cycle time.
• For GC/MS/MS the Agilent Pesticides & Environmental Pollutants (P&EP) MRM database provided numerous candidate transitions and collision energies, enabling selection of matrix‑optimized quantifier/qualifier transitions for each analyte.
• LC/MS/MS dMRM transitions were adapted from prior Agilent application work to cover polar and thermally labile pesticides.
• Matrix‑specific selection of MRM transitions was emphasized to mitigate matrix suppression/enhancement and to enhance robustness in cocoa liquor.

Used instrumentation

• GC/MS/MS: Agilent 8890 GC coupled to a 7010D triple‑quadrupole MS. Typical configuration: HP‑5Q capillary column (30 m × 0.25 mm, 0.25 µm), helium carrier, split injection (1 µL, 5:1), oven ramp to 310 °C. Source and transfer line at ~280 °C; N2 collision and He quench gases applied; dMRM acquisition used for 76 GC‑amenable pesticides.
• LC/MS/MS: Agilent 1290 Infinity III UHPLC coupled to a 6475 triple‑quadrupole MS. Column: ZORBAX RRHD Eclipse Plus C18 (2.1 × 150 mm, 1.8 µm). Mobile phases: 5 mM ammonium formate + 0.1% formic acid (water) and methanol; flow 0.4 mL/min; injection 2 µL. ESI source with typical drying/sheath gas settings; dMRM acquisition used for 308 LC‑amenable pesticides.
• Sample preparation hardware: QuEChERS AOAC kits, Captiva EMR‑GPD 6 mL cartridges, positive‑pressure manifold (PPM‑48), Geno/Grinder, vortexers and centrifuges.

Main results and discussion

• Scope: Total coverage of 366 unique pesticides: 76 by GC/MS/MS, 308 by LC/MS/MS, with 18 analytes common to both platforms.
• Linearity: All targets met R2 ≥ 0.99 across matrix‑matched calibration ranges (GC 2.5–100 ng/mL; LC 0.5–50 ng/mL).
• Recovery: More than 92% of analytes achieved recoveries between 70% and 120% after QuEChERS extraction and EMR‑GPD cleanup. Very few analytes were outside this range.
• Precision: Reproducibility testing (six replicate injections of prespiked extracts) yielded RSDs below 20% for all pesticides, demonstrating good method precision.
• Method complementarity: Chemical classes guided platform choice — nonpolar, halogenated and thermally stable pesticides (e.g., legacy chlorinated compounds, HCH, DDT family) were best analyzed by GC/MS/MS; polar and thermally labile compounds (e.g., neonicotinoids and many sulfonylureas) were measured by LC/MS/MS. For the 18 overlapping analytes results from both platforms were comparable in linearity, recovery and precision.
• Practical examples: Triazophos showed higher sensitivity by LC/MS/MS in this matrix, while chlorpyrifos was more sensitively detected by GC/MS/MS, illustrating the importance of dual‑platform workflows for comprehensive coverage.

Benefits and practical applications

• The passthrough EMR‑GPD cleanup effectively reduces lipids, pigments and other coextractives, protecting instrument interfaces and improving quantitation in a highly challenging matrix.
• Combined dMRM acquisition and the use of extensive MRM databases accelerate method development and improve robustness by enabling matrix‑specific transition selection.
• The workflow supports high‑throughput routine testing for regulatory compliance, surveillance and quality control in cocoa and other complex, high‑fat food matrices.

Future trends and applications

• Expansion of curated MRM/transition libraries and smarter software tools will further reduce development time and improve matrix‑adaptive selection of transitions.
• Integration of high‑resolution mass spectrometry (HRMS) as a complementary screening step could improve non‑targeted surveillance and identification of unexpected residues or metabolites.
• Automation of cleanup (e.g., cartridge passthrough on automated platforms) and miniaturization of extraction workflows could increase throughput and reduce solvent consumption.
• Ongoing regulatory changes and lowering of MRLs will drive demand for even greater sensitivity and robust matrix compensation strategies in complex commodities.

Conclusion

The presented workflow combining QuEChERS AOAC extraction, Captiva EMR‑GPD passthrough cleanup and complementary GC/MS/MS and LC/MS/MS in dMRM mode provides a validated, high‑coverage solution for 366 pesticides in cocoa liquor. The method demonstrates excellent linearity, accuracy (majority 70–120% recoveries) and precision (RSD <20%), while protecting analytical systems from matrix contamination. It is well suited for routine regulatory and quality testing of cocoa‑derived products.

Reference

• Chaudhary V., Mongia G., Drake M. Approaches to Determine the Flavor and Flavor Chemistry of Cocoa Beans and Cocoa Liquor. Food Science. (publication on cocoa flavor chemistry).
• European Commission. SANTE/11312/2021: Analytical Quality Control and Method Validation Procedures for Pesticide Residues Analysis in Food and Feed. (Guidance document for method validation).
• Agilent Technologies. Agilent MassHunter Pesticides and Environmental Pollutants (P&EP) MRM Database (P&EP 4.0), G9250AA. (MRM database used for GC/MS/MS transition selection).
• Zou A., et al. Comprehensive LC/MS/MS Workflow of Pesticide Residues in Food Using the Agilent 6470 Triple Quadrupole LC/MS System. Agilent application note 5994‑2370EN, 2020.