Determination of Pesticides in Grapes, Baby Food and Wheat Flour by Automated Online Sample Preparation LC-MS/MS

Significance of the topic

The determination of pesticide residues in food matrices is critical for consumer safety and regulatory compliance. With stringent EU maximum residue limits and the need for high-throughput analysis, automated online sample preparation coupled with LC-MS/MS delivers improved accuracy, reproducibility, and reduced labor requirements.

Objectives and overview of the study

This work presents Method 52213, which integrates automated online cleanup using the Thermo Scientific Transcend TLX system with TurboFlow Technology and a TSQ Quantum Access MAX triple quadrupole mass spectrometer. The method targets 48 pesticides in grapes, composite baby foods, and wheat flour, achieving detection limits below EU MRLs and allowing straightforward extension to additional compounds and matrices.

Used instrumentation

• Thermo Scientific Transcend TLX system with TurboFlow Technology
• TSQ Quantum Access MAX triple quadrupole mass spectrometer
• TurboFlow Cyclone MCX-2 (50 × 0.5 mm) column
• Hypersil GOLD analytical column (150 × 4.6 mm, 5 µm) with Hypersil GOLD guard (10 × 4 mm, 5 µm)
• Transcend TLX autosampler with 100 µL injection syringe
• Auxiliary laboratory equipment: ultrasonic bath, microcentrifuge, vortex shaker

Methodology and instrumentation

Sample (0.5 g) is extracted with acetonitrile and internal standards, followed by ultrasonic extraction, centrifugation and PTFE filtration. The crude extract is directly loaded onto the TurboFlow column to remove macromolecules and pre-concentrate analytes. After online transfer to the analytical LC column, gradient separation is performed under Aria control. Detection is achieved by selected reaction monitoring (SRM) on the TSQ Quantum Access MAX, with quantification via matrix-matched calibration and internal standard response factors.

Main results and discussion

• LODs of 0.8–10.3 ng/g and LOQs of 2.4–31 ng/g across matrices, meeting or exceeding EU regulatory requirements, including the 10 ng/g limit for baby foods.
• Recoveries between 70 % and 125 % at spike levels of 10, 100 and 250 ng/g with RSDs below 20 %.
• Within-day and between-day precision values under 20 % RSD for all target analytes and matrices.
• Robust performance confirmed by varying extraction and processing parameters without significant impact on results.
• Throughput of approximately 100 samples per day with a 13-minute run time per sample.

Benefits and practical applications

• Automated workflow reduces manual handling and potential for cross-contamination.
• Suitable for routine regulatory screening and quality control in food safety laboratories.
• High sensitivity and selectivity enable reliable multi-residue monitoring in diverse food matrices.
• Scalable and adaptable to incorporate additional pesticides and sample types.

Future trends and potential applications

• Expansion of analyte panels and extension to new matrices using the same online cleanup platform.
• Integration of high-resolution mass spectrometry for non-targeted screening.
• Development of greener extraction solvents and miniaturized sample preparation modules.
• Advanced software algorithms for automated data processing and regulatory reporting.

Conclusion

The automated online sample preparation LC-MS/MS method offers a robust, high-throughput solution for multi-residue pesticide analysis in food. Its combination of TurboFlow cleanup and triple quadrupole detection ensures accurate quantification at low levels, making it a valuable tool for food safety and compliance testing.

References

1. IUPAC/AOAC Guidelines for Single-Laboratory Validation of Methods, AOAC International.
2. Harmonized Guidelines for Single-Laboratory Validation of Methods, Association of Analytical Communities.
3. European Regulation 396/2005 on maximum residue levels in food and feed.