Simultaneous multi-element analysis for trace metals in sea water by inductively-coupled plasma/atomic emission spectrometry after batch preconcentration on a chelating resin

Simultaneous determination of speciation parameters of Cu, Pb, Cd and Zn in model solutions of Suwannee River fulvic acid by pseudopolarography

There is a growing awareness of the importance of quantitative determinations of speciation parameters of the trace metals Cu, Zn, Cd and Pb in aqueous samples containing chemically heterogeneous humic substances, especially when they are present together, interacting with one another and competing for specific binding sites of the humic substances. Such determinations require fundamental knowledge and understanding of these complex interactions, gained through basic laboratory-based studies of well-characterized humic substances in model solutions. Since the chemical heterogeneity of humic substances plays an important role in the thermodynamics (stability) and kinetics (lability) of trace metal competition for humic substances, a metal speciation technique such as pseudopolarography that can reveal the special, distinctive nature of metal complexation is required, and it was therefore used in this study. A comparison of the heterogeneity parameters (Gamma) for Zn(II), Cd(II), Pb(II) and Cu(II) complexes in model solutions of Suwannee River fulvic acid (SRFA) shows that GammaCd>GammaZn>GammaPb>GammaCu, suggesting that SRFA behaves as a relatively homogeneous complexant for Zn(II) and Cd(II), whereas it behaves as a relatively heterogeneous complexant for Pb(II) and an even more heterogeneous complexant for Cu(II) under the experimental conditions used. The order of values of log K* (from the differential equilibrium function, DEF) for the trace metals at pH 5.0 follow the sequence: log K*Cu>log K*Pb>log K*Zn>log K*Cd. These results are in good agreement with the literature values. The results of this work suggest the possibility of simultaneously determining several metals in a sample in a single experiment, and hence in a shorter time than required for multiple experiments.

Multiwalled Carbon Nanotube Chemically Modified Gold Electrode for Inorganic As Speciation and Bi(III) Determination

A chemically modified gold electrode has been conveniently prepared by binding multiwalled carbon nanotubes (MWCNTs) to which thiol functions have been tethered. The electrode has been characterized by atomic force microscopy and oxidative desorption experiments and gives excellent results for trace determination of As(III) and Bi(III) in natural and high-salinity waters, overcoming the limitation typical of solid electrodes. A mechanism for As(III) preconcentration at the electrode is proposed and supported by results obtained by two similar chemically modified electrodes (CMEs), the first one prepared with single-walled carbon nanotubes and the second one with a monolayer of (biphenyl)dimethanethiol. The performance obtained with the MWCNTs-CME largely overcomes that obtained by using other devices.

Determination of traces of cadmium in natural water samples by flow injection on-line preconcentration-graphite furnace atomic absorption spectrometry

A flow injection on-line preconcentration-graphite furnace atomic absorption spectrometric method was developed for the determination of traces of cadmium in natural water samples. Cadmium in samples was adsorbed on an iminodiacetate-type chelating resin, Muromac A-1 microcolumn (3 mm i.d. and 10 mm long), and then eluted with 2 mol l-1 HNO3. The eluate was introduced into the injection tip of an autosampler. The eluate zone with the highest analyte concentration was injected into the graphite furnace by cooperation of a peristaltic pump and a syringe pump of the autosampler, which were controlled by a programmable controller. The present system was successfully applied to the determination of cadmium in natural water samples. A detection limit of 0.2 ng l-1 was obtained with 12 ml sample loading. The recoveries were 99 and 108% for tap water (4 ml loading) and underground water (12 ml loading), respectively. Analytical results obtained for a river water reference material (JAC-0031, Japan Society for Analytical Chemistry) were close to the reference value.

Determination of rare earth elements in blood serum reference sample by chelating resin preconcentration and inductively coupled plasma mass spectrometry

Rare earth elements (REEs) in a blood serum reference sample, which is a freeze-dried sample issued from the National Institute for Environmental Studies, Japan, have been determined by inductively coupled plasma mass spectrometry (ICP-MS) after sample digestion and concentration pretreatment. The freeze-dried serum sample (ca. 0.8 g), which corresponded to 10 ml of original blood serum, was digested with HNO3 with heating on a hot plate. The digested sample was then diluted with 100 ml of 0.1 M HNO3, and REEs in the diluted solution were adsorbed on chelating resin (Chelex 100). The resin was then filtered with a glass filter. Finally, REEs on the resin were dissolved with 10 ml of 2 M HNO3 aqueous solution, and the sample solution was analyzed by ICP-MS. The concentrations of all the REEs were successfully determined by the present method. The recovery values of REEs were in the range of 70-80%, and the relative standard deviation of the recovery values in repeated experiments (n = 3) was less than 5% for all REEs. In addition, 20 other elements were also determined by ICP-MS and ICP-AES.