Development of efficient digestion procedures for quantitative determination of cobalt and molybdenum catalyst residues in carbon nanotubes

Whatever the method used for the synthesis of carbon nanotubes (CNTs), they always contain residual catalysts in variable amount. Many methods have been proposed in the literature to purify CNTs, but their efficiency strongly depends on the experimental conditions. Although the presence of residual catalysts in small amount is generally not a problem for many applications, this can become a critical issue when a high purity is required, typically for magnetic properties or for biomedical applications (because of the intrinsic toxicity of most catalysts). Quantification of the amount of residual catalysts is usually obtained by classical chemical analysis, which requires a preliminary digestion (complete mineralisation) of the CNT samples. In this work, we systematically compared 3 different digestion protocols and optimised one, reaching 100% dissolution within a very limited time (1 h) together with the requirement of only a few milligrams of sample, and safe experimental conditions. This method can be easily transferred for use in research laboratories, making accessible the quantitative analysis of CNT samples, and has been validated following ISO/ IEC 17025:2005 for linearity, specificity, intermediate precision, limits of detection and quantification

Determination of toxic elements (mercury, cadmium, lead, tin and arsenic) in fish and shellfish samples. Risk assessment for the consumers

International audienceAlthough fish intake has potential health benefits, the presence of metal contamination in seafood has raised public health concerns. In this study, levels of mercury, cadmium, lead, tin and arsenic have been determined in fresh, canned and frozen fish and shellfish products and compared with the maximum levels currently in force. In a further step, potential human health risks for the consumers were assessed. A total of 485 samples of the 43 most frequently consumed fish and shellfish species in Andalusia (Southern Spain) were analyzed for their toxic elements content. High mercury concentrations were found in some predatory species (blue shark, cat shark, swordfish and tuna), although they were below the regulatory maximum levels. In the case of cadmium, bivalve mollusks such as canned clams and mussels presented higher concentrations than fish, but almost none of the samples analyzed exceeded the maximum levels. Lead concentrations were almost negligible with the exception of frozen common sole, which showed median levels above the legal limit. Tin levels in canned products were far below the maximum regulatory limit, indicating that no significant tin was transferred from the can. Arsenic concentrations were higher in crustaceans such as fresh and frozen shrimps. The risk assessment performed indicated that fish and shellfish products were safe for the average consumer, although a potential risk cannot be dismissed for regular or excessive consumers of particular fish species, such as tuna, swordfish, blue shark and cat shark (for mercury) and common sole (for lead)

Two-year survey of specific hospital wastewater treatment and its impact on pharmaceutical discharges

International audienceIt is well known that pharmaceuticals are not completely removed by conventional activated sludge wastewater treatment plants. Hospital effluents are of major concern, as they present high concentrations of pharmaceutically active compounds. Despite this, these specific effluents are usually co-treated with domestic wastewaters. Separate treatment has been recommended. However, there is a lack of information concerning the efficiency of separate hospital wastewater treatment by activated sludge, especially on the removal of pharmaceuticals. In this context, this article presents the results of a 2-year monitoring of conventional parameters, surfactants, gadolinium, and 13 pharmaceuticals on the specific study site SIPIBEL. This site allows the characterization of urban and hospital wastewaters and their separate treatment using the same process. Flow proportional sampling, solid-phase extraction, and liquid chromatography coupled with tandem mass spectrometry were used in order to obtain accurate data and limits of quantification consistent with ultra-trace detection. Thanks to these consolidated data, an in-depth characterization of urban and hospital wastewaters was realized, as well as a comparison of treatment efficiency between both effluents. Higher concentrations of organic carbon, AOX, phosphates, gadolinium, paracetamol, ketoprofen, and antibiotics were observed in hospital wastewaters compared to urban wastewaters. Globally higher removals were observed in the hospital wastewater treatment plant, and some parameters were shown to be of high importance regarding removal efficiencies: hydraulic retention time, redox conditions, and ambient temperature. Eleven pharmaceuticals were still quantified at relevant concentrations in hospital and urban wastewaters after treatment (e.g., up to 1 μg/L for sulfamethoxazole). However, as the urban flow was about 37 times higher than the hospital flow, the hospital contribution appeared relatively low compared to domestic discharges. Thanks to the SIPIBEL site, data obtained from this 2-year program are useful to evaluate the relevance of separate hospital wastewater treatment

Speciation of metals by sequential extractions of agricultural soils located near a dumpsite for prediction of element availability to vegetables

International audienc

Biomonitoring chronic lead exposure among battery manufacturing workers in Tunisia

International audienc

Experimental analysis of the solidification of Sn-3 wt.%Pb alloy under natural convection

International audienceA quasi-two-dimensional solidification benchmark experiment with controlled thermal boundary conditions is proposed. The experiment consists in solidifying a rectangular ingot of Sn-3 wt.%Pb alloy using two lateral heat exchangers to extract the heat flux from one or two sides of the sample. The temperature difference between the two sides of the heat exchangers may vary from 0 to 40 K and the cooling rate from 0.02 to 0.04 K/s. This slow-cooling condition has been used to promote segregation formation. An array of fifty thermocouples placed on the corresponding sample walls is used to determine the instantaneous temperature distribution. During the solidification process, the temperature field is recorded versus time and analyzed. This makes it possible to estimate the change in temperature due to natural convection, the velocity field and the solidification macrostructure and segregation behavior. After each experiment, the segregation patterns are obtained by X-ray analysis and confirmed by eutectic fraction measurements. The local solute distribution is determined by means of induction coupled plasma analysi

Recent improvements of the ICP/MS capabilities of the 8800 for the petroleum industry

International audienc

Elemental analysis in the refinery industry: total determination and speciation of contaminants using a triple quadrupole ICP/MS Agilent 8800

International audienc

Study of metal and trace metals in shrimps Macrobrachium rosenbergii in creating captivity, aimed at domestic consumption and export.

International audienceWith the increase of global imports and exports, diversification of the food chain, changes of habits and consumer demands become necessary to use new strategies in the food industry, especially in terms of quality management and product safety. The world market currently requires knowledge of the concentrations of toxic contaminants at levels of trace and ultra-trace as well as the establishment of mechanisms that enable food traceability, ensuring the provision of safe and proven quality. To ensure the reliability of these data, since 1994, several international organizations have defined the concept oftraceability, which was modified, and subsequently the European Parliament and the Council of the European Union adopted Regulation (EC) 178/2002, which became mandatory from January 2005. This study aims to determine the content of metals and trace metals in samples of shrimp, Macrobrachium rosenbergii, collected in the Prata City, region of the state of Minas Gerais, Brazil, for the domestic consumption and export. Ten samples of three different sizes (as traceability regulation) were collected at four different sites (breeding ponds available) over two seasons (considered representative of the climate in the region).The elements detected above 30 μg g-1, using Mass Spectrometry Inductively Coupled Plasma (ICP-MS), in different samples analyzed, were the Cu, Zn, Mg and Fe. Already the Cr, Cd, Pb, As and Hg were detected in trace levels. The values of all metals are below acceptable value, for daily consumption per unit, by the Food and Agriculture Organization - United Nations (FAO) and World Health Organization (WHO), with the exception of copper