Brewing Excellence: Quantitating Over 200 Pesticides in Black Tea with Steady Performance and Maximized Uptime by GC/MS/MS

Significance of Pesticide Analysis in Black Tea

Tea is one of the world’s most consumed beverages, and intensive pesticide use in tea cultivation raises health and regulatory concerns. Accurate measurement of trace pesticide residues in black tea is essential to ensure consumer safety and regulatory compliance globally.

Study Objectives and Overview

This work demonstrates a robust workflow to quantify 246 volatile and semi-volatile pesticides in black tea using a state-of-the-art GC/MS/MS system. Key goals included achieving ultra-low limits of quantitation (LOQs), wide dynamic range calibration, high precision over extended sample runs, and minimal instrument downtime.

Sample Preparation

• QuEChERS extraction with acetonitrile (2% formic acid) and EN salts.
• EMR mixed-mode pass-through cleanup using Captiva EMR–GPD cartridges to remove pigments and high-boiling surfactants.
• Final sample dilution (5×) and addition of parathion-d10 internal standard (10 ppb).

Použitá instrumentace

• Agilent 8890 GC with multimode inlet in cold splitless mode, equipped for midcolumn backflushing via the Purged Ultimate Union (PUU) and pneumatic switching device.
• Two identical HP-5ms UI columns (15 m×0.25 mm, 0.25 µm) for analyte separation and backflush.
• Agilent 7010D Triple Quadrupole MS with High Efficiency Source 2.0 (HES 2.0) for enhanced ion transmission and robustness.
• MassHunter Acquisition 13.0 for GC/MS, dynamic MRM (dMRM) using the Pesticides & Environmental Pollutants MRM Database 4.0, and retention time locking functionality.

Methodology Highlights

• dMRM acquisition with up to 749 transitions and 64 concurrent MRMs for high selectivity in complex matrix.
• Retention time locking to ensure consistent compound identification and simplify method transfer.
• Cold splitless injection optimized to reduce carryover of high-abundance tea components (e.g., caffeine).
• Midcolumn backflush reduced cycle time by ~50% and prevented matrix overload in the MS source.

Main Results and Discussion

• Limits of Quantitation: LOQs as low as 0.01 ppb for 34% of analytes; ≤0.1 ppb for 74%; ≤2 ppb for 96%.
• Calibration: Linear or quadratic fits over five orders of magnitude (0.01–1,000 ppb) with R2 > 0.99 and relative standard error < 20%, meeting SANTE 11312/2021 criteria.
• Recovery and Precision: Surrogate tea spiked at 10 and 50 ppb (equivalent to 2 and 10 ppb in extract) showed recoveries within 80–120% and RSD < 20% for all but the most challenging compounds.
• Ruggedness and Throughput: 800 consecutive injections of 2 ppb-spiked tea extract over 17 days yielded RSD < 20% for 176 analytes. No GC inlet or MS source cleaning was required during this period.
• Instrument Health Monitoring: Early Maintenance Feedback dashboard and EM voltage tracking ensured proactive maintenance and consistent performance.

Benefits and Practical Applications

This workflow maximizes laboratory uptime and throughput while delivering ultra-trace sensitivity, wide dynamic range, and regulatory compliance. It is directly applicable to QC labs, food safety testing, and regulatory monitoring of tea and other complex plant matrices.

Future Trends and Potential Applications

• Broader adoption of retention time locking and AI-driven spectral deconvolution to simplify method development and compound confirmation.
• Integration of real-time maintenance feedback with laboratory information management systems (LIMS) to further reduce downtime.
• Extension of this GC/TQ approach to other challenging matrices—herbal products, spices, and environmental samples—for pesticide and pollutant screening.

Conclusion

The optimized QuEChERS-EMR cleanup combined with Agilent’s 8890 GC and 7010D GC/TQ with HES 2.0 offers a highly sensitive, precise, and rugged solution for quantifying over 200 pesticides in black tea. The method achieves low-ppb LOQs, broad calibration range, and sustained instrument performance without frequent maintenance, supporting high-throughput food safety laboratories.

Reference

• SANTE/11312/2021: Analytical Quality Control and Method Validation Procedures for Pesticide Residues Analysis in Food and Feed.
• Agilent Pesticides & Environmental Pollutants MRM Database 4.0.
• Agilent Application Note 5994-4965EN: Five Keys to Unlock Maximum Performance in the Analysis of Over 200 Pesticides in Challenging Food Matrices by GC/MS/MS.