Organophosphorus Pesticides in Apple Matrix by GC/MS/FPD using an Agilent J&W DB-35ms Ultra Inert GC Column

Importance of the Topic

Analysis of organophosphorus pesticide residues in food matrices such as apples is essential to ensure consumer safety and regulatory compliance. These compounds inhibit acetylcholinesterase, posing acute and chronic health risks, especially in vulnerable populations like children. Sensitive, reliable methods that deliver low detection limits and robust quantitation are therefore critical in environmental and food safety testing.

Objectives and Study Overview

This application note describes a rapid, multi-residue method for quantifying trace-level organophosphorus pesticides in apple extracts. The study aims to achieve low ng/mL detection limits using combined GC/MS selective ion monitoring (SIM) and flame photometric detection (FPD), enhanced by capillary flow technology (CFT) and backflush to maximize throughput and reduce carryover.

Methodology

A simplified QuEChERS extraction (Quick, Easy, Cheap, Effective, Rugged, Safe) was employed for sample cleanup. Apple samples were homogenized, spiked at multiple levels (150–750 ng/mL for SIM, 50–250 ng/mL for FPD), and extracted with acetonitrile in the presence of salt packets and dispersive SPE sorbents. Post-extraction, the upper acetonitrile layer was analyzed in a single injection.

Instrumentation

• Agilent 7890 gas chromatograph with 5975C mass selective detector and flame photometric detector in phosphorus mode
• Agilent J&W DB-35ms Ultra Inert column (20 m × 0.18 mm × 0.18 µm) to minimize analyte adsorption and improve peak shape
• Capillary flow technology (CFT) device for a 3:1 split between MSD and FPD ports, with post-run backflush capability
• Agilent 7683B autosampler with a 5 µL syringe

Main Results and Discussion

The DB-35ms UI column achieved baseline resolution of 12 organophosphorus pesticides within 30 minutes, delivering excellent peak symmetry for highly polar analytes such as oxydemeton-methyl and acephate. GC/MS-SIM detection limits ranged from 15 to 25 ng/mL, while FPD detection in phosphorus mode reached 15 ng/mL for most compounds. Recoveries in spiked apple matrices exceeded 75 % (SIM) and 75 % (FPD), with relative standard deviations below 10 %. Backflushing markedly reduced matrix carryover and shortened cycle times by avoiding extended bakeouts.

Benefits and Practical Applications

• Single-injection, multi-detection approach enhances laboratory efficiency and data confidence
• Combined SIM and FPD signals provide complementary selectivity and sensitivity
• QuEChERS sample preparation simplifies workflow while maintaining low-level detection capability
• Backflush technology minimizes downtime and extends instrument cleanliness intervals

Future Trends and Potential Uses

Advancements in column chemistries and multidimensional gas chromatography architectures may further reduce analysis times and improve resolution. Integration of high-resolution mass spectrometry and automated sample preparation could enhance throughput and data quality. Expansion to other food matrices and inclusion of emerging pesticide classes will broaden the scope of routine monitoring.

Conclusion

The described GC/MS/FPD method on an Ultra Inert DB-35ms column, supported by QuEChERS extraction and capillary flow splitting with backflush, offers a robust solution for trace quantitation of organophosphorus pesticides in apples. The approach delivers low detection limits, strong recoveries, and streamlined operation, meeting regulatory requirements for food safety analyses.

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