Bepaling van totaal kwik en kwikspecies in milieu- en biologische monsters

Kwik behoort tot de meest toxische metalen. Het neemt een unieke plaats in omwille van zijn chemische en fysische eigenschappen. Vermits kwik bij kamer-temperatuur vooral in gasvormige fase voorkomt, zal het zich snel via de atmosfeer verspreiden in hydro-, bio- en lithosfeer. Door zijn relatief inerte vorm kan het over lange afstanden getransporteerd te worden en dient het beschouwd te worden als een globale polluent. De toxiciteit van kwik hangt af van de chemische vorm waarin het voorkomt. Zo zijn organokwikverbindingen veel toxischer dan anorganisch kwik. Methylkwik, dat voornamelijk gevormd wordt in aquatisch milieu door biotische en abiotische processen, wordt geaccumuleerd in vis, waardoor het in de voedselketen terecht komt. Daardoor is het heel belangrijk om een onderscheid te kunnen maken tussen de verschillende species. In een eerste luik van dit werk werd voor de bepaling van kwik in omgevingslucht een manuele bemonsterings- en analysemethode op punt gesteld en 2 commercieel verkrijgbare semi-automatische monitoren geëvalueerd, waarna veldtesten werden uitgevoerd in Vlaanderen. Dit werk werd uitgevoerd ter voorbereiding van de uitbouw van een kwikimmissiemeetnet in Vlaanderen, in opdracht van de Vlaamse Milieumaatschappij. In een tweede luik werden de mogelijkheden nagegaan van elektro-thermische vervluchtiging inductief gekoppeld plasma massaspectrometrie (ETV-ICPMS) voor de bepaling van totaal kwik en kwikspecies in biologische monsters. Deze methode laat de directe bepaling toe vanuit vaste monsters, waardoor uitgebreide monstervoorbereidingen, die gepaard kunnen gaan met contaminatie, verliezen en/of speciestransformatie, vermeden worden. Hiertoe werd een zelfgemaakte gasvormige isotopisch aangerijkte Hg-standaard gegenereerd en isotopendilutie als kalibratiemethode toegepast, wat in die combinatie een vernieuwende aanpak was. Er werden vis-, haar-, slib- en sedimentmonsters geanalyseerd

Comparison of pyrolysis and microwave acid digestion techniques for the determination of mercury in biological and environmental materials

Microwave digestion reduction-aeration and pyrolysis combined with cold vapour atomic absorption and cold vapour atomic fluorescence are compared for the determination of total mercury in several biological and environmental matrices. The biological samples were digested in a mixture of HNO3/H2O2, the environmental samples in a mixture of HNO3/HClO4. After reduction with SnCl2, the mercury was collected by two-stage gold amalgamation. After microwave digestion reduction-aeration, detection limits of 1.4 ng g(-1) and 0.6 ng g(-1) were obtained for cold vapour atomic absorption spectrometry (CVAAS) and cold vapour atomic fluorescence spectrometry (CVAFS), respectively, for 250 mg of environmental samples. For biological samples (500 mg) the detection limits were 0.7 ng g(-1) (CVAAS) and 0.4 ng g(-1) (CVAFS). After pyrolysis, detection limits of 3.5 ng g(-1) and 1.6 ng g(-1) for CVAAS and CVAFS, respectively, were obtained for a 10 mg sample. Pyrolysis can only be applied when the organic content of the sample is not too high. Accurate results were obtained for 8 certified reference materials of both environmental and biological origin. In addition, a real sludge sample was analysed

Computed tomography-based joint locations affect calculation of joint moments during gait when compared to scaling approaches

Hip joint moments are an important parameter in the biomechanical evaluation of orthopaedic surgery. Joint moments are generally calculated using scaled generic musculoskeletal models. However, due to anatomical variability or pathology, such models may differ from the patient's anatomy, calling into question the accuracy of the resulting joint moments. This study aimed to quantify the potential joint moment errors caused by geometrical inaccuracies in scaled models, during gait, for eight test subjects. For comparison, a semi-automatic computed tomography (CT)-based workflow was introduced to create models with subject-specific joint locations and inertial parameters. 3D surface models of the femora and hemipelves were created by segmentation and the hip joint centres and knee axes were located in these models. The scaled models systematically located the hip joint centre (HJC) up to 33.6 mm too inferiorly. As a consequence, significant and substantial peak hip extension and abduction moment differences were recorded, with, respectively, up to 23.1% and 15.8% higher values in the image-based models. These findings reaffirm the importance of accurate HJC estimation, which may be achieved using CT- or radiography-based subject-specific modelling. However, obesity-related gait analysis marker placement errors may have influenced these results and more research is needed to overcome these artefacts.peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=gcmb20status: publishe

Direct determination of methylmercury and inorganic mercury in biological materials by solid sampling-electrothermal vaporization-inductively coupled plasma-isotope dilution-mass spectrometry

This paper reports on the use of solid sampling-electrothermal vaporization-inductively. coupled plasma mass spectrometry (SS-ETV-ICPMS) for the direct and simultaneous determination of methylmercury and inorganic mercury in biological materials. The main advantage of this fast and sensitive method is that no sample preparation is required. In this way, the sample throughput can be considerably increased, problems of contamination and analyte losses are kept to a minimum and, even more important, the original chemical form of the different analyte species in the solid samples is preserved. To achieve this goal, a solid sample is inserted into a graphite furnace of the boat-in-tube type, and is subsequently submitted to an appropriate temperature program, leading to the separate vaporization of methylmercury and inorganic mercury, which are transported into the ICP by means of an argon carrier gas. The separation was accomplished within 75 s. For the quantification of the two peaks, species-unspecific isotope dilution was used. For this purpose, a stable flow of argon loaded with gaseous Hg isotopically enriched in Hg-200 was generated using a permeation tube that was constructed in-house. Its emission rate was determined by collecting the mercury released during a given time interval on a gold-coated silica absorber, after which the amount, collected was released by heating of the absorber and determined by cold vapor atomic absorption spectrometry (CVAAS) and cold vapor atomic fluorescence spectrometry (CVAFS). A reference material from the Canadian National. Research Council (NRC) (TORT-2) was used to assess the accuracy of the,method. For.,the application of the method to samples with diverse mercury contents, the spike/sample ratio can be optimized by varying the emission rate of the permeation tube simply by adapting its temperature. To prove the feasibility of this approach, two reference materials (BCR 463 and DORM-2) with a methylmercury content more than 10 times higher than that of TORT-2 were also analyzed. The detection limits obtained for 1 mg of sample (2 ng g(-1) and 6 ng g(-1) for methylmercury and inorganic mercury, respectively) were found to be sufficiently low for this kind of application and are competitive when compared to other techniques

Simulation tool for predicting the impact of acetabulum reconstruction on hip muscles

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CT-based virtual shape reconstruction for severe glenoid bone defects

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Computer-based planning method for shape reconstruction of severely damaged glenoids using CT data

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