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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

A Comparative Analysis of Per- andPolyfluoroalkyl Substances (PFAS) and ExtractableOrganofluorine (EOF) Using Solid PhaseExtraction-Weak Anion Exchange and Ion PairExtraction in SerumMarichal SalamehSpring 2021Independent project

Salameh, Marichal January 2021 (has links)
Per- and polyfluorinated substances (PFAS) are compounds that consist of a carbon chainbackbone that is partially or entirely fluorinated, with an addition of a functional group. SomePFAS are known as persistent organic pollutants (POPs) and have therefore been drawing a lot ofattention as well as increased concerns. PFAS have been detected in humans, wildlife and theenvironment and some have exhibited toxic effects such as hepatotoxicity, immunotoxicity,reproductive toxicity and endocrine disruption as well as being persistent and bioaccumulative.Serum, plasma and whole blood have been used as biomonitoring matrices in many studies toevaluate human exposure to PFAS. Restrictions have been applied to some PFAS, but thesecompounds are still ubiquitous. This study will investigate the performance (recovery, matrixeffect (ME) in terms of intra-/inter-day repeatability) of ion-pair extraction (IPE) and solid phaseextraction with weak anion exchange (SPE-WAX). The extraction methods were adapted fromliterature and 13 PFAS were selected for this work based on prior biomonitoring studies. Thetarget PFAS content was analyzed with liquid chromatography coupled with tandem massspectrometry (LC-MS/MS). The extraction methods were also compared for extractableorganofluorine (EOF) extraction in terms of blank levels as well as the amount extracted withdifferent methods; the EOF content was measured with combustion ion chromatography (CIC).The EOF levels were used to estimate the amount of unidentified organofluorine (UOF), to avoidunderestimating potential health hazards. Samples extracted using IPE had an average ionizationenhancement of 9%, while SPE-WAX showed an average ionization suppression of -1%. SPEWAXshowed higher average recoveries for procedural blanks (78%), horse serum (96%) andhuman serum (95%) in comparison to IPE (69%, 36%, 88%, respectively). The CIC analysis forEOF content was observed to be below MDL (<50 ng/mL F) with some contaminations observedin the procedural blanks.
22

Childhood and adolescent exposure to chemicals found in personal care products

Khan, Nahiyan Saiyara 12 1900 (has links)
Contexte : Les produits de soins personnels contiennent plusieurs substances chimiques dont l'exposition est préoccupante pour les jeunes vu leur plus grande susceptibilité aux expositions chimiques. Aucune revue publiée n’a étudié l'exposition des jeunes aux substances chimiques dans ces produits. Objectif : Cette revue de la portée vise à synthétiser des études de biosurveillance décrivant les concentrations de parabènes, phénols, phtalates et substances per- et polyfluoroalkylées (PFAS) après l'utilisation de produits de soins personnels chez les jeunes âgés de 5 à 19 ans. Méthodes : La recherche a été effectuée dans MEDLINE, Embase et Global Health. L’éligibilité des articles a été évaluée. Les résultats des études éligibles ont été résumées et décrites. Résultats : Trente-sept études ont été incluses, la première étant publiée en 2013. La majorité des études étaient transversales (n=35) et incluaient plus de 100 participants (n=27). Les substances chimiques les plus fréquemment étudiées étaient les phtalates (n=23), suivies des parabènes et des phénols (chacun n=18), puis des PFAS (n=1). La matrice biologique principalement utilisée était l'urine (n=36). Plusieurs études (n=31) ont rapporté au moins une association positive entre les produits de soins personnels et certaines classes chimiques, comme entre le maquillage et les parabènes; la lotion et les phénols; et le parfum et les phtalates. Conclusion : Plus d'études sur ce sujet sont nécessaires pour documenter l'importance relative de l'utilisation des produits de soins personnels par rapport à l'exposition totale aux substances chimiques. L’uniformisation des questionnaires de collecte de données pourrait aider à réduire l'hétérogénéité des résultats. / Background: Personal care products (PCPs) contain a variety of chemicals including parabens, phenols, phthalates, and per- and polyfluoroalkyl substances (PFAS). Exposure to these chemicals is of concern for children and adolescents, as they are known possess an increased susceptibility to chemical exposures. To date, no published review has explored youth exposure to chemicals found in PCPs. Objective: This scoping review aimed to provide an overview of biomonitoring studies that describe the concentrations of parabens, phenols, phthalates, and PFAS following PCP use among children and adolescents of any age from 5 to 19 years old. Methods: The search was conducted in MEDLINE, Embase, and Global Health. Articles were screened and assessed for eligibility. From eligible studies, data were extracted to summarize and describe the findings. Results: Thirty-seven studies were included, the first of which appeared in 2013. The majority of studies were cross-sectional (n=35) and included more than 100 participants (n=27). The most frequently studied chemicals were phthalates (n=23), followed by parabens and phenols (each n=18), and then PFAS (n=1). The biological matrix mainly used was urine (n=36). Thirty-one studies reported at least one positive association between personal care products and certain chemical classes, such as between makeup and parabens; lotion and phenols; and perfume and phthalates.
23

Development and comparison of analytical methods for the determination of PFASs as sum parameters in environmental samples using HR-CS-GFMAS

Simon, Michael Fabian 28 February 2024 (has links)
Im ersten Teil wurde Probenvorbereitungs-Methoden und instrumentelle Methoden zur Organofluor-Bestimmung verglichen, um Vor- und Nachteile bei der Summenparameter-Analytik von per- und polyfluorierten Alkylverbindungen (PFAS) zu identifizieren. Daher wurden Oberflächenwasserproben aus der Spree in Berlin und Industrieabwasserproben mit zwei PFAS-Summenparametern analysiert – dem extrahierbaren (EOF) und dem adsorbierbaren organisch gebundenen Fluor (AOF). Beide PFAS-Summenparameter wurden mit zwei fluorsensitiven Detektionssystemen analysiert – Hochauflösender Kontinuumstrahler-Graphitofen Molekülabsorptionsspektrometrie (HR-CS-GFMAS) und combustion Ionenchromatographie (CIC). HR-CS-GFMAS erwies sich im Vergleich zu CIC als der empfindlichere und schnellere Ansatz mit höherer Präzision. Im zweiten Teil wurde eine neue Methode zur PFAS-Summenparameteranalyse und EOF-Bestimmung in Bodenproben auf Basis von HR-CS-GFMAS entwickelt und optimiert. EOF-Massenanteile wurden bei mehrfacher Extraktion und Nutzung der Festphasenextraktion (SPE) zur Entfernung anorganischen Fluors untersucht. Bei einem Vergleich der optimierten Methode mit und ohne SPE zeigte sich eine drastische Diskriminierung von Organofluor-Verbindungen mittels SPE. Im dritten Teil wurden Organofluor-Massenbilanzen in aquatischen Systemen anhand von Oberflächenwasser- und Schwebstoffproben (SPM) untersucht. SPM-Proben wurden mit vier komplementären Analysemethoden analysiert – target und non-target, direct total oxidizable precursor assay (dTOPA) und EOF. Daher wurden drei Organofluor-Massenbilanzansätze für die räumlich und zeitaufgelöste SPM-Probenanalyse verwendet: (I) Identifizierung von oxidierbaren PFAS-Vorläufer, (II) Identifizierung des Anteils der identifizierten und nicht identifiziertes EOF und (III) PFAS-target, PFAS dTOPA, non-target-Screening und EOF-Analyse, um das nicht identifizierte EOF aus Ansatz (II) weiter zu entschlüsseln. / In the first part, a comparison of sample preparation and instrumental methods for organofluorine determination was used to identify advantages and disadvantages in sum parameter analysis of per- and polyfluoroalkyl substances (PFASs). Therefore, surface water samples from the Spree River in Berlin, Germany and industrial effluent samples were analyzed using two PFAS sum parameters – the extractable (EOF) and adsorbable organically bound fluorine (AOF). Both PFAS sum parameters were analyzed using two fluorine sensitive detection systems – high-resolution-continuum source-graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) and combustion ion chromatography (CIC). HR-CS-GFMAS turned out to be the more sensitive and faster approach accompanied with higher precision compared to CIC. In the second part, a new method for PFAS sum parameter analysis and EOF determination in soil samples based on HR-CS-GFMAS was developed and optimized. EOF mass fractions were investigated upon multiple extraction and utilization of solid phase extraction (SPE) for inorganic fluorine removal. In a comparison of the optimized method with and without SPE, a highly biased discrimination of organofluorines using SPE was shown. In the third part, organofluorine mass balances were investigated in aquatic systems using surface water and suspended particulate matter (SPM) samples. SPM samples were analyzed using 4 complementary analytical methods – target and non-target HRMS, direct total oxidizable precursor assay (dTOPA) and EOF. Therefore, 3 organofluorine mass balance approaches were used for SPM sample analysis in spatial and time resolved manner: (I) Identification of oxidizable PFAS precursors, (II) Identification of the proportion of identified and unidentified EOF and (III) PFAS target, PFAS dTOPA, non-target screening and EOF analysis to further unravel the unidentified EOF from approach (II).

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