Analysis of Polybrominated Diphenyl Ether Flame Retardants in Environmental Matrices Using Atmospheric Pressure Chemical Ionization GC-MS/MS

Importance of the topic

Polybrominated diphenyl ethers (PBDEs) are persistent, bioaccumulative flame retardants that undergo long-range environmental transport and accumulate in air, soil, water and biota. Global regulatory frameworks (Stockholm Convention) and national monitoring programs require trace-level, high-confidence data for PBDE surveillance. Analytical workflows must therefore combine high sensitivity, selectivity, robustness and sustainable operation to support regulatory compliance, long‑term trend studies and environmental risk assessment.

Study objectives and overview

This application note evaluates an alternative analytical approach for regulatory-quality PBDE analysis by transferring a reference GC-EI-HRMS method to GC coupled with atmospheric pressure chemical ionization (APCI, marketed as APGC) and a tandem quadrupole mass spectrometer (Xevo TQ Absolute). Goals were to: adapt the method to an all-nitrogen gas configuration, maintain or improve sensitivity and specificity across 25 target analytes (24 PBDE congeners plus hexabromobiphenyl), achieve ppt-level quantitation, and demonstrate operational advantages (speed, robustness, reduced training and lower running costs) relative to magnetic sector EI HRMS.

Methodology

Sample preparation and quality controls were performed at Environment and Climate Change Canada (Quebec Laboratory for Environmental Testing). Calibration included five-point curves spanning more than three orders of magnitude with concentration ranges adjusted by bromination degree (tri–penta, hexa–octa, nona–deca groups). Blanks, low/mid/high QCs and labeled internal standards were used to assess precision and accuracy.

Chromatography and injection strategy were optimized to address the thermally labile, high-boiling congeners (notably BDE 209), including pulsed splitless injection and a carrier gas flow-ramping program to reduce residence time at elevated transfer line temperature.

Used instrumentation

GC:

• Agilent 8890 GC
• Column: Restek Rtx-1614, 15 m × 0.25 mm ID × 0.10 μm film
• Injection: SSL pulsed splitless, 1 μL, 260 °C, 20 psi for 1.2 min; 4 mm ID single taper liner with wool
• Temperature program: 110 °C → 190 °C (30 °C/min) → 220 °C (3 °C/min) → 280 °C (20 °C/min, 3 min) → 310 °C (30 °C/min, 7 min); total runtime 27 min
• Carrier gas: Nitrogen, programmed from 0.80 mL/min ramping to 4.1 mL/min

Mass spectrometry and ionization:

• Waters Xevo TQ Absolute tandem quadrupole MS
• APGC (atmospheric pressure chemical ionization) source at 150 °C; heated transfer line at 300 °C
• Corona current 1.0 μA; cone gas 260 L/hr N2; auxiliary gas 200 L/hr N2; makeup gas 350 mL/min N2; collision gas (CID) 0.40 mL/min N2
• Detector gain 0.20; unit mass resolution quadrupoles (0.9 Da peak width)
• Data acquisition by MRM transitions; quantitation via waters_connect software

Main results and discussion

Linearity, sensitivity and quantitation:

• Twenty-five analytes were quantified with linear calibration curves spanning >3 orders of magnitude and an average r2 = 0.999885 (no value < 0.999584).
• Limits of quantitation in the low ppt range were achieved for the analyte panel.

Precision and accuracy:

• Four labeled recovery standards: %RSD < 10% (mean 8.29%). Six labeled internal standards: mean %RSD 1.55% (none > 2.5%).
• QC precision: high and mid QCs < 10% RSD; all QCs (low/mid/high) < 15% RSD. Accuracy fell within 70–130% for nearly all analytes and levels; exceptions were BDEs 196, 197 and 207 at the lowest QC in two injections.

Chromatography and BDE 209 behavior:

• Using nitrogen carrier gas with a flow ramp preserved separation and elution order compared with the helium reference method; some retention time shifts occurred but total runtime remained 27 min.
• Flow ramping to higher carrier flow before elution of BDE 209 reduced its thermal residence time, improving peak shape and preventing degradation. Symmetric peak shapes were obtained (example a/b = 0.993 and width ~10.3 s; later QC asymmetry values ~1.012–1.020).

MS/MS transition development and confirmation:

• Multiple precursor isotopes from the heavy bromination provided abundant precursor ions; up to six MRM transitions were used for some congeners, increasing confirmatory power and troubleshooting capability.
• Ion ratios between the most intense MRM and the sum of the two most intense transitions were reproducible and well within typical confirmatory thresholds (reference allows ±15%).

Operational advantages and sustainability:

• All-nitrogen gas configuration (carrier, makeup, auxiliary, CID gas) eliminates reliance on helium, reducing operational cost and addressing recent helium supply concerns.
• Tandem quadrupole APGC MS/MS provided acquisition speed, robustness and comparable or better specificity and sensitivity than legacy EI GC-HRMS while reducing instrument maintenance and operator training time.

Benefits and practical applications

Key practical advantages demonstrated by the method include:

• Regulatory-grade PBDE monitoring capability with ppt LOQs and strong confirmatory data (multiple MRMs, consistent ion ratios).
• Improved laboratory throughput due to 27 min runtime and faster MS acquisition speed.
• Reduced maintenance and training requirements compared with magnetic sector EI HRMS workflows.
• Lower running costs and improved sustainability by using nitrogen for all gas functions rather than helium and separate reagent gases.

Future trends and potential uses

Expected directions and opportunities:

• Wider adoption of atmospheric pressure ionization GC sources (APCI/APGC) coupled to triple quadrupole MS for persistent organic pollutant (POP) surveillance, facilitating harmonization of methods across regulatory laboratories.
• Further refinement of MRM panels and isotope-labeled standards to enhance confirmatory power for highly brominated congeners and to address occasional low-level QC deviations observed for specific BDEs.
• Expansion of all-nitrogen operational modes and optimization of flow-programming strategies to accommodate other thermally labile, high-boiling analytes.
• Integration into long-term biomonitoring and environmental trend studies where robustness, throughput and sustainability are priorities.

Conclusions

APGC coupled to a tandem quadrupole (Xevo TQ Absolute) and operated in an all-nitrogen configuration provided equal or better analytical performance compared with traditional GC-EI-HRMS for a 25‑analyte PBDE panel. The method delivered ppt-level quantitation, excellent linearity and precision, robust handling of the challenging BDE 209 congener, and practical benefits including reduced training, lower operational costs and improved sustainability. These attributes support APGC–TQ MS/MS as a viable, modern alternative for demanding regulatory and monitoring applications.

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