Organophosphorus Residues in Olive Oil by GC/FPD with Agilent J&W DB-35ms Ultra Inert

Importance of the topic

The analysis of organophosphorus pesticide residues in olive oil is critical due to the high lipid content of the matrix and widespread consumption of olive oil in human diets. These pesticides can concentrate during oil extraction, posing acute and chronic health risks. Developing robust, sensitive, and rapid analytical methods ensures consumer safety, regulatory compliance, and reliable monitoring of food products.

Objectives and Study Overview

This application note describes a streamlined workflow to quantify 16 organophosphorus pesticides in olive oil at low parts per billion levels. The method combines a simplified QuEChERS extraction, analyte protectant addition, and gas chromatography with a flame photometric detector (FPD) in phosphorus mode, complemented by GC/MS confirmation. Goals included fast chromatographic separation (<16 minutes), low detection limits (10–15 ng/mL), high recoveries (63–110%), and precision (RSD < 9%).

Methodology and Instrumentation

Sample preparation utilized a modified QuEChERS approach: 3 g of oil was diluted with water, extracted with acetonitrile, and cleaned using dispersive SPE with MgSO₄ and NaCl salts. A second cleanup step targeted fats, followed by addition of 0.5 mg/mL L-gulonolactone as an analyte protectant. Chromatographic analysis employed an Agilent 7890 GC/5975C MSD with a 7683B autosampler and a 30 m×0.25 mm×0.25 µm Agilent J&W DB-35ms Ultra Inert column. Helium carrier gas at constant pressure (28.85 psi) and a temperature program from 95 °C to 290 °C enabled separation of all pesticides in under 16 minutes. A capillary flow technology splitter directed effluent 1:1 to the MSD (SIM mode) and the FPD (phosphorus mode). Automated backflush removed late-eluting matrix components to minimize carryover and extend column and source life.

Main Results and Discussion

The method achieved baseline resolution of 16 organophosphorus pesticides in under 16 minutes. Polar analytes such as methamidophos, acephate, omethoate, and dimethoate exhibited sharp peak shapes on the Ultra Inert column. Analyte protectant addition significantly enhanced signal response by mitigating matrix-induced adsorption and degradation. Detection limits were 10 ng/mL for most pesticides and 15 ng/mL for the more challenging compounds. Calibration curves in matrix yielded correlation coefficients (R²) ≥ 0.999. Spiked recovery studies at 20, 100, and 500 ng/mL gave recoveries of 63–110% with RSDs below 9%.

Benefits and Practical Applications of the Method

• High throughput: complete separation in under 16 minutes and streamlined QuEChERS extraction.
• Low detection limits suitable for regulatory MRLs in olives and olive oil.
• Robust peak shape and linearity across a wide dynamic range.
• Selective phosphorus detection with FPD and confirmatory SIM analysis with GC/MS.
• Reduced maintenance through backflush and ultra inert inlet and column components.

Future trends and potential applications

Further developments may include integration of multi-residue screening panels for other pesticide classes in high-fat matrices, miniaturized sample preparation, and automated online cleanup. Advances in column chemistry and detector sensitivity will push detection limits lower. Data-driven approaches and AI-enhanced spectral interpretation could streamline confirmation and compliance reporting.

Conclusion

The combination of modified QuEChERS extraction, analyte protectant, ultra inert GC column, split effluent to FPD and MSD, and backflush capability delivers a rapid, sensitive, and reliable method for trace analysis of organophosphorus pesticides in olive oil. The workflow meets regulatory requirements, minimizes matrix effects, and offers high laboratory productivity.

Used Instrumentation

• Agilent 7890 GC with Agilent 5975C MSD
• Agilent 7683B autosampler (5 µL syringe)
• Agilent J&W DB-35ms Ultra Inert column, 30 m×0.25 mm×0.25 µm
• Flame Photometric Detector in phosphorus mode
• Capillary Flow Technology splitter (G3180B) with post-column backflush
• Dispersive SPE kit for fatty samples (Agilent QuEChERS AOAC)

References

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