Routine determination of phthalates in vegetable oil by single quadrupole GC-MS

Importance of the Topic

Phthalate esters are widely used as plasticizers and can leach into fatty foods such as vegetable oils, raising concerns due to their classification as endocrine disruptors. Robust analytical methods are essential to protect consumers and comply with regulatory limits set by authorities like EFSA, China, and Taiwan.

Study Objectives and Overview

This study evaluated the Thermo Scientific ISQ 7000 single quadrupole GC-MS system equipped with an Advanced Electron Ionization (AEI) source for routine determination of 13 phthalates in a challenging vegetable oil matrix. Key performance metrics included method selectivity, sensitivity, linearity, recoveries, and robustness under real-world conditions.

Methodology

Vegetable oil samples were spiked at 5, 25, and 50 µg/kg levels. Extraction involved acetonitrile vortexing, ultrasonication, centrifugation, evaporation, and hexane reconstitution. Calibration standards (0.5–250 ng/mL) in n-hexane corresponded to 5–2500 µg/kg on-matrix. Timed SIM acquisition was optimized via CDS software for improved selectivity. Instrument detection limits (IDLs) were determined by 18 replicate injections with 99% confidence. Limits of quantification (LOQs) were set at the lowest levels with <15% RSD and stable ion ratios.

Instrumentation

• TRACE 1310 GC with AS 1310 autosampler
• TraceGOLD TG-5MS column (30 m × 0.25 mm × 0.25 µm)
• ISQ 7000 single quadrupole MS with AEI source
• Operating conditions: EI at 45 eV, source 350 °C, transfer line 300 °C, helium carrier
• Timed-SIM mode targeting quantifier and two qualifier ions

Main Results and Discussion

SIM acquisition delivered enhanced selectivity and sensitivity versus full scan, with signal-to-noise improvements (e.g., DEHP S/N increased from 97 to 337). Estimated IDLs ranged from 0.01 to 3 pg on-column. LOQs in vegetable oil were 5–25 µg/kg with peak area RSDs below 15% and stable ion ratios. Calibration curves (0.5–250 ng/mL) showed R2 > 0.998 and response factor RSDs <10%. Recoveries at 5, 25, and 50 µg/kg ranged from 80% to 102% (RSD ≤6.8%), demonstrating method accuracy and precision. The AEI source’s focused ion beam reduced contamination and maintenance frequency.

Benefits and Practical Applications

The method enables sensitive, selective, and robust routine monitoring of phthalates in fatty food matrices. Reduced matrix load and improved ionization efficiency extend maintenance intervals, lowering operational costs and maximizing laboratory throughput.

Future Trends and Applications

Advances may include integration with automation and data analytics for real-time QC, miniaturized GC-MS platforms for field testing, and novel ionization technologies for broader compound coverage. Regulatory harmonization will drive standardized workflows across global markets.

Conclusion

The ISQ 7000 GC-MS with AEI source demonstrated excellent sensitivity (IDLs down to 0.01 pg), linearity (R2 > 0.998), accuracy (recoveries 80–102%), and robustness for phthalate analysis in vegetable oil, offering a cost-effective solution for routine food safety testing.

References

• Commission Regulation (EU) No 10/2011 on plastic materials in contact with food, Official Journal of the European Union.
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• Yang J et al., Taiwan food scandal: illegal use of phthalates as clouding agents, Food Chem. Toxicol. 58:362–368, 2013.
• Serrano SE et al., Phthalates and diet: a review of food monitoring and epidemiology data, Environ. Health 13:43, 2014.