Christine Scriver

Certification of a fish otolith reference material in support of quality assurance for trace element analysis

Production and certification activities relating to the development of a new Certified Reference Material (FEBS-1) based on a fish otolith matrix are described. The material was prepared from 4.5 kg of dried saggital otolith harvested from the red snapper (Lutjanus campechanus), ball milled and sieved to <200 mesh, homogenized, irradiated, bottled into 1 g aliquots and certified for major, minor and trace element composition using inductively coupled plasma mass spectrometry (ICP-MS), isotope dilution-ICP-MS, neutron activation, ICP-optical emission spectrometry and X-ray fluorescence. Several laboratories participated in this activity, providing for a robust estimate of each measurand. Certified values for seven elements (Ba, Ca, Li, Mg, Mn, Na and Sr) are reported, accompanied by full GUM uncertainty estimates. Reference values for Cd, Cu, Ni, Pb and Zn are also provided; these elements were considered to be not certifiable because of the large component of uncertainty contributed by homogeneity. This CRM will be of interest to those laboratories requiring quality assurance of measurements of bulk elemental composition of otoliths and other marine aragonites.

Determination of total mercury in biological samples using flow injection CVAAS following tissue solubilization in formic acid

Total mercury in biological samples was determined by flow injection (FI) cold vapour atomic absorption spectrometry (CVAAS) following tissue solubilization with formic acid. A mixture of potassium bromide and potassium bromate was used to decompose organomercury compounds prior to their reduction with sodium borohydride. A gold amalgam system was used to achieve lower detection limits when required. National Research Council Canada certified reference materials dogfish liver (DOLT-3), dogfish flesh (DORM-2) and lobster hepatopancreas (TORT-2), as well as oyster tissue (NIST SRM 1566b) and mussel tissue (NIST SRM 2976) were used to assess the accuracy of the method. The method of standard additions provided the most accurate results. Limit of detection (LOD) for Hg in the solid sample of 0.001 and 0.01mugg(-1) were achieved with and without amalgamation, respectively. The precision of measurement for 1.6ngml(-1) methylmercury was 2.7% using the amalgam system.

Rapid and controllable covalent functionalization of single-walled carbon nanotubes at room temperature

We report a rapid and efficient procedure to functionalize SWNT where free radicals generated at room temperature by a redox reaction between reduced SWNT and diacyl peroxide derivatives were covalently attached to the SWNT wall.

Coupled thermogravimetry, mass spectrometry, and infrared spectroscopy for quantification of surface functionality on single-walled carbon nanotubes

AbstractWe have successfully applied coupled thermogravimetry, mass spectrometry, and infrared spectroscopy to the quantification of surface functional groups on single-walled carbon nanotubes. A high-purity single-walled carbon nanotube sample was subjected to a rapid functionalization reaction that attached butyric acid moieties to the nanotube sidewalls. This sample was then subjected to thermal analysis under inert desorption conditions. Resultant infrared and mass spectrometric data were easily utilized to identify the desorption of the butyric acid groups across a narrow temperature range and we were able to calculate the degree of substitution of the attached acid groups within the nanotube backbone as 1.7 carbon atoms per hundred, in very good agreement with independent analytical measurements made by inductively coupled plasma optical emission spectrometry (ICP-OES). The thermal analysis technique was also able to discern the presence of secondary functional moieties on the nanotube samples that were not accessible by ICP-OES. This work demonstrates the potential of this technique for assessing the presence of multiple and diverse functional addends on the nanotube sidewalls, beyond just the principal groups targeted by the specific functionalization reaction. Figure3D contour map of the FTIR spectra of the species desorbed from the GAP-functionalized SWCNT sample as a function of temperature.

Speciation without chromatography: Part 2. Determination of tributyltin by chloride generation flow injection atomic absorption spectrometry

A procedure is described for the quantitation of tributyltin in aqueous samples and extracts based on its relatively high volatility in halide media, permitting vapour phase sampling from the headspace above such samples.Tributyltin chloride (TBT-C1) was purged from various chloride containing aqueous matrices and collected on the surface of an iridium treated graphite tube for subsequent quantitation by graphite furnace atomic absorption. Iodide, bromide and chloride matrices were compared for their generation efficiency. The effect of acidity of the sample was also studied. An absolute detection limit of 1.3 ng TBT (as tin) was estimated, corresponding to a detection limit of 0.33 ng ml 1 for a 4 ml sub-sample. Method validation was achieved using NRCC PACS-2 (sediment) Certified Reference Material, for which reasonable agreement between certified and measured values of tributyltin content was obtained. A procedural concentration limit of detection of 66 ng g 1 TBT in the sediment could be achieved.