Identification and Quantification of 19 Phthalic Acid Esters in Chinese Liquors Using GC-MS/MS

Importance of the Topic

The analysis of phthalic acid esters (PAEs) in alcoholic beverages is critical due to their potential endocrine-disrupting and teratogenic effects. Chinese liquors, with high ethanol content, pose a particular challenge for accurate PAE detection. Establishing a reliable method supports risk assessment and quality control in food safety and public health.

Goals and Study Overview

The study aimed to develop a simple, accurate and cost-effective GC-MS/MS method to identify and quantify 19 PAEs in various Chinese liquors. Key objectives included enhancing selectivity and sensitivity, minimizing matrix interferences, and reducing analysis time compared to conventional approaches.

Methodology and Instrumentation

Sample Preparation:

• Accurately pipette 10 mL liquor into a vial and heat in a water bath at 85 °C for 30 min to volatilize ethanol and aroma compounds.
• Cool to room temperature, add 2 mL n-hexane and vortex for 1 min for liquid-liquid extraction.
• Allow phase separation and transfer the hexane layer to an autosampler vial for GC-MS/MS analysis.

Instrumental Analysis:

• Gas chromatograph (Shimadzu GCMS-TQ8030) in MRM mode for enhanced selectivity.
• Column: Rxi-5Sil MS (30 m × 0.25 mm, 0.25 µm); carrier gas helium at 37 cm/s; splitless injection (1 min) at 250 °C.
• Temperature program: 90 °C (1 min) → 210 °C (2 min) at 15 °C/min → 250 °C (5 min) at 5 °C/min → 300 °C (4 min) at 25 °C/min.
• Mass spectrometry: EI ionization, argon collision gas, source 230 °C, interface 280 °C, solvent cut 4 min, detector voltage tuning + 0.3 kV.

Main Results and Discussion

• Repeatability and Reproducibility:

• Within-day repeatability (n=5) RSD < 6% in both SIM and MRM modes.
• Day-to-day reproducibility in MRM mode RSD < 6%, superior to SIM (> 15%).

• Sensitivity and Detection Limits:

• MRM provided improved selectivity and lower limits of detection (LODs: 0.02–21.45 µg/L) compared to single-quadrupole GC/MS.

• Recovery and Accuracy:

• Recoveries for 19 PAEs ranged from 70% to 125%, with ethanol removal enhancing extraction efficiency and reducing interferences.

Benefits and Practical Applications

• The water bath pretreatment simplifies sample cleanup and shortens preparation to ~30 min.
• Use of GC-MS/MS in MRM mode ensures robust quantification and reliable identification even in complex matrices.
• The method supports routine monitoring in food safety laboratories, quality assurance/quality control (QA/QC) settings, and regulatory compliance.

Future Trends and Applications

• Integration with automated sample preparation systems for higher throughput.
• Expansion to other beverage and food matrices, including low-alcohol and non-alcoholic products.
• Coupling with data-processing software for real-time quantification and trend analysis.
• Development of high-resolution MS techniques for simultaneous screening of additional plasticizers and emerging contaminants.

Conclusion

The described GC-MS/MS method offers a streamlined, sensitive and reproducible approach for detecting 19 phthalic acid esters in Chinese liquors. Its combination of water bath pretreatment and MRM analysis achieves reliable quantification, making it well suited for food safety monitoring and risk assessment.