Multiresidue Pesticide Analysis in Black Tea and Orange Matrix Using the Agilent 6470B Triple Quadrupole LC/MS System

Significance of the topic

The accurate detection of pesticide residues in food is critical for consumer safety and regulatory compliance. Complex matrices such as black tea and citrus fruits challenge analytical methods due to extensive matrix effects and low maximum residue limits set by authorities. High-sensitivity instrumentation and robust sample preparation are essential to reliably quantify trace levels of multiple pesticide classes in diverse food products.

Objectives and study overview

This study aimed to develop and validate a multiresidue screening protocol capable of detecting 244 pesticides in two demanding food matrices: organic loose‐leaf black tea and whole organic oranges. Using an Agilent 6470B triple quadrupole LC/MS system coupled with an Agilent 1290 Infinity II UHPLC platform, the work assessed sensitivity relative to a default maximum residue limit (MRL) of 10 µg/kg, evaluated calibration performance, and examined matrix effects and recoveries.

Methodology and sample preparation

Samples were prepared using a modified QuEChERS approach:

• 2 g of black tea wetted and incubated with 8 mL water, homogenized oranges (10 g) prepared similarly.
• Extraction with 10 mL acetonitrile, addition of Agilent EN extraction salts, vigorous shaking and centrifugation.
• Dispersive SPE cleanup using matrix-appropriate Agilent QuEChERS EN kits, centrifugation, filtration through 0.45 µm membranes.
• Spiking of extracts with a comprehensive pesticide mix to prepare seven calibration levels (0.5–100 ppb) and determination of method detection limits (MDL) and lower limits of quantitation (LLOQ).

Used Instrumentation

• Agilent 1290 Infinity II UHPLC: high-speed pump, multisampler with cooler, multicolumn thermostat.
• ZORBAX RRHD Eclipse Plus C18 column (3.0 × 100 mm, 1.8 µm) at 40 °C, 2 µL injection, binary gradient (5 mM ammonium formate/0.1% formic acid in water and methanol) at 0.4 mL/min over 14.5 min.
• Agilent 6470B triple quadrupole LC/MS with Jet Stream source and VacShield maintenance-free interface.
• Dynamic MRM acquisition with fast polarity switching, unit mass resolution, 500 ms cycle time; data analysis via Agilent MassHunter with 1/x-weighted linear regression ignoring origin.

Main results and discussion

Retention times remained stable and all 244 pesticides were baseline‐separated within a 14.5 min gradient. Calibration curves demonstrated excellent linearity (R² > 0.99), precision (RSD < 20%) and accuracy (80–120%) at and above LLOQ. In orange extracts, 243 of 244 compounds exhibited LLOQs ≤ 10 ng/g; in black tea, 239 of 244 achieved this sensitivity. Recoveries at the default MRL (10 µg/kg) fell within SANTE guidelines for approximately 50% of the pesticides in orange and 40% in tea, reflecting stronger matrix effects in the tea extract. Twelve pesticides were detected in the ‘‘organic’’ blanks, underscoring the need for sensitive screening.

Contributions and practical applications

This workflow demonstrates that the 6470B triple quadrupole LC/MS platform achieves regulatory sensitivity for multiresidue pesticide analysis in challenging matrices. Its high uptime, minimal maintenance, and robust performance make it suitable for routine QA/QC laboratories monitoring food safety. Matrix-matched calibration is recommended for heavily pigmented or complex samples to correct for suppression or enhancement.

Future trends and potential applications

• Integration of high-resolution MS for non-targeted screening alongside targeted quantitation.
• Automation of sample preparation to enhance throughput and reproducibility.
• Development of greener extraction solvents and miniaturized cleanup techniques.
• Implementation of advanced data analytics and informatics for rapid decision support in food safety.

Conclusion

The Agilent 6470B triple quadrupole LC/MS coupled with a UHPLC system and optimized QuEChERS protocol delivers reliable quantitation of 244 pesticides at levels below European MRLs in complex food matrices. The method’s high sensitivity, accuracy, and robustness support its adoption in regulatory and industrial laboratories.

References

1. Title 7 U.S. Code of Federal Regulations – Part 205. US-EPA.
2. SANTE/12682/2019 European Commission guidelines on pesticide residue analysis.
3. Title 40 U.S. Code of Federal Regulations – Part 180. US-EPA.
4. Regulation (EC) No 396/2005. European Commission pesticide residues database.