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A facile supported liquid membrane (SLM) system for the selective and efficient transport of silver ion is introduced. The SLM used is a thin porous polyvinyldifluoride membrane impregnated with hexathia-18-crown-6 (HT18C6) dissolved in nitrophenyloctyl ether. HT18C6 acts as a specific carrier for the uphill transport of Ag+ ion as its picrate ion paired complex through the SLM. In the presence of thiosulfate ion as a suitable stripping agent in the strip solution, transport of silver occurs almost quantitatively after 4 h. The selectivity and efficiency of silver transport from aqueous solutions containing other Mn+ cations such as Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Hg2+, Fe3+ and Cr3+ ions were investigated.

The oxidation of ketoconazole on a bare carbon paste electrode was studied voltammetrically. The results indicated that the process is irreversible and controlled by an adsorption-extraction process which allows the accumulation of the drug at the electrode surface. After the optimization of solution pH, accumulation variables and instrumental parameters, sensitive differential pulse and linear sweep voltammetric peaks were obtained whose peak currents were linearly proportional to the ketoconazole concentration over the ranges 2.4 x 10(-8)-4.8 x 10(-7) and 9.1 x 10(-7)-1.0 x 10(-5) M, respectively. Based on these findings, a simple procedure was developed for the determination of ketoconazole in human urine and formulations.

A simple, reliable and relatively fast method has been developed to selectively separate and concentrate trace amounts of lead from aqueous samples for the measurement by flame atomic absorption spectrometry. By the passage of aqueous samples through an octadecyl-bonded silica membrane disk modified by a recently synthesized bis(anthraquinone)sulfide, Pb(2+) ions adsorb quantitatively and almost all matrix elements will pass through the disk to drain. The retained lead ions are then stripped from the disk by minimal amount of acetic acid as eluent. The proposed method permitted large enrichment factors of about 300 and higher. The limit of detection of the proposed method is 50 ng Pb(2+) per 1000 ml. The effects of various cationic interferences on the recovery of lead in binary mixtures were studied. The method was successfully applied to the determination of lead in soil and water samples.

A PVC membrane sensor for cerium(III) ions based on 1,3,5-trithiane as membrane carrier was prepared. The sensor has a linear dynamic range of 1.0 x 10(-1)-5.0 x 10(-5) M, with a Nernstian slope of 19.4+/-0.4 mV decade(-1), and a detection limit 3.0 x 10(-5) M. It has a fast response time of < 15 s and can be used for at least 5 months without any considerable divergence in potentials. The proposed sensor revealed comparatively good selectivities with respect to alkali, alkaline earth, and some transition and heavy metal ions and could be used in a pH range of 5.0-8.0. It was used as an indicator electrode in potentiometric titration of oxalate and fluoride ions and in determination of F- ion in some mouth wash preparations.

A simple and reliable method has been developed to selectively separate and concentrate trace amounts of silver ion from aqueous samples for the subsequent measurement by atomic absorption spectrometry. Ag+ ions are absorbed quantitatively during passage of aqueous samples through an octadecyl-bonded silica membrane disk modified by hexathia-18-crown-6. Almost all matrix elements will pass through the disk to drain. The retained Ag+ ions are then stripped from the disk with a minimal amount of thiosulfate solution as eluent. The proposed method permitted large enrichment factors of about 200 and higher. The limit of detection of the proposed method is 50 ng Ag+ per 1,000 mL. The effects of various cationic interferences on the recovery of silver in binary mixtures were studied. The method was applied to the recovery of Ag+ ions from different synthetic and water samples.

A simple and reliable method for rapid extraction and determination of uranium in natural waters using octadecyl-bonded silica membrane disks modified with tri-n-octylphosphine oxide (TOPO) and spectrophotometry with dibenzoylmethane is presented. Extraction efficiency and the influence of sample matrix, type, and optimum amount of extractant, flow rates, and type and minimum amount of organic eluent were evaluated. The maximal capacity of the membrane disks modified by 50 mg of TOPO was found to be 4033 micrograms of uranium. The limit of detection of the proposed method is 100 ng/1000 mL. The method was applied to the extraction and determination of uranium in natural waters.

Eight different recently synthesized macrocyclic diamides were studied to characterize their abilities as strontium ion carriers in PVC membrane electrodes. The electrode based on 1,13-diaza-2,3;11,12-dibenzo-4,7,10-trioxacyclopentadecane-14,15-dione exhibits a Nernstian response for Sr(2+) ions over a wide concentration range (1.0 × 10(-)(1)-3.2 × 10(-)(5) M) with a limit of detection of 8.0 × 10(-)(6) M (0.7 ppm). The response time of the sensor is ∼10 s, and the membrane can be used for more than three months without observing any deviation. The electrode revealed comparatively good selectivities with respect to many alkali, alkaline earth, and transition metal ions. It was used as an indicator electrode in potentiometric titration of carbonate ions with a strontium ion solution.

A novel triiodide ion-selective electrode based on a charge-transfer complex of iodine with 2,4,6,8-tetraphenyl-2,4,6,8-tetraazabicyclo[3.3.0]octane as membrane carrier was prepared. The electrode has a linear dynamic range between 5.0 × 10(-)(2) and 3.5 × 10(-)(6) M, with a near-Nernstian slope of 54.7 ± 0.8 mV decade(-)(1) and a detection limit of 2.0 × 10(-)(6) M. The potentiometric response is independent of the pH of the solution in the pH range 4.0-10.5. The electrode possesses the advantages of low resistance, short conditioning time, fast response, and, especially, very good selectivities over a wide variety of other anions. The electrode can be used for at least 10 months without any considerable divergence in potentials. It was used as an indicator electrode in potentiometric titration of triiodide ions.

The solubility of four recently synthesized 1,8-dihydroxy-9,10-anthraquinone derivatives, as potential complexing agents in some extraction and membrane transport experiments, have been measured in supercritical carbon dioxide. The measurements were carried out in the pressure range 120-400 atm at temperatures 35, 45, 55, 65, and 75 degrees C. The measured solubilities were correlated using the model proposed by Chrastil. The calculated results show good agreement with the experimental data.

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 Pb(2+) over a wide concentration range (1.0x10(-2)-4.0x10(-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 Pb(2+) over a wide variety of other metal ions and could be used in a pH range of 2.0-7.0. It was used as an indicator electrode in potentiometric titration of lead ions and in direct determination of lead in water samples.

We give evidence for the formation of mixed-metal complexes of tetracarboxylate-18-crown-6 in the form of Al(3+)-macrocycle-M(Z+), with M(Z+) being an alkali or an alkaline earth cation. These binuclear systems are characterized by potentiometric p[H] titrations and the equilibrium constants for all major complexes formed are described. The results are presented in the form of distribution diagrams revealing the concentrations of individual complex species as a function of p[H]. The stability of the resulting mixed-metal complexes with Al(3+) and alkali and alkaline earth cations vary in the order Na(+)>K(+)>Cs(+) and Ca(2+)>Sr(2+)>Ba(2+). The complex behavior can be rationalized in terms of electrostatic interactions and direct coordination of the cations by the carboxylate groups from the crown ether periphery.

A method for rapid extraction and determination of some crown ethers in aqueous matrices using octadecyl-bonded silica membrane disks and gas chromatography is presented. Extraction efficiency and the influence of vacuum pressure. pH, and type and least amount of eluting solvent used to extract the crown ethers from the membrane disks were evaluated. Extraction efficiencies > 95% were obtained for benzo-15-crown-5, benzo-18-crown-6 and dicyclohexyl-18-crown-6 using 5 ml of acetonitrile as eluting solvent. The limit of detection of the proposed method for the determination of the crown ethers is reported.

The complex formation of Hg(2+) with some macrocyclic crown ethers in nitrobenzene, acetonitrile and dimethylformamide solutions was studied by differential pulse polarography at 25 degrees C. The stoichiometry and stability of the complexes were determined by monitoring the shift in the Hg(2+) differential pulse peak potential against the ligand concentration. The stability of the resulting 1:1 complexes vary in the order dicyclohexyl-18-crown-6 > 18-crown-6 > 15-crown-5 > dibenzo-18-crown-6 > dibenzo-24-crown-8 > benzo-15-crown-5 > 12-crown-4. There is an inverse relationship between the complex stability and the Gutmann donor number of solvents.

The fluorescent signal of T1(+) was employed as a sensitive probe to study the complexation reactions between this cation and several macrocyclic ligands in methanol solution at 20 degrees C. The stability constants of the resulting 1:1 complexes were determined and found to vary in the order C222 > C221 > 18C6 > DC18C6 > DB30C10 > DB18C6 > 15C5 > DA18C6 > B15C5 > DA15C5. The influence of a number of members in the macrocycle the nature of substituents on the polyether ring and of the dimensionality of the ligands on the stability and selectivity of the complexes is discussed.

The acidity constants of some synthetic derivatives of 9,10-anthraquinone and 9-anthrone in methanol-water mixtures at 25 degrees have been determined spectrophotometrically. A linear reverse relationship is observed between pK(a1) of all acids and the mole fraction of methanol. The influence of substituents in the molecular structure on the ionization constants is discussed.

The complexation reactions between Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions and benzo-15-crown-5, dicyclohexyl-18-crown-6, dibenzo-18-crown-6 and 1,10-diaza-18-crown-6 have been studied in dimethylsulphoxide solution at 25 degrees by means of a competitive spectrophotometric method using murexide as a metallochromic indicator. With the exception of Pb(II)(benzo-15-croqn-5)(2) the stoichiometry of the resulting complexes was found to be 1:1. The formation constants of the complexes were determined, and found to follow the Irving-Williams rule for the cations of the first transition series. It was found that the metal ion-18-crown interactions are strongly dependent on the nature of the substituents on the ring.

The complexation reactions between murexide and Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+) ions have been studied spectrophotometrically in dimethylsulphoxide solution at 25 degrees . The stoichiometry of the complexes was found to be 1:1. The stability constants of the complexes were determined, and found to follow the Irving-Williams rule for the cations of the first transition series. In dimethylsulphoxide solution, the complexes are much more stable than those in aqueous solution.

The concentration formation constant for the 1:1 complex between copper(II) and murexide in aqueous solutions has been measured as a function of ionic strength by spectrophotometry at 25 degrees . There is an inverse relationship between the K(c) values and ionic strength. The formation constant at infinite dilution was found to be 6.16 x 10(4). The distance of closest approach for the Cu(2+) ion was estimated as 4.3 +/- 0.3 A.

The complexation reactions between murexide and Co(2+), Ni(2+) and Cu(2+) in C(2)H(5)OH-H(2)O mixtures have been investigated spectrophotometrically. The formation constants of the 1:1 complexes formed increase in the order Co(2+) < Ni(2+) < Cu(2+) for all solvent mixtures studied, and log K(f) is a linear function of the mole fraction of ethanol. The heat of complexation was determined calorimetrically for the nickel and copper complexes. The values of DeltaH degrees and DeltaS degrees are solvent-dependent, and all three complexes have negative DeltaH degrees and positive DeltaS degrees values.

The complexes of murexide with alkali-metal cations have been studied spectrophotometrically in methanol, dimethylformamide and dimethylsulphoxide media at 25 degrees . The stoichiometry of the complexes was found to be 1:1. The formation constants of the complexes were determined, and found to decrease in the order Na(+) > K(+) > Rb(+) approximately Li(+) for all solvents studied. The complex formation constants varied inversely with the Gutmann donicity of the solvents.