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Page de résumé pour ULgetd-05072015-105612

Auteur : L'homme, Benjamin
E-mail de l'auteur : Benjamin.Lhomme@doct.ulg.ac.be
URN : ULgetd-05072015-105612
Langue : Anglais/English
Titre : Analytical strategies for ultra-trace measurement of dioxins and related compounds in biological matrices
Intitulé du diplôme : Doctorat en sciences
Département : FS - Département de chimie
Jury :
Nom : Titre :
Covaci, Adrian Membre du jury/Committee Member
Eppe, Gauthier Membre du jury/Committee Member
Pirard, Catherine Membre du jury/Committee Member
Schachtele, Alexander Membre du jury/Committee Member
Leyh, Bernard Président du jury/Committee Chair
Focant, Jean-François Promoteur/Director
Mots-clés :
  • Mass spectrometry/Spectrométrie de masse
  • Two-dimensional gas chromatography/Chromatographie gazeuse bidimentionelle
  • Persistent organic pollutants/Polluants organic persistants
  • Cryogenic zone compression/Compression cryogénique de zone
Date de soutenance : 2015-05-08
Type d'accès : Restreint/Intranet
Résumé :

The human exposure to persistent organic pollutants (POPs) is a concern since these compounds are ubiquitous in the environment. This class of compounds group different families such as the polychlorodibenzo-p-dioxins (PCDDs), the polychlorodibenzofurans (PCDFs), the polychlorinated biphenyls (PCBs), the organochlorine pesticides (OCPs), and the halogenated flame-retardants (HFRs). Their use, their release in the environment, their presence in foodstuffs, as well as in various goods on the market are mostly regulated through international conventions, like the Stockholm convention on POPs, and at the European and national levels. Despite the proactive approach in order to reduce the overall exposure to POPs, levels of contaminants (even banned) are still found in the environment and in the human body. In this thesis, we developed several methods of analysis of POPs in different samples. The first was a confirmatory method for PCDD/Fs and PCBs analysis in food and feed following a new European Regulation No 709/2014 that recently allowed the use of gas chromatography (GC) coupled to triple quadrupole mass spectrometry (GC-QQQMS/MS) for this purpose. We fully validated the method on vegetable oil matrix around the maximum level of 1.50 ng WHO2005TEQ/kg. We showed that all analytical criteria, specific to this instrumentation, laid down by the Regulation were met, which indicates that the QQQMS/MS can successfully be used in the legal context for confirmatory purposes and could be an alternative to high-resolution sector field mass spectrometry (HRMS) in this context. The proper establishment of limits of quantitation was a key point in the discussion along with other analytical criteria proposed in the European Regulation, as new interpretations were necessary for the use of triple quadrupole mass spectrometry due to its different features from the HRMS. In addition, we developed in parallel a method for the analysis of Dechloranes in food. The measurement of ultra-trace levels of compounds from this emerging class of flame-retardants was possible after optimization of the injections parameters by means of experimental design, and of fragmentation pathways. Eventually, we reported relatively low levels in various food matrices and preliminary data about the significance of this route of exposure for humans. Besides food analysis, we developed a screening method to quickly assess levels of contaminants in human blood, involving a minimally invasive sampling technique and a couple of drops of blood. The instrumentation was first based on cryogenic zone compression (CZC) hyphenated to high-resolution time of flight mass spectrometry (HRTOFMS) applied to the analysis of two markers of exposure in regular driedblood spots (DBS) typically used for newborn sampling. The second approach was based on GC-QQQMS/MS applied to the analysis of a broader range of OCPs and NDL-PCBs (30 analytes) in 40 μL blood. The blood was however collected using a novel Volumetric Absorptive MicroSampling (VAMS) method, directly inspired by the DBS but offering a control on the volume of blood sampled, hence opening the door to quantitation. The sample preparation of the VAMS dried sample was miniaturized and only 2 mL of solvents were necessary to prepare a sample, which makes it environmentally friendly. The focus was especially drawn to maximize the sensitivity via the optimization of the ionization energy and the electron multiplier voltage in order to reach appropriate low limits of quantitation. In this context of ultra-low volume of blood, background levels arose as the limitation of the method owing to the small signals coming from samples and closing the gap with blanks. Nevertheless, this patient-friendly approach is perfectly suitable for fast screening of population and could be useful in the context of UNEP campaigns where samples are hardly collected.

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