George Horvai - Academia.edu (original) (raw)
Papers by George Horvai
Journal of Chromatography A, Dec 1, 2005
Molecularly imprinted polymers (MIP) have recently been prepared inside the pores of silica based... more Molecularly imprinted polymers (MIP) have recently been prepared inside the pores of silica based HPLC packing materials. Detailed physical and chromatographic characterization of such a silica-MIP composite material is presented. The chromatographic peak shape obtained with the uniformly sized spherical silica-MIP composite is mainly determined by the nonlinear adsorption isotherm. Comparison of the composite with the conventional sieved and grinded bulk MIP is therefore based on the nonlinear isotherm and not on retention factors and plate numbers.
Chemia Analityczna, 2005
A critical assessment of the suitability ofmolecularly imprinted polymers (MIP) for HPLC and bind... more A critical assessment of the suitability ofmolecularly imprinted polymers (MIP) for HPLC and binding assays is presented. The goal of this paper is to draw attention to a few simple facts about MIPs which are relevant foran analytical chemist but which have apparently not yet been collected in such concise form.
Journal Of Macromolecular Science, Part A, Apr 1, 1972
Analytica Chimica Acta, Aug 1, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Journal of Chromatography A, Jun 1, 2006
Molecularly imprinted polymers (MIPs) have frequently been characterized by quantities which are ... more Molecularly imprinted polymers (MIPs) have frequently been characterized by quantities which are easily determined from experiments but have no theoretical foundation. This makes it difficult to compare different MIP preparations or to transfer MIP based methods to different experimental conditions. Since the adsorption isotherms of MIPs are markedly nonlinear, one can build a better characterization strategy on isotherms as shown by examples in this paper.
Analytica Chimica Acta, Dec 1, 1976
Two types of commercial lead(II)-selective electrode, the Orion 94-82 and the R%iSka lead Selectr... more Two types of commercial lead(II)-selective electrode, the Orion 94-82 and the R%iSka lead Selectrode, are compared. Calibration curves were determined in both buffered and unbuffered lead-ion solutions repeatedly for several weeks. Selectivities with respect to copper(silver(I), mercury(II), lron(III), zinc and cadmium were examined as well as the pH response by the mixed solution method. The response times of the electrodes were also studied.
Analytica Chimica Acta, Feb 1, 2008
A molecularly imprinted polymer (MIP) for the template phenytoin has been prepared by gamma initi... more A molecularly imprinted polymer (MIP) for the template phenytoin has been prepared by gamma initiated copolymerization of methacrylamide and ethylene glycol dimethacrylate. The progress of polymerization was studied by measuring the monomer conversions and the template binding properties of the resulting polymers, respectively. The consumption rate of the two monomers showed different course. There was no difference observed in the polymerization rates of the MIP and the control polymer (NIP). The template binding properties of the MIP and the NIP changed considerably with the progress of the polymerization process and became similar to those of the thermally initiated polymers after full conversion.
Journal of Physical Chemistry C, Jun 19, 2019
Amphiphilic surfactants are changing the surface tension of solutions by adsorbing at its surface... more Amphiphilic surfactants are changing the surface tension of solutions by adsorbing at its surface. In general, however, little is known about the actual distribution of the surface tension across the interface, as well as about the extent of the contribution of different moieties to the surface tension. Here, we consider the liquid-vapor interface of the solutions of five different amphiphilic molecules, representative of anionic, cationic and non-ionic (alcoholic) surfactants. We investigate, by means of molecular dynamics simulation, the contribution of various chemical species and moieties to the surface tension distribution in these aqueous solutions at various surface coverages. We find that the headgroups of alcoholic surfactants give a negligible contribution to the surface tension. The opposite is true for ionic surfactants, whose effect depends on their 'hardness' within the Hofmeister series, even though there is a large compensation between ions and counterions. In addition, we find that water molecules contribute negatively to the surface tension when they are hydrating the ionic headgroups and counterions, instead of being exposed to the vapor phase.
Journal of Physical Chemistry B, Jun 1, 2005
The orientational order of the molecules at the liquid-vapor interface of acetone has been invest... more The orientational order of the molecules at the liquid-vapor interface of acetone has been investigated by computer simulation. To fully describe the orientational preferences of the acetone molecules, the bivariate joint distribution of two independent orientational parameters has been determined at different layers of the interface. The strength of the orientational ordering of the interfacial molecules has been found to be liquid-like rather than crystal-like. The obtained results have revealed that the interfacial acetone molecules have dual orientational preferences. The main symmetry axis of the molecules declines by about 50-70 degrees from the interface normal axis, pointing toward the liquid phase in both of the preferred orientations. However, the plane of the molecules in the orientation preferred on the liquid side of the interface is perpendicular to the interfacial plane, whereas the other preferred orientation, which is present on the vapor side of the interface, corresponds to the alignment obtained from this orientation by an almost 90 degrees rotation around the main symmetry axis. Because the population of the liquid side is higher than that of the vapor side of the interface, the first of the two preferred orientations is the dominant alignment over the entire interface, in good agreement with recent experimental findings (Chen, H.; Gan, W.; Wu, B. H.; Wu, D.; Zhang, Z.; Wang, H. F. Chem. Phys. Lett. 2005, 408, 284).
Journal of Physical Chemistry C, Nov 17, 2010
ABSTRACT
Journal of Physical Chemistry B, Oct 7, 2005
Monte Carlo simulation of the vapor-liquid interface of water-methanol mixtures of different comp... more Monte Carlo simulation of the vapor-liquid interface of water-methanol mixtures of different compositions, ranging from pure water to pure methanol, have been performed on the canonical (N, V, T) ensemble at 298 K. The analysis of the systems simulated has revealed that the interface is characterized by a double layer structure: methanol is strongly adsorbed at the vapor side of the interface, whereas this adsorption layer is followed at its liquid side by a depletion layer of methanol of lower concentration than in the bulk liquid phase of the system. The dominant feature of the interface has been found to be the adsorption layer in systems of methanol mole fractions below 0.2, and the depletion layer in systems of methanol mole fractions between 0.25 and 0.5. The orientation of the molecules located at the depletion layer is found to be already uncorrelated with the interface, whereas the methanol molecules of the adsorption layer prefer to align perpendicular to the interface, pointing straight toward the vapor phase by their methyl group. Although both the preference of the molecular plane for a perpendicular alignment with the interface and the preference of the methyl group for pointing straight to the vapor phase are found to be rather weak, the preference of the methyl group for pointing as straight toward the vapor phase as possible within the constraint imposed by the orientation of the molecular plane is found to be fairly strong. One of the two preferred orientations of the interfacial water molecules present in the neat system is found to disappear in the presence of methanol, because methanol molecules aligned in their preferred orientation can replace these water molecules in the hydrogen-bonding pattern of the interface.
Journal of Chromatography B: Biomedical Sciences and Applications, Sep 1, 1997
An automated analytical procedure is described for the parallel determination of L-3,4-dihydroxyp... more An automated analytical procedure is described for the parallel determination of L-3,4-dihydroxyphenylalanine (levodopa, L-dopa, LD) and the analogous hydrazine compound carbidopa (CD) in dog plasma by ion-pair high-performance liquid chromatography with electrochemical detection (HPLC-ED). After deproteinization of the plasma samples with perchloric acid the catecholamines were extracted from the supernatant by adsorption on a small column filled with alumina. The extraction and redissolution were automatically performed in a flow injection analysis unit (FIA) coupled to the HPLC system. The performance of the whole system was tested on dog plasma samples including specimens taken after oral administration of the anti-Parkinsonism drug Duellin, which is a combination tablet of levodopa and carbidopa.
Physical Chemistry Chemical Physics, 2004
ABSTRACT
Journal of Chemical Physics, Jul 16, 2002
The preferential orientation of the water molecules near the water/1,2-dichloroethane interface i... more The preferential orientation of the water molecules near the water/1,2-dichloroethane interface is analyzed in detail at different distances from the interface on the basis of a grand canonical ensemble Monte Carlo simulation. The orientation of the individual water molecules is described by the angular polar coordinates of the interface normal vector in a local coordinate frame fixed to the particular water molecule, and the bivariate joint distribution of the two polar angles is calculated. It is found that water molecules have two distinct orientational preferences, and these two preferences exist simultaneously among the water molecules penetrating farthest into the organic phase. In the first preferred orientation the plane of the molecule is parallel to the interface, whereas in the second the molecular plane is aligned perpendicularly to the interface and the molecular dipole vector declines from the plane parallel to the interface by about 30° pointing toward the organic phase. The first of the two preferred orientations is found to be present in the entire interfacial region and also, to a smaller extent, in the subsurface water layer adjacent to the interface. The second orientational preference is only present among the water molecules penetrating farthest into the organic phase. The two orientations correspond to the alignment of a hydrogen bonded pair of water molecules, in which the molecule located toward the aqueous phase has the first, whereas the one on the organic side the second of the two preferred orientations. The obtained picture is in a clear contrast with the findings of previous studies, in which the orientation of the water molecules was described by monovariate distributions of the alignment of one or more selected molecule-fixed vectors. In order to understand the origin of the difference between the present results and earlier findings we also calculate the monovariate distributions of the direction of three of such molecular vectors, i.e., the dipole vector of the water molecule, the vector joining the two H atoms, and the vector perpendicular to the molecular plane. The comparison of the obtained monovariate distributions with the bivariate joint distribution of the two polar angles reveals that the averaging of the bivariate distribution over any of its two angles completely obscures the dual orientational preference. The present study clearly points out the importance of choosing appropriate statistical distributions in the analysis of simulation results and demonstrates the pitfalls of averaging over too many variables.
Analytical Chemistry, Nov 1, 1986
Impedance measurements of the high-frequency bulk semicircle provide bulk resistance and geometri... more Impedance measurements of the high-frequency bulk semicircle provide bulk resistance and geometric capacitance values of two-and three-component membranes: plasticizer, poly(vinyl chiorlde) (PVC), and valinomycin in combinations. Intrinslc conductivity Is traced to previously postulated counterions from slightly dissoclated fixed sites in PVC. Bulk resistances of vaiinomycln-free membranes were determined for three commercial PVC types, at short soaking thnes. Bulk resistances increase with soaking times, but with different time dependences for KCI, NaCi, or pure H,O. Dielectric constants of membranes are always greater than for dry component values. Part of thls increase may depend on water content, but there is an increase from motion of plastlcized PVC chains, presumably C-Ci bonds. Responses are dominated by fixed sites and impurity counterions, modified by charge trapping in water regions (in the absence of carrier). Increased charge carrier concentration results from the presence of carriers that solubilize ions in the organic regions. Neutral carrier ion selective electrodes (ISEs), e.g., the K+-selective electrode with valinomycin as selective extractant/carrier, have been fabricated mainly with plasticized poly(viny1 chloride) (PVC) matrices (1,2). Typical membranes consist of 33 wt % PVC, 66% plastizicer, and 1% neutral carrier. Choices of plasticizer and of low-concentration additives, like sodium tetraphenylborate, have been optimized for several neutral carriers and sample matrices (2 , 3). PVC has been regarded as an inert matrix for the plasticizer to yield a structureless organic membrane that dissolves the neutral carrier (4). Studies of electrical properties of plasticized PVC, e.g., conductivity, dielectric constant, and dielectric loss,
Chemical Physics Letters, May 1, 2008
Molecular dynamics simulations of O 2 solvated at the vicinity of water/1,2-dichloroethane (DCE) ... more Molecular dynamics simulations of O 2 solvated at the vicinity of water/1,2-dichloroethane (DCE) and water/CCl 4 liquidliquid interfaces are reported. The distribution of oxygen along the interface normal is investigated. The results show that the choice of the algorithm ...
Analytical Letters, Apr 1, 1989
In quantitative analysis by direct potentioroetry. e.g. when using ion-selective electrodes, situ... more In quantitative analysis by direct potentioroetry. e.g. when using ion-selective electrodes, situations arise where corrections appear necessary to account Tor activity coefficient and liquid junction potential effects. It is shown here that one can select an optimal composition for the standard or reference solution and thereby achieve two goals simultaneously: to reduce the error terms to a minimum and to
Elsevier eBooks, 1989
ABSTRACT This study confirms and extends earlier results showing that neutral carrier ion-selecti... more ABSTRACT This study confirms and extends earlier results showing that neutral carrier ion-selective electrode membranes made from plasticized PVC are low capacity, selective ion-exchangers. The ion exchange selectivity constants agree well with the potentiometric selectivity coefficients. Ion exchange sites are attributed to ionizable impurities in the chemicals used for membrane preparations. Non-ionic surfactants incorporated into the membranes lead to the appearence of high interfacial resistance which behaves as charge transfer resistance.
Journal of Chromatography A, Dec 1, 2005
Molecularly imprinted polymers (MIP) have recently been prepared inside the pores of silica based... more Molecularly imprinted polymers (MIP) have recently been prepared inside the pores of silica based HPLC packing materials. Detailed physical and chromatographic characterization of such a silica-MIP composite material is presented. The chromatographic peak shape obtained with the uniformly sized spherical silica-MIP composite is mainly determined by the nonlinear adsorption isotherm. Comparison of the composite with the conventional sieved and grinded bulk MIP is therefore based on the nonlinear isotherm and not on retention factors and plate numbers.
Chemia Analityczna, 2005
A critical assessment of the suitability ofmolecularly imprinted polymers (MIP) for HPLC and bind... more A critical assessment of the suitability ofmolecularly imprinted polymers (MIP) for HPLC and binding assays is presented. The goal of this paper is to draw attention to a few simple facts about MIPs which are relevant foran analytical chemist but which have apparently not yet been collected in such concise form.
Journal Of Macromolecular Science, Part A, Apr 1, 1972
Analytica Chimica Acta, Aug 1, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Journal of Chromatography A, Jun 1, 2006
Molecularly imprinted polymers (MIPs) have frequently been characterized by quantities which are ... more Molecularly imprinted polymers (MIPs) have frequently been characterized by quantities which are easily determined from experiments but have no theoretical foundation. This makes it difficult to compare different MIP preparations or to transfer MIP based methods to different experimental conditions. Since the adsorption isotherms of MIPs are markedly nonlinear, one can build a better characterization strategy on isotherms as shown by examples in this paper.
Analytica Chimica Acta, Dec 1, 1976
Two types of commercial lead(II)-selective electrode, the Orion 94-82 and the R%iSka lead Selectr... more Two types of commercial lead(II)-selective electrode, the Orion 94-82 and the R%iSka lead Selectrode, are compared. Calibration curves were determined in both buffered and unbuffered lead-ion solutions repeatedly for several weeks. Selectivities with respect to copper(silver(I), mercury(II), lron(III), zinc and cadmium were examined as well as the pH response by the mixed solution method. The response times of the electrodes were also studied.
Analytica Chimica Acta, Feb 1, 2008
A molecularly imprinted polymer (MIP) for the template phenytoin has been prepared by gamma initi... more A molecularly imprinted polymer (MIP) for the template phenytoin has been prepared by gamma initiated copolymerization of methacrylamide and ethylene glycol dimethacrylate. The progress of polymerization was studied by measuring the monomer conversions and the template binding properties of the resulting polymers, respectively. The consumption rate of the two monomers showed different course. There was no difference observed in the polymerization rates of the MIP and the control polymer (NIP). The template binding properties of the MIP and the NIP changed considerably with the progress of the polymerization process and became similar to those of the thermally initiated polymers after full conversion.
Journal of Physical Chemistry C, Jun 19, 2019
Amphiphilic surfactants are changing the surface tension of solutions by adsorbing at its surface... more Amphiphilic surfactants are changing the surface tension of solutions by adsorbing at its surface. In general, however, little is known about the actual distribution of the surface tension across the interface, as well as about the extent of the contribution of different moieties to the surface tension. Here, we consider the liquid-vapor interface of the solutions of five different amphiphilic molecules, representative of anionic, cationic and non-ionic (alcoholic) surfactants. We investigate, by means of molecular dynamics simulation, the contribution of various chemical species and moieties to the surface tension distribution in these aqueous solutions at various surface coverages. We find that the headgroups of alcoholic surfactants give a negligible contribution to the surface tension. The opposite is true for ionic surfactants, whose effect depends on their 'hardness' within the Hofmeister series, even though there is a large compensation between ions and counterions. In addition, we find that water molecules contribute negatively to the surface tension when they are hydrating the ionic headgroups and counterions, instead of being exposed to the vapor phase.
Journal of Physical Chemistry B, Jun 1, 2005
The orientational order of the molecules at the liquid-vapor interface of acetone has been invest... more The orientational order of the molecules at the liquid-vapor interface of acetone has been investigated by computer simulation. To fully describe the orientational preferences of the acetone molecules, the bivariate joint distribution of two independent orientational parameters has been determined at different layers of the interface. The strength of the orientational ordering of the interfacial molecules has been found to be liquid-like rather than crystal-like. The obtained results have revealed that the interfacial acetone molecules have dual orientational preferences. The main symmetry axis of the molecules declines by about 50-70 degrees from the interface normal axis, pointing toward the liquid phase in both of the preferred orientations. However, the plane of the molecules in the orientation preferred on the liquid side of the interface is perpendicular to the interfacial plane, whereas the other preferred orientation, which is present on the vapor side of the interface, corresponds to the alignment obtained from this orientation by an almost 90 degrees rotation around the main symmetry axis. Because the population of the liquid side is higher than that of the vapor side of the interface, the first of the two preferred orientations is the dominant alignment over the entire interface, in good agreement with recent experimental findings (Chen, H.; Gan, W.; Wu, B. H.; Wu, D.; Zhang, Z.; Wang, H. F. Chem. Phys. Lett. 2005, 408, 284).
Journal of Physical Chemistry C, Nov 17, 2010
ABSTRACT
Journal of Physical Chemistry B, Oct 7, 2005
Monte Carlo simulation of the vapor-liquid interface of water-methanol mixtures of different comp... more Monte Carlo simulation of the vapor-liquid interface of water-methanol mixtures of different compositions, ranging from pure water to pure methanol, have been performed on the canonical (N, V, T) ensemble at 298 K. The analysis of the systems simulated has revealed that the interface is characterized by a double layer structure: methanol is strongly adsorbed at the vapor side of the interface, whereas this adsorption layer is followed at its liquid side by a depletion layer of methanol of lower concentration than in the bulk liquid phase of the system. The dominant feature of the interface has been found to be the adsorption layer in systems of methanol mole fractions below 0.2, and the depletion layer in systems of methanol mole fractions between 0.25 and 0.5. The orientation of the molecules located at the depletion layer is found to be already uncorrelated with the interface, whereas the methanol molecules of the adsorption layer prefer to align perpendicular to the interface, pointing straight toward the vapor phase by their methyl group. Although both the preference of the molecular plane for a perpendicular alignment with the interface and the preference of the methyl group for pointing straight to the vapor phase are found to be rather weak, the preference of the methyl group for pointing as straight toward the vapor phase as possible within the constraint imposed by the orientation of the molecular plane is found to be fairly strong. One of the two preferred orientations of the interfacial water molecules present in the neat system is found to disappear in the presence of methanol, because methanol molecules aligned in their preferred orientation can replace these water molecules in the hydrogen-bonding pattern of the interface.
Journal of Chromatography B: Biomedical Sciences and Applications, Sep 1, 1997
An automated analytical procedure is described for the parallel determination of L-3,4-dihydroxyp... more An automated analytical procedure is described for the parallel determination of L-3,4-dihydroxyphenylalanine (levodopa, L-dopa, LD) and the analogous hydrazine compound carbidopa (CD) in dog plasma by ion-pair high-performance liquid chromatography with electrochemical detection (HPLC-ED). After deproteinization of the plasma samples with perchloric acid the catecholamines were extracted from the supernatant by adsorption on a small column filled with alumina. The extraction and redissolution were automatically performed in a flow injection analysis unit (FIA) coupled to the HPLC system. The performance of the whole system was tested on dog plasma samples including specimens taken after oral administration of the anti-Parkinsonism drug Duellin, which is a combination tablet of levodopa and carbidopa.
Physical Chemistry Chemical Physics, 2004
ABSTRACT
Journal of Chemical Physics, Jul 16, 2002
The preferential orientation of the water molecules near the water/1,2-dichloroethane interface i... more The preferential orientation of the water molecules near the water/1,2-dichloroethane interface is analyzed in detail at different distances from the interface on the basis of a grand canonical ensemble Monte Carlo simulation. The orientation of the individual water molecules is described by the angular polar coordinates of the interface normal vector in a local coordinate frame fixed to the particular water molecule, and the bivariate joint distribution of the two polar angles is calculated. It is found that water molecules have two distinct orientational preferences, and these two preferences exist simultaneously among the water molecules penetrating farthest into the organic phase. In the first preferred orientation the plane of the molecule is parallel to the interface, whereas in the second the molecular plane is aligned perpendicularly to the interface and the molecular dipole vector declines from the plane parallel to the interface by about 30° pointing toward the organic phase. The first of the two preferred orientations is found to be present in the entire interfacial region and also, to a smaller extent, in the subsurface water layer adjacent to the interface. The second orientational preference is only present among the water molecules penetrating farthest into the organic phase. The two orientations correspond to the alignment of a hydrogen bonded pair of water molecules, in which the molecule located toward the aqueous phase has the first, whereas the one on the organic side the second of the two preferred orientations. The obtained picture is in a clear contrast with the findings of previous studies, in which the orientation of the water molecules was described by monovariate distributions of the alignment of one or more selected molecule-fixed vectors. In order to understand the origin of the difference between the present results and earlier findings we also calculate the monovariate distributions of the direction of three of such molecular vectors, i.e., the dipole vector of the water molecule, the vector joining the two H atoms, and the vector perpendicular to the molecular plane. The comparison of the obtained monovariate distributions with the bivariate joint distribution of the two polar angles reveals that the averaging of the bivariate distribution over any of its two angles completely obscures the dual orientational preference. The present study clearly points out the importance of choosing appropriate statistical distributions in the analysis of simulation results and demonstrates the pitfalls of averaging over too many variables.
Analytical Chemistry, Nov 1, 1986
Impedance measurements of the high-frequency bulk semicircle provide bulk resistance and geometri... more Impedance measurements of the high-frequency bulk semicircle provide bulk resistance and geometric capacitance values of two-and three-component membranes: plasticizer, poly(vinyl chiorlde) (PVC), and valinomycin in combinations. Intrinslc conductivity Is traced to previously postulated counterions from slightly dissoclated fixed sites in PVC. Bulk resistances of vaiinomycln-free membranes were determined for three commercial PVC types, at short soaking thnes. Bulk resistances increase with soaking times, but with different time dependences for KCI, NaCi, or pure H,O. Dielectric constants of membranes are always greater than for dry component values. Part of thls increase may depend on water content, but there is an increase from motion of plastlcized PVC chains, presumably C-Ci bonds. Responses are dominated by fixed sites and impurity counterions, modified by charge trapping in water regions (in the absence of carrier). Increased charge carrier concentration results from the presence of carriers that solubilize ions in the organic regions. Neutral carrier ion selective electrodes (ISEs), e.g., the K+-selective electrode with valinomycin as selective extractant/carrier, have been fabricated mainly with plasticized poly(viny1 chloride) (PVC) matrices (1,2). Typical membranes consist of 33 wt % PVC, 66% plastizicer, and 1% neutral carrier. Choices of plasticizer and of low-concentration additives, like sodium tetraphenylborate, have been optimized for several neutral carriers and sample matrices (2 , 3). PVC has been regarded as an inert matrix for the plasticizer to yield a structureless organic membrane that dissolves the neutral carrier (4). Studies of electrical properties of plasticized PVC, e.g., conductivity, dielectric constant, and dielectric loss,
Chemical Physics Letters, May 1, 2008
Molecular dynamics simulations of O 2 solvated at the vicinity of water/1,2-dichloroethane (DCE) ... more Molecular dynamics simulations of O 2 solvated at the vicinity of water/1,2-dichloroethane (DCE) and water/CCl 4 liquidliquid interfaces are reported. The distribution of oxygen along the interface normal is investigated. The results show that the choice of the algorithm ...
Analytical Letters, Apr 1, 1989
In quantitative analysis by direct potentioroetry. e.g. when using ion-selective electrodes, situ... more In quantitative analysis by direct potentioroetry. e.g. when using ion-selective electrodes, situations arise where corrections appear necessary to account Tor activity coefficient and liquid junction potential effects. It is shown here that one can select an optimal composition for the standard or reference solution and thereby achieve two goals simultaneously: to reduce the error terms to a minimum and to
Elsevier eBooks, 1989
ABSTRACT This study confirms and extends earlier results showing that neutral carrier ion-selecti... more ABSTRACT This study confirms and extends earlier results showing that neutral carrier ion-selective electrode membranes made from plasticized PVC are low capacity, selective ion-exchangers. The ion exchange selectivity constants agree well with the potentiometric selectivity coefficients. Ion exchange sites are attributed to ionizable impurities in the chemicals used for membrane preparations. Non-ionic surfactants incorporated into the membranes lead to the appearence of high interfacial resistance which behaves as charge transfer resistance.