2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P56 STRATEGIES TO REDuCE DETECTION
LIMITS IN ThE ANALySIS OF bROMINATED
FLAME RETARDANTS IN ENVIRONMENTAL
SAMPLES
MICHAELA náPRAVníKOVá, JAnA PULKRABOVá,
PETRA HRáDKOVá, JAKUB SCHůREK, JAn
POUSTKA and JAnA HAJŠLOVá
Institute of Chemical Technology, Prague, Department of
Food Chemistry and Analysis, Technická 3, 166 28 Prague 6,
Czech Republic,
michaela.napravnikova@vscht.cz
Introduction
Polybrominated diphenyl ethers (PBDEs) represent
an important class of brominated flame retardants (BFRs)
which are widely used in various consumer products such as
electronic equipment, textiles and plastics 1 . These chemicals
are highly persistent and bioaccumulative what leads to their
ubiquitous occurrence in the environment 2 , both in abiotic
and biotic matrices.
Compared to major group of organohalogenated persistent
organic pollutants (POPs) such as polychlorinated biphenyls
(PCBs), the levels of PBDEs in respective environmental
compartments are typically lower by one order of magnitude.
On this account, low detection limits (LODs) are needed for
their reliable control.
Gas chromatography coupled to mass spectrometry
(GC/MS) operated in either electron ionization mode (EI)
or in negative chemical ionization (nCI) are commonly
employed analytical procedures of determination these compounds
3 . In nCI mode monitoring of abundant bromine ions
(m/z 79 and 81) provides a more sensitive and selective option
compared to EI. nowadays, comprehensive two-dimensional
(orthogonal) gas chromatography coupled to time-of-flight
mass spectrometry (GC × GC/TOFMS) has become another
challenging alternative to analyze very complex PBDEs mixtures
4 .
In any case, achieving low LODs is also associated with
the amount of sample introduced into GC system. The most
commonly used GC injection technique for PBDEs is a splitless
injection mode 3 , however, several studies were reported
a possibility to employ a large-volume programmed-temperature
vaporizer injection (PTV) in the determination of these
compounds 5 .
This paper presents the method performance characteristics
obtained in several GC systems used for quantification
of PBDEs.
Experimental
For our experiments a standard mixture of most common
PBDE congeners (BDEs no. 28, 47, 49, 66, 85, 99, 100, 153,
154 and 183) purchased from AccuStandard inc. (USA) was
used. The real-life sample containing trace amount of PBDEs
was a purified extract obtained from fish tissue by procedure
s445
described by Hajšlová et al. 6 . To assess LODs achievable
under various GC conditions following set-up were tested:
• PTV-GC/MS (EI),
• PTV-GC/MS (nCI),
• GC/TOFMS (EI),
• PTV-GC/TOFMS (EI).
P T V - G C / M S ( E I ) a n d P T V - G C / M S
( n C I )
GC/MS analyses were performed on an Agilent 6890n
gas chromatograph coupled to a mass selective detector
(Agilent 5975XL Inert MSD) equipped with quadrupole
analyzer operated in nCI or EI mode using splitless or PTV
injection. The GC conditions were as follows: a DB-XLB
capillary column (15 m × 250 μm i.d. × 0.1 μm, J&W Scientific);
a oven temperature program: from 105 °C (held for
vent time) to 260 °C (held for 1 min) at 50 °C min −1 then to
300 °C at 20 °C min –1 and held for 3 min; carrier gas: helium
with constant flow 1.5 ml min −1 . The MS was operating in the
selected ion monitoring (SIM) mode (monitored ions were
m/z 79, 81, 159, 161 and m/z 406, 484, 564, 484, 562 for
nCI and EI mode, respectively). The MS (nCI) parameters
were as follows: reagent gas: methane; temperatures of MSD
interface, ion source, and quadrupole: 280 °C, 150 °C, and
150 °C, respectively. The temperatures of MSD interface,
ion source and, quadrupole for MS (EI) system were 280 °C,
230 °C and, 150 °C, respectively.
Four parameters for PTV injection were tested: vent
time (VT), vent flow (VF), injection volume (IV) and splitless
period. Starting injection temperature was 50 °C (held
4.6 min) and it was ramped to 350 °C at 500 °C min –1 .
G C / T O F M S a n d P T V - G C / T O F M S
The analyses were performed on a Pegasus 4D instrument
(Leco, USA) consisting of an Agilent 6890n gas chromatograph
equipped with splitless and/or PTV injector and
a Leco Pegasus III high-speed time-of-flight mass spectrometer.
The same, DB-XLB capillary column was used for
determination of analytes. The GC conditions were similar
to PTV–GC/MS system. The interface temperature was
280 °C. The MS acquisition rate was 11 Hz, the mass range
35–850 amu, the ion-source temperature 300 °C, and the detector
potential –1875 V.
Results
In the first part of this study, the implementation and optimalization
of a PTV injection coupled with GC/MS (EI and/
or nCI mode) was realized. A solvent standard solution of
above mentioned PBDE congeners was used for optimalization
PTV injection conditions. Optimal parameters assessed
by the comparison of a peak height of individual analytes
were as follows:
•
•
vent time: 90 s
vent flow: 60 ml min –1