Qualitative and Quantitative Analysis of Brominated Flame Retardants (PBB and PBDE)

On 13 February 2003 the European Union published the new regulation on electric and electronic waste, (WEEE, Waste Electrical and Electronic Equipment) as well as the restriction of the use of certain hazardous substances in electric and electronic equipment (RoHS). Thus both regulations became effective, and in January 2005 they were transferred into national law. According to RoHS, lead, mercury, cadmium, chromium (VI), polybrominated biphenyls (PBB) and polybrominated diphenylethers (PBDE) are forbidden from July 2006. Shimadzu, one of the leading manufacturers of analytical instrumentation offers the complete hardware and software for the secure identification of hazardous substances as well the know-how and competence.

Figure 1

Brominated Flame Retardants

Brominated flame retardants have been used for decades in various consumer products. Because of their risk for health and the suspected cancerogenity of some of the congeners these compounds are forbidden to be used in new electric and electronic parts or shall not exceed the limit of 1000 ppm. Particularly, pentabromdiphenylether (PentaBDE) and octabromodiphenylether (OctaBDE) are mentioned, the latter is used in the polymers ABS and PS. Currently, mainly DecaBDE is used as flame retardant in the polymers PS, PE, ABS and polyester.

Figure 2

GC–MS-Analysis of PBB and PBDE

For the analysis of brominated flame retardants (PBB; PBDE, Figure 1) in concentrations < 5% to the ppm-range the method of GC–MS is used. With GC–MS, it is possible to identify and also quantify small amounts of contaminants by comparison with standard samples and their specific retention times and mass spectra.

For GC–MS analysis, there are two possibilities. For screening of the samples, the method of pyrolysis GC–MS can be used. This method has the advantage that the samples are measured directly without tedious sample preparation. In a pyrolysis oven, the samples are heated and the polybrominated substances are evaporated from the polymer. This evaporation takes place at relatively low temperatures of 300–400 °C. At these temperatures the polymers are not decomposed. The Pyrolyser Py-2020iD from Shimadzu uses the so-called double-shot method. In a first step, the PBBs and PBDEs are evaporated from the polymer (Thermodesorption). In a second step, the polymers are decomposed at high temperatures (>550 °C).

Figure 3

After evaporation from the polymer, the PBB´s and PBDE´s are separated by gas chromatography and detected in the mass spectrometer. Figure 2 shows such a pyrolysis chromatogram. The PBDEs can be identified unambiguously by their mass spectra (Figure 3). The polymer itself can be identified by using the unique F-Search library. The F-Search library contains the GC–MS TIC´s of polymers. By using the mass spectra of the polymer fragments the polymer itself is identified automatically. With the double-shot method information on the use of brominated flame retardants as well as on the polymer itself can be obtained using the same sample. Particularly for a screening method, the use of the autoshot auto sampler for the Py-200iD is of great advantage. It can analyse up to 48 samples.

Quantitative Analysis of PBB and PBDE

For the quantitative analysis of PBBs and PBDEs, a sample preparation in the laboratory is required. In a first step, the samples are extracted. For soluble polymers, the samples are dissolved in the corresponding solvent and subsequently the brominated flame retardants are extracted by liquid/liquid or Soxhlet-Extraction. For non-soluble polymers, a Soxhlet-Extraction is used directly. The extract is cleaned afterwards by solid phase extraction or by gel permeation chromatography (GPC). The best cleaning of the samples for sure is achieved by using GPC, but GPC also requires more time and effort than solid phase extraction. The sample is then prepared for the GC–MS analysis with liquid injection. Figure 4 shows the quantitative detection of PBDE in a polystyrene sample.

Figure 4

Summary

With GC–MS, small amounts of PBB and PBDE can also be detected. Pyrolysis GC–MS is used as a screening method with the advantage that sample preparation is unnecessary. Quantitative results can be obtained after sample preparation (extraction and cleaning) by liquid injection. The Shimadzu GC–MS-QP2010 and the Pyrolyser Py-2020iD are instruments with high sensitivity for this type of analysis. Both instruments can also be equipped with auto samplers for efficient routine analysis.

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