Determine the Phthalate Content in E-liquid

Importance of the Topic

Phthalates are commonly used plasticizers found in a variety of materials including e-liquid formulations. Their potential to leach into inhalable aerosols raises concerns regarding consumer safety and regulatory compliance. Accurate determination of phthalate content in e-liquids is essential to ensure products meet national food safety standards and protect public health.

Objectives and Study Overview

This study aimed to develop and validate a gas chromatography–mass spectrometry (GC-MS) method for the simultaneous quantification of eighteen phthalate esters in e-liquid matrices. The method was designed to achieve robust separation, sensitive detection, and compliance with the National Food Safety Standards applicable to e-cigarette products.

Methodology and Instrumentation

Sample extracts were analyzed by GC-MS in selected ion monitoring (SIM) mode. Chromatographic separation employed an SH-I-5Sil MS capillary column (30 m × 0.25 mm I.D., 0.25 µm film thickness). The temperature program started at 60 °C (1 min), ramped to 220 °C at 20 °C/min (1 min hold), then to 250 °C at 5 °C/min (1 min), and finally to 290 °C at 20 °C/min (7.5 min). A 1.0 µL splitless injection at 260 °C was used with constant flow helium (81 mL/min). Mass spectrometric detection was performed in electron ionization (EI) mode with an ion source temperature of 230 °C and an interface temperature of 280 °C.

Instrumentation Used

• GC-MS System: Shimadzu GCMS-QP™2010 NX
• Column: SH-I-5Sil MS (30 m × 0.25 mm I.D., 0.25 µm)
• Data Acquisition: Selected Ion Monitoring (SIM)

Main Results and Discussion

The developed method achieved baseline separation of eighteen phthalates with retention times ranging from 7.74 min (dimethyl phthalate) to 21.14 min (dinonyl phthalate). Each compound was monitored using a characteristic quantitative ion (e.g., m/z 149 for most esters, m/z 131 for DMP, m/z 225 for DPhP, m/z 279 for DNOP, and m/z 293 for DINP). Chromatograms demonstrated clear peak resolution and high signal-to-noise ratios under SIM conditions, enabling sensitive detection and reliable quantitation in e-liquid samples.

Benefits and Practical Applications of the Method

• High sensitivity and selectivity via SIM detection, reducing interferences from matrix components.
• Efficient analysis with a total run time under 30 minutes, supporting high throughput in quality control laboratories.
• Comprehensive coverage of commonly regulated phthalates to ensure compliance with safety standards.

Future Trends and Potential Applications

Advancements may include automation of sample preparation, coupling with tandem mass spectrometry for enhanced specificity, and expansion to other plasticizers or emerging contaminants in e-liquids. Integration of high-throughput screening and data analytics could further streamline regulatory testing workflows.

Conclusion

The validated GC-MS SIM method provides a reliable, sensitive, and efficient approach for quantifying a broad range of phthalate esters in e-liquid products, ensuring compliance with safety regulations and supporting consumer protection.

Reference

• Shimadzu Corporation. Application News 03-GCMS-407, First Edition, September 2022.