Unstoppable analysis of pesticides residues in black tea using triple quadrupole GC-MS

Importance of Topic

Monitoring pesticide residues in black tea is essential to ensure consumer safety and regulatory compliance. As botanical products gain popularity worldwide, sensitive and reliable analytical methods are required to detect contaminants at trace levels. High-throughput laboratories must achieve low detection limits while minimizing downtime and matrix interference.

Objectives and Study Overview

This study evaluates the performance of a Thermo Scientific TSQ 9610 triple quadrupole mass spectrometer coupled to a TRACE 1610 gas chromatograph for quantifying over 200 pesticide residues in black tea. The goal is to demonstrate method sensitivity, linearity, accuracy, precision, and robustness in accordance with SANTE/12682/2019 guidelines.

Methodology and Instrumental Setup

Sample Preparation:

QuEChERS extraction with water and acetonitrile followed by solid-phase cleanup using a graphitized carbon black/PSA cartridge. Extracts were concentrated and reconstituted in toluene for GC-MS/MS analysis.

Chromatography and Mass Spectrometry:

• Gas chromatograph: Thermo Scientific TRACE 1610 GC
• Column: TraceGOLD TG-5SILMS, 30 m × 0.25 mm × 0.25 µm (with 10 m SafeGuard)
• Injector: iConnect Split/Splitless (SSL), splitless mode for 1 min at 260 °C, flow 1.4 mL/min He
• Autosampler: AI/AS 1610
• Ion source: NeverVent Advanced Electron Ionization (AEI)
• Mass spectrometer: TSQ 9610 triple quadrupole with XLXR detector
• Acquisition: timed-Selected Reaction Monitoring (t-SRM), minimum three transitions per compound
• Data system: Chromeleon 7.3 CDS, full compliance with 21 CFR Part 11

Main Results and Discussion

Linearity and Sensitivity:

Matrix-matched calibration curves covered 0.01–200 ng/mL with correlation coefficients (R²) > 0.99 for selected pesticides. Limits of quantitation met the typical maximum residue level (MRL) of 0.01 mg/kg.

Accuracy and Precision:

Recoveries for 20 representative analytes spiked at 10, 25, and 50 ppb ranged between 80 % and 120 % (except thermally labile folpet). Intra-day precision (%RSD) was below 10 % for most compounds at the 10 ppb level, complying with SANTE criteria.

Robustness:

Continuous injection of black tea extracts spiked at 50 ppb over 124 injections showed peak area %RSDs below 10 % for all target analytes (except folpet). No maintenance of inlet or ion source was required, demonstrating minimal downtime.

Benefits and Practical Applications

The combined TSQ 9610/TRACE 1610 platform offers:

• High sensitivity for trace-level detection in complex botanical matrices
• Reliable quantitation meeting global MRL requirements
• Streamlined workflow with NeverVent technology reducing instrument downtime
• Automated data processing and compliance checking via Chromeleon CDS

Future Trends and Potential Applications

• Expansion to other botanical products and food matrices for multi-residue screening
• Integration of advanced cleanup techniques and online sample preparation
• Application of machine learning algorithms for enhanced data interpretation
• Development of broader pesticide libraries and isotope-labeled standards

Conclusion

The TSQ 9610 GC-MS/MS system combined with the TRACE 1610 GC and NeverVent AEI source provides a highly sensitive, accurate, and robust method for multi-residue pesticide analysis in black tea. It meets SANTE/12682/2019 validation criteria while maximizing laboratory productivity and ensuring consumer safety.

References

1. SANTE/12682/2019, Analytical quality control and method validation procedures for pesticide residues analysis in food and feed.