Search results for "Potentiometric"
showing 10 items of 157 documents
Examination of the least-squares method applied to the evaluation of physicochemical parameters with linearized equations
1989
Physicochemical parameters are frequently evaluated by the least-squares method after linearization of the equation which relates the experimental variables to the parameters of interest. When a given set of data is treated to evaluate (n+1) parameters. (n+2) nominally identical linearized equations are possible; each of these leads to different sets of values of the parameters which are also affected by different variances. These differences are also observed when statistical weights are used. Two methods for establishing which one of the (n+2) equations is best for fitting the data, i.e., simulation of experiments and propagation of errors, are discussed, compared and applied to a potenti…
Aza–oxa macrocyclic ligands functionalised with naphthylmethyl fluorescent groups
2000
Abstract Compounds L 1 and L 2 were obtained by reaction of 2-(bromomethyl)naphthalene with 1,4,10-trioxa-7,13-diazacyclopentadecane and 1,4,7-trioxa-10-azacyclododecane, respectively. These receptors contain aza–oxa crowns attached covalently to fluorescent groups. The protonation and coordination behaviour of L 1 and L 2 against metal ions has been studied in dioxane:water (70:30 v/v, 25°C, 0.1 M potassium nitrate) using potentiometric methods. All metal ions studied form complexes with L 1 and L 2 with the logarithm of the formation constants L+M 2+ =[M(L)] 2+ in the sequence Cd 2+ ≅Pb 2+ , Zn 2+ 2+ for L 1 and Zn 2+ 2+ 2+ 2+ 2+ for L 2 . The fluorescent behaviour of L 1 and L 2 was stud…
Sequestering ability of polyaminopolycarboxylic ligands towards dioxouranium(VI) cation
2006
Abstract In the present paper, some results of an investigation (at t = 25 °C by potentiometry, ISE-H+ glass electrode) on the sequestering ability of five different polyaminopolycarboxylic ligands [Nitrilotriacetate (NTA), ethylenediamine-N,N,N′,N′-tetraacetate (EDTA), ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetate (EGTA), diethylenetriamine-N,N,N′,N″,N″-pentaacetate (DTPA), triethylenetetraamine-N,N,N′,N″,N′′′,N′′′-hexaacetate (TTHA)] towards dioxouranium(VI) cation in sodium chloride aqueous solutions, at I = 0.7 mol L−1 are reported. Calculations performed on potentiometric data gave evidence of the formation of the following species (log β in parenthesis): UO2(NTA)H0 (12…
Protocol for development of various plants leaves extract in single-pot synthesis of metal nanoparticles
2012
This article is aimed to extend a simple protocol for preparation of various plant leaves extract and their application to green synthesis of the metallic nanoparticles. Five plant leaves extract showed mild reduction and stabilization ability for silver and gold nanoparticles (AgNPs and AuNPs) at room temperature. The particle size range varied from 25 to 42 nm and 21 to 47 nm for AgNPs and AuNPs, respectively. Plant leaves extract-mediated nanoparticles were characterized to confirm the shape, size, crystallinity, and content using different spectroscopic investigations. Differences in stability of nanoparticles at different pH were also measured by zeta potential.
Protonation constants and association of polycarboxylic ligands with the major components of seawater
2000
Apparent protonation constants, log βjH*, of 11 carboxylic acids were determined potentiometrically ([H+]-glass electrode) in artificial seawater containing six of the major components (Na+, K+, Mg2+, Ca2+, Cl-, and SO42-) at different salinities: S (‰) = 5, 15, 25, 35, 45. Values of log βjH* were fitted by the simple polynomial equation log βjH* = log TβjH + a1S1/2 + a2S + a3S3/2 (log TβjH = protonation constants at infinite dilution; a1, a2, a3 = empirical parameters), for mono-, di-, and tricarboxylates. For carboxylic anions with charge < −3, a better fit was obtained using the equation log βjH* = log TβjH + b1I + b0z* log(1 + b2I) (b0, b1, b2 = empirical parameters, z* = square sum of…
Interaction of the Dioxouranium(VI) Ion with Aspartate and Glutamate in NaCl(aq) at Different Ionic Strengths
2005
The formation of complexes species of the dioxouranium(VI) ion with aspartic and glutamic acids was studied in the pH range of 3 to 6 at 25 °C by potentiometric measurements (H+−glass electrode). R...
Unusual binding ability of α,β-dehydrodipeptides towards metal ions
1994
Abstract Ni II , Zn II and Co II complexes of α,β-dehydro-dipeptides (containing Gly, Leu, Ala, Val or Phe residues) were studied by potentiometric and spectroscopic methods. Deprotonation and coordination of amide nitrogens occurred in all cases around the physiological pH range. The dipeptides with composition of Xaa-Δ-Ala formed octahedral species, while Gly-Δ-Xaa (Xaa = Leu or Phe) formed square planar bis complexes with Ni II .
Extended structures of copper(II) complexes with 2-di1H-2-imidazolylmethylmalonate (DIMMAL), a versatile bis(imidazole)–bis(carboxylate) ligand: Solu…
2008
Abstract Copper(II) complexes of 2-di1H-2-imidazolylmethylmalonate (DIMMAL) have been studied by potentiometric methods. The data revealed that the CuHL 2 - and CuL 2 2 - species are prevalent in the studied pH range. Moreover, this paper reports the synthesis, structure solution and spectroscopic characterization of two new DIMMAL containing complexes, (NH4)2[Cu(DIMMAL)2] · 4H2O (1) and [Cu(DIMMAL)(en)(H2O)] · 5H2O (2). The structure of compound 1 consists of centrosymmetric mononuclear anionic [Cu(DIMMAL)2]2− units, NH 4 + cations and lattice water molecules, in which DIMMAL2− acts as a tridentate ligand through two imidazole nitrogen atoms and one oxygen atom from a carboxylate group. Th…
(o-Hydroxyphenyl)methylphosphonic acids: Synthesis and potentiometric determinations of their pKaValues
1993
(o-Hydroxyphenyl)methylphosphonic acids are readily obtained from o-(bromomethyl)- or o-(hydroxymethyl)phenols and trialkyl phosphites. Subsequent hydrolysis leads to the corresponding phosphonic acids. For a series of such compounds, the pKa values have been determined by potentiometry. Their dependence on additional substituents in the aromatic ring is discussed in terms of electronic and steric effects.
Electrochemical determination of boron in minerals and ceramic materials
2004
Abstract A method for quantitatively determining boron in minerals and ceramic materials is described. It is based on the abrasive attachment of mixtures of ZnO plus sample to PIGEs. After a reductive deposition step, square wave voltammograms recorded for those modified electrodes immersed into 0.10 M NaCl+0.25 M mannitol provide well-defined stripping peaks at −0.85 and −0.15 V vs. AgCl/Ag for the oxidation of Zn and B, respectively. The quotients between the peak areas and the peak currents for the stripping oxidation of B and Zn vary linearly with the molar ratio of B and Zn in the mixture, thus providing an electrochemical method for determining the boron content in solid samples. Resu…