Le germanium est un métalloïde « stratégique » dans l’industrie high-tech, notamment pour la transition énergétique et le secteur des communications. Étant distinctement sidérophile, lithophile, chalcophile et organophile, le Ge possède un fort potentiel comme traceur géochimique. Ces travaux de thèse visent à améliorer la compréhension de la géochimie du cycle du Ge et des facteurs qui contrôlent son incorporation dans les minéraux et les gisements métalliques. Les cibles de cette étude concernent le gisement filonien à Zn de Saint-Salvy (Massif Central, France), le gisement filonien à Cu de Barrigão (Ceinture pyriteuse ibérique, Portugal), et le gisement à Zn–Cu de Kipushi (R.D. Congo). Les porteurs de Ge les plus importants sont respectivement la sphalérite (jusqu’à 2580 ppm), la chalcopyrite (jusqu’à 5750 ppm) et la réniérite (5,0–9,1 %). Les résultats montrent qu’il existe une relation de premier ordre entre la concentration en Ge dans la sphalérite et le type de gisement. La spectroscopie XANES par rayonnement synchrotron met en évidence la présence de Ge4+ en site tétraédrique dans les sulfures analysés. Les corrélations élémentaires observées dans la sphalérite et la chalcopyrite suggèrent une incorporation du Ge par co-substitutions, e.g., 3Zn2+ ↔ Ge4+ + 2(Cu,Ag)+ et 3Fe3+ ↔ 2Ge4+ + Cu+, ou via la création de lacunes cristallographiques, e.g., 2Zn2+ ↔ Ge4+ + ?. La corrélation positive δ74Ge–[Ge]ZnS des sphalérites de Saint-Salvy indiquerait que coefficient de partage (KdGe) augmenterai avec T. Les compositions isotopiques δ74Ge des sulfures étudiés varient de –5,72‰ à +3,67‰. Les compositions légères mesurées dans les gisements de Saint-Salvy et Barrigão semblent liées à des variations de température des fluides (basse à moyennes T) lors de l’incorporation de Ge en système ouvert, alors que la tendance marquée vers les compositions isotopiques lourdes à Kipushi indiquerait un fractionnement de Rayleigh. / Germanium is a critical metalloid in many high-tech industries, especially for the energy transition and the communication sector. Being distinctly siderophile, lithophile, chalcophile and organophile, Ge can be a particularly useful geochemical tracer. This thesis aims at understanding the Ge geochemistry and the factors controlling its concentration in Ge-bearing minerals and ore deposits. Three contrasted Ge-bearing deposits were studied, the Saint-Salvy Zn vein-type deposit, French Massif Central, the Barrigão Cu vein-type deposit, Iberian pyrite belt, Portugal, and the Kipushi Zn–Cu carbonate-hosted deposit, Central African copper-belt, D.R. Congo. The most important Ge-bearing minerals are sphalerite (up to 2580 ppm Ge), chalcopyrite (up to 5750 ppm Ge), and renierite (5.0–9.1 wt.% Ge). The results show a first order relation between the Ge content and the deposition temperature. Synchrotron-based XANES spectroscopy showed that Ge4+ occur in tetrahedral sites in the studied sulphides. Element correlations suggest that Ge is chiefly incorporated in sphalerite and chalcopyrite through coupled substitutions, e.g., 3Zn2+ ↔ Ge4+ + 2(Cu,Ag)+ and 3Fe3+ ↔ 2Ge4+ + Cu+, respectively, or via the creation of lattice vacancies, e.g., 2Zn2+ ↔ Ge4+ + ?. The positive δ74Ge–Ge content correlation observed in sphalerite from Saint-Salvy could indicate that Ge partition coefficient (KdGe) increases with temperature. Ge isotopes in sulphides yield δ74Ge values spanning from –5.72‰ to +3.67‰. The light δ74Ge compositions of Saint-Salvy and Barrigão ores appear to be related to variations in low to moderate fluid temperatures during Ge uptake in open system (e.g., fluid cooling), while the trend towards heavy δ74Ge compositions observed at Kipushi likely translates a Rayleigh fractionation effect during ore formation in closed system, associated with significant fluid modification.

La surveillance radiologique de l’environnement est un enjeu majeur pour étudier l Impact des activités industrielles et humaines mettant en œuvre des substances radioactives. Umalyse de l:tImet Pu présents à l’échelle des ultra-traces dans les sols et les sédiments (- mBq.kg-1) est souvent menée par spectrométrie (après séparation chimique. Ces méthodes souffrent de plusieurs inconvénients. Les objectifs de cette thèse sont par conséquent de simplifier la méthode de séparation et d'obtenir une limite de détection basse et un temps d’analyse relativement court en utilisant lICPMS-HR couplé au système d’introduction Apex-Q/ACM. Sur la base des données de la littérature, une méthode chimique utilisant une seule résine d’extraction chromatographique (DGA) est proposée pour isoler les concentrations ultra-traces d’Am et de Pu des différents types d'éléments interférents. La méthodologie proposée a été évaluée avec des solutions synthétiques avant l'utilisation de solutions de lixiviation d’échantillons préalablement analysés par spectrométrie alpha. La méthode retenue demande plusieurs procédure d’élution pour pouvoir séparer les majeurs, les interférents isobariques, les lanthanides, l’uranium et le thorium. Des rendements de chimie supérieurs à 90% pour Am et 60% pour Pu ont pu être mesurés. La robustesse de la méthode d’analyse a été validée avec un standard de référence certifié (AIEA-38S) .Enfin, le protocole analytique d’isolation et de dosage des ultra-traces d241Am et de 239Pu par ICP-MS-HR solution a été appliqué à des échantillons de sédiments échantillonnés dans l’estuaire de la Loire pour caractériser L’état radiologique du fleuve. / Radiological monitoring of the environment is a key issue for studying the impact of industrial and human activities using radioactive substances. The analysis of Am and Pu present at ultra-trace concentrations in soils and sediments (-mBq.kg-l) is often carried out by spectrometry after chemical separation. This procedure suffers from several drawbacks (multi-step separation process and long coun.tingtime). The objectives of this PhD are consequently simplify separation process and to achieve a low limit of detection with a relatively short analysis time using a high-resolution plasma source mass spectrometer HR-ICP-MScoupled to the introduction system Apex-Q/ACM. Base on literature data, a chemical methodology using a single column extraction chromatography resin (DGA) is proposed for isolating ultra-trace concentrations of Am and Pu from different types of interfering elements. The proposed methodology is assessed with synthetic solutions prior to the use of real leaching solutions previously analyzed by alpha spectrometry. The chosen method requires several elution procedures in order to separate the majors element, isobaric interferes, lanthanides, uranium and thorium. Recovery yields greater than 90% for Am and 60% for Pu were determined. The robustness of the analytical method was validated with a certified reference standard sample (IAEA-385). Finally, the analytical process for isolation and analysis of 241Am and 239Pu at ultra-trace concentration by ICP-MS-HRsolution was applied to samples of sediment taken from Loire estuary to characterize the radiological status of this river.

Inductively coupled plasma (ICP) is a promising low pressure, high density plasma source for material processing and is of great importance to modern plasma technology. This thesis summarizes the results of experimental study in a cylindrical ICP by using a single Langmuir probe (LP) and optical emission spectroscopy (OES). <p>The electron energy distribution function (EEDF), which contains important information of ICP plasma and is necessary for an accurate kinetic description of the low-pressure discharges, has been investigated with the Langmuir probe by using the alternating current (ac) method. Measurements were carried out in different gases including both atomic (argon, helium) and molecular (hydrogen, nitrogen) gases. The effects of the external discharge parameters such as gas pressure and radio frequency (rf) power have been investigated and the different mechanisms that influence the formation of the EEDF have been discussed. The radial dependence of the EEPF in the argon plasma has also been evaluated. <p>The average electron energy and electron density have also been obtained by direct measurement of the electron current-voltage (I-V) curve and the result is consistent with the power balance equation.<p> Optical emission spectroscopy has been used to study the importance of neutral gas heating in the ICP. The method used is based upon simulating and fitting the nitrogen emission band (the transition from,uCΠ30'=V to,gBΠ30"=V). Both nitrogen and argon plasmas have been studied separately and significant neutral heating has been found.

Inositol phosphates (IPs) represent a major part of the organic phosphorus found in the environment, which makes their identification and quantification very important. The goal of this project was to explore the possibility of quantification of IPs with inductively coupled plasma - atomic emission spectrometry (ICP - AES). This paper deals with the creation of an in-house IP standard and the considerations for the successful linking of high performance liquid chromatography (HPLC) with ICP - AES. Experiments with different nebulizers, mobile phases, standard solutions and model substance were performed. The proposed optimal conditions for the ICP experiments are: the use of a modified Lichte nebulizer, mobile phase without methanol and the use of standards matched to the mobile phase. Adenosine monophosphate (AMP) was found to be a good model substance and showed that the band broadening from HPLC to ICP – AES was approximately a factor of 2. Limits of detection for AMP were 5 µM for HPLC and 20 µM for ICP – AES. The optimal way to create an in-house standard was using the potassium salt of IP6 and treating it for 90 minutes at a temperature of 120 ºC with 3.2 M acetic acid.

Inductively coupled plasma (ICP) is a promising low pressure, high density plasma source for material processing and is of great importance to modern plasma technology. This thesis summarizes the results of experimental study in a cylindrical ICP by using a single Langmuir probe (LP) and optical emission spectroscopy (OES). <p>The electron energy distribution function (EEDF), which contains important information of ICP plasma and is necessary for an accurate kinetic description of the low-pressure discharges, has been investigated with the Langmuir probe by using the alternating current (ac) method. Measurements were carried out in different gases including both atomic (argon, helium) and molecular (hydrogen, nitrogen) gases. The effects of the external discharge parameters such as gas pressure and radio frequency (rf) power have been investigated and the different mechanisms that influence the formation of the EEDF have been discussed. The radial dependence of the EEPF in the argon plasma has also been evaluated. <p>The average electron energy and electron density have also been obtained by direct measurement of the electron current-voltage (I-V) curve and the result is consistent with the power balance equation.<p> Optical emission spectroscopy has been used to study the importance of neutral gas heating in the ICP. The method used is based upon simulating and fitting the nitrogen emission band (the transition from,uCΠ30'=V to,gBΠ30"=V). Both nitrogen and argon plasmas have been studied separately and significant neutral heating has been found.

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The application of inductively-coupled plasma (ICP) spectrometry for the analysis of solutions and slurries is reviewed. The critical parameters which affect analytical performance are identified and methods for the optimisation of the ICP for such applications demonstrated. Particle size of the suspended sample is shown to be the most important factor in the analysis of slurry samples. It is demonstrated that only particles less than 8 um in diameter reach the plasma even when the maximal diameter injector tube (3 mm i.d.) is used. Accordingly various methods for the reduction of particle size have been investigated and milling shown to be the preferable approach. A low cost method using blown zirconia spheres in a screw-cap plastic bottle agitated on a flask shaker was developed. Using this method it proved possible to analyse a wide variety of solid samples using slurry atomisation using both ICP- atomic emission spectrometry (ICP-AES) and ICP-mass spectrometry (ICP-MS) with aqueous calibration. Results are presented for the elemental analysis of certified reference material (CRM) soils, catalyst samples, a zeolite, titanium dioxide, P.T.F.E. powder, and unfiltered natural waters by slurry atomisation ICP-AES. Comparison by other techniques showed excellent accuracy for major, minor and trace elements and equivalent precision to solution analysis. The CRM soils, catalysts and the zeolite were also analysed by ICP-MS using slurry atomisation with similar success and enhanced accuracy at the trace level. Aluminium proved to be an exception and generally low recoveries (80-90%) were observed for this element using slurry atomisation. Finally the uses of the simplex optimisation algorithm to improve analytical performance, particularly in ICP-AES, is discussed. A computer program to facilitate the use of simplex optimisation for a variety of instrumentation was written and its use in three different analytical techniques demonstrated. The necessary hardware and software modifications to a commercially available ICP spectrometer to enable automated simplex optimisation are described. The prospects for such intelligent self-optimising instrumentation are discussed as is the potential extension of the application of slurry analysis by ICP-AES and ICP-MS.