Interaction of mixed-donor macrocycles containing the 1,10-phenanthroline subunit with selected transition and post-transition metal ions: metal ion recognition in competitive liquid-liquid solvent extraction of Cu(II), Zn(II), Pb(II), Cd(II), Ag(I), and Hg(II)

Two new mixed aza-thia crowns 5-aza-2,8-dithia[9]-(2,9)-1,10-phenanthrolinophane (L(4)) and 2,8-diaza-5-thia[9]-(2,9)-1,10-phenanthrolinophane (L(7)) have been synthesized and characterized. The coordination behavior of L(4) and L(7) toward the metal ions Cu(II), Zn(II), Pb(II), Cd(II), Hg(II), and Ag(I) was studied in aqueous solution by potentiometric methods, in CD3CN/D2O 4:1 (v/v) by (1)H NMR titrations and in the solid state. The data obtained were compared with those available for the coordination behavior toward the same metal ions of structurally analogous mixed donor macrocyclic ligands L(1)-L(3), L(5), L(6): all these contain a phenanthroline subunit but have only S/O/N(aromatic) donor groups in the remaining portion of the ring and are, therefore, less water-soluble than L(4) and L(7). The complexes [Cd(NO3)2(L(5))], [Pb(L(7))](ClO4)2 x 1/2MeCN, [Pb(L(4))](ClO4)2 x MeCN, and [Cu(L(7))](ClO4)2 x 3/2MeNO2 were characterized by X-ray crystallography. The efficacy of L(1)-L(7) in competitive liquid-liquid metal ion extraction of Cu(II), Zn(II), Cd(II), Pb(II), Ag(I), and Hg(II) was assessed. In the absence of Hg(II), a clear extraction selectivity for Ag(I) was observed in all systems investigated.     

Polarographic indication of the end-point in chelometric titrations with triethylenetetraminehexa-acetic acid

The application of d.c. and square-wave polarographic measurements for the indication of the end-point in titrations with triethylenetetraminehexa-acetic acid (TTHA) has been studied. TTHA has ten co-ordinating groups and forms complexes with metal to ligand ratios of either 1:1 or 2:1, depending on the metal and experimental conditions. The shape of the titration curves, determined by the dependence of the limiting current (peak current of the square-wave polarographic curve) or of the half-wave potential (peak potential) on the amount of TTHA added indicates the composition of the complex formed in the titration. The composition of this complex as determined from the studied titration curves agrees with that predicted by theory. Titrations with polarographic indication of the end-point were also applied for direct titrations of binary mixtures of metal ions. The resulting titration curves indicated the existence of mixed dinuclear complexes and also the kinetic factors involved in the reactions between two different metal ions and TTHA.     

Coordination chemistry of N-aminopropyl pendant arm derivatives of mixed N/S-, and N/S/O-donor macrocycles, and construction of selective fluorimetric chemosensors for heavy metal ions

The coordination chemistry of the N-aminopropyl pendant arm derivatives (L1c-4c) of the mixed donor macrocyclic ligands [12]aneNS2O, [12]aneNS3, [12]aneN2SO, and [15]aneNS2O2(L1a-4a) towards Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) in aqueous solution has been investigated. The protonation and stability constants with the aforementioned metal ions were determined potentiometrically and compared, where possible, with those of the unfunctionalised macrocycles. The measured values show that Hg(II) and Cu(II) in water have the highest affinity for all ligands considered, with the N-aminopropyl pendant arm weakly coordinating the metal centres. Crystals suitable for X-ray diffraction analysis were grown for the perchlorate salt (H2L1c)(ClO4)2.dmf, and for the 1 : 1 complexes [Cd(L3a)(NO3)2](1), [Cu(L4a)dmf](ClO4)2(2), [Zn(L1c)(ClO4)]ClO4(3), [Cd(L1c)(NO3)]NO3(4), and [Hg(L2c)](ClO4)2(5). Their structures show the macrocyclic ligands adopting a folded conformation, which for the 12-membered systems can be either [2424] or [3333] depending on the nature of the metal ion. L1c-4c were also functionalised at the primary amino pendant group with different fluorogenic subunits. In particular the N-dansylamidopropyl (Lnd, n= 1-4), and the N-(9-anthracenylmethyl)aminopropyl (Lne, n= 1, 2, 4, ) pendant arm derivatives of L1a-4a were synthesised and their optical responses to the above mentioned metal ions were investigated in MeCN/H2O (4 : 1 v/v) solutions.     

'Thiacalix[4]aniline' as a highly specific extractant for Au(III) and Pd(II) ions

Thiacalix[4]aniline (4), a cyclic tetramer of p-tert-butylaniline bridged with four sulfides, extracted Au(III) and Pd(II) ions specifically from acidic solutions among 41 metal ions including soft metal ions such as Hg(II), Cd(II), Zn(II), Pb(II), and Cu(II).     

Synthesis and coordination properties of new macrocyclic ligands: equilibrium studies and crystal structures

The synthesis and characterization of two new macrocyclic ligands, the bis-macrocyclic compound 2,6-bis(1,4,13-triaza-7,10-dioxacyclopentadec-1-ylmethyl)phenol (L) and 38-methoxy-1,4,13,16,19,28-hexaaza-7,10,22,25-tetraoxatricyclo[14.14.7.1(32,36)]octatriconta-32,34,Delta(36,38)-triene (L1) are reported. Equilibrium studies of basicity and coordination properties toward metal ions such as Cu(II), Zn(II), Cd(II) and Pb(II) were performed for ligand by potentiometric measurements in aqueous solution (298.1 +/- 0.1 K, I= 0.15 mol dm(-3)). L behaves as a hexaprotic base (logK(1)= 10.93, logK(2)= 9.70, logK(3)= 8.79, logK(4)= 8.05, logK(5)= 6.83, logK(6)= 2.55). All metal ions form stable mono- and dinuclear complexes: logK(MLH(-1))= 25.61 for Cu(II), 15.37 for Zn(II), 12.58 for Cd(II) and 13.79 for Pb(II); logK(M(2)LH(-1))= 31.61 for Cu(II), 23.38 for Zn(II), 24.49 for Cd(II) and 23.68 for Pb(II). All these dinuclear species show a great tendency to add the OH(-) group: the equilibrium constant for the addition reaction was found to be logK(M(2)LH(-1)OH)= 4.77 for Cu(II), 5.66 for Zn(II), 2.8 for Cd(II) and 3.18 for Pb(II). In the case of Ni(II), kinetic inertness prevents the possibility of solution studies. The dinuclear solid adducts [Ni(2)H(-1)L(N(3))(3)].EtOH and [Cu(2)H(-1)L(N(3))](ClO(4))(2) were characterized by X-ray analysis.     

Studies on metallochromic indicators--I. Pyrocatecholphthalein as metallochromic indicator

Pyrocatecholphthalein has been used as a metallochromic indicator for the direct complexometric titrations of a number of metal ions with EDTA, both in acidic and in alkaline medium. Th, Bi(III), Ba, Sr, Ca, Mg, Mn(II), Pb(II), Cu(II), Cd, Ni, Co(II) and Zn have been successfully titrated. In comparison with Pyrocatechol Violet, this dyestuff gives sharper end-points when the titrations are done at high pH.     

Metal-ion-coordinating properties of the dinucleotide 2'-deoxyguanylyl(5'-->3')-2'-deoxy-5'-guanylate (d(pGpG)3-): isomeric equilibria including macrochelated complexes relevant for nucleic acids

The interaction between divalent metal ions and nucleic acids is well known, yet knowledge about the strength of binding of labile metal ions at the various sites is very scarce. We have therefore studied the stabilities of complexes formed between the nucleic acid model d(pGpG) and the essential metal ions Mg2+ and Zn2+ as well as with the generally toxic ions Cd2+ and Pb2+ by potentiometric pH titrations; all four ions are of relevance in ribozyme chemistry. A comparison of the present results with earlier data obtained for M(pUpU)- complexes allows the conclusion that phosphate-bound Mg2+ and Cd2+ form macrochelates by interaction with N7, whereas the also phosphate-coordinated Pb2+ forms a 10-membered chelate with the neighboring phosphate diester bridge. Zn2+ forms both types of chelates with formation degrees of about 91% and 2.4% for Zn[d(pGpG)]cl/N7 and Zn[d(pGpG)]-cl/PO, respectively; the open form with Zn2+ bound only to the terminal phosphate group, Zn[d(pGpG)]-op, amounts to about 6.8 %. The various intramolecular equilibria have also been quantified for the other metal ions. Zn2+, Cu2+, and Cd2+ also form macrochelates in the monoprotonated M[H;d(pGpG)] species (the proton being at the terminal phosphate group), that is, the metal ion at N7 interacts to some extent with the P(O)2(OH)- group. Thus, this study demonstrates that the coordinating properties of the various metal ions toward a pGpG unit in a nucleic acid differ: Mg2+, Zn2+, and Cd2+ have a significant tendency to bridge the distance between N7 and the phosphate group of a (d)GMP unit, although to various extents, whereas Pb2+ (and possibly Ca2+) prefer a pure phosphate coordination.     

Metal Ions Uptake by Chelating Resin Derived from o-Substituted Benzoic Acid and its Synthesis,Characterization and Properties

Summary: Chelating resin [AFM] was synthesized by condensation of Anthranilic acid, Formaldehyde with m-Cresol. The chelating resin was characterized by FTIR Spectra, Elemental Analysis and SEM Photographs. The thermal behavior of the resin was characterized by TGA. The thermodynamic parameters such as Activation Energy (E_a), Order of decomposition (n), Entropy of decomposition (S*), Enthalpy (H*) and Free energy (G*) were calculated by Coats and Redfern method using TGA graph. The chelating behaviour of the prepared resin was studied out with using some metal ions [Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II)]. The sorption capacities of metal ions is found in the following order, Pb(II) < Zn(II) < Cd(II) < Cu(II) < Ni(II). The rate of half exchange was rapid t_1/2 < 20 min for lead ion. The separation of binary mixtures [Cu(II) and Zn(II) in brass and Pb(II) and Cd(II)] was successfully carried out using K_d value.     

Stripping voltammetry study of ultra-trace toxic metal ions on highly selectively adsorptive porous magnesium oxide nanoflowers

We have demonstrated highly selective and sensitive detection of Pb(II) and Cd(II) using a highly selective adsorptive porous magnesium oxide (MgO) nanoflowers. The MgO nanoflower-modified glassy carbon electrode was electrochemically characterized using cyclic voltammetry; and the anodic stripping voltammetric performance of bound Pb(II) and Cd(II) was evaluated using square wave anodic stripping voltammetry (SWASV) analysis. The MgO nanoflower-modified electrode exhibited excellent sensing performance toward Pb(II) and Cd(II) that was never observed previously at bismuth (Bi)-based electrodes. Simultaneous additions of Pb(II) and Cd(II) were investigated in the linear range from 3.3 to 22 nM for Pb(II) and 40 to 140 nM for Cd(II), and detection limits of 2.1 pM and 81 pM were obtained, respectively. Some foreign ions, such as Cu(II), Zn(II) and Cr(III) do not interfere with the detection of Pb(II) and Cd(II). To the best of our knowledge, this is the first example of a highly adsorptive metal oxide with hierarchical micro/nanostructure that allows the detection of both Pb(II) and Cd(II) ions.     

A POTENTIOMETRIC STUDY OF METAL CHELATES WITH TETRAETHYLENEPENTAAMINEHEPTA-ACETIC ACID

Abstract

The protonation constants of tetraethylenepentaamineheptaacetic acid, TPHA, were determined by potentiometric titration in aqueous solution at an ionic strength of 0.10 M KNO₃ and at 25°C. The formation constants of various metal-TPHA complexes were also obtained by titrating mixtures of metal to ligand in molar ratios of 1 :1 and 2:1. Calculations were performed with the computer program BEST. Individual stability constants are reported for Co(II). Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II) with TPHA as well as their related pro-tonated species. The stabilities of the 1:1 complexes parallel to those of similar complexes with DTPA and TTHA. However the 2: 1 complexes have significantly larger log K _ML's than their TTHA counterparts. The extra stability of the 2:1 metal-TPHA complexes is explained in terms of ligand denticity and steric effects. Mercury(II)-TPHA complexes exhibited the highest formation constants and the copper-TPHA complexes had slightly higher log K _ML's than those for Co(II), Ni(II), Zn(II), Cd(II) and Pb(II).     

Analytical applications of triethylenetetraminehexaacetic acid : Part I. the influence of TTHA on the polarographic reduction of some metal ions

The influence of triethylenetetraminehexaacetic acid (TTHA) on the d.c. and square-wave polarographic curves of Cu(II), Pb(II), Cd(II), Ni(II), Co(II), Zn(II), Fe(III), Bi(III), Sb(III), As(III) and In(III) has been investigated in several supporting electrolytes over the pH range 1–13. The E_{$\text{1}\text{2}$} and E_p values with and without a 10-fold excess of TTHA are compared. Some analytical applications are suggested.     

New fluorescence PET systems based on N2S2 pyridine-anthracene-containing macrocyclic ligands. spectrophotometric, spectrofluorimetric, and metal ion binding studies

Three new fluorescent devices for protons and metal ions have been synthesized and characterized, and their photophysical properties have been explored; these are the macrocycles 7-(9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L1) and 7-(10-methyl-9-anthracenylmethyl)-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L2) and the bis macrocycle 7,7'-[9,10-anthracenediylbis(methylene)]bis-3,11-dithia-7,17-diazabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L3). All these systems have a pyridil-thioether-containing macrocycles as a binding site and an anthracene moiety as a signaling agent. The coordination properties of these ligands toward Cu(II), Co(II), Ni(II), Zn(II), and Pd(II) have been studied in solution and in the solid state. The addition of these metal ions to dichloromethane solutions of L1, L2, and L3 produce strong changes in the absorption and emission spectra of these ligands. The stoichiometry of the species, formed at 298 K, have been determined from absorption and fluorescence titrations. The Co(II) and Cu(II) complexes of L1 have been studied by EPR spectroscopy. This last complex and its free ligand have also been characterized by X-ray crystallography.     

Simultaneous Determination of Copper(II), Lead(II) and Zinc(II) at Bismuth Film Electrode by Multivariate Calibration

In this work, simultaneous determination of Cu(II), Pb(II) and Zn(II) ions at low concentration levels (ppb) by square wave anodic stripping voltammetry on a Bi(III) film electrode plated in situ at a glassy carbon electrode (GCE) is described. A chemometric approach was used to overcome the overlapping peaks of Cu(II) and Bi(III), the competition of the electrodeposited Cu and Bi for the surface of the GCE and the formation of Cu‐Zn intermetallic compounds. The construction of the multivariate calibration models, based on partial least squares regression, allowed the simultaneous determination of Cu (in the concentration range 8.0 to 20.1 ppb), Pb (2.0 to 30.0 ppb) and Zn (29.7 to 90.4 ppb) with most of the prediction errors obtained in the external validation set for the three models lower than 16, 11 and 26 %, respectively. Finally, this method was used for the determination of these trace metal ions in surface river water samples with satisfactory results [errors below 10, 5 and 32 % for Cu(II), Pb(II) and Zn(II), respectively].     

Model peptides based on the binding loop of the copper metallochaperone Atx1: selectivity of the consensus sequence MxCxxC for metal ions Hg(II), Cu(I), Cd(II), Pb(II), and Zn(II)

The amino acid sequence MxCxxC is conserved in many soft-metal transporters that are involved in the control of the intracellular concentration of ions such as Cu(I), Hg(II), Zn(II), Cd(II), and Pb(II). A relevant task is thus the selectivity of the motif MxCxxC for these different metal ions. To analyze the coordination properties and the selectivity of this consensus sequence, we have designed two model peptides that mimic the binding loop of the copper chaperone Atx1: the cyclic peptide P(C) c(GMTCSGCSRP) and its linear analogue P(L) (Ac-MTCSGCSRPG-NH2). By using complementary analytical and spectroscopic methods, we have demonstrated that 1:1 complexes are obtained with Cu(I) and Hg(II), whereas 1:1 and 1:2 (M:P) species are successively formed with Zn(II), Cd(II), and Pb(II). The complexation properties of the cyclic and linear peptides are very close, but the cyclic compound provides systematically higher affinity constants than its unstructured analogue. The introduction of a xPGx motif that forms a type II beta turn in P(C) induces a preorganization of the binding loop of the peptide that enhances the stabilities of the complexes (up to 2 orders of magnitude difference for the Hg complexes). The affinity constants were measured in the absence of any reducing agent that would compete with the peptides and range in the order Hg(II) > Cu(I) > Cd(II) > Pb(II) > Zn(II). This sequence is thus highly selective for Cu(I) compared to the essential ion Zn(II) that could compete in vivo or compared to the toxic ions Cd(II) and Pb(II). Only Hg(II) may be an efficient competitor of Cu(I) for binding to the MxCxxC motif in metalloproteins.     

Silica gel modified with N-(3-propyl)-O-phenylenediamine: functionalization, metal sorption equilibrium studies and application to metal enrichment prior to determination by flame atomic absorption spectrometry.

The use of the chemically modified silica gel N-(3-propyl)-O-phenylenediamine (SiG-NPPDA) adsorbent, for the preconcentration and separation of trace heavy metals, was described. SiG-NPPDA sorbs quantitatively (90-100% recovery) trace amounts of nine heavy metals, viz., Cd(II), Zn(II), Fe(III), Cu(II), Pb(II), Mn(II), Cr(III), Co(II) and Ni(II) at pH 7-8. The sorption capacity varies from 350 to 450 micromol g(-1). Desorption was found to be quantitative with 1-2 M HNO3 or 0.05 M Na2EDTA. The distribution coefficient, Kd and the percentage concentration of the investigated metal ions on the adsorbent at equilibrium, C(M,eqm)% (Recovery, R%), were studied as a function of experimental parameters. The logarithmic values of the distribution coefficient, log Kd, ranges between 4.0 and 6.4. Some foreign ions caused little interference in the preconcentration and determination of the investigated nine metals by flame atomic absorption spectrometry (AAS). The adsorbent and its formed metal chelates were characterized by IR (absorbance and/or reflectance), potentiometric titrations and thermogravimetric analysis (TGA and DTG). The mode of chelation between the SiG-NPPDA adsorbent and the investigated metal ions is proposed to be due to the reaction of the investigated metal ions with the two nitrogen atoms of the SiG-NPPDA adsorbent. The present adsorbent coupled with flame AAS has been used to enrich and determine the nine metal ions in natural aqueous systems and in certified reference materials (RSD < or = 5%). The copper, iron, manganese and zinc present in some pharmaceutical vitamin samples were also preconcentrated on SiG-NPPDA adsorbent and determined by flame AAS (RSD < or = 4.2%). Nanogram concentrations (0.07-0.14 ng ml(-1)) of Cd(II), Zn(II), Fe(III), Pb(II), Cr(III), Mn(II), Cu(II), Co(II) and Ni(II) can be determined reliably with a preconcentration factor of 100.     

Poly-L-Histidine Attached Poly(glycidyl methacrylate) Cryogels for Heavy Metal Removal

Poly-L-histidine immobilized poly(glycidyl methacrylate) (PGMA) cryogel discs were used for the removal of heavy metal ions [Pb(II), Cd(II), Zn(II) and Cu(II)] from aqueous solutions. In the first step, PGMA cryogel discs were synthesized using glycidyl methacrylate (GMA) as a basic monomer and methylene bisacrylamide (MBAAm) as a cross linker in order to introduce active epoxy groups through the polymeric backbone. Then, the metal chelating groups are incorporated to cryogel discs by immobilizing poly-L-histidine (mol wt ≥ 5000) having poly-imidazole ring. The swelling test, fourier transform infrared spectroscopy and scanning electron microscopy were performed to characterize both the PGMA and poly-L-histidine immobilized PGMA [P-His@PGMA] cryogel discs. The effects of the metal ion concentration and pH on the adsorption capacity were studied. These parameters were varied between 3.0–6.0 and 10–800 mg/L for pH and metal ion concentration, respectively. The maximum adsorption capacity of heavy metal ions of P-His@PGMA cryogel discs were 6.9 mg/g for Pb(II), 6.4 mg/g for Cd(II), 5.6 mg/g for Cu(II) and 4.3 mg/g for > Zn(II). Desorption of heavy metal ions was studied with 0.1 M HNO₃ solution. It was observed that cryogel discs could be recurrently used without important loss in the adsorption amount after five repetitive adsorption/desorption processes. Adsorption isotherms were fitted to Langmuir model and adsorption kinetics were suited to pseudo-second order model. Thermodynamic parameters (i.e. ΔH° ΔS°, ΔG°) were also calculated at different temperatures.     

Coordination chemistry of a new cofacial binucleating macropolycycle derived from 1,4,7-triazacyclononane

We have prepared and characterized a new phenol-based compartmental ligand (H(2)L) incorporating 1,4,7-triazacyclononane ([9]aneN(3)), and we have investigated its coordination behavior with Cu(II), Zn(II), Cd(II), and Pb(II). The protonation constants of the ligand and the thermodynamic stabilities of the 1:1 and 2:1 (metal/ligand) complexes with these metal ions have been investigated by means of potentiometric measurements in aqueous solutions. The mononuclear [M(L)] complexes show remarkably high stability suggesting that, along with the large number of nitrogen donors available for metal binding, deprotonated phenolic functions are also involved in binding the metal ion. The mononuclear complexes [M(L)] show a marked tendency to add a second metal ion to afford binuclear species. The formation of complexes [M(2)(H(2)L)](4+) occurs at neutral or slightly acidic pH and is generally followed by metal-assisted deprotonation of the phenolic groups to give [M(2)(HL)](3+) and [M(2)(L)](2+) in weakly basic solutions. The complexation properties of H(2)L have also been investigated in the solid state. Crystals suitable for X-ray structural analysis were obtained for the binuclear complexes [Cu(2)(L)](BF(4))(2).(1)/(2)MeCN (1), [Zn(2)(HL)](ClO(4))(3).(1)/(2)MeCN (2), and [Pb(2)(L)](ClO(4))(2).2MeCN (4). In 1 and 2, the phenolate O-donors do not bridge the two metal centers, which are, therefore, segregated each within an N(5)O-donor compartment. However, in the case of the binuclear complex [Pb(2)(L)](ClO(4))(2).2MeCN (4), the two Pb(II) centers are bridged by the phenolate oxygen atoms with each metal ion sited within an N(5)O(2)-donor compartment of L(2)(-), with a Pb.Pb distance of 3.9427(5) A.     

Metal-catalysed oxidation processes in thiosemicarbazones: new complexes with the ligand N-{2-([4-N-ethylthiosemicarbazone]methyl)phenyl}-p-toluenesulfonamide

The coordination behaviour of a new thiosemicarbazone Schiff-base building block, N-{2-([4-N-ethylthiosemicarbazone]methyl)phenyl}-p-toluenesulfonamide, H2L1 (1), incorporating a bulky tosyl group, towards Mn II, Fe II, Co II, Ni II, Cu II, Zn II, Cd II, Ag I, Sn II, and Pb II has been investigated by means of an electrochemical preparative procedure. Most metal complexes of L1 have the general formula [M(L1)]2.nX (M=Mn, Fe, Co, Ni, Cu, Cd, Pb; n=0-4, X=H2O or CH3CN), as confirmed by the structure of [Pb(L1)]2 (15), in which the lone pair on lead is stereochemically active. This lead(II) complex shows an intense fluorescence emission with a quantum yield of 0.13. In the case of silver, the complex formed was found to possess a stoichiometry of [Ag2(L1)]2.3H2O. During reactions with manganese and copper metals, interesting catalysed processes have been found to take place, with remarkable consequences regarding the ligand skeleton structure. In synthesising the manganese complex, we obtained an unexpected dithiolate thiosemicarbazone tosyl ligand, H2L2, as a side-product, which has been fully characterised, including by X-ray diffraction analysis. In the case of copper, the solid complex has the formula [CuL1]2, but the crystallised product shows the copper atoms coordinated to a new cyclised thiosemicarbazone ligand, H2L3, as in the structures of the complexes [Cu(L3)]2.CH3CN (8) and [Cu(L3)(H2O)]2.CH3CN.H2O (9). The zinc complex [Zn(L1)]4 (12) displays a particular tetranuclear zeolite-type structure capable of hosting small molecules or ions, presumably through hydrogen bonding.     

Antimony Film Electrode Prepared In Situ in Hydrogen Potassium Tartrate in Anodic Stripping Voltammetric Trace Detection of Cd(II), Pb(II), Zn(II), Tl(I), In(III) and Cu(II)

An antimony film electrode (SbFE) was prepared in situ on a glassy carbon support and in a new supporting electrolyte, a saturated solution of hydrogen potassium tartrate in which Sb(III) ions were complexed using tartrate. Its performance in anodic stripping voltammetric (ASV) determination of Cd(II), Pb(II), Zn(II), Tl(I), In(III) and Cu(II) traces was examined. It was found that 1.2 mg/L of Sb(III) yields the finest quality SbFE for analytical purposes. The procedure with in situ SbFE ensures well‐defined anodic stripping voltammetric curves of the investigated elements, low detection limits (0.5–3.8 µg/L), good reproducibility (1–5 %) and satisfactory sensitivity (32–184 nA/(µg/L)).     

Selective Electrochemical Analysis of Various Metal Ions at an EDTA Bonded Conducting Polymer Modified Electrode

An EDTA‐bonded conducting polymer modified electrode was prepared and characterized by FT‐IR. The modified electrode was used for the selective electrochemical analysis of various trace metal ions such as, Cu(II), Hg(II), Pb(II), Co(II), Ni(II), Fe(II), Cd(II), and Zn(II) at the different pHs by linear sweep and square wave voltammetry. Dynamic ranges were obtained using square wave voltammetry from 0.1 μM to 10.0 μM for Co(II), Ni(II), Cd(II), Fe(II), and Zn(II) and 0.5 nM to 20 nM for Cu(II), Hg(II), and Pb(II) after 10 min of preconcentration. The detection limits were determined to be 0.1 nM, 0.3 nM, 0.4 nM, 50.0 nM, 60.0 nM, 65.0 nM, 80.0 nM, and 90.0 nM for Cu(II), Hg(II), Pb(II), Co(II), Ni(II), Cd(II), Fe(II), and Zn(II), respectively. The technique offers an excellent way for the selective trace determination of various heavy metal ions in a solution.