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Environmental Article

Analysis of Brominated Flame Retardants on an Rxi™-5ms

Optimizing Method Conditions to Reliably Quantify BFRs

By Jason Thomas, Environmental Chemist
  • Minimal breakdown, symmetric peaks for heat-sensitive PBDEs.
  • Complex samples well resolved, for reliable identifications.
  • Low bleed baselines help ensure accurate quantification.

Brominated flame retardants (BFRs) are widely used but potentially harmful materials currently being monitored in the environment. Analysis of higher molecular weight polybrominated diphenyl ethers (PBDEs) can present a particular problem: relatively high temperatures are required to elute them from a GC column, but they are easily debrominated at elevated temperatures. Poor peak shapes and extraneous peaks from breakdown products can complicate the analysis. Therefore, several key parameters must be optimized to ensure proper analysis of these compounds.

Of special interest and concern is BDE-209, the primary component in the “deca” commercial mixture — the most used PBDE mix presently in production. Because of BDE-209’s tendency to break down on-column, residence time in the column must be minimized, ideally by using a high volumetric flow of carrier gas. In this work, we used a flow of 3.1mL/min. Also, and again due to the thermally labile nature of BDE-209, the oven temperature must be kept below 300°C throughout the analysis — a consideration which often is overlooked. Figures 1 and 2 illustrate the importance of keeping the oven temperature below 300°C. Similarly, the injector temperature must be kept low enough to minimize breakdown, yet high enough to volatilize this high molecular weight compound. We used an injector temperature of 220°C. Finally, contact between BDE-209 and metal injector components must be minimized. This can be accomplished by using a Siltek® treated Uniliner® inlet liner. Following these precautions, we analyzed BDE-209 and the PBDEs listed in EPA Method 527, using an Rxi™-5ms column. We observed minimal peak skewing and interference from breakdown peaks, as shown in Figure 3.

The complexity of two other commercial PBDE mixtures, “penta” and “octa”, and the variety of other classes of BFRs (polybrominated biphenyls, polybrominated biphenyl ethanes, tetrabromobisphenol A, hexabromocyclododecane) make a simultaneous analysis for several types of BFRs a great challenge. Figure 4 shows an analysis of a very comprehensive mix of BFRs — the Wellington mix — on an Rxi™-5ms column. Even without optimization of the analysis, separation is very respectable and peak shapes for the most problematic compounds, BDE-209 and DBDPE, are good.

In conclusion, method parameters must be carefully controlled when analyzing BFRs, in order to obtain reliable, quantifiable results. An Rxi™-5ms column is a good choice for this application.


Figure 1  Significant peak fronting occurs at elevated temperatures.

Conditions same as Figure 4, below.

Figure 2  Excellent peak symmetry below 300°C.

Conditions same as Figure 4, below.

Figure 3  Symmetric peaks and a low bleed baseline for BDE-209 and EPA Method 527 target BFRs, using an Rxi™-5ms column.

See Figure 4, below, for peak listing.

Column:

Rxi™-5ms, 15m, 0.25mm ID, 0.25µm (cat.# 13420)

Sample:

US EPA Method 527 brominated diphenyl ethers, with BDE-209

Inj.:

1.0µL splitless (hold 1 min.), 4mm Siltek® gooseneck inlet liner (cat.# 20798-214.1)

Instrument:

Agilent 6890

Inj. temp.:

220°C

Carrier gas:

helium, constant flow

Linear velocity:

40cm/sec. @ 100°C

Oven temp.:

100°C (hold 1 min.) to 295°C @ 25°C/min. (hold 7 min.)

Det.:

ECD @ 300°C

Figure 4  A complex mix of BFRs is resolved on an Rxi™-5ms column.

  1. BDE-1
  2. BDE-2
  3. BDE-3
  4. BDE-10
  5. BDE-7
  6. BDE-15
  7. BDE-30
  8. BDE-17
  9. BDE-28
  10. PBEB
  11. HBB
  12. BDE-49
  13. BDE-71
  14. BDE-47
  15. BDE-66

  1. BDE-77
  2. BDE-100
  3. BDE-119
  4. BDE-99
  5. BDE-85
  6. BDE-126
  7. BDE-154
  8. BB-153
  9. BDE-153
  10. BDE-139
  11. BDE-140
  12. BDE-138
  13. BDE-156
  14. BDE-169
  15. BDE-184

  1. BDE-183
  2. BDE-191
  3. BTBPE
  4. BDE-180
  5. BDE-171
  6. BDE-201
  7. BDE-204
  8. BDE-197
  9. BDE-203
  10. BDE-196
  11. BDE-205
  12. BDE-208
  13. BDE-207
  14. BDE-206
  15. BDE-209
  16. DBDPE

Column:

Rxi™-5ms, 15m, 0.25mm ID, 0.25µm (cat.# 13420)

Sample:

Wellington BFR-PAR Mix (Wellington Laboratories Inc., Guelph, Ontario, Canada; Wellington cat.# BFR-PAR)

Inj.:

1.0µL splitless (hold 1 min.), 4mm Siltek® gooseneck inlet liner (cat.# 20798-214.1)

Inj. temp.:

220°C

Carrier gas:

helium, constant flow

Linear velocity:

40cm/sec. @ 100°C

Oven temp.:

100°C (hold 1 min.) to 295°C @ 25°C/min. (hold 7 min.)

Det.:

ECD @ 300°C