Fast, Single-Run Analysis of Polybrominated Diphenyl Ethers (PBDEs), Including Decabromodiphenyl (BDE-209)

Apr 28, 2014
Volume 10, Issue 7

Polybrominated diphenyl ethers (PBDEs), which were formerly used as flame retardants, are aromatic, nonpolar compounds now included on the Stockholm Convention's list of persistent organic pollutants (POPs). Although their use has been restricted or banned in many areas, low levels of PBDEs can bioaccumulate in biological, environmental, and food sources resulting in detrimental health effects. Gas chromatography (GC) column technologies permit the fast quantitation of all PBDE congeners including decabromodiphenyl ether BDE-209 in a single analytical run, eliminating the need for the multiple columns and instrumentation traditionally required. Comparison of existing methods and the single-test method are included, highlighting improved sensitivity and shortened run times.

Photo Credit: Kim Westerskov/Getty Images
Polybrominated diphenyl ethers (PBDEs) consist of 209 individual conformations called congeners, which vary in toxicity. They are now included on the Stockholm Convention's list of persistent organic compounds (POPs).1 Analytical testing of these congeners is performed by high-resolution gas chromatography with high-resolution mass spectrometry (HRGC–HRMS) to achieve the lowest levels of detection possible. Despite this advanced instrumentation, accurate and well resolved separations of all congeners remains difficult.

PBDE analysis is historically problematic for two main reasons: the sheer number of compounds and analyte instability. In addition, some congeners are thermally labile, sensitive to column activity, or both. The most notorious of these reactive congeners is BDE-209 — decabromodiphenyl ether. Complete testing of BDE-209 is especially important because it can break down in the body or the environment to even more toxic congeners.

To resolve all 209 congeners, many laboratories analyze a single list of PBDEs using two separate tests. The first test uses a detailed method that resolves most congeners and traditionally uses a low polarity column of 60 m × 0.25 mm dimensions. This configuration typically results in nearly hour-long run times. As a result, the latest eluting congener BDE-209 frequently displays dramatically reduced peak response because of an extended exposure to thermal degradation and column activity.

Laboratories are therefore often forced to analyze this compound with a second method, using a separate instrument and a much shorter, thinner phase column to provide less retention. This allows a lower elution temperature and helps address thermal stability issues for BDE-209. However, thinner phase columns are often more susceptible to activity, leading to peak tailing and more difficult quantitation. This article addresses the contribution of thermal stability and column activity to BDE-209 breakdown and also describes an optimized method that resolves BDE-209 and other important congeners.

Experimental Conditions

Two experiments were performed. Excluding the oven programme (A and B), conditions were the same for both separations in experiment 1. Instrumentation used was a GC/ECD system (Agilent Technologies). Instrumentation used for experiment 2 was a HRGC–HRMS.

Experiment 1:

Description: Collection of BDE-209 thermal stability data; Column: 10 m × 0.18 mm, 0.18-μm, "general purpose" 5% phenyl-arylene phase (Phenomenex); Injection: Split 10:1 at 250 °C, 1 μL; Oven Programme: A: 100 °C for 1 min to 300 °C at 10 °C/min for 30 min, B: 100 °C for 1 min to 250 °C at 10 °C/min for 30 min; Carrier Gas: Helium at 3.0 mL/min (constant flow); Detector: Electron Capture (ECD) at 350 °C.

Experiment 2:

Description: PBDE congener separations on an application-specific 5% phenyl-arylene column deactivated specifically for reactive compounds; Column: 20 m × 0.18 mm, 0.18-μm, Zebron ZB-SemiVolatiles (Phenomenex), Injection: Splitless at 85 °C, 5 μL; Oven Programme: 70 °C for 1.25 min to 240 °C at 20 °C/min to 320 °C at 50 °C/min for 18 min; Carrier Gas: Helium at 0.85 mL/min (constant flow); Detector: High Res Mass Spec (HRMS) at 325 °C. A PTV in solvent vent mode with temperature programme to 320 °C in 2 min was used.

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