Determination of Pesticides in Tea Automated with FREESTYLE QuEChERS and LC-MS/MS

Importance of the topic

The analysis of pesticide residues in tea is critical for ensuring food safety and regulatory compliance. Tea, as a complex matrix with high levels of pigments and polyphenols, poses challenges for mass spectrometric detection due to matrix effects. Automating clean-up steps can enhance precision and throughput in routine pesticide monitoring laboratories.

Objectives and overview of the study

This study evaluates an automated, non-dispersive clean-up approach using the FREESTYLE QuEChERS system coupled with direct injection LC-MS/MS. Tea samples were spiked with a 220-pesticide mix to assess recovery, reproducibility, and matrix suppression reduction.

Methodology and instrumentation

• Sample preparation: 2 g homogenised tea extracted with water and acetonitrile, followed by salt addition and centrifugation.
• Automated clean-up: FREESTYLE BASIC robotic platform with SPE module processes 60 samples unattended, retaining matrix components on cartridges.
• Instrumentation: Direct injection into Agilent 1290 HPLC linked to an API 5500 triple quadrupole mass spectrometer in positive SMRM mode.
• Chromatographic conditions: RP-18 column with a rapid gradient from 5 to 100 percent methanol in 5 minutes, 0.7 mL/min, 30 °C.

Main results and discussion

The automated workflow achieved recoveries between 60 and 120 percent for 82 percent of the pesticides. A few compounds exhibited recoveries outside this range due to matrix ion suppression or enhancement; most showed relative standard deviations below 20 percent. UV absorbance scans (200–800 nm) demonstrated a clear reduction of co-extracted matrix components after clean-up.

Benefits and practical applications

Automating the QuEChERS clean-up step enhances sample throughput (up to 120 samples per run) and precision, delivers cleaner extracts, and reduces operator variability. The system supports 24/7 operation, making it suitable for high-throughput routine analyses in food safety, QA/QC, and regulatory laboratories.

Future trends and potential applications

Further development may extend automated clean-up to other challenging matrices such as herbal supplements or complex foodstuffs. Integration with high-resolution mass spectrometry and machine-learning-driven data processing can further improve sensitivity and workflow efficiency.

Conclusion

The FREESTYLE QuEChERS automation provides a reliable, reproducible, and high-throughput solution for pesticide residue analysis in tea, significantly reducing matrix interferences and supporting regulatory compliance.

Used instrumentation

• FREESTYLE QuEChERS BASIC robotic platform and SPE module
• Agilent Infinity II 1290 HPLC with direct injection module
• API 5500 Triple Quad mass spectrometer with Turbo Spray ESI

References

None provided.