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Seminar | Materials Science

The Development of Alternative Green Analytical Approaches for the Analysis of Unconventional Environmental Contaminants

MSD Seminar

Abstract: The need for more robust, high-throughput analytical methodologies continues to grow as the analytical challenges of the modern world progress. This is apparent from the lowering advisory limits on environmental contaminants to the generation of novel anthropogenic wastes. To date, there are a variety of matrices, contaminants and analytical tools that are still not well understood or reliably accounted for in the literature. This presentation will explore three major projects focused on the development of alternative green and rapid analytical tools for the analysis of unconventional or emerging organic pollutants.

The first project [1] will discuss a strategy for detecting and quantifying per- and polyfluoroalkyl substances (PFAS) by coupling solid phase microextraction (SPME) to direct analysis in real time (DART) mass spectrometry. Current methodologies for PFAS analysis rely on liquid chromatography – mass spectrometry (LC-MS), however, there is a need for more rapid routine monitoring. DART-MS permits ultra-rapid quantification of samples, in this case just under 20 s per sample. This approach was optimized employing a central composite design (CCD) to better understand the interactions of DART-MS parameters with each other and their effect on PFAS fragmentation. Perfluorooctanoic acid (PFOA), hexafluoropropylene oxide dimer acid (GenX), perfluorooctane sulfonic acid (PFOS) and perfluoro-1-butanesulfonate (PFBS) were used as model analytes with limits of quantitation (LOQs) of 10, 50, 50 and 25 ng/L obtained, respectively.

The second project [2,3] will focus on the untargeted analysis of unconventional oil and gas wastes, in particular produced water (PW). These wastes contain various organic solubles of disparate physicochemical properties along with heavy metals, naturally-occurring radioactive materials (NORMs) and dissolved salts. The extraction of organic solubles was performed using thin film – SPME utilizing hydrophilic-lipophilic balance (HLB) particles embedded in polydimethylsiloxane (PDMS) and immobilized on a carbon mesh surface. This approach allows the removal of filtration steps while still preconcentrating analytes for untargeted analysis through gas chromatography – mass spectrometry (GC-MS). Data deconvolution methods were employed for putative compound identification. Samples were also analyzed for trace rare earth elements and hazardous metals (Pb, U, Cr, Cd) utilizing inductively coupled plasma – mass spectrometry preceded by selective extraction using a new coordinating sorbent, poly(pyrrole-1-carboxylic acid. and the data obtained were modeled through partial least squares-discriminant analysis (PLS-DA), facilitating the robust chemical discrimination of sampling sites.

The third project [4] describes the development of a novel LC separation approach for the analysis of the cyanoneurotoxin β-N-methylamino-L-alanine (BMAA) and its two major isomers, 2,4-diaminobutyric acid (DABA) and N-(2- aminoethyl) glycine (AEG). Typical approaches use conventional hydrophilic interaction chromatography (HILIC) for this separation however, these methods are approximately 30 min long and cause matrix effects when used with complex matrices. This work investigates retention mechanisms these analytes on various stationary phases for liquid chromatography. Fluorophenyl stationary phases provided efficient separation of these analytes in maximum 8 min, through a mixed-mode interaction by both the fluorophenyl moiety and free silanol groups acting as an ion-exchange mechanism. Coupled to mixed-mode SPME (benzene sulfonic acid/C8 particles embedded in polyacrylonitrile), LOQs were 2.5 μg/L for BMAA and AEG and 5 μg/L for DABA, with BMAA-d3 used for internal standard correction.