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- Mullin, Lauren Gayle, 1984-
(author)
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Advances in Mass Spectrometry for the Analysis of Emerging Persistent Organic Pollutants
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Mass spectrometry (MS) is a technique widely implemented for the measurement of environmental pollutants. A critical tool for the analysis of persistent organic pollutants (POPs) over several decades, MS as coupled with liquid and gas chromatography (LC and GC) techniques enables the analysis of emerging POPs. The aim of this thesis was to investigate the use of alternative MS-based techniques to assist specific analytical challenges including separation of stereoisomers using supercritical fluid chromatography (SFC), reduced ionization competition with appropriate mobile phase additives, and applied rotationally averaged collision-cross section (CCS) of ions via ion mobility measurements of emerging POPs.Chromatographic efficiency improvements for the brominated flame retardant, hexabromocyclododecane (HBCDD), were implemented through the development of two supercritical fluid chromatography (SFC) methods. Based on the inherent qualities of supercritical fluids, separation of both predominant diastereomers and respective enantiomers was performed in a shorter time with wider chromatographic resolution using SFC than existing LC methods.Turning next to MS ionization considerations, the emerging perfluoroalkyl substance hexafluoropropylene oxide-dimer acid (HFPO-DA) was investigated. Following a survey of analytical methodologies for HFPO-DA, the challenge of extreme dimer formation, in-source fragmentation and very low [M-H]- production was described. Method development using alternative mobile phase additives in currently used LC-MS acquisition techniques was deployed.Finally, ion mobility spectrometry (IMS) was implemented in a non-targeted acquisition study of indoor dust samples. This study used IMS coupled with quadrupole time-of-flight MS to identify a wide range of contaminant classes, including emerging POPs. Identification confidence is a challenge currently facing non-targeted studies, and the use of prediction mechanisms of analyte IMS gas-phase separations was explored.Through applying diverse alternative techniques, increased method performance was explored for emerging POPs analyses.
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- Mullin, Lauren Gayle, 1984-, et al.
(author)
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Analysis of hexafluoropropylene oxide-dimer acid (HFPO-DA) by liquid chromatography-mass spectrometry (LC-MS) : Review of current approaches and environmental levels
- 2019
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In: TrAC. Trends in analytical chemistry. - : Elsevier. - 0165-9936 .- 1879-3142. ; 118, s. 828-839
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Research review (peer-reviewed)abstract
- Emerging per- and polyfluorinated compounds (PFAS) compounds are of increasing interest for environmental monitoring, one being hexafluoropropylene oxide-dimer acid (HFPO-DA), commonly referred to as GenX. The following review describes existing liquid chromatography-mass spectrometry (LC-MS) methods used to analyse HFPO-DA, including sample preparation and method sensitivity relative to other PFAS. Analytical challenges are also described, in particular the significant formation of in-source fragmentation, dimer and dimer adducts which detract from [M-H](-) signal. Lastly, detected levels of HFPO-DA in environmental and biological samples are compared across the limited number of available field exposure studies, which found several mu g/L concentrations in water samples taken near fluorochemical plant discharges.
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- Mullin, Lauren Gayle, 1984-, et al.
(author)
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Biomonitoring of GC and LC amenable environmental contaminants using a single MS platform
- 2016
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In: Organohalogen Compounds. - : Eco-Informa Press. - 1026-4892. ; 78
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Journal article (peer-reviewed)abstract
- Monitoring of environmental contaminants in biological samples is typically performed by targeted analysis using a tandem quadrupole system on separate GC and LC platforms in order to cover the expansive range of compounds. Use of multiple systems can add complexity to the analysis and increase turnaround times for samples to be reported. The work that will be presented will show the analysis of common environmental contaminants in a biomonitoring context on a single high resolution mass spectrometric (HRMS) platform. The compounds of interest include:GC amenable compounds: Halogenated pesticides, BFRs, PCBs and PCDD/FsLC amenable compounds: Perfluoroalkyl substances, HBCDD/TBBP-A and phosphorus-based flame retardants
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- Riddell, Nicole, 1979-, et al.
(author)
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Enantioselective Analytical- and Preparative-Scale Separation of Hexabromocyclododecane Stereoisomers Using Packed Column Supercritical Fluid Chromatography
- 2016
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In: Molecules. - Basel, Switzerland : MDPI AG. - 1431-5157 .- 1420-3049. ; 21:11
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Journal article (peer-reviewed)abstract
- Hexabromocyclododecane (HBCDD) is an additive brominated flame retardant which has been listed in Annex A of the Stockholm Convention for elimination of production and use. It has been reported to persist in the environment and has the potential for enantiomer-specific degradation, accumulation, or both, making enantioselective analyses increasingly important. The six main stereoisomers of technical HBCDD (i.e., the (+) and (-) enantiomers of α-, β-, and γ-HBCDD) were separated and isolated for the first time using enantioselective packed column supercritical fluid chromatography (pSFC) separation methods on a preparative scale. Characterization was completed using published chiral liquid chromatography (LC) methods and elution profiles, as well as X-ray crystallography, and the isolated fractions were definitively identified. Additionally, the resolution of the enantiomers, along with two minor components of the technical product (δ- and ε-HBCDD), was investigated on an analytical scale using both LC and pSFC separation techniques, and changes in elution order were highlighted. Baseline separation of all HBCDD enantiomers was achieved by pSFC on an analytical scale using a cellulose-based column. The described method emphasizes the potential associated with pSFC as a green method of isolating and analyzing environmental contaminants of concern.
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