Determination of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts by electrothermal atomic absorption spectrometry after preconcentration by column solid phase extraction

Methods are described for the determination of trace and ultra trace amounts of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts. Separation and preconcentration of trace metals is achieved by a column solid phase extraction procedure using silica gel modified with derivatives of dithiocarbamates — Na-DDTC (sodium diethyldithio-carbamate and HMDTC (ammonium hexamethylene-dithiocarbamate) as column packing material. The influence of the sorbent preparation procedure on the degree of sorption of the trace analytes is examined for different pH values of the sample solution. Isobutylmethyl ketone (IBMK) is proposed as an effective eluent for quantitative elution of retained metal ions. Optimal instrumental parameters for ETAAS determination of preconcentrated elements in organic eluate are presented. Practical application of sorbents in analysis of natural waters and alkali and alkaline earth salts is demonstrated. Proposed preconcentration procedure combined with ETAAS determination of trace analytes allows the determination of 0.04 g l^–1 Cd, 0.1 g l^–1 Cr, Cu, and Mn and 0.3 g l^–1 Co, Fe, Ni and Pb in natural waters and 1.10^–7% Cd, 3.10^–7% Cr and Mn, 7.10^–7% Co, Ni and Pb and 2.10^–6% Cu and Fe in alkali and alkaline earth salts.     

Transformations of metal species in ageing humic hydrocolloids studied by competitive ligand and metal exchange

Transformations of metal species (particularly Al, Ca, Fe, Mg, Mn, Zn) in ageing humic hydrocolloids were studied, applying a competitive ligand and metal exchange approach. For this purpose, metal-containing hydrocolloids, freshly collected from humic-rich German bog lake waters (Hohlohsee (HO), Black Forest; Venner Moor (VM), Muensterland; Arnsberger Wald (AW), Northrhine-Westfalia) and conventionally pre-filtered through 0.45 m membranes, were subjected on-site to an exchange with EDTA and Cu(II) ions, respectively, as a function of time. EDTA complexes gradually formed, metal fractions exchanged by Cu(II) (as well as free Cu(II) concentrations) were operationally discriminated by means of a small time-controlled tangential-flow ultrafiltration unit (nominal cut-off: 1 kDa). Metal and DOM (dissolved organic matter) fractions obtained this way were determined off-site using instrumental methods (AAS, ICP-OES, carbon analyzer). After weeks of storage, the collected hydrocolloids were studied again by this approach. The EDTA availability of colloid-bound metals (particularly Al and Fe) exhibited different ageing trends, dependent on the sample (VM: decrease of Fe availability (98–76%), HO: increase of Fe availability (76–82%)). In contrast, the Cu(II) exchange equilibria of colloid-bound metals revealed merely low availability of Al (16–38%) and Fe (5–11%) towards Cu(II) ions, also dependent on ageing effects. In particular, the conditional copper exchange constants K_ex obtained from the exchange between Cu(II) ions and available metal species (such as Ca, Mg, Mn, Zn) exhibited a strong decrease (by a factor of 2–100) during sample storage, indicating considerable non-equilibria complexation of these metal ions in the original bogwaters studied on-site.     

Cation-exchange separation and colorimetric determination of some elements in trace analysis of platinum-rhodium (10%) alloys

Summary A method of separation and colorimetric determination of trace amounts (10^–4–10^–5%) of Cu, Al, Fe, Bi, Pb, Mn, Cd, Zn, Co, and M in platinum-rhodium (10%) alloys has been developed. The elements to be determined are retained on a column containing the strongly acidic cation-exchanger Amberlite IR-120, from dilute hydrochloric acid medium (p_H 1–1.5), while platinum and rhodium pass through in the form of anionic chloride complexes. The individual metals are eluted and concentrated and then separated by extraction and carrier precipitation. The metals are determined by means of sensitive colorimetrie methods with dithizone (Cu, Bi, Pb, Cd, Zn), eriochromecyanine R (Al), 2-nitroso-1-naphthol (Co),-furildioxime (Ni), 1-(2-pyridylazo)-2-naphthol (Mn), and thiocyanate (Fe). The error of the determination does not exceed 15%.

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Zusammenfassung Eine Trennungs- und Bestimmungsmethode für Spuren (10^–4 bis 10^–5%) von Cu, Al, Fe, Bi, Pb, Mn, Cd, Zn, Co und Ni in PIatm-Rhodium-(10%)-Legierungen wurde ausgearbeitet.Die angeführten Elemente werden mit Amberlit IR-120 aus der verd. salzsauren Lösung (p_H 1 bis 1,5) von Platin und Rhodium getrennt, die als Anionchloridkomplexe im Eluat bleiben. Die einzelnen Metalle werden nach Elution aus ihrer Lösung durch Extraktion bzw. Mitfällung getrennt und kolorimetrisch mit Dithizon (Cu, Bi, Pb, Cd, Zn), Eriochromcyanin R (Al), 2-Nitroso-1-naphthol (Co),-Furildioxim (Ni), 1-(2-Pyridylazo)-2-naphthol (Mn) und Rhodanid (Fo) bestimmt. Der Fehler beträgt weniger als 15%,

     

Nachweis und Bestimmung von Spuren toxikologisch wichtiger Metallionen mit Hilfe der Ringofenmethode

Zusammenfassung Es wird eine Methode zum Nachweis und zur Bestimmung von Metallen aus hochverdünnten Lösungen (Konzentrationsbereich 10^–4 bis 10^–7 Mol/l) beschrieben, bei welcher die Metallspuren zur Anreicherung gefÄllt, filtriert und mit Hilfe der Ringofenmethode auf Papierfilter übertragen werden.Das besonders für toxikologische Untersuchungen bestimmte spurenanalytische Verfahren ist sowohl für den qualitativen Nachweis von Cu, Cd, Sb, Pb, Bi, Hg, Fe, Zn, Mn, Cr und Tl geeignet (Nachweisgrenze in 5 ml Probelösung von 0,1–0,8 g), wie auch für die halbquantitative Bestimmung von Cu, Cd, Sb, Pb, Bi, Hg, Fe, Zn und Tl nach der Methode der Ringofentüpfelcolorimetrie.Die halbquantitativen Bestimmungen lassen sich noch mit insgesamt 4–8 g des entsprechenden Metalls in 10 ml Probelösung ohne Schwierigkeiten durchführen. Die Genauigkeit der Methoden entspricht den Anforderungen bei spurenanalytischen Untersuchungen.

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Summary A method for the identification and determination of metals from highly dilute solutions (concentrations of 10^–4–10^–7 Moles/l) is described; the traces of the metals are precipitated, filtrated and transferred to filter-paper by means of the ringoven method.This trace analytical procedure is especially determined for qualitative and semiquantitative toxicological investigations. Cu, Cd, Sb, Pb, Bi, Hg, Fe, Zn, Mn, Cr and Tl can be identified (identification limits between 0,1–0,8 g in 5 ml of test solution).The semi-quantitative determination of Cu, Cd, Sb, Pb, Bi, Hg, Fe, Zn, and Tl can likewise be carried out. 4–8 g only of the respective metal in 10 ml of test solution are needed. The reproducibility of the various determinations is satisfactory for trace analytical investigations.

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Herrn Prof. Dr. Ing. Fritz Feigl zum 75. Geburtstag herzlichst gewidmet.     

On the mechanism of racemisation of dichlorobis(ethylenediamine)-metal chlorides [metal = cobalt(III) or chromium(III)] in the solid state

Summary In the solid state l-cis-[M(en)₂Cl₂]Cl [M=cobalt(III) or chromium(III)] undergoes thermal racemisation smoothly at 158 °C without anycis-trans interconversion. The values of k_rac, H and S are 6 × 10^–6s^–1, 218 kJM^–1 and 156.1 JK^–1M^–1 for the cobalt(III) complex and 3.5 × 10^–5s^–1, 229.7 kJM^–1 and 197.9 JK^–1M^–1 for the chromium(III) complex, respectively. The results are only in accord with a rhombic twist mechanism of the type originally proposed by Ray and Dutt for [M(AA)₃] complexes.     

New methods for acceleration of meat sample preparation prior to determination of the metal content by atomic absorption spectrometry

Focused microwave-assisted digestion and ultrasound leaching have been applied for the extraction of Pb, Cd, Cr, Cu, Fe, Zn, Ca, and Mg from raw meat. Semimembranous muscle (SM) of raw pig ham was used for optimizing both the digestion and extraction steps by multivariate approaches. The detection and quantification limits were 0.5 and 0.9 g kg^–1 for Pb, 0.06 and 0.1 g kg^–1 for Cd, 0.2 and 1.2 g kg^–1 for Cr, 0.4 and 3 g kg^–1 for Cu, 0.04 and 0.1 mg kg^–1 for Fe, 0.012 and 0.017 mg kg^–1 for Zn, 0.3 and 0.4 mg kg^–1 for Ca, and 0.01 and 0.03 mg kg^–1 for Mg. The precision, expressed as relative standard deviation (RSD), ranged between 2.5 and 9.6% for focused microwave-assisted digestion and between 3.5 and 10.6% for ultrasound leaching. The methods were then compared with a reference method and applied to a certified reference material (bovine muscle 184, from the BCR). The t-test, applied to the results obtained from focused microwave-assisted digestion, revealed that they are in agreement (p>0.01) with the certified and estimated values in the case of Pb, Cd, Cr, Cu, Fe, Ca, Mg, and Zn but not in that of Fe. In the case of ultrasound leaching, only the extraction of Pb, Cu, and Ca was quantitative. The method based on microwave digestion provides more accurate and precise results than ultrasound leaching. These new procedures have many advantages with regards to conventional methods, namely, reduction of the extraction time, simplification of the process, avoidance of chemical emissions to the atmosphere, and no losses of metals by volatilization.     

Performance of a new nebulizer system for simultaneous determination of Sb,Sn (hydride generation), V,and Zn by ICP–OES

A new nebulizer system is described that extends the analytical capability of the inductively coupled plasma technique to include the simultaneous determination of two elements Sb and Sn (hydride-forming), with two conventional elements, V and Zn. The main advantage of this system is its simultaneous determination of elements that form volatile hydrides and elements that do not, without any instrumental changes. Optimization of reaction and instrumental conditions was performed to characterize the new system. The performance of the new nebulizer system was evaluated by studying the effect of some transition metals (Ni, Cu, Co, and Fe, 1–1000 mg L^–1) on the Sb, Sn, V, and Zn emission signals (1 mg L^–1). Interferences from transition metal ions were found to be insignificant for determination of the four elements in presence of L-cysteine. Long-term and short-term stability was also evaluated. The precision, expressed as RSD for 15 replicate measurements was 0.7% for Sb, 1.7% for Sn, 2.5% for V, and 2.3% for Zn at 200 g L^–1 of each analyte. The detection limits obtained were 0.52, 1.3, 3.2, and 4.7 g L^–1 for Sb, Sn, V, and Zn, respectively. Spike and recovery experiments were performed on the NIST 1643c trace metals in water standard reference material and results were in agreement with the certified values.     

Kinetic and mechanistic studies on the interaction of<Emphasis Type="SmallCaps">DL</Emphasis> -Penicillamine with the hydroxopentaaquarhodium(III) ion

The kinetics of interaction between DL-Penicillamine and [Rh(H₂O)₅OH]²⁺ have been studied spectrophotometrically as a function of [Rh(H₂O)₅OH²⁺], [DL-Pen], pH and temperature. The reaction has been monitored at 242 nm, the _max of the substituted complex and where the spectral difference between the reactant and product is a maximum. The reaction rate increases with [DL-Pen] and reaches a limiting value at a higher ligand concentration. From the experimental findings an associative interchange mechanism for the substitution process is suggested. The activation parameters (H}=35.8 ± 1.6 kJ mol^–1, S=–209 ± 5 J K^–1 mol^–1) support the proposition. The negative G ⁰ (–13.6 kJ mol^–1) for the first equilibrium step also supports the spontaneous formation of an outersphere association complex.     

Analytical fractionation of aquatic humic substances and their metal species by means of multistage ultrafiltration

The molecular-size fractionation of aquatic humic substances (HS) and their metal species by means of a novel sequential-stage ultrafiltration (UF) device equipped with five appropriate ultramembranes (1, 5, 10, 50 and 100 kD) is described. First of all, the concentration dynamics of macromolecules, particulary HS, during five-stage UF and its subsequent washing step has been modelled. Based on these results, the fractionation of aquatic HS (from ground and bog water) by means of multistage UF has been optimized for an analytical scale (10 ml sample, 1 mg/ml HS, 10 ml washing solution, pH 6.0). The molecular size-distribution of selected aquatic HS (BOC 1/2 from the DFG-Versuchsfeld Bocholt, VM 5 from Venner Moor, Germany) studied by five-stage UF exhibited strong systematic influences of the procedure used for their isolation. The molecular-size distribution of HS obtained by on-line UF and gel permeation chromatography (GPC) showed a satisfactory agreement in the range 1–50 kD. Moreover, when interrupting multistage UF for > 48 h a slow transformation in the HS samples has been found as gradually additional HS fractions of < 1 kD have been formed. Besides unloaded HS molecules, the molecular-size distribution of freshly formed metal species of HS (1.0 mg metal/g HS of Al(III), Cd(II), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II), Zn(II), each) has been characterized by multistage UF as a function of pH-value, degree of loading and complexation time. Metal determinations as carried out by flame AAS, showed that considerable metal fractions in HS especially are present in molecules > 50 kD, which seemed to be rather acid-inert. With complexation times of < 2 days a transient shift of the molecular size distribution of both HS and their metal species (e.g., Al(III), Fe(III) to higher values (> 10 kD) has been found.     

Application of laser ablation–inductively coupled plasma-mass spectrometry (LA–ICP–MS) to investigate trace metal spatial distributions in human tooth enamel and dentine growth layers and pulp

Human tooth enamel provides a nearly permanent and chronological record of an individuals nutritional status and anthropogenic trace metal exposure during development; it might thus provide an excellent bio archive. We investigated the micro-spatial distribution of trace metals (Cu, Fe, Mg, Sr, Pb, and Zn) in 196×339 m² raster pattern areas (6.6×10⁴ m²) in a deciduous tooth using laser ablation-inductively coupled plasma-mass spectrometry (LA–ICP–MS). Ablated areas include prenatal and postnatal enamel, the neonatal line, the dentine–enamel junction (DEJ), dentine, and the dentine–pulp junction. Topographic variations in the surface elemental distribution of lead, zinc, strontium, and iron intensities in a deciduous tooth revealed heterogeneous distribution within and among regions. ⁴³Ca normalized elemental intensities showed the following order: Sr>Mg>>Zn>Pb>Fe>Cu. Elevated zinc and lead levels were present in the dental pulp region and at the neonatal line. This study demonstrates the ability of LA–ICP–MS to provide unique elemental distribution information in micro spatial areas of dental hard tissues. Elemental distribution plots could be useful in decoding nutrition and pollution information embedded in their bio apatite structure.Presented in part at the 2002 Winter Conference on Plasma Spectrochemistry, Scottsdale, AZ, January 6–12, 2002. The poster was selected as an outstanding poster presentation.     

Electrode kinetics in cyanide silver-plating electrolytes at different surface coverages by lead adatoms

Effective values of exchange current i ₀, cathodic and anodic transfer coefficients and , and cathodic and anodic reaction orders with respect to cyanide ions (P _c, P _a) are measured in cyanide silver-plating electrolytes at different surface coverages by lead adatoms . With increasing coverage, i ₀ and increase from 5 × 10^–5 A cm^–2 and 0.24 in pure solutions to 8 × 10^–5 A cm^–2 and 0.3 at = 0.4, with P _c and P _a hardly altering. The cathodic process markedly accelerates at = 0.6, while at 0.5 the kinetics of the cathodic process is unstable. Different effects of lead adatoms on cathodic and anodic gold and silver plating in cyanide solutions are due to lead salts not affecting the metal substrate dissolution mechanism in the latter case.__________Translated from Elektrokhimiya, Vol. 41, No. 4, 2005, pp. 468–474.Original Russian Text Copyright © 2005 by Bek, Shuraeva.     

Kinetic Parameters of Gold Dissolution in Cyanide Solutions: The Effect of Complex Cyanide Ions of Mercury

The kinetics of the gold dissolution in cyanide solutions is studied at constant values of the coverage () of the gold surface by mercury atoms. The constancy of is ensured by maintaining an identical value of the duration (t) of contact of electrode with solution (after renewing its surface by cutting off a thin surface layer of metal) at a potential of –1.3 V, at which the discharge of mercury ions is limited by their diffusion to the electrode. At t = const kinetic dependences of the gold dissolution process correspond to the Tafel equation. Effective values of exchange current i ₀, transfer coefficient , and reaction order by cyanide ions P are determined. With increasing value of their magnitude increases from values 10^–5 A cm^–2, 0.1, and 0.17 that are characteristic of purely cyanide solutions (composition 0.1 M KCN, 0.1 M KOH, and 0.01 M KAu(CN)₂) to i ₀ 2 × 10^–4 A cm^–2, = 0.46, and P 1 at t = 270 s. These results are compared with the data obtained earlier during similar investigations in solutions containing thallium, lead, and bismuth. Common and individual features in the behavior of mercury-containing electrolytes are revealed. It is shown that the possible mechanism of the acceleration of the gold dissolution process in the presence of catalytically active atoms, which had been proposed in these works, may be used also for explaining the action of mercury atoms on this process.     

2,3-Dihydroxypyridine-loaded cellulose: a new macromolecular chelator for metal enrichment prior to their determination by atomic absorption spectrometry

New macromolecular chelators have been synthesized, by loading 2,3-dihydroxypyridine (DHP) on cellulose via linkers -NH-CH₂-CH₂-NH-SO₂-C₆H₄-N=N- and -SO₂-C₆H₄-N=N-, and characterized by elemental analysis, TGA, IR, and CPMAS ¹³C NMR spectra. The cellulose with DHP anchored by the shorter linker had better sorption capacity (between 69.7 and 431.1 mol g^–1) for Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II), and Fe(III)) than the other (51.9–378.1 mol g^–1); the former was therefore studied in detail as a solid extractant for these metal ions. The optimum pH ranges for quantitative sorption (recovery 97.6–99.8%) on this matrix were: 7.0–9.0, 6.0–9.0, 3.0–8.0, 6.0–8.0, 6.0–9.0, 6.0–7.0, and 2.0–6.0 respectively. Desorption was quantitative with 0.5 mol L^–1 HCl and 0.5 mol L^–1 HNO₃ (for Pb). Simultaneous sorption (at pH 7.0) of all metal ions other than Fe(III) was possible if their total concentration did not exceed the sorption capacity (lowest value). The recovery of seven metal ions from their mixture at pH 6.0 was nearly quantitative when the concentration level of each metal ion was 0.2 g mL^–1. The optimum flow rate of metal ion solutions for quantitative sorption of metal onto a column packed with DHP-modified cellulose was 2–7 mL min^–1, whereas for desorption the optimum flow rate for the acid solution was 2–4 mL min^–1. The time needed to reach 50% of the total loading capacity (t_1/2) was <5 min for all the metal ions except Ni and Pb. The limit of detection (blank+3s) was from 0.70 to 4.75 g L^–1 and the limit of quantification (blank+10s) was between 0.79 and 4.86 g L^–1. The tolerance limits for NaCl, NaBr, NaI, NaNO₃, Na₂SO₄, Na₃PO_4, humic acid, EDTA, Ca(II), and Mg(II) for sorption of all metal ions are reported. The column packed with DHP-anchored cellulose can be reused at least 20 times for enrichment of metal ions in water sample. It has been used to enrich all the metal ions in pharmaceutical and water samples before their determination by flame AAS. RSD for these determinations was between 1.1 and 6.9%.     

Spectrophotometric determination of iron after separation of its 9,10-phenanthrenequinone monoximate on microcrystalline naphthalene

A sensitive and selective spectrophotometric method has been developed for the determination of iron as Fe(II) or Fe(III) using 9,10-phenanthrenequinone monoxime (PQM) as the complexing agent. Fe(II) and Fe(III) react with PQM to form coloured water insoluble complexes which can be adsorbed on microcrystalline naphthalene in the pH ranges 3.7–6.2 and 2.0–8.4, respectively. The solid mass consisting of the metal complex and naphthalene is dissolved in DMF and the metal determined spectrophotometrically by measuring the absorbances Fe(II) at 745 nm and Fe(III) at 425 nm. Beer's law is obeyed over the concentration range 0.5–20.0 g of iron(II) and 20–170.0 g of Fe(III) in 10 ml of DMF solution. The molar absorptivities are 1.333 × 10⁴ 1 · mole^–1 · cm^–1 for Fe(II) and 2.428 × 10³1· mole^–1 · cm^–1 for Fe(III). The precision of determination is better than 1%. The interference of various ions has been studied and the method has been employed for the determination of iron in various standard reference alloys, bears, wines, ferrous gluconate, human hair and environmental samples.     

Triterpene glycosides of alfalfa. III. Medicoside I

On the basis of chemical transformations and with the aid of physicochemical results, the structure of glycoside I isolated from the roots of the plantMedicago sativa has been established as hederagin 3-O-[O--L-arabinopyranosyl-(1 2)--D-glucopyranosyl-(1 2)--L-arabinopyranoside] 28-O--D-glucopyranoside. Compound (I), C₅₂H₈₄O₂₂, mp 210–212°C, [] _D ²¹ +38.4° (c 1.48; methanol). Acid hydrolysis of (I) led to hederogenin (II) — C₃₀H₄₈O₄, mp 326–330°C, [] _D ²³ +84.2° (c 0.19; pyridine. The Hakomorimethylation of glycoside (I) yielded the permethylate (IV) — C₆₅H₁₁O₂₂ [] _D ²³ +41.6° (c 1.79; methanol). The GLC analysis of the products of the methanolysis of compound (IV) showed the presence of 3,4,6-tri-O-methyl-D-glucopyranose, 2,3,4,6-tetra-O-methyl-D-glucopyranose, 3,4-di-O-methyl-L-O-arabinopyranose, and 2,3,4-tri-o-methyl-L-arabinopyranose. The alkaline hydrolysis of glycoside I gave compound (III) with mp 230–233°C, [] _D ²¹ +35.2° (c 0.21; methanol), which was identified as medicoside C. Details of the PMR spectrum are given for compound (IV) and of the IR spectrum for compound (I).Institute of the Chemistry of Plant Substances of the Uzbek Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 607–610, September–October, 1986.     

Adsorption behaviour of some metal complexes with ferron on Zeo-Karb-226: An atomic absorption spectrophotometric (AAS) study

Summary The adsorption behaviour of ten metal complexes Cr(III), Cr(VI), Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Cd(II) and Pb(II) with ferron on Zeo-Karb-226 in the H⁺ form was investigated at eight different pH-values in order to develop a preconcentration technique for trace amounts of these elements in aqueous solution. The concentrations of the remaining unadsorbed metal ions were determined by atomic absorption spectrophotometry. Under the present experimental conditions, Cr(III) and Pb(II) can be quantitatively determined within the pH range 4–8, while for Cd(II), the optimum pH-range is 7–11. But at pH 11, more than 95% of Cu(II) and Co(II) can be extracted from aqueous solution. The suitability of the technique has been evaluated by analyzing cadmium in simulated water samples. The results indicate that as low as 5 g 1^–1 of CD can be recovered with more than 96% efficiency from 11 of simulated water solution.

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Adsorptionsverhalten einiger Metallkomplexe mit Ferron an Zeokarb-226: eine AAS-Untersuchung

Zusammenfassung Das Adsorptionsverhalten der Komplexe von Cr(III), Cr(VI), Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Cd(II) und Pb(II) mit Ferron an Zeokarb-226 in der H⁺-Form wurde bei acht verschiedenen pH-Werten untersucht, um eine Anreicherungsmethode für Spuren dieser Elemente zu entwickeln. Die Konzentrationen der verbliebenen nicht adsorbierten Metallionen wurden mit Hilfe der AAS bestimmt. Cr(III) und Pb(II) können im pH-Bereich 4–8 quantitativ erfaßt werden, während der optimale Bereich für Cd(II) bei pH 7–11 liegt. Bei pH 11 werden jedoch mehr als 95% Cu(II) und Co(II) aus der wäßrigen Lösung extrahiert. Der Nutzen des Verfahrens wurde durch Bestimmung von Cd(II) in simulierten Wasserproben erwiesen. Noch 5 g/l Cd können zu mehr als 96% aus 11 Wasserprobe wiedergefunden werden.

     

Heavy element contamination of surface waters in the region Banská Štiavnica (SR) measured by radionuclide X-ray fluorescence analysis

Heavy metals (Pb, Cd, Mn, Cu, Zn, Fe) were determined in surface waters in the surroundings of the depositories of the mining shrubs in the region of Banská tiavnica (SR) by radionuclide X-ray fluorescence analysis. Allowed concentrations of the determined metals are exceeded numerously (multiplicity in some cases was 10³–10⁶).     

Characterization of Hollow Chemical Garden Fibers from Metal Salts and Water Glass

Hollow fibers formed from water glass and metal salts of IIA(Ca), VIIB(Fe, Co, Ni) and IB(Cu) groups were characterised in this study. Fragile fibres obtained herein broke down into small pieces during isolation and drying. Quantitative information about morphology, chemical composition and surface structure of the fibres were obtained. The diameter and wall thickness of the fibers were around 50 and 3 . respectively. They had particulate inner and smooth outer surfaces. Fibers had variable composition with metal (II) oxide/SiO₂ ratio in the range 0.31 to 1.02. While group VIIB metal (II) fibres were amorphous, group IIA and IB metal (II) fibres were partially crystalline All the fibres had pores both in micro pore and meso pore region. The B.E.T surface area from N₂ adsorption data was in the range of 10–249 m³ g^–1 and 8–176 m² g^–1 from Langmuir and B.E.T models respectively.     

Preconcentration of transition metal ions from ethanol solution onN-acyl-N′-benzoylthiourea — Modified silica gel

Silica gel was chemically modified with anN-acyl-N-benzoylthiourea group. This material behaved as a selective means of preconcentrating Cu(II), Zn(II) and Cd(II) from ethanol by the column technique. Ethanolic solutions having 6 mol of the metal ions were percolated through the column and retentions of 100% were achieved for all metals. Zinc and copper were eluted quantitatively from the column bed with 5mL of ethanolic O.1molL^–1 (for Zn) and 0.9 mol L^–1 (for Cu) citric acid. Cadmium was recovered totally with 60 mL of ethanolic 2.0 mol L^–1 citric acid. The modified silica was shown to be chemically stable after various adsorption-elution cycles (at least twenty).