UV-Aufschlu? organischer Wasserinhaltsstoffe bei spurenanalytischen Multielement-Anreicherungen, speziell an Chelat-Ionenaustauschern

Zusammenfassung Der Einfluß organischer Wasserinhaltsstoffe (z. B. Huminsäure, Ligninsulfonsäure, Acetat, Citrat, EDTE) auf analytische Multielement-Anreicherungen (Cu²⁺, Fe³⁺, Mn²⁺, Pb²⁺ und Zn²⁺) an einem Chelat-Ionenaustauscher (Cellulose-Hyphan) wird beschrieben. Erwartungsgemäß verursacht der starke Chelatbildner EDTE erhebliche Störungen. Bereits mg/l-Konzentrationen an EDTE senken die analytische Spurenwiederfindung auf 0 (Pb²⁺) bis 50% (Mn²⁺). Durch eine oxidierende UV-Photolyse (Hg-Niederdruck-Strahler, 70 W, 1 h bei 45° C) lassen sich die störenden Wasserinhaltsstoffe (<200 mg/l) einfach und schnell aufschließen. Der UV-Aufschluß wird in seiner Abhängigkeit von Zeit, Oxidationsmittel (H₂O₂) sowie von organischen bzw. anorganischen Matrices (Ethanol bzw. NaCl) untersucht. Er zeichnet sich im Spurenbereich (je 20 g/l Cd²⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Pb²⁺, Zn²⁺) durch gute Reproduzierbarkeit und niedrige Blindwerte (z. B. Fe, Zn<1 g/l) aus. Die Elemente werden mit der Flammen-AAS bestimmt.

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UV-photolysis of dissolved organic matter as sample pretreatment for the analytical multielement-enrichment, especially on chelating ion-exchangers

Summary The influence of water-dissolved organic matter (e.g. humic acid, lignin sulphonic acid, acetate, citrate, EDTE) on the analytical multielement-enrichment (e.g. Cu²⁺, Fe³⁺, Mn²⁺, Pb²⁺, Zn²⁺) on a chelating ion-exchanger (Cellulose-Hyphan) is described. As expected, the strong chelating agent EDTE causes large interferences. Thus, mg/l-concentrations of EDTE lower the analytical recovery rate to values between 0 (Pb²⁺) and 50% (Mn²⁺). In a fast and simple manner, the interfering organic matters in waters (<200 mg/l) can be eliminated by an oxidizing UV-irradiation (Hg-low-pressure lamp, 70 W, 1 h at 45° C). This UV-photolysis is investigated as function of the time, the oxidant (H₂O₂) and organic resp. inorganic matrices (ethanol resp. NaCl). At the trace level (20 g/l Cd²⁺, Cu²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Pb²⁺, Zn²⁺, each) it shows a good reproducibility and low blank values (e.g. Fe, Zn<1 g/l). The elements are determined by flame-AAS.

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Herrn Prof. Dr. H. Weisz zum 60. Geburtstag gewidmet     

Application of Chitosan Functionalized with 8-Hydroxyquinoline: Determination of Lead by Flow Injection Flame Atomic Absorption Spectrometry

This work describes the application of chitosan – chemically modified with 8-hydroxyquinoline – in a simple and efficient preconcentration system using flow injection flame atomic absorption spectrometry (FI-FAAS) for the determination of Pb²⁺ ions. The efficiency of the chelating resin and the accuracy of the proposed method were evaluated by the metal ion recovery technique in samples of mineral water, potable water and lake water. The recovery of Pb²⁺ ions from spiked solutions was less than 70% due to matrix effects, which were eliminated by addition of Ba²⁺ metal ions, resulting in recoveries of approximately 100% for all water samples. Ag⁺, Cd²⁺, Cu²⁺, Mn²⁺, Ni²⁺, Zn²⁺, Hg²⁺, Ca²⁺, Mg²⁺, Cr³⁺, Al³⁺ and Fe³⁺ metal ions were studied with respect to their interference with Pb²⁺ metal ion determination, and the chelating resin exhibited high selectivity for Pb²⁺ at pH 7. The analytical properties of merit were obtained using the parameters previously optimized. The method shows high precision with a relative standard deviation (R.S.D.) of 1.1% (n=7) for a solution containing 50µgL^–1 of Pb²⁺ and a detection limit (L.O.D.) of 1.7µgL^–1.     

Laser induced breakdown spectroscopy (LIBS) as an analytical tool for the detection of metal ions in aqueous solutions

Laser induced breakdown spectroscopy (LIBS) is applied to analyze aqueous solutions of Li⁺, Na⁺, Ca²⁺, Ba²⁺, Pb²⁺, Cd²⁺, Hg²⁺ and Er³⁺ and suspensions of ErBa₂Cu₃O_x particles (d=0.2 m). An excimer (308 nm) pumped dye laser with laser pulse at 500 nm and pulse energy at 22±2 mJ is used to produce plasma in aqueous solution. Plasma emission lines of the elements are detected by a photodiode array detector. Detection limits of the metal ions are 500 mg/l for Cd²⁺, 12.5 mg/l for Pb²⁺, 6.8 mg/l for Ba²⁺, 0.13 mg/l for Ca²⁺, 13 g/l for Li⁺ and 7.5 g/l for Na⁺. No mercury and erbium emission can be detected, even at Hg²⁺ and Er³⁺ concentrations of up to the g/l range. On the other side, for Er in suspensions of ErBa₂Cu₃O_x particles a more than 10³ times higher sensitivity is found than for dissolved Er³⁺. This result gives a possibility to analyze colloid-borne metal ions with an increased sensitivity.     

Simultaneous determination of trace levels of lead(II) and copper(II) by square wave stripping voltammetry using a glassy carbon electrode modified with hierarchical gold dendrites

A glassy carbon electrode was modified with gold hierarchical dendrites (Au HDs) by one-step electrodeposition in the presence of cytosine, which plays an important role in the formation of the Au HDs. This approach is simple, fast, feasible, controllable, without any seed, template, or surfactant. The modified electrodes were used for the simultaneous determination of Pb²⁺ and Cu²⁺ by square wave stripping voltammetry. The peak currents show good linear relationship with concentrations of Pb²⁺ and Cu²⁺ in the range of 5.0 to 15.0 μM. The recoveries of the spiked water samples are in the range of 94.0 %–107.4 % for Pb²⁺ and Cu²⁺, and their relative standard deviation are in the range of 2.7 %–4.3 % for Pb²⁺ and Cu²⁺, respectively (n?=?3).

A reactive electrode (reactrode) for the voltammetric determination of heavy metals in laboratories and for use as a passive monitor in remote analysis

The use of a reactive electrode (reactrode) consisting of graphite, a solid ion exchanger (HYPHAN) and paraffin for the batch analysis of Cd²⁺, Cu²⁺, Pb²⁺ and Hg²⁺ in aqueous samples and as a passive monitor for these metal ions is described. The metal ions are accumulated on the reactrode surface at an open-circuit potential in an ion-exchange reaction. After the accumulation, the ion exchanger-bonded metal ions are reduced to the metals which remain on the electrode surface. In a following step, the metals are anodically dissolved which is recorded by differential-pulse voltammetry. The 3s detection limits for the analysis of drinking water are: 1.1×10^-7 mol/l for Pb²⁺, 5×10^-8 mol/l for Hg²⁺ and 2.4×10^-7 mol/l for Cu²⁺.The reactrode developed can be used for the passive monitoring of heavy metals in aqueous streams if the reactrode is mounted in a wall-jet cell which is part of a flow-through system. Using this arrangement, it has been possible to determine Hg²⁺, Cu²⁺ and Pb²⁺ in drinking water after 20 hours of accumulation.     

An Investigation into the Suitability of Bismuth as an Alternative to Gold‐Amalgam as a Working Electrode for the In Situ Determination of Chemical Redox Species in the Natural Environment

The suitability of the bismuth film working electrode was investigated as an alternative to the gold‐amalgam electrode used in solid state microelectrodes for in situ voltammetric analysis of redox chemistry in the natural environment (e.g., lakes, oceans, sedimentary pore waters). Chemical redox species measurable with the Au‐amalgam include O₂, H₂S, S , S₂O , Fe²⁺, Fe³⁺, Mn²⁺, I^?. Bismuth was electrochemically deposited to form a solid film analogous to the Au‐amalgam on a polished gold disk electrode. The useable potential window of the Bi‐film was found to be narrower than that of the Au‐amalgam, precluding the detection of dissolved O₂, I^? and S₂O , whose redox potentials fall outside the Bi‐film's range. The Bi‐film was able to detect free H₂S/HS^? and total sulfide (AVS), but not Fe²⁺ or Mn²⁺. The Bi‐film was less sensitive to low levels of total sulfide (<10 μM) than the Au‐amalgam; however, the Bi‐film was able to accurately quantify very high concentrations of sulfide (at least 15 mM), with a linear response up to an order of magnitude higher than that of the Au‐amalgam. Thus the Bi‐film appears to have limited application as an alternative to the Au‐amalgam microelectrode for in situ analysis of redox species in natural waters.     

Zinc oxide nanostructured platform for electrochemical detection of heavy metals

ZnO nanoparticles (ZnO-NP) were prepared by a facile precipitation technique using di-isopropyl amine as precipitating agent. The morpho-structure and porosity of the as-prepared nano-powder were investigated by FT-IR analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET analysis. By drop-casting, a composite film was deposited to obtain ZnO-NP-Nafion/GCE modified electrode. The modified electrode was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and square wave anodic stripping voltammetry (SWASV) for the detection of Pb²⁺, Cd²⁺, Cu²⁺, and Fe³⁺, and it was successfully applied for the detection of Pb²⁺ and Cu²⁺ in real water samples.     

Ma?analyse und Katalyse I.

Zusammenfassung Einige in der Literatur beschriebene Verfahren zur quantitativen Analyse mit Hilfe katalytischer Reaktionen werden kurz besprochen.Die Anwendung von katalysierbaren Reaktionen zur Endpunktsindikation bei maß analytischen Bestimmungen im klassischen Sinn wird beschrieben. Der Katalysator dient als Maßlösungsreagens, titrierbar sind Substanzen, welche die Katalysatorwirkung sehr stark vermindern (durch Fällung oder Komplexbildung). Der erste überschüssige Tropfen der Maßlösung beschleunigt das Indicatorreaktionsgemisch. Einige praktische Beispiele illustrieren diese Arbeitsweise. Namentlich die Titration von ÄDTA mit Kobaltmaßlösung (Tiron + Perborat als Indicator) und die Rücktitration mit Kobaltmaßlösung zur Bestimmung einer Reihe von Metallionen (Cu²⁺, VO²⁺, Ni²⁺, Pb²⁺, Cd²⁺, Hg²⁺, Mn²⁺) dürfte von Interesse sein.

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Summary Some methods already described in literature for quantitative analysis using catalytic reactions are briefly summarized.The application of catalytic reactions for the end-point indication in volumetric analysis in the classical sense is described: The catalyst itself serves as titrimetric reagent; substances can be titrated which are able to distinctly diminish the catalytic action (by precipitation or by complex formation). The first drop in excess of the titrant catalyses the indicator reagent mixture.Some practical examples illustrate this method. Especially the titration of EDTA with cobalt standard solution (tirone + perborate as indicator) and the backtitration with cobalt standard solution for the determination of a number of metal ions (Cu²⁺, VO²⁺, Ni²⁺, Pb²⁺, Cd²⁺, Hg²⁺, Mn²⁺) seems to be of interest.

     

Metal bioaccumulation by the freshwater algaScenedesmus quadricauda

Bioaccumulation of six metals (Cu²⁺, Cu⁺, Mo⁶⁺, Mn²⁺, V⁵⁺, Ni²⁺) and their combinations by algaScenedesmus quadricauda was determined by using radio nuclide X-ray fluorescence (RXFA). The metals were added into the cultivation medium in concentrations corresponding with EC₅₀ value for each metal. The obtained results indicate that Ni²⁺, Cu²⁺ and Cu⁺ were accumulated in high amounts (20%, 17.5% and 15.19%) the Mo⁶⁺ ion (<0.2%) was accumulated in the lowest amount. For metal-metal interactions in accumulation of metal ions by algaS. quadricauda three types of answers were determined: inhibition (MoCu²⁺, Ni, Mn, V; VNi, Mn; MnNi, Cu²⁺, Cu⁺; Cu⁺Ni; Cu²⁺Ni; NiMn, V), enhancement (VCu⁺; Cu²⁺Mn;Cu⁺V, Mn; MnV; NiCu²⁺, Cu⁺) and neutral effect (VMo; Cu²⁺Mo; Cu⁺Mo; MuMo; NiMo).     

Electrodeposition of lead on to a graphite probe for electrothermal atomic absorption spectrometry

A simple system for controlled potential electrodeposition on to a graphite probe electrode is described. Totally pyrolytic graphite was found to be better for electrodeposition than microporous glassy carbon or electrographite coated with pyrolytic graphite. Lead can be deposited by anodic and cathodic processes as PbO₂ and Pb, respectively. Potentials of + 1.2 to + 2.0 V were best for anodic deposition and – 0.8 to– 2.0 V were best for cathodic deposition. With an electrodeposition time of 120 s, AAS sensitivity gains of × 9 and × 3.5 were achieved for anodic and cathodic deposition, respectively, in comparison with the results obtained by direct injection of 20 1 sample volumes on to the probe. The lead cathodic process was unaffected by NaCl concentrations up to 10^–2 M, but only 10^–3 M NaCl could be tolerated by anodic deposition.     

Metal ion complexation in acetonitrile by upper-rim allyl-substituted, di-ionized calix[4]arenes bearing two dansyl fluorophores

The influence of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Ag⁺, Cd²⁺, Co²⁺, Fe²⁺, Hg²⁺, Mn²⁺, Pb²⁺, Zn²⁺ and Fe³⁺ on the spectroscopic properties of two dansyl (1-dimethylaminonaphthalene-5-sulfonyl) groups linked to the lower rims of a series of three, structurally related, di-ionized calix[4]arenes is investigated by means of absorption and emission spectrophotometry. Di(tetramethylammonium) salts of the di-ionized ligands, L, L1, and L2, which differ in having no, two and four allyl groups, respectively, on the upper rim of the calix[4]arene scaffold, are utilized for the spectrofluorimetric titration experiments in MeCN. On complexation by alkaline earth metal cations, the emission spectra undergo marked red shifts and quenching of the dansyl fluorescence. These effects are weaker with alkali metal cations. Transition metal cations and Pb²⁺ interact strongly with the ligands. In particular, Fe³⁺, Hg²⁺ and Pb²⁺ cause greater than 99% quenching of the dansyl fluorescence.     

In situ voltammetric measurement of trace elements in lakes and oceans

A submersible probe with a flow-through cell allowing in situ voltammetric measurements by means of either a mercury film or a mercury drop electrode has been developed. The various possibilities of voltammetric measurements in the presence of dissolved oxygen have been reviewed and tested. Optimum conditions for the determination of trace metals in oxygenated waters have been found. In situ determinations of Mn(II) in anoxic lake water and of trace metals (Cu²⁺, Pb²⁺, Cd²⁺, Zn²⁺) in oxygen-saturated sea water are reported.     

Stopped-flow kinetic determination of a binary mixture: Simultaneous determination of europium and cerium

A kinetic method is proposed for the simultaneous determination of europium(II) and cerium(III), based on their inductive action on the Cr(VI)-iodide redox reaction in weak acidic medium. The reaction rate was followed by the stopped-flow spectrophotometric technique using starch-iodine complex as indicator. The method can be used for the determination of europium and cerium after reduction with zinc metal powder in the concentration ranges 0–2.1 and 0–1.8 g/ml, respectively. The detection limits are 0.015 g/ml Eu and 0.010 g/ml Ce. 100 to 1000 times higher concentrations of other rare earth metal ions and Th⁴⁺, Al³⁺, Mn²⁺, Hg²⁺, Co²⁺, Ni²⁺, Cu²⁺, Pb²⁺ do not interfere. The method is applied to the determination of europium and cerium in a synthetic sample and in barium yttrium fluoride fluorescent material, with relative standard deviation of about 4%.     

Determination of copper(II) and zinc(II) in blood by spectrophotometry and polarographic methods

Summary Determination of copper with picramine R and of copper and zinc by amalgam polarographic technique with accumulation, have been developed for samples of 0.2–1 ml of blood.

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Zusammenfassung Die Bestimmung von Kupfer mit Pikramin R und von Kupfer und Zink durch Polarographie nach elektrolytischer Anreicherung als Amalgam aus 0,2 bis 1 ml Blut wurde ausgearbeitet.

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Reference solution 1 contains (g/ml): 900 NaCl, 400 NaHPO₄, 200 KC1, 100 CaCl₂, 10 NaHCO₃, 6 Zn²⁺, 1.5 Cu²⁺, 1 AI³⁺+, 0.5 Ti⁴⁺, 0.2 Mn²⁺, 0.1 Pb²⁺, 0.06 Co²⁺, 0.05 Ni²⁺.Reference solution 2 is the same plus Fe³⁺, 500 g/ml.     

A hybrid mesoporous material functionalized by 1,8-naphthalimide-base receptor and the application as chemosensor and absorbent for Hg2+ in water

A novel hybrid material (SBA-P1) is prepared through the functionalization of mesoporous silica (SBA-15) with a 1,8-naphthalimide-based dye by sol-gel reaction. The characterization results of elemental analysis (EA), X-ray powder diffractometer (XRD) and spectroscopic methods demonstrate the fluorescence dye P1 is successfully grafted onto the inner surface of SBA-15 and the organized structure is preserved. SBA-P1 can detect Hg²⁺ with high selectivity to Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Mn²⁺, Ni²⁺, Co²⁺, Ag⁺, Cr³⁺, and Mg²⁺, Ca²⁺, Li⁺, Na⁺, K⁺ in water and sensitivity to environmentally relevant mercury in complex natural samples. The quenching fluorescence detection is also reversible by treating with EDTA/base. Furthermore, its fluorescence intensity keeps stable in the physiologically relevant pH range. The extraction ability of SBA-P1 is also estimated by inductively coupled plasma source mass spectrometer (ICP), showing that approximately 90% of the Hg²⁺ ion is extracted. These results imply that the hybrid material has potential application for sensing and removing of Hg²⁺ ions in waste water and working as toxicide for acute mercury poisoning.     

TiC Working Electrode. Voltammetric Characteristics and Application for Determination of Lead Traces by Stripping Voltammetry

The TiC working electrode was tested as a novel, potential electrode for anodic stripping voltammetric determination of lead(II) ions traces. To demonstrate the practical applicability of the TiC electrode, an underpotential deposition/dissolution (UPD) phenomena system in electrolyte without removal of oxygen was tested. The electrode was constructed be means of mounting a TiC disk (Ø=3.5 mm) in a resin body. Three compositions of TiC were tested differing in stoichiometry, namely TiC_0.6, TiC_0.8, and TiC_1.0. The key problem is the method of electrochemical activation of the TiC electrode. No or improperly activated electrode is not polarized and is unsuitable as a voltammetric sensor. The TiC electrode was used for the determination of Pb²⁺ in concentrations ranging from 1 to 100 nM. The instrumental parameters, composition of supporting electrolyte and procedures of the electrode activation were optimized. The repeatability of DP ASV runs in synthetic solutions covering the entire concentration range is better than 3%. The calibration curve is characterized by a correlation coefficient of at least 0.999. The detection limit was 2 nM for an electrodeposition time of 30 s. The method enables determination of Pb²⁺ in the presence of, among the others, high excesses of Cd, Cu, In, Sb, Se, and Tl ions as well as surfactants, Triton X‐100 and humic acids. The analysis of Pb²⁺ in synthetic solutions with and without surfactants, certified reference material and natural water samples have been performed. The voltammetric data were associated with the structural characterization of the electrode surface using scanning electron microscopy (SEM) and X‐ray fluorescence spectroscopy (XRF).     

Kinetics and mechanism of Pb2+ ion promoted aquation of tris-oxalatochromate(III) in acid perchlorate media

Summary In low acid (0.02 M HClO₄) media, Pb²⁺ ion strongly catalyses the aquation of Cr(ox) ₃ ^3– to givecis-Cr(ox)₂(OH₂) ₂ ^– ion. The catalytic efficiency of Pb²⁺ as represented by the second order rate constant, k_pb (3.76 × 10^–4 M^–1 s^–1 at 25 °C; I, 1.0 M perchlorate), for the Pb²⁺ catalysed path is remarkably higher than might be expected on the basis of K_pb-ox, the first formation constant for the lead-oxalate complex. This catalytic superiority of Pb²⁺ has been found to result mainly from a comparatively much lower H (65.2 ±0.8 kJ mol^–1) value which more than compensates for the relatively unfavourable S value (–93.2 ±2.4 JK^–1mol^–1) for this catalysed path. This low S value is, however, in line with the entropy of hydration of Pb²⁺ ion. These facts, together with the different LFER plots, have been utilised to propose a plausible mechanism for such catalysed reactions.