Esta tese demonstra a aplicação da análise por injeção seqüencial (SIA) para determinação de sulfeto utilizando a química da formação do azul de metileno, a qual se baseia em dois reagentes: solução de cloridrato de dimetil p-fenileno diamina (DMPD) 3,63 mmol L-1 em meio de HCI 1,1 mol L-1 e solução de cloreto de ferro (III) 19 mmol L-1, também em meio de HCI 1, 1 mol L-1. Estas soluções foram aspiradas para dentro de uma bobina coletora do sistema SIA como duas zonas de reagente, entre as quais aspirava-se a solução da amostra. Em condições otimizadas o limite de detecção foi calculado em 40 µg L-1 de S2-, com uma faixa dinâmica de resposta linear entre 0,05 e 2,0 mg L-1 . Esta faixa linear pode ser ampliada até 32 mg L-1 utilizando-se uma etapa de diluição in-line para concentrações maiores do que 2,0 mg L-1 de S2- . As características de robustez do sistema SIA que utiliza uma bomba de pistão, confere alta estabilidade para as curvas analíticas (precisão de 4%), minimizando a trabalhosa preparação de padrões de S2-. O método foi aplicado na determinação de sulfeto volatilizável por ácidos (AVS) em sedimentos coletados em reservatórios da região metropolitana de São Paulo (RMSP) e no reservatório de Barra Bonita no rio Tietê, localizado 270 km a jusante em relação à cidade de São Paulo. As concentrações de AVS foram 9 a 14 mg kg-1 nos sedimentos de Barra Bonita e entre 1,2 e 14 g kg-1 nos sedimentos dos reservatórios Billings, Pirapora e Rasgão. Esta tese também descreve o acoplamento da análise por injeção seqüencial com análise por fluxo monossegmentado (SI-MSFA) para determinação de sulfeto em níveis de concentração típicos de águas residuais. As curvas analíticas foram construídas por diluição in-line de uma única solução padrão. A robustez do método proposto foi verificada construindo-se curvas analíticas em diferentes dias de trabalho e comparando-se os coeficientes angulares, os quais apresentaram um desvio padrão relativo de 5,2% (n=5) para uma faixa de concentração entre 0,17 e 1,0 mg L-1 de S2-. A freqüência de amostragem foi de 38 análises por hora, com um limite de detecção de 40 µg L-1. A adequabilidade do método SI-MSFA para realizar adições de padrão para determinação de S2- também foi descrita. Amostras simuladas foram analisadas pelo método proposto, apresentando taxas de recuperação entre 70 e 115%, demonstrando a adequabilidade do método SI-MSFA para realizar análise in-situ de S2- em estações automáticas de monitoramento. / This thesis demonstrates the application of sequential injection analysis (SIA) to perform sulfide determination using the methylene blue chemistry, based on two reagents: 3.63 mmol L-1 N,N dimethyl-p-phenylene diamine hydrochloride in 1.1 mol L-1 HCI solution and 19 mmol L-1 FeCl3, also in 1.1 mol L-1 HCI. These solutions are aspirated inside the holding coil of the sequential injection system as two reagent zones sandwiching the sample zone. Under optimized conditions, the detection limit was calculated at 40 µg L-1 S2-, with a linear dynamic range from 0.05 to 2 mg L-1 S2-. This linear range can be extended up to 32 mg L-1 using in-line dilution for sulfide concentrations greater than 2 mg L-1. The robust characteristic of the SI system with syringe pump leads to very stable analytical curves (precision of 4%), minimizing the laborious preparation of sulfide standards. The method was applied in the determination of acid volatile sulfide in river sediments collected at the Metropolitan Area of São Paulo (MASP) City and at the Barra Bonita reservoir, located in the Tietê River, 270 km down river from São Paulo City. The concentrations of acid volatile sulfide were 9 to 14 mg kg-1 in the Barra reservoir and between 1.2 and 14 g kg-1 in sediments from Billings, Pirapora and Rasgão reservoirs. This thesis also describes the coupling of Sequential Injection with Monosegmented Flow Analysis (SI-MSFA) for determination of sulfide at typical concentrations in wastewaters. The analytical curves were constructed by in-line dilution of a single stock standard solution. The robustness of the proposed method was checked constructing analytical curves in different working days and comparing the slopes, which had a relative standard deviation of 5.2 % (n = 5) for a concentration window inside the monosegment between 0.17 and 1.0 mg L-1 S2-. The analytical throughput was 38 samples per hour and the limit of detection was 40 µg L-1. The feasibility of the SI-MSFA approach to perform standard additions for S2- determination was also described. Simulated samples analyzed by the proposed method showed recoveries between 70 and 115%, demonstrating the feasibility of the SI-MSFA method to perform in-situ analysis of S2- in automatic monitoring stations.

Processos de fotodegradação de compostos orgânicos tóxicos têm sido bastante estudados. Este trabalho trata da aplicação do processo foto-Fenton para a degradação de atrazina em água (composto modelo). O efeito das concentrações dos seguintes compostos foi avaliado: peróxido de hidrogênio (2 a 6 mmol L-1) e ferrioxalato de potássio (0,2 a 1 mmol L-1). Os experimentos foram realizados em um reator com lâmpada UV - 8W (254nm). O processo de fotodegradação foi monitorado por medidas de espectrofotometria de absorção molecular automatizada por injeção seqüencial (SIA) para determinação de peróxido de hidrogênio e por cromatografia a líquido de alta eficiência (CLAE) para determinação de atrazina e metabólitos. Os experimentos demonstram que o processo de foto-Fenton é viável para o tratamento de atrazina em água. / Photo-degradation processes of toxic organic compounds have been widely studied. This work describes the application of the photo-Fenton process for degradation of atrazine in water. Atrazine was used as a model compound. The effects of the concentration of the following substances were evaluated: hydrogen peroxide (1 to 6 mmol L-1) and potassium ferrioxalate (0.2 to 1 mmol L-1). The experiments were accomplished in a reactor with an 8W UV lamp at 254 nm. The photo-degradation was monitored by molecular absorption spectrophotometry automated by sequential injection analysis (SIA) for determination of hydrogen peroxide and by high performance liquid chromatography (HPLC) for determínation of atrazine and its metabolites. Experimental results demonstrated that the photo-Fenton process is feasíble for the treatment of atrazine.

Compostos químicos provenientes de várias origens como tráfico, agricultura, industria e efluentes domésticos são transportados à longas distâncias e podem atingir os corpos hídricos. A proliferação de compostos orgânicos sintéticos desencadeou a preocupação sobre seus efeitos tóxicos. Esses compostos sintéticos podem estar afetando o meio ambiente. Mesmo em concentrações muito baixas, eles interferem no sistema endócrino, tanto nos seres humanos quanto nos animais e também nas outras formas de vida que compõem os ecossistemas. Este trabalho teve como objetivo realizar estudo analítico-ambiental na Represa Billings, afim de verificar a ocorrência de poluentes orgânicos em amostras de água e sedimento. Foram analisados pesticidas organoclorados (OCs), bifenilas policloradas (PCBs), hidrocarbonetos policíclicos aromáticos (PAHs) e fármacos. Foram realizadas quatro campanhas para coleta de água e sedimento, em julho e novembro de 1999, maio de 2000 e janeiro de 2001. O sedimento foi coletado em perfil vertical, sendo possível verificar o acúmulo da contaminação. Foram validadas metodologias analíticas para determinação de poluentes orgânicos persistentes, como pesticidas organoclorados, bifenilas policloradas (PCBs), hidrocarbonetos policíclicos aromáticos (PAHs) em amostras de água. O método incluiu a extração em fase sólida (SPE) e análise por CG/MS. Para a determinação de fármacos em água e sedimento foi empregada a extração em fase sólida (SPE) e análise por LC/MS-MS. Foram detectados nos sedimentos e nas águas do reservatório Billings hidrocarbonetos policíclicos aromáticos, bifenilas policloradas, pesticidas organoclorados, fármacos como ibuprofen, diclofenac e cafeína. A presença desses compostos no reservatório é devido a associação com as fontes potenciais como o material particulado atmosférico e os efluentes industriais e municipais. / Chemicals from a wide range of sources as traffic, industry, agriculture and domestic wastewater are transported over long distances and can reach the aquatic environment. There is great concern about the proliferation of synthetic organic chemicals and their toxic effects as these chemicals may be affecting the environment. Even at low levels, they interfere in the endocrine system both in humans and in animals and other living organism. The aim of this study was to carry out an analytical-environmental analysis in the Billings reservoir, near the city of São Paulo in order to assess the occurrence of organic pollutants in water and sediment. Chlorinated pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and pharmaceuticals were analyzed. Sediments and water were collected during July and November 1999, May 2000 and January 2001. Sediments were collected in core samples that provided vertical delineation of contamination. Validation of the analytical procedure in order to determine persistent organic pollutants such as chlorinated pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic (PAHs) in water samples was carried out. Solid phase extraction (SPE) was used for sample preparation and detection and confirmation by GC/MS. The determination of pharmaceuticals was performed by tandem LC-MS(LC/MS-MS) after a solid phase extraction. Chlorinated pesticides, polychlorinated biphenyls, polycyclic aromatic and pharmaceuticals such Ibuprofen, Diclofenac and caffeine were detected.in sediment and water. The conclusion of the study was the occurrence of these compounds in the reservoir is due to sources like atmospheric particles, municipal and industrial waste.

En ny komplex aspekt i frågan om vattenkvalité är ackumuleringen av organiska föroreningar.Den begränsade utbredningen av vattenrening i Brasilien såväl som i andra utvecklingsländervisar på ett tydligt behov av utveckling av billiga och effektiva metoder för provtagning ivatten. Bristen på den här typen av metoder försvårar idag möjligheterna att kontrolleravattenkvalitén och på så vis även arbetet med att säkerställa de sanitära förhållandena ivattentillgångar. Det här examensarbetet innehåller en sammanfattande genomgång avprinciperna för den passiva provtagningsmetoden med namnet ”Diffusive Gradients in Thin‐Films (DGT)”, som direktöversatt får det svenska namnet ”Diffusiva gradienter i tunnfilmer”.När metoden används för provtagning för att upptäcka olika organiska ämnen i vattnetbenämns den som o‐DGT.Målet med detta arbete är att ta fram en metod med målet att specifikt upptäcka olika typerav nya framväxande organiska föroreningar som i de flesta fall förekommer bara i väldigt lågakoncentrationer i vår miljö. Grundliga undersökningar genomfördes för att få svar på huruvidabiokol kan fungera som den bindande agenten i DGT apparatur och verka för att kunnaupptäcka och identifiera dessa ämnen på ett effektivt sätt.Resultaten från de undersökningar som genomförts hittills visar på att biokol har godpotential att tillämpas som bindande agent i filter för bruk i o‐DGT apparatur. De organiskaföreningarna av intresse i denna studie kunde alla detekteras, kvantifieras och identifieras.För optimering av provtagningsmetoden bör vidare studier vid varierande förhållanden medhänsyn till pH, temperatur och jonkoncentration genomföras, såväl som studier av detbindande lagrets egenskaper i förhållande till koncentration av biokol och lagrets tjocklek.Detta för att kunna optimera tekniken, och förhoppningsvis bidra till ett konventionelltanvändande av biokol på adsorberande agent i o‐DGT anordningar i framtiden. / A new complex aspect in the matter of water quality is the occurrence of emerging organicpollutants and contaminants in waste water. The currently low extent to which treatment ofwaste water is performed in Brazil, and in the world as a whole, there is a considerable needfor development of cheap and accurate in‐situ sampling methods for far‐reaching studies ofsurface water quality. The lack of such methods today makes the maintenance andestablishing of sanitary safety difficult. This diploma work gives a brief introduction to thebasic principles of the passive sampling method known as Diffusive Gradient in Thin‐films(DGT). A method that could be useful for such monitoring of quality in water bodies worldwide.The aim of this study is to develop a method, for the detection of organic emerging pollutantsand contaminants – i.e. compounds, which usually are present at very low concentrationswhen found in the environment as a result of human activity. More specifically, this workinvestigates the potential and usefulness of the application of DGT devices in detection oforganic compounds that can affect human health and ecosystems, even at lowconcentrations, however, their effects still are in need of further investigations.This study focuses on both purely technical as well as practical points of views. The efficiencyof organic DGT (o‐DGT) with biochar as the adsorbing agent is examined targeting thedetection of organic pollutants and contaminants in surface water. In this sense, the specificaim of the work is to evaluate the performance of biochar as adsorbing agent. This workshowed that the performance of biochar as the adsorbing agent in binding layers in o‐DGTsample devices can be considered as satisfactory since all compounds of interest in this studywas successfully detected, quantified an identified. Further investigations in the future areneeded to determine the effects of varying pH, temperature and ion concentration in thedeployment media, as well as the properties of the binding layer in relation to concentrationof biochar and the thickness of the layer. These in order to optimize the method for in‐situwater sampling, aiming conventional use of biochar as the adsorbing agent in the future.

The elemental analysis of soil is useful in forensic and environmental sciences. Methods were developed and optimized for two laser-based multi-element analysis techniques: laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and laser-induced breakdown spectroscopy (LIBS). This work represents the first use of a 266 nm laser for forensic soil analysis by LIBS. Sample preparation methods were developed and optimized for a variety of sample types, including pellets for large bulk soil specimens (470 mg) and sediment-laden filters (47 mg), and tape-mounting for small transfer evidence specimens (10 mg). Analytical performance for sediment filter pellets and tape-mounted soils was similar to that achieved with bulk pellets. An inter-laboratory comparison exercise was designed to evaluate the performance of the LA-ICP-MS and LIBS methods, as well as for micro X-ray fluorescence (μXRF), across multiple laboratories. Limits of detection (LODs) were 0.01-23 ppm for LA-ICP-MS, 0.25-574 ppm for LIBS, 16-4400 ppm for µXRF, and well below the levels normally seen in soils. Good intra-laboratory precision (≤ 6 % relative standard deviation (RSD) for LA-ICP-MS; ≤ 8 % for µXRF; ≤ 17 % for LIBS) and inter-laboratory precision (≤ 19 % for LA-ICP-MS; ≤ 25 % for µXRF) were achieved for most elements, which is encouraging for a first inter-laboratory exercise. While LIBS generally has higher LODs and RSDs than LA-ICP-MS, both were capable of generating good quality multi-element data sufficient for discrimination purposes. Multivariate methods using principal components analysis (PCA) and linear discriminant analysis (LDA) were developed for discriminations of soils from different sources. Specimens from different sites that were indistinguishable by color alone were discriminated by elemental analysis. Correct classification rates of 94.5 % or better were achieved in a simulated forensic discrimination of three similar sites for both LIBS and LA-ICP-MS. Results for tape-mounted specimens were nearly identical to those achieved with pellets. Methods were tested on soils from USA, Canada and Tanzania. Within-site heterogeneity was site-specific. Elemental differences were greatest for specimens separated by large distances, even within the same lithology. Elemental profiles can be used to discriminate soils from different locations and narrow down locations even when mineralogy is similar.

Coastal forest retreat in the Florida Keys during the 20th century has been attributed to a combination of sea level rise and hurricane storm surge impacts, but the interactions between these two disturbances leading to forest decline are not well understood. The goal of my research was to assess their effects over a period spanning more than two decades, and to examine the relationships between these press and pulse disturbances and freshwater availability in pine rockland, hardwood hammock, and supratidal scrub communities. Impacts and recovery from two storm surges, Hurricanes Georges (1998) and Wilma (2005), were assessed with satellite-derived vegetation indices and multiple change detection techniques. Impacts were greater at lower elevations, and in hardwood hammock, spectral signatures indicative of plant stress and productivity returned to pre-disturbance levels within a few years. In pine rockland, impacts were predominately related to Hurricane Wilma, however, a similar return to pre-disturbance conditions was absent, suggesting that trajectories of disturbance recovery differed between the two communities. Long-term monitoring of forest composition, structure, and groundwater salinity showed that compositional shifts in the low shrub stratum were associated with salinization of the freshwater resource attributable to sea level rise. Throughout the course of twelve months of climate and groundwater monitoring (2011-2012), groundwater salinity generally decreased in response to large precipitation events. Modeling of geophysical data indicated that groundwater salinity was an important predictor of community type. Isotopic analysis of d18O in plant stem water and foliar d13C was used to determine temporal and spatial patterns in water use and plant stress in two community dominants, slash pine, Pinus elliottii var. densa, and buttonwood, Conocarpus erectus. Both species relied heavily on groundwater, and plant stress was related to increasing groundwater salinity. The results of this work suggest that the interaction of press and pulse disturbances drive changes in community composition by causing mortality of salt-sensitive species and altering the freshwater resource.

The Biscayne Aquifer is a primary source of water supply in Southeast Florida. As a coastal aquifer, it is threatened by saltwater intrusion (SWI) when the natural groundwater flow is altered by over-pumping of groundwater. SWI is detrimental to the quality of fresh groundwater sources, making the water unfit for drinking due to mixing and reactions with aquifer minerals. Increasing water demand and complex environmental issues thus force water utilities in South Florida to sustainably manage saltwater intrusion and develop alternative water supplies (e.g., aquifer storage and recovery, ASR). The objectives of this study were to develop and use calibrated geochemical models to estimate water quality changes during saline intrusion and during ASR in south Florida. A batch-reaction model of saltwater intrusion was developed and important geochemical reactions were inferred. Additionally, a reactive transport model was developed to assess fate and transport of major ions and trace metals (Fe, As) at the Kissimmee River ASR. Finally, a cost-effective management of saltwater intrusion that involves using abstraction and recharge wells was implemented and optimized for the case of the Biscayne Aquifer. Major processes in the SWI areas were found to be mixing and dissolution-precipitation reactions with calcite and dolomite. Most of the major ions (Cl, Na, K, Mg, SO4) behaved conservatively during ASR while Ca and alkalinity were affected by carbonate reactions and cation exchange. A complex set of reactions involving thermodynamic equilibrium, kinetics and surface complexation reactions was required in the ASR model to simulate observed concentrations of Fe and As. The saltwater management model aimed at finding optimal locations and flow rates for abstraction and recharge wells. Optimal solutions (i.e., minimum total salt and total cost Pareto front) were produced for the Biscayne Aquifer for scenarios of surface recharge induced by climate change-affected precipitation. In general, abstraction at the maximum rate near the coast and artificial recharge at locations much further inland were found to be optimal. Knowledge developed herein directly supports the understanding of SWI caused by anthropogenic stressors, such as over-pumping and sea level rise, on coastal aquifers.

An automated on-line SPE-LC-MS/MS method was developed for the quantitation of multiple classes of antibiotics in environmental waters. High sensitivity in the low ng/L range was accomplished by using large volume injections with 10-mL of sample. Positive confirmation of analytes was achieved using two selected reaction monitoring (SRM) transitions per antibiotic and quantitation was performed using an internal standard approach. Samples were extracted using online solid phase extraction, then using column switching technique; extracted samples were immediately passed through liquid chromatography and analyzed by tandem mass spectrometry. The total run time per each sample was 20 min. The statistically calculated method detection limits for various environmental samples were between 1.2 and 63 ng/L. Furthermore, the method was validated in terms of precision, accuracy and linearity. The developed analytical methodology was used to measure the occurrence of antibiotics in reclaimed waters (n=56), surface waters (n=53), ground waters (n=8) and drinking waters (n=54) collected from different parts of South Florida. In reclaimed waters, the most frequently detected antibiotics were nalidixic acid, erythromycin, clarithromycin, azithromycin trimethoprim, sulfamethoxazole and ofloxacin (19.3-604.9 ng/L). Detection of antibiotics in reclaimed waters indicates that they can’t be completely removed by conventional wastewater treatment process. Furthermore, the average mass loads of antibiotics released into the local environment through reclaimed water were estimated as 0.248 Kg/day. Among the surface waters samples, Miami River (reaching up to 580 ng/L) and Black Creek canal (up to 124 ng/L) showed highest concentrations of antibiotics. No traces of antibiotics were found in ground waters. On the other hand, erythromycin (monitored as anhydro erythromycin) was detected in 82% of the drinking water samples (n.d-66 ng/L). The developed approach is suitable for both research and monitoring applications. Major metabolites of antibiotics in reclaimed wates were identified and quantified using high resolution benchtop Q-Exactive orbitrap mass spectrometer. A phase I metabolite of erythromycin was tentatively identified in full scan based on accurate mass measurement. Using extracted ion chromatogram (XIC), high resolution data-dependent MS/MS spectra and metabolic profiling software the metabolite was identified as desmethyl anhydro erythromycin with molecular formula C36H63NO12 and m/z 702.4423. The molar concentration of the metabolite to erythromycin was in the order of 13 %. To my knowledge, this is the first known report on this metabolite in reclaimed water. Another compound acetyl-sulfamethoxazole, a phase II metabolite of sulfamethoxazole was also identified in reclaimed water and mole fraction of the metabolite represent 36 %, of the cumulative sulfamethoxazole concentration. The results were illustrating the importance to include metabolites also in the routine analysis to obtain a mass balance for better understanding of the occurrence, fate and distribution of antibiotics in the environment. Finally, all the antibiotics detected in reclaimed and surface waters were investigated to assess the potential risk to the aquatic organisms. The surface water antibiotic concentrations that represented the real time exposure conditions revealed that the macrolide antibiotics, erythromycin, clarithromycin and tylosin along with quinolone antibiotic, ciprofloxacin were suspected to induce high toxicity to aquatic biota. Preliminary results showing that, among the antibiotic groups tested, macrolides posed the highest ecological threat, and therefore, they may need to be further evaluated with, long-term exposure studies considering bioaccumulation factors and more number of species selected. Overall, the occurrence of antibiotics in aquatic environment is posing an ecological health concern.

Condensed phase membrane introduction mass spectrometry (CP-MIMS) is a direct, in situ analysis technique that is well suited to persistent organic pollutants, pesticides, and other small molecules. In CP-MIMS, neutral analytes permeate a hollow fibre membrane, typically polydimethylsiloxane (PDMS), driven by a concentration gradient. Analytes are subsequently dissolved by a liquid (condensed) solvent acceptor phase that is continuously flowed through the membrane lumen, which finally entrains the analytes to a mass spectrometer for detection. The membrane rejects charged and particulate matrix components, therefore eliminating sample cleanup that is otherwise necessary for conventional (i.e., chromatographic) techniques. However, larger analytes may suffer from relatively lengthy response times and lower sensitivity. A heptane cosolvent was therefore doped into the PDMS membrane, resulting in a polymer inclusion membrane (PIM). Through a system coupling CP-MIMS to electrospray ionization (ESI), the use of a PIM for model compounds resulted in faster response (~3×) and improved sensitivity (~3.5×, parts per trillion level detection limits). While effective for the demonstration of the PIM, pairing ESI with CP-MIMS represents an inherent incongruity: ESI is effective for polar, hydrophilic analytes, whereas CP-MIMS (i.e., PDMS membranes) is effective for hydrophobic analytes. CP-MIMS was therefore coupled with liquid electron ionization (LEI) as a more suitable ionization strategy. In LEI, the post-membrane solvent flow is entrained at nanolitre per minute flowrates to a LEI source, where the liquid is sequentially nebulized, vaporized, and ionized. The CP-MIMS-LEI coupling was optimized for the measurements of polycyclic aromatic hydrocarbon (PAH) isomer classes from aqueous samples, demonstrating low ng/L detection limits and response times (≤1.6 min). CP-MIMS-LEI was also applied to PAH isomer classes from soil samples, demonstrating rapid sample throughput (15 samples/hr) and low μg/kg detection limits, and additionally was quantitatively comparable to conventional techniques. A similar CP-MIMS-LEI system was applied to online monitoring of catalytic oxidation and alkylation reactions, demonstrating quantitative, real-time results for harsh, complex organic reaction mixtures. A significant analytical improvement was conducted by intentionally exploiting the already present liquid acceptor phase as an in situ means of providing liquid chemical ionization (CI) reagents for improved analyte sensitivity and selectivity (i.e., CP-MIMS-LEI/CI). Acetonitrile and diethyl ether were used as a combination acceptor phase/CI reagent system (i.e., proton transfer reagents) for the direct analysis of bis(2-ethylhexyl)phthalate from house dust (6 mg/kg detection limit). CP-MIMS-LEI/CI was then applied to PAHs from soils. Using methanol and dichloromethane combination acceptor phase/CI reagents, CP-MIMS-LEI/CI was shown to quantify and resolve PAH isomers from direct soil analyses via diagnostic PAH adduct ions: [M+CH2Cl+CH3OH-HCl]+ or [M+CHCl2-HCl]+. Using these selective ions, CP-MIMS-LEI/CI was again shown to be rapid (15 soils/hr), sensitive (ng/g detection limits) and quantitatively comparable to gas chromatography-MS for PAH measurements (average percent difference of -9% across 9 PAHs in 8 soil samples). The results across this thesis present a compelling argument for direct, quantitative screening from complex samples using CP-MIMS-LEI/CI, particularly given the simple workflow and short analytical duty cycle. / Graduate

Microtransplantation of mammalian neurolemma into Xenopus laevis oocytes has been used to study ion channels in terms of their structure and function in the central nervous system. Use of microtransplanted neurolemma is advantageous in that tissue can be obtained from various sources, ion channels and receptors are present in their native configuration and they can be used to evaluate numerous channelpathies caused by environmental toxicants. Here we show that Xenopus oocytes injected with fragments of rat brain neurolemma successfully express functional native ion channels that are assembled in their own plasma membrane. Using a high throughput two electrode voltage clamp (TEVC) electrophysiological system, currents that were sensitive to tetrodotoxin (TTX), omega-conotoxin MVIIC, and tetraethylammonium (TEA) were detected, indicating the presence of multiple voltage-sensitive ion channels (voltage-sensitive sodium, calcium and potassium channels, respectively). In this current research, a “proof-of-principle” experiment was conducted where TTX-sensitive voltage-sensitive sodium channel (VSSC) currents were measured. VSSCs are a well-established site of action for 1,1,1-trichloro-2,2-di(4-chlorophenyl)ethane (DDT) but not for its non-toxic metabolite 1,1-bis-(4-chlorophenyl)-2,2-dichloroethene (DDE). A differential sensitivity of DDT versus DDE on TTX-sensitive sodium current in neurolemma-injected oocytes was determined. DDT elicited an increase in depolarization-dependent, TTX-sensitive sodium current while DDE had no significant effect. Additionally, DDT resulted in a slowing of sodium channel inactivation kinetics whereas DDE has no similar effect. These results are consistent with the findings obtained using heterologous expression of single isoforms of rat brain VSSCs by injecting cRNA into Xenopus oocytes. By demonstrating the classic structural activity relationship of DDT and DDE on mammalian voltage-gated sodium channels isolated in rat brain neurolemma, this study supports the use of automated high-throughput electrophysiology to study the effects of various environmental toxicants on multiple mammalian cellular targets. More importantly, using rat brain neurolemma ensures that the proteins of interest have been transcribed and have undergone all the necessary post-translational modifications before they were injected and expressed in the Xenopus oocytes which is not the case for traditional heterologous expression.