Cadmium: toxicology and analysis. A review

Palladium and platinum are important catalytic metals, and it would be highly advantageous to be able to use surface enhanced Raman spectroscopy (SERS) to study reactive species and intermediates on their surfaces. In this paper we describe the use of templated electrodeposition through colloidal templates to produce thin (<1 μm) films of palladium and platinum containing close packed hexagonal arrays of uniform sphere segment voids. We show that, even though these films are not rough, when the appropriate film thickness and sphere diameter are employed these surfaces give stable, reproducible surface enhancements for Raman scattering from molecules adsorbed at the metal surface. We report SERS spectra for benzenethiol adsorbed on the structured palladium and platinum surfaces of different thicknesses and void diameters and show that, for 633 nm radiation, enhancements of 1800 and 550 can be obtained for palladium and platinum, respectively.

SERS at Structured Palladium and Platinum Surfaces

Copper (Cu) is an integral part of many important enzymes involved in a number of vital biological processes. Even though Cu is essential to life, it can become toxic to cells, at elevated tissue concentrations. Oxidative damage due to Cu has been reported in recent studies in various tissues. In this study, we aimed to determine the effect of excess Cu on oxidative and anti-oxidative substances in brain tissue in a rat model. Sixteen male Wistar albino rats were divided into two groups: the control group, which was given normal tap water, and the experimental group, which received water containing Cu in a dose of 1 g/l. All rats were sacrificed at the end of 4 wk, under ether anesthesia. Cu concentration in the liver and in plasma alanine aminotransferase (ALT) and aspartate transaminase (AST) activities were determined. There were multiparameter changes with significant ALT and AST activity elevation and increased liver Cu concentration. In brain tissue, Cu concentration, superoxide dismutase (SOD) activities, malondialdehyde (MDA) levels and glutathione (GSH) concentrations were determined. Brain Cu concentration was significantly higher in rats receiving excess Cu, compared with control rats (p < 0.05). Our results showed that SOD activities and GSH levels in brain tissue of the Cu-intoxicated animals were significantly lower than in the control group (p < 0.01 and p < 0,001, respectively). The brain MDA levels were found to be significantly higher in the experimental group than in the control group (p < 0.001). The present results indicate that excessive Cu accumulation in the brain depressed SOD activities and GSH levels and resulted in high MDA levels in brain homogenate due to the lipid peroxidation induced by the Cu overload.

Copper intoxication; antioxidant defenses and oxidative damage in rat brain.

Atom trapping and in situ preconcentration techniques for flame atomic absorption spectrometry

In situ electrochemical surface enhanced Raman spectra (SERS) for an immobilized monolayer of a flavin analogue (isoalloxazine) at nanostructured silver surfaces are reported. Unique in the present study, the flavin is not directly adsorbed at the Ag surface but is attached through a chemical reaction between cysteamine adsorbed on the Ag surface and methylformylisoalloxazine. Even though the flavin is held away from direct contact with the metal, strong surface enhancements are observed. The nanostructured silver surfaces are produced by electrodeposition through colloidal templates to produce thin (<1 μm) films containing close-packed hexagonal arrays of uniform 900 nm sphere segment voids. The sphere segment void (SSV) structured silver surfaces are shown to be ideally suited to in situ electrochemical SERS studies at 633 nm, giving stable, reproducible surface enhancements at a range of electrode potentials, and we show that the SER spectra are sensitive to subfemtomole quantities of immobilized flavi...

Quantitative electrochemical SERS of flavin at a structured silver surface.

A slotted quartz tube used with an air-acetylene flame increases the residence time of atoms in the light path of an atomic-absorption spectrometer, thus increasing the analytical sensitivity. With this technique lead and cadmium were determined in whole blood following precipitation of cells and protein with trichloroacetic acid, copper and zinc were determined in serum diluted 1 + 20 and the measurement of metals in urine was investigated. Rapid, accurate analyses can be achieved using continuous aspiration or, when there is limited volume of sample, by discrete nebulisation. Long-term performance was assessed during a period of 3 months.

Applications of a slotted quartz tube and flame atomic-absorption spectrometry to the analysis of biological samples

The use of a slotted quartz tube in flame atomic-absorption spectrometry increases the sensitivity for various elements, including copper and zinc. A method for the determination of copper or zinc in serum following 21-fold dilution with water is described. Thus 20 µl of sample can be added to 0.4 ml of de-ionised water and three 100-µl aliquots injected into the nebuliser (aliquot microsampling). Precisions below 5% have been obtained for sera containing normal levels of either copper or zinc. The method has been shown to be inappropriate for the determination of normal levels of copper in urine.

Determination of copper and zinc in serum and urine by use of a slotted quartz tube and flame atomic-absorption spectrometry

Initial studies carried out on a commercially available slotted quartz tube used to increase the sensitivity of a flame atomic-absorption technique for the determination of trace metals are described. Basic performance data are presented and the various advantages of the slotted quartz tube are demonstrated by reference to the determination of cadmium, lead, copper and zinc in environmental and clinical samples.

Use of a slotted quartz tube to enhance the sensitivity of conventional flame atomic-absorption spectrometry

Simple and rapid procedure for the determination of lead in whole blood by use of a slotted tube and discrete nebulisation flame atomic-absorption spectrometry

A series of bis-bipyridyl complexes, cis-[CrIII(bpy)2(L)(L′)] (L = OH, L′ = OH2 monomer; L = L = OH dimer; L = L = Cl; and L, L′ = polyacrylic acid) were studied at silver and glassy carbon electrodes by cyclic voltammetry. On reduction, slow electron transfer reactions giving adsorbed species are evident from the cyclic voltammograms. In situ surface-enhanced Raman spectroscopy (SERS) of the aquahydroxo and dimer complexes shows a broad, intense Cr–O vibration at around 550 cm–1. This arises as the exciting line (514.5 nm) is close to resonance with the lowest energy absorption band assigned to a ligand field transition (4A2g → 4T2g). At –0.4 V SERS spectra show features of both the normal Raman spectrum of [Cr(bpy)3]3+ and the colloidal SERS of [Cr(bpy)3]2+ and can be explained by the presence of partially-reduced adsorbed species. The electron is localized first on to the metal and then on to one of the bpy ligands as follows: [CrIII(bpy0)2X2]n+ + e →[CrII(bpy0)2X2](n–1)+ and [CrII(bpy0)2X2](n–1)+ + e →[CrII(bpy–)(bpy0)2X2](n–2)+. Although the SERS evidence suggested that the integrity of the complexes is maintained during the reaction, prolonged electrolysis leads to hydrolysis and/or substitution of the complexes. Thus [(PVP)2-Cr(bpy)2]3+ can be electrosynthesized by reduction of cis-[Cr(bpy)Cl2]+ at a PVP modified glassy carbon electrode and shows a characteristic peak at –0.32 V.

Andrew Taylor

Papers

Applications of a slotted quartz tube and flame atomic-absorption spectrometry to the analysis of biological samples

Determination of copper and zinc in serum and urine by use of a slotted quartz tube and flame atomic-absorption spectrometry

Use of a slotted quartz tube to enhance the sensitivity of conventional flame atomic-absorption spectrometry

Simple and rapid procedure for the determination of lead in whole blood by use of a slotted tube and discrete nebulisation flame atomic-absorption spectrometry

Electrochemistry and surface-enhanced Raman spectroscopy (SERS) of adsorbed chromium–bipyridyl complexes†