Environmental & Analytical Toxicology

Comparison of Electron Impact and Electron Capture Negative Ionization for the Quantification of Polybrominated Diphenyl Ethers in Human Plasma

Abstract

Yan-Ping Lin, Isaac N. Pessah and Birgit Puschner

Polybrominated diphenyl ethers (PBDE) are persistent organic pollutants that are strongly associated with disrupted endocrine and immune functions. Due to the increasing health concerns, it is critical to quantify PBDEs in human specimens. Gas chromatography (GC) - mass spectrometry (MS) with electron impact (EI) and electron capture negative ionization (ECNI) sources were optimized to compare the quantification for ten PBDEs in 0.5 ml of human plasma. Source parameters, including electron energy, emission current, source temperature, focus lens and flow rate of the ECNI source reagent gas (methane), were optimized to achieve the best performances of EI-MS and ECNI-MS. The limits of quantification (LOQ) in human plasma ranged from 20 to 497 fg injected into GC/ECNI-MS compared to 519 to 2966 fg when using GC/EI-MS. Especially for highly brominated congeners, GC/ECNI-MS provided much lower LOQs than GC/EI-MS. Obtaining the necessary LOQs with GC/ECNI-MS, the method was validated according to the US Food and Drug Administration guidance for industry using standard materials purchased from the National Institute of Standards and Technology (NIST). The validated GC/ECNI-MS method was used to measure the concentrations of ten tetra-, penta- and hexa-PBDE congeners in maternal human plasma. Tetra-PBDEs, especially BDE-47, were identified as the predominant PBDE burdens in human plasma.