Quantitative Analysis of Pesticides in Celery and Grape

Importance of the Topic

Rapid and accurate determination of pesticide residues in fruits and vegetables is essential to ensure food safety and comply with regulatory limits. Celery and grapes represent commonly consumed produce with significant pigment content that can interfere with detection. A robust sample preparation and cleanup approach is critical to minimize matrix effects and achieve reliable quantitation by LC/MS/MS.

Objectives and Study Overview

The study aimed to compare the performance of the Agilent Bond Elut QuEChERS Universal dispersive SPE kits containing either Carbon S or graphite carbon black (GCB) sorbents. Both 2 mL and 15 mL dSPE formats were evaluated. Key goals included:

• Assessing recovery and reproducibility for 45 representative pesticides in celery and grape matrices.
• Evaluating pigment removal efficiency and matrix cleanup.
• Validating quantitative performance in terms of linearity, accuracy, and precision.

Methodology and Instrumentation

Sample Preparation

• Homogenized 15 g of celery or grape with 15 mL acetonitrile containing 1% acetate buffer following AOAC 2007.01 QuEChERS extraction.
• Shake for 5 minutes, centrifuge at 4 000 rpm and 10 °C.
• Transfer supernatant to dSPE tubes: 8 mL for 15 mL kits and 1 mL for 2 mL kits.
• Clean up with either 50 mg PSA/50 mg C18/7.5 mg Carbon S (or GCB) plus MgSO4, shake, and centrifuge.
• Dilute 200 µL of extract with water and inject 2 µL to LC/MS/MS.

Instrumentation

• LC System: Agilent 1290 Infinity II with Poroshell 120 EC-C18 column, 2.1×100 mm, 2.7 µm at 40 °C.
• Mobile phases: water and methanol both containing 4.5 mM ammonium formate, 0.5 mM ammonium fluoride, 0.1% formic acid.
• Gradient 0–20 min, flow 0.4 mL/min, autosampler at 10 °C.
• MS Detection: Agilent 6470A triple quadrupole with Jet Stream electrospray, dynamic MRM, gas temp 250 °C, sheath gas 350 °C.

Main Results and Discussion

Recovery and Precision

• The Carbon S dSPE delivered over 80% average recovery and ≤10% RSD for more than 90% of the 45 pesticides in both matrices.
• Planar pesticides showed significantly improved recoveries with Carbon S compared to GCB, especially at low spiking levels (4 ng/g).
• Both 2 mL and 15 mL Carbon S formats outperformed or matched the traditional GCB kits in reproducibility.

Pigment Removal

• Visual comparison of celery extracts after cleanup indicated equivalent decolorization for Carbon S and GCB sorbents, ensuring minimal matrix coloration.

Method Validation

• Calibration curves were linear over 0.5–100 ng/g with R2 > 0.997 for all targets.
• Accuracy ranged above 75% for nonplanar and above 60% for planar pesticides.
• Precision was demonstrated with RSDs below 10% at both 4 ng/g and 50 ng/g levels.

Benefits and Practical Applications

The novel Carbon S cleanup provides a better balance between pigment removal and analyte recovery. Laboratories can achieve more consistent quantitation of sensitive planar pesticides while maintaining efficient cleanup. The universal kit simplifies method selection across various high-pigment produce.

Future Trends and Opportunities

• Extension of Carbon S cleanup to other challenging matrices such as berries and leafy greens.
• Integration with automated sample preparation platforms for high throughput analysis.
• Development of hybrid sorbents combining Carbon S with polymeric phases for enhanced selectivity.
• Application of green solvents and miniaturized QuEChERS formats for reduced solvent consumption.
• Use of chemometric and AI-driven data processing to further correct matrix effects.

Conclusion

The Agilent Bond Elut QuEChERS Universal dSPE kit with Carbon S sorbent offers superior performance in pesticide analysis of celery and grapes. Improved recoveries for planar compounds, robust reproducibility, and equivalent pigment removal make this approach a reliable solution for food safety testing by LC/MS/MS.

Reference

• Yang X and Li Z. Quantitative Analysis of Pesticides in Celery and Grape Using the Agilent Bond Elut QuEChERS Universal dispersive SPE Kit with Carbon S cleanup by LC/MS/MS. Agilent Technologies Application Note, 2022.