Importance of PBDEs
Polybrominated diphenyl ethers are a group of brominated flame retardants used primarily as additives in various plastics and polymers. Due to their widespread use as well as their tendency to leach from the polymer matrices, PBDEs have become a major class of environmental pollutants. The ability to bio-accumulate and the structural similarities to PCBs have led to concern over the possible health effects of PBDE exposure.
Challenges for Analysis
As with PCBs, the separation and identification of PBDE congeners and related metabolites present a significant analytical challenge due to the co-elution of compounds and nearly identical mass spectra. The traditional approach of using C13 labeled compounds has been successfully utilized for both internal standard quantification, and as an internal standard for calculating relative retention indices. However, this approach is expensive and cannot be used with electron capture detector methods.
A less expensive and more versatile approach to the problem is the synthesis and use of mono and di-fluorinated analogs of the native BDEs.
Advantages of FBDEs
These compounds offer several advantages over the C13 labeled counterparts:
- They are more cost-effective
- They can be used with electron capture detection
- They add 18/36 mass units resulting in fewer problems with co-elution
- They have been shown to provide improved precision in PBDE analyses
These attributes are pertinent whether the FBDEs are used for quantitative analysis, or as markers to calculate relative retention indices. Figure 1 illustrates the usefulness of using the fluorinated analog to avoid the co-elution between the native BDE and the C13 labeled internal standard.
Elution times which are independent of the native analogs enable the analyst to calculate relative retention data which provide more accurate identifications within congener mixes.
Figure 2 shows a separation of all 42 TetrabromoBDE’s on a MS-5 GC column. There are only 25 chromatographic peaks present which indicates a number of co-elutions. However, all 42 homologs can be identified through the use of relative retention data calculated for two different selectivity GC columns. The mass spectral differences between the fluorinated and native BDEs makes them excellent choices as brackets for the native compounds.
The number and variety of FBDEs also make them a logical and cost effective choice when analyzing realworld samples for BDEs. Compounds having from one to nine bromine substitutions are available to help with any analytical challenge.