Tandem GC/MS Analysis of Sub-pg/μL Quantities of PBDEs, Including BDE-209 Using the Novel High Efficiency EI Source

Importance of the Topic

Polybrominated diphenyl ethers (PBDEs) are widely used flame retardants known for their environmental persistence, bioaccumulation in fatty tissues, and potential endocrine disruption and carcinogenic effects. Reliable monitoring of PBDEs, especially decabromo-diphenyl ether (BDE-209), is critical in environmental and human health studies, but traditional GC/MS approaches often struggle to reach sub-picogram detection limits and handle thermal decomposition of heavy congeners.

Objectives and Study Overview

This work aims to demonstrate the performance of a novel High Efficiency Electron Ionization Source (HES) coupled to an Agilent 7890B/7010 triple quadrupole GC/MS system for quantifying sub-picogram-per-microliter levels of PBDE congeners, including BDE-209. The study evaluates analytical sensitivity, linearity, selectivity, and practical applicability in serum samples against established sector field and accurate mass methods.

Methodology and Instrumentation

Sample Preparation:

• Weighed 2 g of human serum into 16×100 mm glass tubes.
• Added 13C-labeled internal standards and performed acidified liquid–liquid extraction using automated Gilson 215 handlers.
• Repeated extraction and combined organic phases, then evaporated to dryness.
• Cleaned up lipids via a two-layer RapidTrace SPE cartridge (activated silica gel over sulfuric acid–silica gel) and eluted with 5 % dichloromethane in hexane.
• Evaporated eluates, reconstituted with recovery standard, and transferred to GC vials.

Instrumentation and Conditions:

• GC/MS: Agilent 7890B with 7010 triple quadrupole and the new HES in EI mode.
• Column: HP-Ultra 1, 17 m×0.2 mm ID, 0.11 µm film.
• Injection: 2 µL pulse splitless, inlet at 260 °C, 20 psi until 0.6 min.
• Carrier gas: helium at 1 mL/min constant flow; quench gas flow increased to 4 mL/min to reduce neutral noise.
• Oven program: 10 °C/min to 300 °C, hold 4.5 min.
• Transfer line/source at 290 °C; quadrupoles at 150 °C; nitrogen collision gas at 1.5 mL/min.
• Data acquisition: Multiple reaction monitoring (MRM) optimized for each PBDE congener.

Results and Discussion

The High Efficiency Source enhanced ion flux 10–20× compared to conventional EI sources, yielding significantly lower noise and higher signal for all PBDEs. Key findings include:

• Limit of quantitation for BDE-209 at 0.2 pg/µL (0.4 pg on column).
• Excellent linear calibration across 0.2–100 pg/µL for tri- to deca-brominated congeners using a single concentration range.
• Clear chromatographic separation without excessive thermal breakdown of BDE-209, despite using a longer 17 m column.
• MRM transitions provided high selectivity, and detector gain adjustments prevented saturation at high-abundance ions.

Benefits and Practical Applications

Integration of the HES with tandem GC/MS offers:

• Robust trace-level quantitation of PBDEs in complex biological matrices, including serum.
• Improved method simplicity by maintaining a single calibration curve across all congeners.
• Flexibility to monitor additional halogenated pollutants (PBBs, PCBs) using similar workflows.
• Reduced reliance on high-resolution sector instruments, lowering capital and operational costs.

Future Trends and Applications

Emerging opportunities include coupling HES-GC/MS with multidimensional separations (GC×GC) for enhanced resolution of isomers, miniaturized sample preparation techniques to reduce solvent use, and expanded monitoring of emerging halogenated contaminants at ultratrace levels. Integration with automated data processing and on-site portable GC/MS platforms may further streamline environmental and clinical surveillance.

Conclusion

The novel High Efficiency EI Source significantly improves sensitivity and selectivity for PBDE analysis on a triple quadrupole GC/MS, enabling reliable sub-picogram quantitation of BDE-209 and other congeners in serum. This advancement simplifies workflows, reduces costs, and broadens the applicability of tandem GC/MS for persistent organic pollutant monitoring.

References

1. EPA Technical Fact Sheet – Polybrominated Diphenyl Ethers (PBDEs) and Polybrominated Biphenyls (PBBs), January 2014.
2. Sjödin A. et al. Semiautomated extraction and cleanup method for measuring persistent organic pollutants in human serum. Anal. Chem. 2004, 76, 1921–1927.
3. Jones R.; Edenfield E.; Anderson S.; Zhang Y.; Sjödin A. Organohalogen Compd. 2012, 74, 97–98.