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Environmental Article

Reliable Quantification of Brominated Flame Retardants by GC/MS

New Rxi™-5ms Column Minimizes PBDE Breakdown and Peak Skewing

By Jason Thomas, Environmental Chemist
  • Minimal on-column breakdown, symmetric peaks for heat-sensitive PBDEs.
  • Complex mixtures well resolved, for reliable identifications.
  • Noise-free baselines help ensure accurate quantification.

Because of their widespread past and present use in industry, brominated flame retardants (BFRs) recently have come under scrutiny as potentially harmful environmental pollutants. Some classes of these materials already have been removed from production, particularly in Europe, as a result of their potential toxicity and bioaccumulative nature. Both formerly used materials and classes of BFRs that remain in production now are being monitored to determine their presence in the environment. US EPA Method 527, for example, addresses the concern for BFRs in the environment by including several commonly encountered BFRs in its target analyte list.

As more BFRs come under regulation, others come into use to replace those that have been discontinued, and a great variety of potentially monitored compounds is coming into existence. Increasingly complicated mixtures of these components must be analyzed. There also is concern that some materials that remain in use, because they are not considered a significant threat to human health, can be broken down into toxic varieties in the environment, through microbial reduction1 or other means.

Among the most common and most analyzed-for classes of BFRs are the polybrominated diphenyl ethers (PBDEs). Some of the higher molecular weight PBDEs present a particular problem: relatively high temperatures are required to elute them from a capillary GC column, but they are easily debrominated at elevated temperatures. Consequently, analysis of PBDEs puts great demands on the analytical system, which must include finely optimized analytical conditions and a highly inert column that can separate these compounds effectively. Figure 1 shows our new, exceptionally inert Rxi™-5ms columns have the characteristics needed to separate thermally labile PBDEs with minimal on-column breakdown or peak skewing.

Of special interest and concern is BDE-209, the primary component in the “deca” commercial mixture — the most-used PBDE mix presently in production. BDE-209 is particularly susceptible to debromination, both in the injector and on the column, and the analysis can be characterized by very poor peak shape for this analyte and extraneous peaks from its breakdown products. It is critical to pass this compound through the column as quickly as possible, while maintaining oven temperature below 300°C — the point at which BDE-209 quickly breaks down. Figure 2 shows that by using an Rxi™-5ms column, BDE-209 can be analyzed with good peak symmetry and a relatively noise-free baseline, along with the five BFRs on the EPA Method 527 target compound list.

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 all BFRs a great challenge. Figure 3 shows an analysis of a very comprehensive mix of BFRs — the Wellington mix (Wellington catalog # BFR-PAR) — on an Rxi™-5ms column. Even under these unoptimized conditions, separation is very respectable and peak shapes for the most problematic compounds, BDE-209 and DBDPE, are good.

From these results we suggest that exceptional inertness, ultra-low bleed, and appropriate selectivity make an Rxi™-5ms column the exceptional choice for analysis of BFRs.


Figure 1   An Rxi™-5ms column separates PBDEs well, with minimal on-column breakdown or peak skewing.

  1. 1,3-dimethyl-2-
    nitrobenzene (surr.)
  2. acenaphthene d-10 (int. std.)
  3. dimethoate
  4. atrazine
  5. propazine
  6. phenanthrene d-10 (int. std.)
  7. vinclozolin
  8. prometryne
  9. bromacil
  10. malathion
  11. thiocarb
  1. chlorpyrifos
  2. parathion
  3. terbufos sulfone
  4. S-bioallethrin
  5. oxychlordane
  6. nitrofen
  7. Kepone
  8. norflurazon
  9. hexazinone
  10. triphenylphosphate (surr.)
  11. chrysene d-12 (int. std.)
    12.
  1. bifenthrin
  2. BDE-47
  3. mirex
  4. BDE-100
  5. BDE-99
  6. perylene d-12 (surr.)
  7. hexabromobiphenyl
  8. fenvalerate
  9. esfenvalerate
  10. BDE-153
    11.

Column:

Rxi™-5ms, 30m, 0.25mm ID, 0.25µm (cat.# 13423)

Sample:

527 Pesticide Calibration Standard #1 (cat.# 33007), 527 Pesticide Calibration Standard #2 (cat.# 33008), 527 Surrogate Standard (cat.# 33009), 527 Internal Standard Mix (cat.# 33010), Method 527 PBDE Standard (cat.# M-527_BDE) from AccuStandard, New Haven, CT

Instrument:

Perkin Elmer Clarus 500 GC/MS

Inj.:

0.5µL splitless (hold 1 min.), 1mm split/splitless inlet liner (cat.# 21718)

Inj. temp.:

250°C

Carrier gas:

helium, constant flow

Linear velocity:

40cm/sec. @ 50°C

Oven temp.:

50°C (1 min.) to 210°C @ 25°C/min. (hold 4 min.) to 290°C @ 5°C/min., to 320°C @ 25°C/min. (hold 2 min.)

Det.:

MS

Transfer line temp.:

275°C

Source temp.:

180°C

Figure 2   Symmetric peaks and an uncomplicated baseline for BDE-209 and EPA Method 527 target BFRs, using an Rxi™-5ms column.

  1. BDE-47
  2. BDE-100
  3. BDE-99
  4. hexabromobiphenyl
  5. BDE-153
  6. BDE-209

Column:

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

Sample:

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

Instrument:

Agilent 6890

Inj.:

1.0µL splitless (hold 1 min.), 4mm Siltek® treated single gooseneck inlet liner (cat.# 20799-228.5)

Inj. temp.:

220°C

Carrier gas:

helium, constant flow

Linear velocity:

40cm/sec. @ 100°C

Oven temp.:

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

Det.:

ECD @ 300°C

Figure 3   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
  1. BDE-71
  2. BDE-47
  3. BDE-66
  4. BDE-77
  5. BDE-100
  6. BDE-119
  7. BDE-99
  8. BDE-85
  9. BDE-126
  10. BDE-154
  11. BB-153
  12. BDE-153
  1. BDE-139
  2. BDE-140
  3. BDE-138
  4. BDE-156
  5. BDE-169
  6. BDE-184
  7. BDE-183
  8. BDE-191
  9. BTBPE
  10. BDE-180
  11. BDE-171
  1. BDE-201
  2. BDE-204
  3. BDE-197
  4. BDE-203
  5. BDE-196
  6. BDE-205
  7. BDE-208
  8. BDE-207
  9. BDE-206
  10. BDE-209
  11. 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

References

  1. He, J., K.R. Robrock, and L. Alvarez-Cohen Microbial Reductive Debromination of Polybrominated Diphenyl Ethers (PBDEs) Environ. Sci. Technol. 40 (14): 4429-4434 (2006).