Analysis of multiclass emerging endocrine disrupting compounds in matrices predictive of environmental exposures using liquid chromatography high resolution mass spectrometry
Creators: name: Lazofsky, Abigail
Publisher: name: No Publisher Supplied
Year: 2023

description: Endocrine disrupting compounds (EDCs) are a class of emerging contaminants that have been previously detected in drinking water sources. Environmentally, EDCs are found as mixtures containing multiple classes at trace amounts. Chronic exposure to low doses of chemical mixtures with the same toxicological endpoint can result in synergistic health effects, highlighting the need to proactively detect these compounds so that mitigation strategies can be developed. Traditionally, analytical tools utilized for EDC analysis have relied on highly sensitive methods tailored towards a finite number of analytes or a specific compound class. However, with the rate of globally manufactured chemicals expected to continuously increase, there is a need to expand the analytical capabilities to cover a larger scope of contaminants simultaneously so that decisions about high-risk, high-priority pollutants could be made in a time efficient and cost-effective manner. The main objective of this dissertation was to develop and validate novel multiclass methods using liquid chromatography high-resolution mass spectrometry (LC-HRMS) to analyze various emerging EDCs in matrices predictive of environmental exposure. This was achieved by: 1) Comparing the performance of 4 LC-MS instruments to identify the best platform for the characterization of endocrine disruptive mycotoxins, 2) developing, validating, and applying a sensitive method to measure 8 quaternary ammonium compounds on the surfaces of treated buses, and 3) developing, validating, and applying a multiclass method to measure 94 unique EDCs in environmental surface waters, and 4) creating a framework for database searching to identify unknown environmental contaminants. Aim 1 determined the analytical instrument which would best facilitate the investigation of multiclass EDCs. A comparison of 4 different liquid chromatography mass spectrometry (LC-MS) platforms was performed through the analysis of human urine samples by means of two low-resolution and two high-resolution mass spectrometers. Using analytical figures of merit to rank instrument performance, it was determined that the Q Exactive HF Hybrid Quadrupole-Orbitrap (Orbitrap), a high-resolution platform, provided the best sensitivity, selectivity, and mass accuracy needed for trace analysis of Zearalenone and its metabolites, a group of well-known mycotoxins and EDCs. Notably, the Orbitrap was capable of discriminating the analyte of interest from coeluting concomitant ions found in the same mass windows, an essential consideration for analysis of complex environmental mixtures. Aim 2 utilized the high-resolution Orbitrap to analyze a new class of emerging contaminants, quaternary ammonium compounds (QACs), and their occurrence on public transportation vehicles. QACs, which saw a boom in use following the COVID-19 pandemic, are reported respiratory hazards and EDCs typically found in cleaning and disinfectant products. QACs have distinct sub-categories related to their chemical structure, allowing for preliminary exploration of multiclass analysis while limiting the number of physio-chemically unique compounds. A new surface sampling protocol and LC-MS method was created to analyze 8 QACs, including one novel chemical. This method was then used to determine the relative surface concentrations of 2 different cleaning products containing QACs after their application on NJ Transit buses. Aim 3 developed and validated a novel targeted LC-HRMS method for the analysis of 94 unique EDCs in surface water. Chromatographic separation was achieved in under 50 minutes through the optimization of column type, mobile phase composition, gradient elution, oven temperature, flow rate, and injection volume. The method was validated in terms of linearity (R2 = 0.914 ± 0.19), limit of detection (73.4% ≤ 10 ng/mL), intra-day (5.12% ± 5.4%) and inter-day (34.6% ± 34%) precision, and mass accuracy (93.6% ≤ 5ppm). The final method was utilized for the analysis of 2 sets of environmental water samples collected from New Jersey (n=8) and Ohio (n = 5). In the NJ river water samples, 12 compounds were detected at concentrations above their detection limits and were as follows: 2-biphenylol (2.62 ng/mL), dichloroacetic acid (9.31 ± 0.7 ng/mL), diethylstilbestrol (0.16 ± 0.1 ng/mL), TEP (0.078 ± 0.04 ng/mL), caffeine (0.62 ng/mL), triclocarban (0.20 ± 0.03 ng/mL), PFHxA (0.02 ± 0.01 ng/mL), Glucophage (0.14 ± 0.1 ng/mL), Sudaphed (0.31 ng/mL), Topamaz (0.21 ± 0.03 ng/mL), Zyrtec (0.10 ± 0.04 ng/mL), and DEP (2.80 ± 1.1 ng/mL). Dichloroacetic acid was the only compound with concentrations measured above its proposed health guideline of 0.2 µg/L. In the OH well and surface water samples, all showed the presence of EDCs, namely antimicrobials (1-6 compounds), herbicides (2-5 compounds), and pharmaceuticals (2-5 compounds). Overall, this method was sensitive enough to detect various EDCs at environmentally relevant levels. Aim 4 expanded upon the chromatography optimized in Aim 3 to transition method application into the identification of unknown contaminants. A simple procedure for unknown compound identification was developed using LC-HRMS/MS and the NIST 23 Mass Spectral Library. Using a known standard mixture containing 22 EDCs, the database searching procedure was successfully able to identify 12 compounds without relying on targeted MS experiments. Additionally, an unknown peak was identified as a general phthalate, a common group of endocrine disrupting contaminants found in laboratory environments. This is a significant application demonstration for the field of non-targeted analysis, as lack of comprehensive LC-MS databases has continuously made unknown identification of many environmental contaminants challenging.