Albena Detcheva

Study of some palladium-containing chemical modifiers in graphite furnace atomic absorption spectrometry

Several chemical modifiers based on palladium have been evaluated: the individual Pd(II) and the mixed modifiers Pd + Zr, Pd + W, Pd + Zr + citric acid, Pd + W + citric acid. The mechanisms by which these chemical modifiers stabilize analytes and control atomization have been suggested. Factors that might have an influence on the characteristic mass and non-spectral interferences are discussed. The advantages and limitations of the palladium-tungsten modifiers are shown.

Calibration possibilities and modifier use in ETV ICP OES determination of trace and minor elements in plant materials

AbstractThe possibilities for universal calibration based on multi-element aqueous standard solutions and graphite laboratory reference materials (graphite standards) for the electrothermal vaporization inductively coupled plasma optical emission spectrometric (ETV ICP OES) determination of Al, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, P, Pb, S, Sr, Ti, V, and Zn in plant materials were investigated. A commercially available state-of-the-art ETV device was coupled with an Echelle ICP spectrometer equipped with a charge-injection-device (CID) camera for spectral detection. The transition area between transport tube and ETV graphite tube and the gas streams for inner gas, bypass gas, and modifier gas were optimized to achieve best transport efficiencies. The influence of four gaseous modifiers (CCl4, CHCl3, CCl2F2, and C3H8) added to the inner gas was studied. Five reference materials (RM P-Alfalfa, Lucerne; NIES CRM No.9 “Sargasso”; CTA-VTL-2 Virginia Tobacco Leaves; NIST SRM 1515 Apple Leaves; IAEA-V-10 Hay Powder) were used for method validation. If certified reference materials are not available, calibration against graphite standards or dried aqueous standard solutions is possible. Three carbonization procedures as sample pretreatment for the plant materials were investigated. FigurePicture of the ETV system (sample changer and graphite-tube furbace) used in this work

Validation of Mercury Determination by Solid Sampling Zeeman Atomic Absorption Spectrometry and a Specially Designed Furnace

Certified reference materials (CRMs) of different origin were used to validate the direct determination of total mercury by solid sampling Zeeman atomic absorption spectrometry (SS-ZAAS) and a specially designed furnace. The temperature program provides only for one step. Atomisation of mercury and pyrolysis of the matrix is performed at a constant temperature in the range of 900-1000 degrees C. Calibration points achieved by CRMs and aqueous solutions are covered by one calibration line, indicating the absence of matrix effects. Relatively high amounts of chlorine, known for causing problems in mercury determination do not influence analytical results. The excellent accuracy of the method results in a very good agreement with the certified values. The precision of SS-ZAAS measurements in a range from 0.5 to 50ng Hg does not exceed 3% R.S.D. A limit of quantification of 0.008mugg(-1) Hg was achieved.

Total reflection X-ray fluorescence analysis of trace elements in Bulgarian bottled mineral waters of low and high mineral content

The trace elements S, Cl, K, Ca, Mn, Fe, Ni, Cu, Zn, As, Br, Rb and Ba in Bulgarian bottled mineral waters of low and high total dissolved solids (TDS) content were determined by total reflection X-ray fluorescence (TXRF) analysis using gallium as internal standard. The water samples were analysed after simple preparation consisting in three-fold sequential pipetting/drying of 5 μL portions of the water sample mixed with the internal standard on the quartz holders. The precision of the obtained results is characterised by an RSD of 5–16%. The lower limits of detection (LLDs) in waters of TDS content of 160–420 mg L−1 were in the low µg L−1 range, whereas those in the water with TDS content of 2900 mg L−1 were higher by a factor of 5–15. There is a good agreement between the results for the trace element content obtained by TXRF and inductively coupled plasma optical emission spectrometry (ICP-OES) for mineral waters with TDS content in the range from 160 to 2900 mg L−1.

Adsorption of Some Transition Metal Ions [Cu(II), Fe(III), Cr(III) and Au(III)] onto Lignite-based Activated Carbons Modified by Oxidation

The main purpose of the present work was to study the adsorption of some transition metal ions from aqueous solution via a novel porous material obtained from Bulgarian lignite (Chukurovo deposit) and its oxidized modifications. The adsorption of Cu(II), Fe(III), Cr(III) and Au(III) ions was investigated using batch methods to study solutions with different concentrations and acidities. It was found that the adsorption process was affected significantly by the pH value of the aqueous solution. Treatment of the equilibrium data using the linear Langmuir, Freundlich and Dubinin-Radushkevich models allowed the maximum adsorption capacities to be calculated. The uptake of Au(III) ions was almost 100% for the three adsorbents investigated, being greater than 300 mg/ℓ and independent of the pH over the pH range studied. The initial activated carbon proved to be the most suitable for the selective adsorption of Au(III) ions from aqueous solutions in the presence of other transition metal ions, while its oxidized modification Ch-P exhibited an enhanced adsorption efficiency towards transition metals.

Synthesis, characterization and adsorption properties of nanostructured hybrid materials modified by boron and zirconium

AbstractThe adsorption properties of two new nanostructured hybrid materials containing B2O3 and ZrO2 were studied. The new organic-inorganic materials were synthesized via a sol-gel method. As a modifying agent, a quantity of 10 wt.% Zr(OPr)4 or B(OCH3)3 was added. The structure of the hybrid materials was investigated by means of (Fourier transform infrared spectroscopy (FTIR), x-ray diffractometry (XRD), scanning electron microscopy (SEM), (atomic force microscopy (AFM) and nuclear magnetic resonance spectroscopy (NMR). Based on the obtained data, the most probable cross-linking mechanism for the derived gels was proposed. The characterization of texture parameters of both materials was carried out with the use of low-temperature adsorption of nitrogen. Adsorption of Cu(II), Fe(III), Cr(III), Cd(II) and Pb(II) ions on both materials was investigated using multi-component solutions with different concentrations and acidity by means of the batch method. Kinetics of adsorption was also investigated. Pseudo-first order, pseudo-second order and intraparticle diffusion models were used to analyze kinetic data. The adsorption was significantly affected by the pH value. Equilibrium data were fitted to linear Langmuir, Freundlich and Dubinin-Radushkevich models and maximum adsorption capacities were calculated.

Feasibility of ETV-ICP-OES for Characterization of Archaeological Glasses

In the present study the possibilities of electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) for characterization of archaeological glasses were investigated. The objects of our research were fragments of a colorless late antique Roman flat window glass (fifth century A.D.) and colored medieval glass bracelets (eleventh–twelfth century A.D.) excavated in the region of Pernik (West Bulgaria). The finely ground glass samples were analyzed directly and CHF3 was used as evaporation and transport modifier. Dried aqueous standard solutions and certified reference materials with different matrix (glass, fly ash, and stream sediment) were used as calibration standards. No matrix effects were observed by the optimized conditions. Measurements were performed using common calibration curves obtained with all appropriate calibration standards and major, minor, and trace element concentrations were determined. ETV-ICP-OES analytical data were used to establish the type of glass, the fluxing agents, the typical coloring and decoloring elements, and the recipe norm.

Bulgarian natural diatomites: modification and characterization

Natural Bulgarian diatomite modified by oxidation with sulfuric acid and H2O2 or by coating with manganese oxide was characterized considering its chemical composition, surface area, pore volume, and structure. Modified diatomites displayed larger surface area and pore volumes in comparison with untreated natural diatomite, which favored their sorption behavior. Sorption properties of diatomites towards Fe3+, Pb2+, Cu2+, Cd2+, Mn2+, Ni2+, Co2+, Cr3+, Pd2+, Ca2+, and Mg2+ were investigated and their sorption capacities were determined. Sorption properties of manganese oxide-modified diatomite were superior to those of diatomite modified by oxidation. Owing to its high sorption capacity towards Co2+, Ni2+, Pb2+, Cr3+, Fe2+, Cu2+, and Cd2+, the manganese oxide-modified diatomite is a promising low-cost sorbent for selective removal of milligram amounts of these toxic metal ions from contaminated water.

Adsorption properties of a nanostructured hybrid material containing aluminium towards some metal ions

AbstractIn the present work the adsorption of some transition metal ions from aqueous solutions on a silica-based nanostructured hybrid material modified by aluminium was investigated. The novel organic-inorganic material was synthesized via a sol-gel method through hydrolysis and co-condensation reactions. Its structure was characterized by means of SEM, XRD and FTIR. Based on the data obtained the most probable cross-linking mechanism for the derived xerogel was proposed. The characterization of its texture parameters was carried out by low-temperature adsorption of nitrogen. The adsorption properties of this material with respect to Cu(II), Cr(III) and Pb(II) ions from single-component aqueous solutions and multi-component aqueous solutions containing also Cd(II) and Fe(III) were evaluated. The effect of contact time, acidity of initial solutions and metal ion concentrations was investigated using the batch method. Pseudo-first order, pseudo-second order and intraparticle diffusion models were used to analyze kinetic data. In all cases the adsorption was significantly affected by the pH value. Equilibrium modelling data were fitted to linear Langmuir, Freundlich and Dubinin-Radushkevich models. Best fit was observed for Langmuir model, which showed determination coefficients greater than 0.992 for all ions studied. The maximum adsorption capacities for single- and multi-component adsorption were calculated.

Slurry sampling ETAAS determination of sodium impurities in optical crystals of potassium titanyl phosphate and potassium gadolinium tungstate.

Slurry sampling ETAAS was successfully applied to the determination of sodium impurities in single crystals of potassium titanyl phosphate (KTP) and potassium gadolinium tungstate (KGW). Platform atomizers coated with titanium carbide or tungsten carbide, respectively, were used in order to avoid sensitivity drift due to the changes in the composition and the structure of the platform surface. Calibration curves with aqueous standards could be used for the KGW slurry (no matrix effects); analysis of KTP slurry required the standard additions method. The precision of the proposed method was better than 3% R.S.D. The results obtained by the present method showed a good agreement with those obtained by an independent method-flame AAS after sample digestion, which is an evidence for the good accuracy of the proposed method.