Analysis of Phthalate with Hydrogen Carrier Gas

Significance of the Topic

Phthalates are widely used plasticizers that can leach from consumer and electronic products, posing human health and environmental risks. Regulatory frameworks such as EU RoHS 2015/863 and REACH restrict their use in polymer materials. Traditional GC/MS analyses rely on helium as a carrier gas, but recent helium shortages and cost increases have driven the search for effective hydrogen-based alternatives.

Objectives and Overview

This study evaluates hydrogen as a carrier gas for GC/MS analysis of 10 common phthalates using an Agilent 8890 GC coupled to a 5977C MSD with the HydroInert ion source. Key aims include:

• Demonstrating chromatographic performance and system stability with hydrogen
• Verifying method sensitivity, linearity, and detection limits
• Assessing recovery and precision in polymer and cable matrices
• Highlighting the benefits of the HydroInert source and backflush technique

Methodology

The analysis follows IEC 62321-8 guidelines using solvent extraction and SIM detection.

• Reagents: High-purity phthalate standards, THF and ACN solvents
• Standards: Calibration prepared at 0.2–5 µg/mL with benzyl benzoate as internal standard
• Sample preparation: Ultrasonic extraction of polymer and cable samples, matrix precipitation in ACN, filtration, and GC/MS injection

Instrumentation

• Gas chromatograph: Agilent 8890 with split/splitless inlet and 7693A autosampler
• Column: DB-5ms Ultra Inert, 30 m × 0.18 mm, 0.18 µm with 5 m guard column
• Carrier gas: Hydrogen at constant flow (0.7 mL/min)
• MS detector: Agilent 5977C MSD with HydroInert source, electron ionization at 70 eV, SIM mode
• Backflush: 4-minute high-pressure backflush to remove nonvolatile residues

Main Results and Discussion

• Chromatographic performance: Comparable elution profiles to helium, complete analysis in 15 minutes including backflush
• Linearity: R² values > 0.996 for all phthalates over 0.2–5 µg/mL; bias within 80–120%
• Detection limits: MDLs between 1.80 and 3.74 mg/kg in polymer matrices with RSDs < 20%
• Recovery and precision: Recoveries of 89.6–101.1% at 50 and 500 mg/kg; repeatability and reproducibility RSD < 20%
• Application to cable samples: Select phthalates detected at or above reporting limits in real-world cables; no significant matrix interference
• Method robustness: Continuous analysis of standards and cable matrices showed area RSD < 7% for all analytes over up to 80 injections

Benefits and Practical Applications

• Helium-free operation reduces gas costs and supply risks
• HydroInert source and backflush technique maintain spectral integrity and minimize maintenance
• Fast throughput with stable quantitation in complex matrices
• Compliance with international standards for phthalate analysis in polymers and electrical products

Future Trends and Opportunities

• Broader adoption of hydrogen carriers for routine GC/MS workflows
• Development of advanced inert ion sources to further lower maintenance
• Integration with automated sample prep and data processing for high-throughput screening
• Extension of this approach to other semi-volatile organic contaminants
• Implementation in regulatory and quality-control laboratories for sustainable operation

Conclusion

The combination of hydrogen carrier gas, Agilent HydroInert source, and backflush capability on the Agilent 8890/5977C GC/MS provides a robust, sensitive, and compliant technique for phthalate analysis. This approach overcomes helium shortages and ensures accurate quantitation in challenging polymer and cable matrices.

References

1. European Commission. Directive 2015/863/EU of 31 March 2015 amending Annex II to Directive 2011/65/EU concerning restricted substances.
2. European Parliament and Council. Regulation (EC) No. 1907/2006 (REACH), establishing a European Chemicals Agency.
3. IEC 62321-8:2017. Determination of certain substances in electrotechnical products – Part 8: Phthalates in polymers by GC-MS.