Comprehensive Pesticide Analysis in Juice Using a Combination of GC/MS and LC/MS Methods

Significance of the Topic

The globalization of the food supply and tightening international regulations have driven the need for highly sensitive, selective, and comprehensive pesticide residue analysis in complex food matrices such as vegetable juice. Over 1,000 pesticides are registered in the US and hundreds more worldwide, with maximum residue levels (MRLs) often set at or below 10 ppb. No single analytical technique can cover the full range of chemical classes and physical properties, necessitating a combined approach to meet regulatory and food-safety requirements.

Objectives and Study Overview

This application note describes the development and validation of complementary gas chromatography–mass spectrometry (GC/MS), tandem GC/MS/MS, and liquid chromatography–tandem mass spectrometry (LC/MS/MS) methods on Agilent platforms. The goal was to detect, identify, and quantify 39 representative pesticides in a vegetable juice matrix down to sub-ppb levels, meeting the demands of regulatory monitoring and quality control.

Methods

• Sample Preparation: QuEChERS extraction in buffered water/acetonitrile followed by dispersive SPE cleanup.
• Calibration: Matrix-matched standards (0.5 ng/mL to 1 µg/mL) using weighted linear regression (1/x).
• GC/MS Screening: Retention Time Locking (RTL), Deconvolution Reporting Software (DRS) in full-scan mode, followed by SIM for confirmation.
• GC/MS/MS Confirmation: Multiple Reaction Monitoring (MRM) with optimized precursor/product transitions, collision energies, and backflush to enhance selectivity.
• LC/MS/MS Analysis: ESI positive-mode MRM on C18 column with formic acid/acetonitrile gradient for polar and thermally labile pesticides.
• Performance Evaluation: Limits of detection (LOD) at S/N ≥3, limits of quantitation (LOQ) at S/N ≥10, linearity (R2 >0.98), and recovery studies at 50 ng/mL and 250 ng/mL spike levels.

Used Instrumentation

• GC/MS: Agilent 7890A GC with 5975C MSD, Electron Ionization, DRS and RTL libraries.
• GC/MS/MS: Agilent 7890A GC coupled to 7000B Triple Quadrupole, MRM in EI mode.
• LC/MS/MS: Agilent 1200 HPLC with ZORBAX Eclipse-Plus C18 column, coupled to 6460 Triple Quadrupole with Jet Stream ESI.

Key Results and Discussion

The combined methods achieved comprehensive coverage of 39 pesticides, exploiting each platform’s strengths:

• GC/MS SIM LOQs: 5–50 ng/mL; GC/MS/MS LOQs: 0.25–10 ng/mL; LC/MS/MS LOQs: 0.1–10 ng/mL.
• Linear dynamic ranges typically spanned 2.5 ng/mL to 1 µg/mL for GC/MS/MS and 0.5 ng/mL to 1 µg/mL for LC/MS/MS with R2 >0.98.
• LOD improvements: GC/MS/MS delivered up to tenfold lower detection limits compared to single-quad SIM; LC/MS/MS excelled for polar carbamates and organophosphates.
• Method complementarity: Nonpolar pyrethroids like bifenthrin were best detected by GC/MS/MS (LOD 0.1 ng/mL), while polar analytes such as acetamiprid and imidacloprid favored LC/MS/MS (LOD <0.25 ng/mL).
• Recoveries for most pesticides at both spike levels ranged from 70 % to 120 %, demonstrating acceptable accuracy and matrix compensation.

Benefits and Practical Applications

The integrated GC and LC mass spectrometry workflow enables:

• Comprehensive multi-residue screening and confirmation in a single laboratory.
• Regulatory compliance with international MRLs down to sub-ppb levels.
• Efficient sample throughput via QuEChERS and streamlined MS methods.
• Improved confidence in identification by using qualifier transitions and retention time locking.

Future Trends and Opportunities

Advances likely to further enhance pesticide analysis include:

• High-resolution and time-of-flight MS for non-targeted screening.
• Automated sample preparation and online SPE methods.
• Expanded spectral libraries and AI-driven deconvolution workflows.
• Miniaturization of extraction protocols and green chemistry approaches.
• Integration of data analytics platforms for real-time compliance monitoring.

Conclusion

By leveraging the complementary capabilities of GC/MS, GC/MS/MS, and LC/MS/MS, laboratories can achieve robust, sensitive, and comprehensive analysis of diverse pesticide classes in complex juice matrices. This multi-platform strategy ensures regulatory compliance, maximizes throughput, and provides the selectivity required for confident residue determination.

References

1. Agilent Technologies. Bond Elut QuEChERS Standard Operating Procedure. 2012.
2. Agilent Technologies. Highly Sensitive and Rugged GC/MS/MS Tool for Pesticide Multiresidue Analysis in Food Samples. Publication 5990-5044EN.
3. Agilent Technologies. Screening for 926 Pesticides and Endocrine Disruptors by GC/MS with Deconvolution Reporting Software and a New Pesticide Library. Publication 5989-5076EN.