Many Doors, One Key Addressing Ecotoxicological, Engineering, Environmental, and Toxicological Questions Using Liquid Chromatography and Mass Spectrometry
Singh, Randolph Reyes
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Pharmaceuticals encompass a huge class of compounds that are used in many aspects of daily life from personal care, healthcare, and agriculture. The increasing demand for these compounds has resulted in their increasing levels in the environment as the pharmaceuticals move from one environmental compartment to another. One major source of pharmaceuticals into the environment are wastewater treatment plants. Many treatment processes are continually developed to address these problems, however, currently employed treatment systems are ineffective at removing the pollutants. Pollutants then end up getting released into the environment where they may persist. There is rising concern about the persistence of pharmaceuticals in the environment because they bring about different detrimental effects that include but are not limited to bioaccumulation, production of toxic disinfection by-products, and the proliferation of antimicrobial resistance. This work will demonstrate the different approaches developed to answer the many environmental challenges in the pursuit of gaining better understanding to help in the solution making process. Chapter 2 focused on the analysis of multiple classes of antimicrobials and pharmaceuticals in different wastewater and surface water samples from across the globe. A solid-phase extraction (SPE) method was developed and used to determine the stability of analytes when stored at two different conditions in the SPE cartridges. The susceptibility of analytes to degrade and its duration during storage is determined. A targeted analysis by liquid chromatography coupled to a triple quadrupole mass spectrometer was also developed and used to determine antimicrobial loading in influent, effluent, and surface water samples from Hong Kong, Philippines, Sweden, Switzerland, and the United States of America. The different challenges associated with performing studies of such magnitude are addressed. Chapter 3 demonstrated of how transformation products of the iodinated contrast media iopromide were identified and how the fate of this molecule was better understood during advanced oxidation. Metabolite profiling tools were utilized together with high-resolution mass spectrometry in order to understand the fate of iopromide, as a model compound, during treatment. Wastewater spiked with iopromide was made to undergo UV/H2O2 advanced oxidation then the transformation products were analyzed using a quadrupole time-of-flight mass spectrometer. The complexity of wastewater prevented the easy identification of transformation products, however by statistically comparing samples before and after advanced oxidation, peaks that were produced due to treatment were identified. After guidelines were set, probable transformation products were identified using the high resolution mass, which afforded the prediction of the exact molecular formula. The identity of the transformation products were verified by performing a fragmentation study. The fate of the transformation products were also assessed during biodegradation. Chapter 4 evaluated the concentrations, bioaccumulation, and the selective uptake of antidepressants in fish living in the Niagara River. Twenty-two target compounds were analyzed, 11 of which were found at part-per-billion levels in WWTP effluents and at part-per-trillion levels in river water samples. The major pollutants observed were the antidepressants: citalopram, paroxetine, sertraline, venlafaxine, and bupropion, and their metabolites norfluoxetine and norsertraline, together with the antihistamine diphenhydramine. These PPCPs were shown to selectively accumulate in various fish organs. The accumulation of these antidepressants by various fish species at different trophic levels was also studied, suggesting that further metabolism occurs once these compounds are inside the organism. The highest bioaccumulation of antidepressants was found in the brain, followed by liver, muscle and gonads. Lastly, Chapter 5 discussed the potential of iodinated contrast media (ICM) to act as disruptors of endocrine function. ICMs were analyzed in fish brain and fish gonad extracts using a hydrophilic interaction chromatography (HILIC) separation method coupled to a triple quadrupole mass spectrometer. The merits of using HILIC for ICM analysis was demonstrated. The in silico binding potential of ICMs to transthyretin, PPAR-?, and glucocorticoid receptors was also discussed. The results demonstrated how ICMs can potentially bind to these proteins. The levels found in fish brain and gonad were found to be at the same concentration range as the natural substrates thyroxine and triiodothyronine. The presence of these ICMs in these two organs present other concerns due to the fact that fish endocrine function mainly occur in the pituitary gland and the gonads.