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The potentiometric determination of the protonation constant of 2-chlorophenol in NaCl media at different ionic strengths and its distribution coefficient between these media and two organic solvents at 25 o C are presented. An automated potentiometric system was used, and the determination of the constants was carried out using both graphical and numerical methods. A thermodynamic model...
The reaction between tetrabutylammonium periodate and phenothiazine in the presence of the strong acids in chloroform was studied by potentiometry and the reaction pathways were determined. The oxidimetric titration conditions of phenothiazine derivatives using a standardized chloroform solution of tetrabutylammonium periodate were optimized and a potentiometric detection of end points was utilized...
A novel iodide ion-selective electrode has been produced based on a molecular deposition technique in which water-soluble porphyrin was alternatively deposited with water-soluble polypyrrole on a 2-aminoethanethiol modified silver electrode. The potentiometric response is independent of pH of the solution between pH 1 and 7, while it is dependent on the nature of the medium. The electrode has a linear...
Cesium ion-selective PVC membrane electrodes based on anilino-(1,3-dioxo-2-indanylidene) acetonitrile derivatives as a novel class of neutral ionophores were examined. The ionophores were p-methoxyanilino-(1,3-dioxo-2-indanylidene) acetonitrile, p-methylanilino-(1,3-dioxo-2-indanylidene) acetonitrile and p-N,N-dimethylanilino-(1,3-dioxo-2-indanylidene) acetonitrile. The anilino-(1,3-dioxo-2-indanylidene)...
A PVC membrane electrode for lead ions based on 5,5′-dithiobis-(2-nitrobenzoic acid) as membrane carrier was prepared. The electrode exhibits a Nernstian response for Pb2+ over a wide concentration range (1.0×10−2–4.0×10−6 M). It has a relatively fast response time and can be used for at least 3 months without any divergence in potentials. The proposed electrode revealed good selectivities for Pb2+...
We examined the variation with ionic strength (I, adjusted with KCl, KNO3, KBr, NaCl or NaClO4) of the formal potential (Econst) for glass electrodes exhibiting a Nernstian response (i.e. Ecell=Econst−slog[H+]). For this purpose, we investigated the different factors included in the formal potential, so we obtained reported values for the liquid junction potential as a function of ionic strength and...
A flow injection potentiometric method for the rapid determination of paraquat in herbicide formulations and biological samples is described. It is based on the utilization of a flow-through potentiometric detector containing polyvinyl chloride-immobilised octamethylcyclotetrasiloxane, a lipophilic plasticizer (tetra-n-undecyl 3,3′,4,4′-benzophenone tetracarboxylate) and membrane additive potassium...
A recently developed methodology for the determination of ion exchange equilibrium constants has been applied to ion exchange systems of 1:2 stoichiometry. Potentiometric titrations with variable ionic strength were carried out. Ionic medium titrations were performed for the estimation of the liquid junction potential. The modified Bromley's methodology and the Wilson model were used for the estimation...
The basicity of the symmetrical and unsymmetrical tetraphenylporphyrins, namely 5,10,15,20-tetraphenylporphyrin (I) (references), 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin (II), a mixture of 5,10-bis(4-nitrophenyl)-15,20-diphenylporphyrin and 5,15-bis(4-nitrophenyl)-10,20-diphenylporphyrin (III), 5,10,15-tris(4-nitrophenyl)-20-phenylporphyrin (IV), 5,10,15,20-tetrakis(4-nitrophenyl)porphyrin (V),...
The formation and stability of protonated spermidine and spermine-carboxylic ligand complexes (seven systems) were studied potentiometrically (H + -glass electrode). ALH r species are formed (A=spermidine, spermine, L z- =acetate, malonate, 1,2,3-propanetricarboxylate, 1,2,3,4-butanetetracarboxylate; r=1...m+n-1, where m and n are the maximum degree of protonation of the...
The response characteristics of some iodide-selective solvent polymeric membrane electrodes based on with N,N′-bis(salicylaldehyde-n-octyl) diimine cobalt(II) (Co(II)SAODI) which is a more lipophilic substitute for a previously reported iodide-carrier are described. The electrode doped with Co(II)SAODI into a plasticized poly(vinyl chloride) membrane exhibits an anti-Hofmeister selectivity pattern...
Acid-base equilibria in ethanol-aqueous solution of 5-acetamido-1,3,4-thiadiazole-2-sulfonamide (acetazolamide, H 2 acm), 5-tertbutyloxycarbonylamido-1,3,4-thiadiazole-2-sulfonamide (B-H 2 ats), 5-amino-1,3,4-thiadiazole-2-sulfonamide (Hats) and 5-amino-1,3,4-thiadiazole-2-thiol (Hatm) at 25 o C, 0.15 mol dm -3 ionic strength (NaNO 3 ), have been investigated...
A new computer program (GLEE, glass electrode evaluation) has been written for the calibration of a glass electrode by means of a strong acid-strong base titration. This program provides an estimate of the carbonate contamination of the base, the pseudo-Nernstian standard potential and slope of the electrode and, optionally, the concentration of the base and pK W. The program runs under...
A fast method for sample treatment of phosphate rock has been developed for the purpose of quantitative leaching (98-100%) of fluoride but less of the interfering cations such as iron and aluminum. Citric acid (0.5 M) was used to extract fluoride in 15-45 min. Leaching of iron and aluminum is minimal, and these ions are complexed with citric acid. The leaching method was optimized with respect to...
Flow injection methods utilising the Karl Fischer (KF) reaction with spectrophotometric and potentiometric detection are described for the determination of the trace water content in various organic solvents. Optimisation of the methods resulted in an accessible (linear) working range of 0.01-0.2% water for many solvents studied with a typical precision of 1-2% R.S.D. Only 50 μl of organic solvent...
An enzymatically modified ammonium ion-selective electrode has been applied for the determination of urea in spent dialysate. The biosensor has been used in a simple flow-injection analysis (FIA) system. The system enables one to perform over 25 dialysate urea nitrogen (DUN) determinations per hour. The interferences from other components of posthemodialysis fluid were eliminated by simultaneous measurements...
Mercury (II) ion-selective PVC membrane sensor based on ethyl-2-benzoyl-2-phenylcarbamoyl acetate (EBPCA) as a novel nitrogen containing sensing material is successfully developed. The sensor exhibits good linear response of 30 mV per decade within the concentration range 10 -6 -10 -3 mol l -1 Hg(II). The sensor shows good selectivity for mercury (II) ion in...
In this paper, the construction and evaluation of an electrode selective to nitrate with improved sensitivity, constructed like a conventional electrode (ISE) but using an operational amplifier to sum the potentials supplied by four membranes (ESOA) is described. The two types of electrodes, without an inner reference solution, were constructed using tetraoctylammonium bromide as sensor, dibutylphthalate...
A new polyvinylchloride membrane sensor for Cd 2+ ions based on tetrathia-12-crown-4 as an ionophore was prepared. The sensor exhibits a Nernstian response for cadmium ions over a wide concentration range (4.0x10 -7 to 1.0x10 -1 M) with a slope of 29+/-1 mV decade -1 . The limit of detection is 1.0x10 -7 M (0.01 ppm). It has a fast response...
A potentiometric sensor based on the use of titanium phosphate (TP) in epoxy matrix membrane is prepared and characterized. The sensor exhibits near-Nernstian response for many anionic species over the concentration range 10 -1 -10 -5 mol l -1 . The origin of response is explained on the basis of the conversion of titanium phosphate cation exchanger into hydrated...
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