Agilent ICP-MS Journal - Agilent Technologies

Detecting "New
PCBs" using GC-ICP-
MS - Challenges of
PBDE Analysis
Steve Wilbur and Emmett Soffey
Agilent Technologies, Bellevue, WA, USA
Introduction
Brominated flame retardants and
especially polybrominated diphenyl
ethers (PBDEs) are under scrutiny
around the world. PBDEs are widely
used as flame retardants in plastics
and are found in the plastics used
in computers, construction materials,
furniture and textiles. Structurally,
they resemble PCBs, dioxins and
furans, with the chlorines substituted
by bromine. It is this similarity in
structure coupled with recent data
showing significant concentrations
in the environment and human and
animal tissues that has raised
concern. A recent study in Sweden
testing archived human breast milk
showed levels 55 times higher in
1997 than in 1972, with the average
concentrations doubling every 5
years. Further studies indicate that
the US is far more contaminated
than Sweden. For example, sewage
sludge in the US contains 10-100
times more PBDE than European
sludge. While the global demand for
PBDEs totaled 150 million pounds
(68 million kg) in 1997, half of that
was used by North American
industries. Every day, the typical
consumer comes in contact with
dozens, if not hundreds of consumer
goods that contain PBDEs. Since
PBDEs are not covalently bound to
the plastics into which they are
incorporated, they are easily released
into the environment. This can occur
through incineration, leaching of
materials in landfills, dust given off
by degrading textiles and foam
materials or even simple evaporation.
Products containing these compounds
typically contain from 5 to 20% of
the product weight as PBDE.
Because PBDEs are poorly soluble
in water, but highly fat soluble, they
are readily bioaccumulated in fatty
tissues of animals and humans. Recent
research on laboratory animals has
shown that low level exposure to
PBDEs can cause permanent
neurological and developmental
damage. Those most at risk are
pregnant women, developing fetuses
and young children. Already levels of
PBDEs found in some mothers and
fetuses are approaching levels known
to impair learning and development
in mice [1].
Regulation
As early as the mid 1980s to early
1990s bans on the use of some PBDEs
were proposed in Germany, Sweden
and the Netherlands. In 1993, using
its Dioxin Ordinance, Germany
officially restricted the use of PBDEs
because of the possibility of releasing
dioxins when incinerated. In February
2003, the EU announced a ban on
two common PBDEs, Penta and
Octa, in all products from August
2004. The EU is also considering a
ban on the use of Deca PBDE in
electronics products by July 2006.
Despite the much higher levels of
PBDEs in North America, the US
government has not imposed any
regulations on their manufacture or
use. Recently the State of California
introduced legislation which would
ban the use of several types of PBDEs
by 2008. However, the California bill
exempts the deca congener from
the ban which is the most widely
used type in electronic products.
Several other states are considering
similar legislation. Several Japanese
electronic companies will be phasing
PBDEs from their products and
other countries and individual
manufacturers are taking steps to
eliminate their use of PBDEs.
Structure
The general structure of the PBDEs
is given in Figure 1. There are ten
possible sites for bromination; five
on each ring. Similar to PCBs and
dioxins, there are a large number of
structural congeners depending on
the number and location of bromine
substitutions. In the case of PBDEs,
there are 209 possible congeners, with
the individual congeners named 1
through 209. The decabromo congener
is PBDE-209.
Figure 1. General chemical structure of a
polybrominated diphenyl ether
Analytical Challenges
Typically, PBDEs are analyzed and
detected like PCBs or Dioxins using
gas chromatography coupled to a
halogen specific detector such as
electron capture or to a mass
spectrometer. However, unlike PCBs,
PBDEs are much more difficult to
separate and detect using
chromatography. This is due to
several differences between PCBs
and PBDEs. PBDEs are high molecular
weight, high boiling-point compounds
which require high temperatures to
elute from the GC column. However,
unlike PCBs, which are very stable
biphenyl compounds, the diphenyl
ether structure makes PBDEs much
more sensitive to degradation under
high temperature GC conditions. In
addition, the large number of bromines
in the higher congeners places the
molecular weight outside the range
of some mass spectrometers.
Furthermore, since bromine elicits
a much lower response by electron
capture than chlorine, the possibility
of interferences from chlorinated
compounds in some samples can be
troublesome. Much work is ongoing
to determine the optimum GC
column dimensions and phase for
PBDE analysis. At present, the
best inertness for the sensitive 209
congener has been shown to be a
short, thin film 5 meter Agilent
DB-5 MS column [2]. Other columns
tested show significant loss of the
209 congener. However, this column
is incapable of completely resolving
all 209 congeners. Intensive research
is ongoing at Agilent to determine
the optimum chromatographic
conditions for this analysis. In the
meantime, only a few of the 209
possible congeners are commonly
used as flame retardants, so
resolution of all 209 is not critical.
The common commercial flame
retardants are called Penta, Octa
and Deca, though, for example, the
Penta product is actually composed
of 45% penta-BDE, 40% tetra and
6% hexa congeners. Worldwide,
the deca product, for which there
is only one congener, is the most
widely used, making up 83% by
weight of the total usage. This
congener is therefore the most
important analytically. It is also
the most difficult to measure.
GC-ICP-MS Analysis
Because the ICP-MS measures only
the bromine, molecular weight is
2 Agilent ICP-MS Journal January 2004 - Issue 18 www.agilent.com/chem/icpms