Search

The need for more robust, high-throughput sample preparation methodologies continues to grow as the analytical challenges of the modern world progress. This is apparent from the lowering advisory limits of environmental contaminants to the generation of novel anthropogenic wastes. Solid phase microextraction (SPME) technologies present unique qualities that enable it to tackle these challenges from an alternative approach. 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 work advances the field of sample preparation with the development of novel extraction and separation workflows for the quantitative analyses of complex environmental matrices. The first project of this work develops a sample preparation method for crude (4-methylcyclohexylmethanol (MCHM), a chemical blend commonly used in the coal industry for the separation of coal from rock, debris and coal dust by froth flotation. This mixture contains (4-methylcyclohexyl)methanol (68–89%), 4-(methoxymethyl)cyclohexanemethanol (4–22%); methyl 4-methylcyclohexanecarboxylate (5%), dimethyl-1,4-cyclohexanedicarboxylate (1%), and 1,4-cyclohexanedimethanol (1–2%), which all occur in the cis and trans diastereoisomeric forms; along with water (4–10%) and methanol (1%). Significant attention regarding the impact of these compounds on human health arose in 2014, when a spill of crude MCHM into the Elk River resulted in the contamination of drinking water for over 300,000 residents in West Virginia and Kentucky in the United States. In response, a series of studies aimed to investigate the mixture’s capacity for long-term exposure by determining the sorption properties of crude MCHM to pipes and linings. Sorbed MCHM was demonstrated to readily desorb from polyethylene into water at levels above the odor threshold, confirming the risk to residents from contaminated tap water pipelines. In light of this, it is imperative to develop analytical tools that enable the detection of crude MCHM components in environmental water samples for routine water monitoring. In this work, two SPME methods, based on fiber and thin film geometry, were developed and validated and coupled to gas chromatography – mass spectrometry (GC-MS). Their performances were compared with a modified solid-phase extraction (SPE) protocol based on EPA Method 522 for the analysis of volatiles in water. Both SPME methods demonstrated lower limits of quantitation (LOQ) compared to the SPE protocol. Thin film solid phase microextraction (TF-SPME), due its superior sensitivity and faster throughput was selected as the optimal extraction approach for 4-MCHM and other constituents of crude MCHM, with LOQ below the odor threshold for aqueous crude MCHM in distilled water at 19–21 °C (0.55 µg L-1).The second project focuses on the untargeted analysis of unconventional oil and gas waste. Produced water (PW), the primary waste byproduct of these operations, contains a diverse number of anthropogenic additives together with the numerous hydrocarbons extracted from the well. Due to potential environmental hazards, it is critical to characterize the chemical composition of this type of waste before proper disposal or remediation/reuse. In this work, a TF-SPME approach was developed and optimized to characterize produced water. The thin film device consisted of hydrophilic-lipophilic balance particles embedded in polydimethylsiloxane and immobilized on a carbon mesh surface. These devices were chosen to provide broad extraction coverage and high reusability. Various parameters were evaluated to ensure reproducible results while minimizing analyte loss. This optimized protocol, consisting of a 15 min extraction followed by a short (3 s) rinsing step, enabled the reproducible analysis of produced water without any sample pretreatment. Extraction efficiency was suitable for both produced water additives and hydrocarbons. The developed approach was able to tentatively identify a total of 201 compounds from produced water samples, by using one-dimensional GC-MS and data deconvolution.The third project continues work on PW. This waste has been shown to contain petroleum distillates, polycyclic aromatic hydrocarbons (PAHs), and organic fracturing additives, along with dissolved salts, heavy metals, and naturally-occurring radioactive materials (NORMs). Identification of these compounds is critical to develop future reuse and disposal protocols to minimize environmental contamination and potential health risks. In this study, versatile extraction methodologies were investigated for the untargeted analysis of PW. TF-SPME with hydrophilic-lipophilic balance particles (HLB) was utilized for the extraction of organic solubles from eight PW samples from the Permian Basin and Eagle Ford formation in Texas. GC-MS analysis found a total of 266 different organic constituents including 1,4-dioxane, atrazine, pyridine, PAHs, and substituted alkyl chain hydrocarbons. The elemental composition of PW was evaluated using dispersive solid-phase extraction (D-SPE) followed by inductively coupled plasma – mass spectrometry (ICP-MS), utilizing a new coordinating sorbent, poly(pyrrole-1-carboxylic acid). ICP-MS analysis confirmed the presence of 29 elements including major (Mg, Mn, Zn, Se, Ag, Ba) and trace rare earth elements, as well as hazardous metals, such as Cr, Cd, Pb, and U. Utilizing chemometric analysis, both approaches facilitated the discrimination of each PW sample based on their geochemical origin with a prediction accuracy above 90% using partial least squares-discriminant analysis (PLS-DA), paving the way for PW origin tracing in the environment.In the fourth project, an introduction method for direct ambient mass spectrometry was developed and tested for drugs and pesticides in the environment. Direct ambient mass spectrometry (AMS) methodologies significantly increase sample throughput, can be adapted for onsite analysis and are often regarded as semi-quantitative by most developed protocols. One of the limitations of AMS, especially for onsite analysis applications, is the irreproducibility of the measurements related to the occurrence of transient microenvironments (TME) and variable background interferences. In this work, we report an effective strategy to minimize these effects by hyphenating, for the first time, arrow solid phase microextraction (Arrow-SPME) to mass spectrometry via a thermal desorption unit (TDU) and Direct Analysis in Real Time (DART) source. The developed method was optimized for extracting and analyzing pesticides and pharmaceuticals from surface water. It was demonstrated that the hyphenation of the SPME and TDU-DART resulted in reduced background contamination, indicating the suitability of the method for onsite analysis even in variable and non-ideal environments. Model analytes were quantified in the low µg/L range with a total analysis time of less than 5 min, linear dynamic ranges (LDR), and interday reproducibility for most compounds being 2.5 – 500 µg/L and 10 %, respectively. The developed approach provides an excellent analytical tool that can be applied for the onsite high-throughput analysis of water samples as well as air and aerosols. Considering the tunability of our extraction process, time-resolved environmental monitoring can be achieved onsite within minutes.Continuing DART related work, the fifth project develops a strategy for analyzing per- and polyfluoroalkyl substances (PFAS), an emerging toxic class of anthropogenic chemicals that are persistent in the environment, are currently regulated at the low part-per-trillion level worldwide. Quantification and screening of these compounds currently rely mostly on liquid-chromatography hyphenated to mass spectrometry. The growing need for quicker and more robust analysis in routine monitoring has been, in many ways, spearheaded by the advent of direct ambient mass spectrometry (AMS) technologies. Direct analysis in real-time (DART), a plasma-based ambient ionization source that permits rapid automated analysis, has been shown to be effective at ionizing a large range of compound classes, PFAS. This work seeks to evaluate the performance of DART-MS for the screening and quantification of PFAS of different classes, employing a central composite design (CCD) to better understand the interactions of DART parameters on the ionization of PFAS. Furthermore, in-source fragmentation of the model PFAS were evaluated based on the evaluated DART parameters. Preconcentration of PFAS from water samples was achieved by SPME and extracts were analyzed using the optimized DART-MS conditions, which allowed obtaining linear dynamic ranges (LDR) between 10 and 5000 ng/L for the model analytes and LOQs of 10, 25 and 50 ng/L for all analytes. The sixth project focuses on developing novel strategies for the extraction and chromatographic separation of the cyanoneurotoxin β-N-methylamino-L-alanine (BMAA) and its structural isomers. Effective quantitative analysis of BMAA and its isomers without the need for derivatization has always been an analytical challenge due to their poor retention and separation on various liquid chromatography (LC) stationary phases. Previous studies that utilized conventional hydrophilic interaction chromatography (HILIC) demonstrate false negatives compared to reverse-phase workflows with derivatization. This work evaluates the chromatographic behavior of BMAA and its isomers, in their underivatized forms, on selected stationary phases, in particular fluorophenyl-based columns, to attain effective retention and separation. Detection and quantification were achieved with an ion-trap mass spectrometer. Extraction and preconcentration were achieved via SPME by assessing the effectiveness of multiple extraction phases, including HLB and mixed-mode (MM). A MM extraction phase consisting of C8 and benzene sulfonic acid moieties permitted the ideal extraction performance of BMAA and its isomers (2,4-diaminobutyric acid, DABA; N-(2-aminoethyl) glycine, AEG). Chromatographic separation was achieved within 8 min on a fluorophenyl stationary phase, ensuring high throughput without derivatization, and showing exceptional improvement from conventional HILIC methods. Limits of quantification in water for BMAA and AEG were 2.5 µg L-1 and DABA was 5 µg L-1, with linear dynamic ranges from 2.5 µg L-1 - 200 µg L-1 for BMAA and AEG and 5 µg L-1 - 200 µg L-1 for DABA. The final, seventh project continues the work of project six but with more focus on complex matrices. BMAA and its isomers have been demonstrated to bioaccumulate in aquatic fauna such as blue crab, these same toxins have also been detected in the brains of patients with amyotrophic lateral sclerosis (ALS) and dementia. A sample preparation method is developed in this work for the extraction of these toxins in brain and blue crab utilizing SPME hyphenated to LC-MS. Through an initial solvent-extraction approach, SPME device fouling and matrix effects were found to be acceptable. Further expansion of this workflow should enable the robust extraction of cyanoneurotoxins from complex matrices with consecutive reuse of the SPME device.