Reversed-phase HPLC determination of Co(II), Ni(II) and Fe(III) as their 2-(2-thiazolylazo)-5-dimethylaminophenol chelates

The optimum chromatographic separation conditions for Co(II), Ni(II), and Fe(III) chelates with 2-(2-thiazolylazo)-5-dimethylaminophenol (TAM) were investigated. The compositions of chelates were also determined by the HPLC method and thus the possible structure of chelates was given. A precolumn derivatization method was used, followed by separation on an octyl-bonded silica stationary phase with a methanol-tetrahydrofuran-water (40:9:51, v/v/v) mobile phase containing pH 5.8 acetate buffer and 1 x 10(-4)M TAM. The detection limits of Co(II), Ni(II), and Fe(III) at 560 nm are 0.03, 0.02 and 0.1 ng (S N = 2 ), respectively. They can be determined by means of the proposed method without interference from other common metal ions and have been determined in five standard alloys with satisfactory results.     

Mixed ligand complexes of benzimidazole and pyrimidine hydroxy azo dyes with some transition metals and glycine, dl-alanine or dl-leucine

The overall formation constants of 1:1:1 ternary complexes of Cu(II), Zn(II), Cd(11) with glycine, dl-alanine or dl-leucine as primary ligands and o-hydroxyphenylyazo derivatives of 2-cyanomethyl benzimidazole (ABI) and barbituric acid (ABA) as secondary ligands have been investigated potentiometrically in 40% (v/v) EtOH. Formation constants of binary systems were also determined under the same experimental conditions (37 degrees C and mu=0.15 mol dm(-3)). The stability of ternary complexes have been quantitatively compared with those of the corresponding binary complexes in terms of the parameters DeltalogK, logX and logX'. The data were interpreted on the basis of statistical considerations and the nature of complexes. The concentration distribution of various species formed in solution was evaluated. The Cu(II) complexes have been synthesized and the coordination sites of the ligands were characterized by means of IR spectroscopy.     

Mono and binuclear Ag(I), Cu(II), Zn(II) and Hg(II) complexes of a new azo-azomethine as ligand: synthesis, potentiometric, spectral and thermal studies

New azo-azomethine dyes were prepared by reaction of p-aminobenzoic acid, o-anisidine, o-nitroaniline, and p-bromoaniline with salicylaldehyde respectively to form azo compounds and then condensation by urea to form 4-(R-arylazo 2-salicylaldene)-urea azo-azomethine derivatives (I(a-d)). The complexes of these ligands with Ag(I), Cu(II), Zn(II) and Hg(II) metal ions were prepared. The structure of the free ligands and their complexes were characterized by using elemental analysis (C, H, N), (1)H NMR, IR and UV-Vis-spectra. The proton dissociation constants of the ligands and the stability constant of their complexes have been determined potentiometrically in 40% (v/v) alcohol-water medium as well as the stoichiometry of complexes were determined conductometrically. The data reveal that the stoichiometries for all complexes were prepared in molar ratios (1:1) and (1:2) (M:L). The electrolytic and nonelectrolytic natures of the complexes were assigned based on molar conductance measurements. The thermogravimetric (TG), and differential thermal analyses (DTA) were studied in nitrogen atmosphere with heating rate 10°C/min. The kinetic and thermodynamic parameters for thermal decomposition of complexes have been calculated by graphical method using Coats-Redfern (CR) method.     

Controlled synthesis and luminescence of semiconductor nanorods

A variety of nearly monodisperse semiconductor nanocrystals, such as CdS, ZnS, and ZnS:Mn, with controllable aspect ratios have been successfully prepared through a facile synthetic process. These as-prepared nanocrystals were obtained from the reactions between metal ions and thioacetamide by employing octadecylamine or oleylamine as the surfactants. The effects of reaction temperature and time, ratios of thioacetamide to inorganic precursors, and the reactant content on the size and crystal purity of the nanorods, have been systematically investigated. The optical properties and the formation mechanism of the nanorods have also been discussed. For the next biolabel applications, these hydrophobic nanocrystals have also been transferred into hydrophilic colloidal spheres by means of an emulsion-based bottom-up self-assembly approach.     

Thermal studies and vibrational analyses of m-methylaniline complexes of Zn(II), Cd(II) and Hg(II) bromides

The complexes having the MBr(2)L(2) (M: Zn, Cd and Hg; L: m-methylaniline) formulae have been prepared and characterized by their elemental analyses, thermogravimetric analyses, IR and Raman spectral studies. IR and Raman bands of the complexes have been assigned as compared with the free ligand. Coordination effects on the internal modes of m-methylaniline have been discussed. Vibrational spectra propose that the [ZnBr(2)(mMA)(2)] complex is in a tetrahedral environment around Zn(II) ion with C(2v) symmetry whereas Cd(II) and Hg(II) complexes have 5-coordinate polymeric bromide bridged structures.     

Simple and rapid spectrophotometric determination of iron after preconcentration as its 1,10-phenanthroline complex on the natural polymer "chitin"

Preconcentration by collection of metal complexes on chitin has been applied to the spectrophotometric determination of iron in water. The iron is collected as its 1,10-phenanthroline (phen) complex on a column of chitin in the presence of tetraphenylborate as counter-ion. The iron(II)-phen complex retained on the chitin is eluted with an acetone-1M acetic acid mixture (8:2 v/v), and the absorbance of the eluate is measured at 512 nm. Beer's law is obeyed over the concentration range 1.1-11.2 mug of iron in 10 ml of eluate. In the presence of EDTA as masking agent, Ca, Mg, Al, Mn, Zn, Cd and Pb do not interfere in concentrations up to 100 times that of iron(II) and Co, Ni and Cu do not interfere in concentrations up to 20 times that of iron(II). Common inorganic anions do not interfere in concentrations up to 10,000 times that of iron(II). The proposed method has been applied to determination of iron in tap water.     

High-performance liquid chromatographic determination of uranium using solvent extraction and bis(salicylaldehyde) tetramethylethylenediimine as complexing reagent

The reagent bis(salicylaldehyde)tetramethylethylenediimine has been used for the determination of dioxouranium(VI), based on complexation in aqueous solution at pH 6, followed by extraction in chloroform and HPLC determination on a Hypersil ODS (3 μm) column. The complex was eluted with the ternary mixture methanol-acetonitrile-water (40:30:30, v/v/v), with UV detection at 260 nm. Oxovanadium(IV), iron(III), copper(II), cobalt(II), nickel(II) and palladium(II) were completely separated and did not interfere in the determination of uranium. The linear calibration range and detection limits have been obtained. The method has been applied to the determination of uranium together with copper, iron and nickel in mineral ore samples.     

Synthesis, spectral characterization, solution equilibria, in vitro antibacterial and cytotoxic activities of Cu(II), Ni(II), Mn(II), Co(II) and Zn(II) complexes with Schiff base derived from 5-bromosalicylaldehyde and 2-aminomethylthiophene

Schiff base namely 2-aminomethylthiophenyl-4-bromosalicylaldehyde (ATS)(4-bromo-2-(thiophen-2-yl-imino)methylphenol) and its metal complexes have been synthesized and characterized by elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance, mass spectra, ESR and thermal analysis (TGA). The analytical data of the complexes show the formation of 1:2 [M:L] ratio of the formula [ML2], where M represents Ni(II), Zn(II) and Cu(II) ions, while L represents the deprotonated Schiff base. IR spectra show that ATS is coordinated to the metal ions in a bidentate manner through azomethine-N and phenolic-oxygen groups. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria. A cytotoxicity of the compounds against colon (HCT116) and larynx (HEP2) cancer cells have been studied. Protonation constants of (ATS) ligand and stability constants of its Cu2+, Co2+, Mn2+, Zn2+ and Ni2+ complexes were determined by potentiometric titration method in 50% (v/v) DMSO-water solution at ionic strength of 0.1 M NaNO3.     

New fluorescent chemosensors for heavy metal ions based on functionalized pendant arm derivatives of 7-anthracenylmethyl-1,4,10-trioxa-7,13-diazacyclopentadecane

Two new ligands 7-anthracenylmethyl-13-methylpyridyl-1,4,10-trioxa-7,13-diazacyclopentadecane (L4) and 7-anthracenylmethyl-13-(2,2-dimethyl-2-hydroxyethyl)-1,4,10-trioxa-7,13-diazacyclopentadecane (L(5)) have been synthesized and characterized. Both derive from 7-anthracenylmethyl-1,4,10-trioxa-7,13-diazacyclopentadecane (L(3)) and differ for having a differently functionalized pendant arm covalently attached to the remaining secondary nitrogen donor of the macrocyclic framework. The protonation and coordination behavior of L(4), L(5), and the unbranched L(3) with metal ions have been studied in MeCN/H2O (1:1 v/v, 298.1 K, I = 0.1 M) using potentiometric methods. The crystal structures of L(3), [(H2L(3))(HL(3))](ClO4)3, and the complex [CdL(3)(NO3)2] have been determined by single-crystal X-ray methods. The fluorescent behavior of L(3)-L(5) in the presence of Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) has been studied as a function of pH in MeCN/H2O (1:1 v/v). The presence of Cu(II), Hg(II), or Pb(II) does not affect the fluorescent behavior observed for the three free ligands upon changing the pH. Interestingly, the fluorescent emission of L(3) and L(5) is selectively enhanced only in the presence of Cd(II) at basic pH. The same effect is observed for L4 in the presence of Cd(II) or Zn(II) at about pH 7.     

Determination of the ubiquinol-10 and ubiquinone-10 (coenzyme Q10) in human serum by liquid chromatography tandem mass spectrometry to evaluate the oxidative stress

A method for the rapid and simultaneous determination of ubiquinone-10 (coenzyme Q10, CoQ(10)) and the reduced form ubiquinol-10 (CoQ(10)H(2)) in human serum by LC-MS-MS with electrospray ionization (ESI) in the positive mode is here proposed. High selective identification and sensitive quantitation of both analytes have been carried out by monitoring the transition from the corresponding precursor ion to the product ion. Prior to the chromatographic analysis, serum samples (100 microl) were subject to a conventional pre-treatment based on protein precipitation, liquid-liquid extraction, evaporation to dryness and reconstitution with 95:5 methanol/hexane (v/v). The overall method has enabled to achieve low detection limits--5.49 and 15.8 ng/ml for CoQ(10) and CoQ(10)H(2), respectively--which were estimated with serum. The accuracy and potential matrix effects have been studied with spiked serum resulting recoveries between 92.82 and 106.97%. The proposed method has been applied to serum samples from healthy middle-age women, in which the CoQ(10)H(2)/CoQ(10) ratio has been used as marker of oxidative stress.     

Development of liquid-liquid extraction and separation method for ruthenium(III) with 2-octylaminopyridine from succinate media: Analysis of catalysts

Ruthenium(III) has been efficiently extracted from 0.05 M sodium succinate at pH 9.5 by 2-octylaminopyridine in xylene and stripped with aqueous 10% (w/v) thiourea solution and determined spectrophotometrically. Various parameters viz., pH, weak acid concentration, reagent concentration, stripping agents, contact time, loading capacity, aq.: org. volume ratio, solvent has been thoroughly investigated for quantitative extraction of ruthenium(III). The utility of method was analyzed by separating the ruthenium(III) from binary mixture along with the base metals like Cu(II), Ag(I), Fe(II), Co(II), Bi(III), Zn(II), Ni(II), Se(IV), Te(IV), Al(III) and Hg(II) as well as platinum group metals (PGMs). Ruthenium(III) was also separated from ternary mixtures like Os(VIII), Pd(II); Pd(II), Pt(IV); Pd(II), Au(III); Pd(II), Cu(II); Fe(II), Cu(II); Ni(II), Cu(II); Co(II), Ni(II); Se(IV), Te(IV); Rh(III), Pd(II); Fe(III), Os(VIII). The stoichiometry 1: 2: 1 (metal: succinate: extractant) of the proposed complex was determined by slope analysis method by plotting graph of logD _[Ru(III)] versus logC _[2-OAP] and logD _[Ru(III)] versus logC _[succinate]. The interference of various cations and anions has been studied in detail and the statistical evaluations of the experimental results are reported. The method was successfully applied for the analysis of ruthenium in various catalysts, synthetic mixtures corresponding to the composition of alloys and minerals.     

Voltammetric determination of copper and lead in gasoline using sample preparation as microemulsions.

A voltammetric method for the determination of Cu(II) and Pb(II) in gasoline using sample preparation as three-component solutions (gasoline:propan-1-ol:water, 25:60:15 v/v/v) is proposed. HNO(3) was employed as a supporting electrolyte and to allow the use of aqueous inorganic standards for calibration, even if the analyte species originally in gasoline is present as a metallo-organic form. A square-wave anodic sequential determination was used by measuring the stripping current of Cu(II) (at +104 mV) using a glassy carbon electrode (GCE) and, in a second run, measuring the Pb(II) stripping current (at -470 mV) using a bismuth-film deposited on the surface of the GCE. The method allowed the quantification of 1.7 x 10(-9) mol L(-1) of Cu and 1.4 x 10(-10) mol L(-1) of Pb employing a 1500-s accumulation time. Recovery tests using analyte spiked three-component solutions prepared with commercial gasoline samples enabled recoveries of Cu and Pb from 97 +/- 8 to 102 +/- 5%.     

Kinetics and mechanism of zinc(II), cadmium(II), and mercury(II) incorporation into meso tetrameta-tolueneporphyrin

The kinetics of Zn(II), Cd(II), and Hg(II) incorporation into meso tetrameta-tolueneporphyri n (H₂T(m-CH₃)PP) in acetone have been studied by means of stopped-flow method. A unified reaction mechanism was proposed and the kinetic parameters were obtained by nonlinear least-square methods. The effect of ionic strength (I) on Cd(II)/H₂T(m-CH₃)PP was investigated. It has been found that there is a negative kinetic salt effect and the relationship of rate constants with ionic strength was obtained. Some solvent effects have also been investigated in this article. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 277–283, 1998.     

Ab initio molecular dynamics study on the electron capture processes of protonated methane (CH5+)

Electron capture dynamics of protonated methane (CH5(+)) have been investigated by means of a direct ab initio molecular dynamics (MD) method. First, the ground and two low-lying state structures of CH5 (+) with eclipsed Cs , staggered Cs and C2v symmetries were examined as initial geometries in the dynamics calculation. Next, the initial structures of CH5 (+) in the Franck-Condon (FC) region were generated by inclusion of zero point energy and then trajectories were run from the selected points on the assumption of vertical electron capture. Two competing reaction channels were observed: CH5 (+) + e (-)--> CH4 + H (I) and CH5 (+) + e (-) --> CH3 + H2 (II). Channel II occurred only from structures very close to the s- Cs geometry for which two protons with longer C-H distances are electronically equivalent in CH5 (+). These protons have the highest spin density as hydrogen atoms following vertical electron capture of CH5 (+) and are lost as H2. On the other hand, channel I was formed from a wide structural region of CH5 (+). The mechanism of the electron capture dynamics of CH5 is discussed on the basis of the theoretical results.     

Potentiometric study on the complex equilibria between ni(ii) and mn(ii) and 3-(2-furyl)-2-mercaptopropenoic and 3-(2-furyl)-2-mercaptopropanoic acids

Complex formation between Ni(II), Co(II) and Mn(II) and 3-(2-furyl)-2-mercaptopropenoic and 3-(2-furyl)-2-mercaptopropanoic acids has been studied using glass electrode potentiometry. Ligand-metal ion mixtures in 10% (v/v) ethanol-water containing 0.1 mol dm^–3KNO₃ were titrated with potassium hydroxide. The e.m.f. data obtained have been analyzed using the linearization method, and initial estimates of protonation constants for the ligands and complex formation constants have been refined with the MINIQUAD program.     

Mixed metal hydroxycarboxylic acid complexes. Spectrophotometric study of complexes of U(VI) with In(III), Cu(II), Zn(II) and Cd(II)

The formation of mixed metal complexes between uranium (VI), as the central metal ion, and aluminium (III), indium (III), copper (II), zinc (II) and cadmium (II), as the additional metal ions, with a hydroxycarboxylic acid chosen between citric, tartaric or malic, has been studied using spectrophotometric methods.The effect of pH has been examined, and the results show that at pH=4 stable complexes are formed for most of the systems. At this pH the method of mole ratio and Job's method of continuous variations, were employed to determine the stoichiometry of the mixed metal complexes. Al(III), In(III) and Cu(II) showed a high tendency to form mixed metal complexes with U(VI), while the formation of complexes is uncertain for Cd(II) and Zn(II). The ratio of the ligand to the total metal ion has been found to be 21 and metal:metal ratios of 11 and 12 have been observed.Represents part of the Ph.D. thesis submitted by Emanuel Manzurola to Ben Gurion University of the Negev.     

Preparation and separation of metallobacteriochlorophylla by reversed-phase high-performance liquid chromatography

Summary Semi-preparative high-performance liquid chromatography has been used for the preparation of copper(II) bacteriochlorophylla [Cu(II)-BChl-a] and zinc(II) bacteriochlorophylla [Zn(II)-BChl-a]. Both compounds are separated on a reversed-phase Inertsil ODS-2 column using a mobile phase of acetone-methanol (2575, v/v). The fractionated metallobacteriochlorophylls (M-Bchl-a) are identified by fast atom bombardment mass spectrometry. The spectroscopic parameters such as the wavelength of absorption maxima and the molar extinction coefficients are determined using pure M-Bchl-a obtained by preparative HPLC. The HPLC method proposed here has been demonstrated to be useful for the purification and determination of components of M-Bchl-a.     

Studies on complex formation between curcumin and Hg(II) ion by spectrophotometric method: A new approach to overcome peak overlap

Complex formation between curcumin and Hg(II) ion MeOH/H₂O (1: 1 v/v) was investigated and monitored by the spectrophotometric method. The absorption peak of unreacted curcumin which was close and overlapped with that of the complex, was removed by calculation using Microsoft Excel, thereby, allowing determination of the stoichiometry of the complex by the mole-ratio and the Job’s continuous variation methods. Both methods indicated that a 1:1 complex of curcumin and Hg(II) was formed in solution. The formation constant of the 1:1 Hg(II) complex was obtained from two methods, the equilibrium concentration calculation and the linear plot of Benesi-Hildebrand equation, as log K = 4.44 ± 0.16 and 4.83 ± 0.02, respectively. The structure is proposed as a tetrahedral complex of Hg(II) with one curcumin and two chloride ions as ligands. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.     

Determination of haloperidol and reduced haloperidol in human serum by liquid chromatography after fluorescence labeling based on the Suzuki coupling reaction

A simultaneous method for the determination of haloperidol (HP) and its metabolite, reduced haloperidol (RHP), in human serum was developed by means of high-performance liquid chromatography (HPLC) with fluorescence detection. Suzuki coupling reaction with a fluorescent arylboronic acid, 4-(4,5-diphenyl-1H-imidazol-2-yl)phenylboronic acid (DPA), was employed to convert HP and RHP into highly fluorescent compounds. HP and RHP were extracted from human serum by liquid-liquid extraction with a mixture of n-hexane and isoamyl alcohol (99:1, v/v) and subsequently labeled by reaction with DPA. Separation of DPA derivatives of HP and RHP was performed on a silica column with a mixture of acetonitrile and H(2)O (90:10, v/v) containing triethylamine and acetic acid as a mobile phase. The proposed method allowed sensitive detection of HP and RHP in human serum with a detection limit (at a signal to noise ratio of 3) of 0.22 and 0.20 ng/mL, respectively. The applicability of the method for therapeutic drug monitoring (TDM) was demonstrated by analyzing human serum samples from schizophrenic patients receiving HP.