Analysis of Pesticides in Tomato and Kale on GC/MS/MS with Agilent Bond Elut QuEChERS High Pigment dSPE with Carbon S

Significance of the Method

The analysis of pesticide residues in highly pigmented food matrices such as tomato and kale presents challenges due to co-extractable pigments that can interfere with GC/MS/MS detection, cause matrix effects, and increase instrument maintenance. Effective pigment removal is essential for achieving reliable, accurate, and repeatable quantitation of trace-level pesticides in food safety and regulatory testing.

Study Objectives and Overview

This work aimed to validate a rapid multiresidue method for planar pesticide analysis in tomato and kale, combining Agilent’s Bond Elut QuEChERS EN extraction kit with a High Pigment dispersive SPE cleanup containing Carbon S sorbent, followed by analysis on an Agilent 8890 GC coupled to a 7010C triple quadrupole MS. The performance was benchmarked against traditional graphitized carbon black (GCB)-based QuEChERS cleanup kits.

Instrumentation Used

• Agilent 8890 GC system with purged Ultimate Union backflush
• Agilent 7010C triple quadrupole GC/MS
• Agilent 7693A automatic liquid sampler (ALS) with multimode inlet and electronic pneumatic control
• Agilent MassHunter Workstation software for data acquisition and analysis

Methodology

Ten-gram homogenized samples of organic tomato or kale were spiked with a mixed pesticide standard and 10 mL acetonitrile. Samples were extracted using QuEChERS EN salts, shaken, and centrifuged. Aliquots of crude extract (1 or 6 mL) were cleaned using High Pigment dSPE tubes containing Carbon S sorbent. After vortexing and centrifugation, extracts were transferred into GC/MS vials. Instrumental analysis employed multiple reaction monitoring (MRM) for target and deuterated internal standards, with matrix-matched calibration from 0.5 to 50 ppb.

Results and Discussion

The Carbon S cleanup delivered efficient pigment removal and minimized analyte loss for planar pesticides. Over 85 % of targets were identified with recoveries between 70 % and 130 % and RSDs below 30 % in both tomato and kale. Carbon S outperformed or matched traditional GCB cleanup, particularly for sensitive compounds like hexachlorobenzene and chlorothalonil. Chromatograms showed reduced background and improved peak shapes, confirming enhanced matrix cleanup.

Benefits and Practical Applications

• Robust removal of chlorophyll, carotenoids, and anthocyanins without sacrificing analyte recovery
• High-throughput sample preparation compatible with existing QuEChERS workflows
• Enhanced GC/MS/MS uptime and reduced maintenance due to cleaner extracts
• Reliable quantitation of trace-level pesticides in regulatory and QA/QC laboratories

Future Trends and Potential Applications

Emerging directions include extending Carbon S-based cleanup to a broader range of food and environmental matrices, miniaturizing QuEChERS for microscale analysis, integrating AI-driven method optimization, and coupling with high-resolution MS for non-polar and polar analytes. Development of hybrid sorbents tailored to specific pigment profiles and automated online cleanup platforms may further streamline pesticide residue workflows.

Conclusion

The validated QuEChERS EN extraction combined with High Pigment dSPE using Carbon S and GC/TQ analysis provides a rapid, reliable, and high-throughput solution for planar pesticide residue testing in deeply colored produce. It offers improved pigment removal and analyte recovery compared to traditional GCB methods, enabling accurate quantitation and reduced instrument downtime.

References

1. González-Curbelo, M. Á.; Trends in Anal. Chem. 2015, 71, 169–185.
2. Varela-Martínez, D. A.; Liquid-Phase Extraction Handbooks in Separation Science, 2020, Chp 14, 399–437.
3. Andrianova, A.; Agilent Technologies Application Note 5994-0799EN, 2019.