Abstract: Four decomposition procedures frequently used for biological material (dry ashing, open wet digestion, wet digestion in a teflon bomb and low-temperature ashing) are optimized for the conversion of biological samples to conducting electrodes suitable for multi-element trace determinations by spark-source mass spectrometry or emission spectrometry. The optimized procedures are evaluated with respect to contamination, retention and preconcentration of the trace elements, homogeneity of the electrodes and precision of the final results. Both dry-ashing methods are prone to losses by volatilization; simple dry ashing suffers from contamination problems during electrode preparation. Wet digestion gives better precision; digestion with nitric/sulfuric acids in an open flask is the method of choice for most elements being simpler and giving lower blanks than the bomb method.

Abstract: All published procedures for multi-element preconcentration of trace elements, prior to x-ray fluorescence analysis of water, are reviewed and critically evaluated. Most preconcentration methods applied to the determination of single elements in water are also listed.

Abstract: For multi-element analysis of human urine, 25-ml samples doped with yttrium as internal standard are evaporated gently and then ashed up to 460°C overnight. The residue is pelletized and analysed by energy-dispersive x-ray fluorescence. Acid addition to facilitate the digestion is not mandatory. Recoveries are nearly quantitative for traces of Fe, Ni, Cu, Zn and Sr, to a lesser extent for lead, but not for arsenic or selenium. The standard deviation per measurement is typically around 6%. The detection limits are such that some 10 elements can be determined simultaneously in normal urine, and possibly more in cases of importance to toxicology or industrial hygiene.

Abstract: The contamination of ground samples by a commercially available Lovibond McCrone Micronizing Mill is discussed. Tracer and weighing experiments showed that abrasion of corundum grinding elements was important, introducing 620 mg of abrasion products per minute of wet grinding. Agate grinding elements were abraded at ⩽6 mg min-1. The abrasion products and grinding elements were analyzed by x-ray fluorescence, spark-source mass spectrometry and neutron activation analysis. Contamination in trace element analysis of geological materials is likely to be negligible for agate grinding elements and, except for a few transition metals, also for corundum grinding elements. Contamination of typical biological samples is significant for a few elements even when agate elements are used, and is absolutely prohibitive for trace analysis when corundum elements are used.

Abstract: Chromium and silicon are determined simultaneously in steel by 14-MeV neutron activation analysis. The activities of 52V(Eγ=1.43 MeV,TView the MathML source=3.76 min) from 52Cr(n,p)52V and 28Al (Eγ=1.78 MeV; TView the MathML source=2.24 min) from 28Si(n,p)28Al are evaluated by mixed γ-ray spectrometry. The influence of manganese and phosphorus, the main interfering elements, is negligible for most stainless steels. The count rate should be limited, to avoid 52V pulse pile-up effects interfering in the 28Al energy region. Precisions in the 2-10% range are reached, depending on the concentrations, for a 10-min analysis time. Results for a series of steel samples are compared with industrial analyses.

Abstract: A fast (10 min) non-destructive determination of copper in. steel and cast iron by 14-MeV neutron activation analysis is described. The 0.511-MeV annihilation radiation of62Cu (T1/2=9.8 min), induced by the reaction63Cu(n,2n)62Cu, is counted by two opposing NaI(Tl) detectors operating in coincidence. An oxygen flux monitor is used to normalise the irradiations. For high phosphorus contents, two measurements are made and the 9-min activity contribution is calculated. As the iron content of the samples is known, the use of pure iron samples allows correction for53Fe activity from the reaction54Fe(n,2n)53Fe(T1/2= 8.9 min). When the phosphorus and silicon activities are low, the procedure of counting and computing can be greatly simplified. Nuclear interferences of most common alloying and impurity elements were investigated.The precision is 23% for steels containing above 1% Cu, andCa. 10% for 0.1%Cu.

Abstract: Stimulated anaerobic dechlorination is generally considered a valuable step for the remediation of aquifers polluted with chlorinated ethenes (CEs). Correct simulation and prediction of this process in situ, however, require good knowledge of the associated biological reactions. The aim of this study was to evaluate the dechlorination reaction in an aquifer contaminated with trichloroethene (TCE) and its daughter products, discharging into the Zenne River. Different carbon sources were used in batch cultures and these were related to the dechlorination reaction, together with the monitored biomarkers. Appropriate kinetic formulations were assessed. Reductive dechlorination of TCE took place only when external carbon sources were added to microcosms, and occurred concomitant with a pronounced increase in the Dehalococcoides mccartyi cell count as determined by 16S rRNA gene-targeted qPCR. This indicates that native dechlorinating bacteria are present in the aquifer of the Zenne site and that the oligotrophic nature of the aquifer prevents a complete degradation to ethene. The type of carbon source, the cell number of D. mccartyi or the reductive dehalogenase genes, however, did not unequivocally explain the observed differences in degradation rates or the extent of dechlorination. Neither first-order, Michaelis-Menten nor Monod kinetics could perfectly simulate the dechlorination reactions in TCE spiked microcosms. A sensitivity analysis indicated that the inclusion of donor limitation would not significantly enhance the simulations without a clear process understanding. Results point to the role of the supporting microbial community but it remains to be verified how the complexity of the microbial (inter)actions should be represented in a model framework. (C) 2013 Elsevier B.V. All rights reserved.

Abstract: A shift from batch processing towards continuous processing is of interest in the pharmaceutical industry. However, this transition requires detailed knowledge and process understanding of all consecutive unit operations in a continuous manufacturing line to design adequate control strategies. This can be facilitated by developing mechanistic models of the multi-phase systems in the process. Since modelling efforts only started recently in this field, uncertainties about the model predictions are generally neglected. However, model predictions have an inherent uncertainty (i.e. prediction uncertainty) originating from uncertainty in input data, model parameters, model structure, boundary conditions and software. In this paper, the model prediction uncertainty is evaluated for a model describing the continuous drying of single pharmaceutical wet granules in a six-segmented fluidized bed drying unit, which is part of the full continuous from-powder-to-tablet manufacturing line (Consigma (TM), GEA Pharma Systems). A validated model describing the drying behaviour of a single pharmaceutical granule in two consecutive phases is used. First of all, the effect of the assumptions at the particle level on the prediction uncertainty is assessed. Secondly, the paper focuses on the influence of the most sensitive parameters in the model. Finally, a combined analysis (particle level plus most sensitive parameters) is performed and discussed. To propagate the uncertainty originating from the parameter uncertainty to the model output, the Generalized Likelihood Uncertainty Estimation (GLUE) method is used. This method enables a modeller to incorporate the information obtained from the experimental data in the assessment of the uncertain model predictions and to find a balance between model performance and data precision. A detailed evaluation of the obtained uncertainty analysis results is made with respect to the model structure, interactions between parameters and uncertainty boundaries. (C) 2013 Elsevier B.V. All rights reserved.

Abstract: In 2008, Museum M in Louvain (Flanders, Belgium) acquired a panel depicting The Anointing at Bethany that is believed once to have adorned the citys former Charterhouse. The panel required conservation treatment, which was preceded by a thorough art-historical and technical examination. It emerged that comparable panels are kept at the Metropolitan Museum of Art and the Riverside Church in New York. Chemical analyses show most of the glass in the panel to have a typical 16th century high-limelow-alkali composition. The conservation treatment was based on the evaluation of these findings and focused very strongly on enhancing the aesthetic balance for an improved reading of the panel.