Analysis of Pesticide Residues in Apple by GC/MS using Agilent Bond Elut QuEChERS Kits for Pre-injection Cleanup

Significance of the Topic

Pesticide residues in fruits pose a serious public health and regulatory challenge. Apples are among the most widely consumed fruits, and ensuring that pesticide levels remain below maximum residue limits (MRLs) is essential for consumer safety and compliance with international standards. The QuEChERS method has emerged as a powerful approach to prepare complex food matrices for multi-residue analysis, combining simplicity and efficiency while reducing solvent use and processing time.

Objectives and Study Overview

This application note evaluates the original non-buffered QuEChERS procedure, using Agilent Bond Elut QuEChERS kits, for the determination of fifteen structurally diverse pesticides in apple homogenates. The study aimed to demonstrate method performance in terms of sensitivity, accuracy, precision and compliance with a 10 ng/g limit of quantitation (LOQ).

Methodology

The sample preparation workflow consisted of two key steps:

• Extraction: 10 g homogenized apple spiked with pesticide standards and internal standard (triphenyl phosphate) were extracted with 10 mL acetonitrile and salting-out using 4 g MgSO₄ and 1 g NaCl.
• Dispersive SPE Cleanup: A 1 mL aliquot of the acetonitrile layer was treated with 50 mg primary-secondary amine (PSA) and 150 mg MgSO₄ to remove polar interferences, organic acids and residual water before GC/MS analysis.

Instrumentation Used

The chromatographic and mass spectrometric analyses were performed on:

• Gas chromatograph: Agilent 7890A equipped with a 30 m × 0.25 mm × 0.25 µm HP-5ms UI capillary column.
• Mass spectrometer: Agilent 5975C quadrupole MSD operating in selective ion monitoring (SIM) mode for enhanced sensitivity and selectivity.

Main Results and Discussion

The method achieved an LOQ of 10 ng/g for all fifteen pesticides. At a high spiking level (200 ng/g), recoveries ranged from 89 % to 102 % with relative standard deviations (RSDs) below 11 %. At the LOQ, recoveries remained acceptable (72 %–103 %) with RSDs under 11 %. Calibration curves exhibited excellent linearity (R² > 0.99) for most analytes; coumaphos showed slightly lower linearity (R² = 0.95) due to baseline irregularities. Matrix blanks revealed minimal interferences, demonstrating effective cleanup.

Benefits and Practical Applications

The combined QuEChERS extraction and dispersive SPE approach offers:

• Rapid sample throughput with minimal hands-on time.
• Reduced solvent consumption and waste generation.
• Robust performance across multiple pesticide classes.
• Compliance with regulatory MRL requirements for food safety laboratories, QA/QC and routine monitoring.

Future Trends and Opportunities

Emerging developments may further enhance multi-residue pesticide analysis:

• Integration of high-resolution mass spectrometry for broader screening of unknown contaminants.
• Automated QuEChERS workflows to improve reproducibility and reduce manual steps.
• Adaptation to a wider variety of commodity matrices, including high-fat and high-pigment samples.
• Coupling with rapid data processing software and machine learning for real-time decision support and expanded compound libraries.

Conclusion

The original non-buffered QuEChERS protocol using Agilent Bond Elut kits, coupled with GC/MS in SIM mode, provides a quick, easy, cheap and effective solution for reliable quantitation of pesticide residues in apple samples. The method meets stringent regulatory requirements and offers a versatile platform for routine food safety analysis.

References

• United States Environmental Protection Agency. Overview of Pesticide Regulation in the USA. U.S. EPA, 2012.
• Anastassiades M., Lehotay S. J., Stajnbaher D., Schenck F. J. Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) Method. J. AOAC Int. 86:412–431 (2003).
• Zhao L., Schultz D., Stevens J. Analysis of Pesticide Residues in Apple Using Agilent Bond Elut QuEChERS European Standard Kits by LC/MS/MS. Agilent Technologies Publication 5990-3938EN (2009).
• Wylie P. Screening for 926 Pesticides and Endocrine Disruptors by GC/MS with Deconvolution Reporting Software. Agilent Technologies Publication 5989-5076EN (2006).