Bohumil Dočekal

Determination of selenium by electrothermal atomic absorption spectrometry. Part 1. Chemical modifiers

The effect of various chemical modifiers, including nitrates of palladium, nickel, magnesium, calcium, lanthanum, europium and aluminium, on the analytical signal of selenium in a graphite furnace was studied. The signals of various selenium compounds, such as selenite, selenate and organic compounds representing different types of selenium forms in body fluids (selenomethionine and trimethylselenium iodide), were evaluated. The shape of the transient signal appears to be influenced not only by the chemical reactions in the graphite–selenium–modifier system, but also very strongly by vaporization effects connected with the physical character of the charred residue. It follows that successful chemical modification involves the application of a considerable excess (higher than 1000-fold) of some metal nitrates, which produce refractory oxides and no thermally stable carbides, and are at the same time capable of quantitative conversion of the analyte into a single form. An integral part of the modifier action is trapping of the resulting compound by the modifier residue.

Determination of trace metals in aluminium oxide by electrothermal atomic absorption spectrometry with direct injection of aqueous suspensions

Abstract Trace amounts (10-5–10-6% w w ) of Ca, Cr, Cu, Fe, Na and Pb in aluminium oxide can be determined by graphite-furnace a.a.s. with injection of stirred sample suspensions into the tube. Calibration is possible either with Al2O3 standards for peak height and peak area measurements, or with standard solutions containing no aluminium for peak area measurements (except for copper). The analytical signals do not depend on the quantity of applied sample (0.02–1 mg Al2O3). Relative standard deviations are 2–6%.

Direct determination of impurities in powdered silicon carbide by electrothermal atomic absorption spectrometry using the slurry sampling technique

A direct method of analysis of powdered silicon carbide for the determination of Al, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Ti, V and Zn based on electrothermal atomic absorption spectrometry (ETAAS) using the slurry sampling technique is described. Possible spectral interferences caused by the refractory matrix components were studied. The technique was optimized with regard to sample preparation, dispensing, thermal pre-treatment and atomization parameters. The accuracy was checked by comparison of the results with those obtained by ETAAS and inductively coupled plasma atomic emission spectrometry involving decomposition of the sample, and by instrumental neutron activation analysis. For most of the elements investigated the achievable limits of detection are at the sub-microgram per gram level.

Radiotracer investigation of hydride trapping efficiency within a graphite furnace

Abstract Efficiencies of hydride generation and in situ trapping in the transversely heated graphite furnace by using Pd modifier were studied for selenium hydride, arsine and stibine by means of the radiotracers 75 Se, 76 As and 122 Sb. The influence of four experimental parameters, i.e. Pd modifier mass, trapping temperature, carrier gas flow rate and the distance of the hydride introduction capillary from the platform surface, on selenium hydride trapping efficiency was investigated by both the radiotracer technique and atomic absorption spectrometry. For selenium hydride, stibine and arsine, generation efficiencies of 78.1 ± 1.5%, 94 ± 4% and close to 100%, respectively, were obtained. For selenium hydride, complete trapping was achieved within a broad variation range of the four experimental parameters studied. At experimental parameters optimized for selenium hydride trapping, the overall efficiencies of hydride generation and trapping for stibine and arsine were 87 ± 4% and 99 ± 2%, respectively.

New resin gel for uranium determination by diffusive gradient in thin films technique.

A new resin gel based on Spheron-Oxin(®) chelating ion-exchanger with anchored 8-hydroxyquinoline functional groups was tested for application in diffusive gradient in thin film technique (DGT) for determination of uranium. Selectivity of uranium uptake from model carbonate loaded solutions of natural water was studied under laboratory conditions and compared with selectivity of the conventional Chelex 100 based resin gel. The affinity of Spheron-Oxin(®) functional groups enables determination of the overall uranium concentration in water containing carbonates up to the concentration level of 10(2) mg L(-1). The effect of uranium binding to the polyacrylamide (APA) and agarose diffusive gels (AGE) was also studied. Uranium is probably bound in both gels by a weak interaction with traces of acrylic acid groups in the structure of APA gel and with pyruvic and sulfonic acid groups in the AGE gel. These sorption effects can be eliminated to the negligible level by prolonged deployment of DGT probes or by disassembling probes after the 1-2 days post-sampling period that is sufficient for release of uranium from diffusive gel and its sorption in resin gel.

Determination of trace impurities in powdered molybdenum metal and molybdenum silicide by solid sampling GFAAS

Abstract A direct atomic absorption spectrometric method for the determination of the elements Cu, K, Mg, Mn, Na and Zn in high purity molybdenum metal and molybdenum silicide powders for microelectronic applications was developed. By using a cup and boat solid sampling technique, the sample preparation step and the contamination risk were considerably reduced, so that these elements could be determined at concentrations down to the sub-ng/g level in a few minutes. Using the maximum applicable sample portion of 80 mg for molybdenum and of 10 mg for molybdenum silicide, limits of detection in the range 0.06 (for Zn)-0.5 ng/g (for Na) and 0.5–4.5 ng/g, respectively, were achieved for the six elements with the boat technique.

Optimization of nickel tetracarbonyl generation and nickel in situ trapping within a transversely heated graphite furnace for atomic absorption spectrometry

Abstract The efficiency of nickel tetracarbonyl generation and of in situ trapping within a transversely heated graphite furnace was studied. The influence of experimental parameters of the flow injection generation system and in situ collection procedure for atomic absorption spectrometric determination of nickel, i.e. pH of reaction mixture, concentration of sodium tetrahydroborate solution, reaction temperature, concentration of various electrolytes, several ‘heavy metal’ ions and hydride forming elements, trapping temperature, position of introduction capillary and carrier gas flow rates on the overall efficiency were investigated. The acidity of the reaction mixture and the kinetics of carbonyl formation are the limiting parameters of the whole generation procedure. The temperature of the tube, gas flow rate and the position of the capillary are the most critical parameters in trapping nickel from nickel tetracarbonyl. Under optimum conditions, an overall efficiency of approximately 80% was found, evaluating atomic absorption spectrometric signals obtained by carbonyl generation/trapping procedure and by conventional liquid sampling procedure.

Determination of trace elements in high-purity molybdenum trioxide by slurry sampling electrothermal atomic absorption spectrometry

A method for the direct determination of Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na and Ni in high-purity molybdenum trioxide by slurry sampling electrothermal atomic absorption spectrometry is described. As a result of the substantial blank reduction achieved by using ‘selected pots’ for the performance of the slurry sampling technique, in the case of elements with high overall concentrations such as Ca, K, Mg and Na, the detection limits can be improved by two orders of magnitude, as compared with the dissolution procedure, reaching 2, 1, 0.5 and 1 ng g–1 for Ca, K, Mg and Na, respectively. Control of the blank for both the solution and the slurry techniques, the background attenuation caused by the molybdenum matrix and sample homogeneity are discussed.

Some aspects of electrothermal atomization of elements from large amounts of involatile matrices

Abstract Non-volatile matrices which cannot diffuse into the graphite walls of an electro-thermal atomizer (as obtained by direct sampling of solids, injection of solutions into tubes with pyrolytic coatings or with a hydrophobic film) make a “miniplatform” in the centre of the atomizing tube. A delay in the temperature increase of this platform at the beginning of the atomization step compared to that of the atomizer walls causes enhancement of the peak height sensitivity. This was proven by atomization of nanogram quantities of copper and iron from solutions of aluminium salts.

Inhaled Cadmium Oxide Nanoparticles: Their in Vivo Fate and Effect on Target Organs

The increasing amount of heavy metals used in manufacturing equivalently increases hazards of environmental pollution by industrial products such as cadmium oxide (CdO) nanoparticles. Here, we aimed to unravel the CdO nanoparticle destiny upon their entry into lungs by inhalations, with the main focus on the ultrastructural changes that the nanoparticles may cause to tissues of the primary and secondary target organs. We indeed found the CdO nanoparticles to be transported from the lungs into secondary target organs by blood. In lungs, inhaled CdO nanoparticles caused significant alterations in parenchyma tissue including hyperemia, enlarged pulmonary septa, congested capillaries, alveolar emphysema and small areas of atelectasis. Nanoparticles were observed in the cytoplasm of cells lining bronchioles, in the alveolar spaces as well as inside the membranous pneumocytes and in phagosomes of lung macrophages. Nanoparticles even penetrated through the membrane into some organelles including mitochondria and they also accumulated in the cytoplasmic vesicles. In livers, inhalation caused periportal inflammation and local hepatic necrosis. Only minor changes such as diffusely thickened filtration membrane with intramembranous electron dense deposits were observed in kidney. Taken together, inhaled CdO nanoparticles not only accumulated in lungs but they were also transported to other organs causing serious damage at tissue as well as cellular level.