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PH12 Analytical Environmental Chemistry of POPs
(PH124) Measuring POPs: Optimized Benchtop GC/MS Parameters for PBDE Measurements.
Ackerman, L1, Wilson, G2, Simonich, S1, 2, 1 Dept. of Chemistry, Oregon State University, Corvallis, OR, USA2 Dept. of Environmental & Molecular Toxicology, Oregon State University, Corvallis, OR, USA
ABSTRACT- Gas chromatographic mass spectrometry (GC/MS) parameters were optimized for the measurement of 36 individual mono through hepta polybrominated diphenyl ether (PBDE) congeners using a low resolution benchtop quadrupole mass spectrometer. An Agilent® 6980 GC coupled with an Agilent® 5973 benchtop quadrupole mass spectrometer, operated in both electron capture negative ionization (ECNI) and electron impact (EI) modes, was used for optimizing the measurement of these persistent organic pollutants (POPs). Baseline separation of 32 of the PBDEs was achieved in 57 minutes on a 30 m column. Partial separations and mass resolution allowed quantitation of the remaining four PBDEs. Both EI-MS and ECNI-MS techniques were optimized and compared for sensitivity and selectivity of PBDE measurements. Optimized parameters included injection port temperature, injection port pressure, GC oven ramp profile, source temperature, electron energy, emission current, buffer gas type, buffer gas pressure, and ions for selected ion monitoring (SIM). Emission current, source temperature, and buffer gas pressure significantly affected PBDE sensitivity for ECNI-MS, while emission current and electron energy primarily affected sensitivity for EI-MS. Congener specific diphenyl ether molecular fragment ions and bromine ions (Br-) were the SIM ions selected for ECNI-MS measurement of PBDEs. Congener specific molecular and molecular fragment ions were used for SIM measurements with EI-MS. Both EI-MS and ECNI-MS showed markedly different sensitivity to levels of bromination. EI-MS was more sensitive (D.L. ∼5ng/mL) to mono brominated PBDEs than ECNI-MS (D.L ∼50ng/mL). ECNI-MS was more sensitive (D.L. ∼1-15 ng/mL) to other PBDEs than EI (D.L. ∼10-100 ng/mL). This optimized GC/ECNI-MS technique can separate and quantify 36 mono though hepta PBDEs, at low ng/mL concentrations in solvent extracts, in less than an hour.
Key words: optimization, PBDEs, MS, GC
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