Method for the determination of 313 Residual Pesticides in Black tea using LCMS-8045 and GCMS-TQ8040 NX

Significance of the topic

Tea is one of the most widely consumed beverages worldwide. To enhance yield and protect crops, a broad spectrum of pesticides is applied during cultivation. Regulatory bodies set stringent maximum residue limits for many pesticides in tea, creating a need for robust analytical methods capable of multi‐residue determination at trace levels.

Objectives and overview of the study

This work describes the development and validation of a high‐throughput, sensitive multi‐residue method for quantifying 313 pesticides in black tea. A modified QuEChERS extraction procedure was combined with ultra‐fast liquid chromatography‐tandem mass spectrometry (LC-MS/MS, Shimadzu LCMS-8045) and gas chromatography-tandem mass spectrometry (GC-MS/MS, Shimadzu GCMS-TQ8040NX) to cover 203 compounds by LC‐MS/MS and 131 by GC‐MS/MS (21 common analytes). Calibration used external standards with 1/C2 weighting over 1–50 μg/L for LC‐MS/MS and 1–15 μg/L for GC‐MS/MS.

Methodology and instrumentation

• Sample preparation: Modified QuEChERS using acidified acetonitrile (LC) or acidified ethyl acetate (GC), with salts (MgSO4, NaCl) for partitioning. Cleanup employed PSA, C18, graphitized carbon black, and additional salts (CaCl2 for GC).
• Reconstitution: After evaporation, extracts were reconstituted in ethyl acetate and diluted threefold for fortified samples.
• LC‐MS/MS conditions: Shim-pack XR-ODS II column, 0.4 mL/min flow, gradient of water/methanol with 2 mM ammonium formate and 0.002% formic acid, run time 21 min, injection 10 μL.
• GC‐MS/MS conditions: SH-Rxi-5Sil MS column, splitless injection (1 μL), helium carrier gas, 25-min oven program from 60 °C to 310 °C.
• Instrumentation: Shimadzu Nexera X2 with LCMS-8045 and AOC-20i with GCMS-TQ8040NX. Method packages and pesticide databases aided rapid method setup. Data processed in LabSolutions Insight.

Main results and discussion

Validation followed SANTE guidelines covering specificity, linearity, recovery, repeatability, and reproducibility.

1. Specificity: Blank responses were below 30% of reporting limits.
2. Linearity: Calibration curves showed R2>0.99 for most analytes within the defined ranges.
3. Recovery: Mean recoveries were 70–120% for 169 compounds in LC-MS/MS and 119 compounds in GC-MS/MS at LOQ; a small subset fell below 70% but met precision criteria.
4. Precision: Repeatability (RSDr) and reproducibility (RSDR) were <20% at LOQ levels for both platforms.
5. LOQs: Achieved 10 µg/kg for 198 LC compounds and 81 GC compounds; higher LOQs were observed for a few analytes.

Benefits and practical applications

• High throughput: Shorter run times and combined LC/GC analysis accelerate sample turnaround.
• Robustness: Lower injection volumes and reduced flow rates extend column life and instrument stability.
• Comprehensive coverage: Simultaneous quantification of a wide range of pesticide classes in a single workflow supports regulatory compliance.
• Ease of use: Preconfigured method packages and automated data processing streamline routine multi‐residue analysis in testing laboratories.

Future trends and potential applications

Continued advancement in mass spectrometric sensitivity and software automation will further lower detection limits and expand coverage of emerging contaminants. Integration with high-resolution MS and rapid sample preparation techniques could enable real-time monitoring of pesticide residues. Applications may extend to other complex matrices, such as herbal products and processed foods.

Conclusion

The presented method offers a simple, sensitive, and reproducible approach for multi‐residue pesticide analysis in black tea. Modified QuEChERS extraction coupled with Shimadzu LC-MS/MS and GC-MS/MS platforms meets regulatory requirements and supports high‐throughput routine testing.

References

1. Anastassiades M., Lehotay S. J., Štajnbaher D., Schenck F. J. Fast and Easy Multiresidue Method Employing Acetonitrile Extraction/Partitioning and “Dispersive Solid-Phase Extraction” for the Determination of Pesticide Residues in Produce, J. AOAC Int., 86, 412–431 (2003)
2. Guidance document on analytical quality control and method validation procedures for pesticide residues and analysis in food and feed. SANTE/12682/2019