Determination of Phthalate Esters in Vegetable Oils Using Direct Immersion Solid-Phase Microextraction and Fast GC Coupled with Triple Quadrupole MS

Importance of the topic

Phthalates are widely used plasticizers and recognized as endocrine disruptors and potential carcinogens. Their lipophilic nature drives migration into fatty foods, including vegetable oils. Monitoring phthalate residues in edible oils is critical for consumer safety, given the absence of regulatory limits and the challenges in quantification due to complex matrices.

Objectives and study overview

This work aimed to develop a simple, solvent-minimized solid-phase microextraction (SPME) method with direct immersion of a polydimethylsiloxane (PDMS) fiber, coupled to fast gas chromatography–triple quadrupole mass spectrometry (GC–QqQ MS) in multiple reaction monitoring (MRM) mode. The method was fully validated and applied to the analysis of eight vegetable oil samples.

Methodology and sample preparation

Oil samples (0.5 g) were vortex-extracted with 3 mL acetonitrile for 30 s and centrifuged. A 100 μm PDMS fiber was immersed in 1.5 mL acetonitrile extract for 20 min at 500 rpm. Fiber desorption was performed in the GC inlet at 280 °C, ensuring complete analyte transfer without carry-over.

Used instrumentation

• Shimadzu GC-2010 Plus gas chromatograph
• Shimadzu GCMS-TQ8040 triple quadrupole mass spectrometer
• SLB-5ms column (10 m × 0.1 mm ID × 0.1 μm df)
• Oven program: 90 °C (5 min) → 310 °C at 30 °C/min → 350 °C at 50 °C/min
• Helium carrier gas; splitless injection for 5 min, then 1:20 split
• Electron ionization; MRM acquisition (mass range 45–360 m/z; 10 Hz; argon collision gas)

Main results and discussion

The direct immersion SPME-GC–QqQ MS method using PDMS in acetonitrile yielded low limits of quantification (0.018–0.053 mg/kg). Calibration was linear (R2>0.996), intra- and inter-day repeatability were <10% CV, and accuracy ranged within ±12%. Real-sample analysis of eight oils revealed higher total phthalates in olive oils (up to 7.9 mg/kg) compared to seed oils, with DiNP+DiDP as the major contributors, reflecting their use as DEHP substitutes and the influence of packaging material.

Benefits and practical applications

The method offers rapid, solvent-sparing preparation, minimal sample handling, and high sensitivity, making it suitable for routine quality control of phthalate residues and migration studies in edible oils.

Future trends and potential applications

Prospective developments include extending the approach to other fatty food matrices, automating SPME procedures, evaluating alternative fiber coatings, integrating high-throughput workflows, and monitoring emerging plasticizer replacements.

Conclusion

The proposed SPME-fast GC–QqQ MS protocol provides a robust, sensitive, and efficient solution for phthalate analysis in vegetable oils, ensuring reliable data for safety assessments.

References

• No dedicated references were provided in the original document.