Potentiometric Membrane Electrodes Research Articles

Hg(II) Ion-Selective Electrodes with PVC Membranes Based on Bis-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one

Abstract A new solid-state contact potentiometric membrane electrode was developed based on bis-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (ionophore), which acts selectively towards the mercury(II) ion. The ionophore was synthesized by the treatment of an amino derivative with oxybis dibenzaldehyde. The potentiometric behavior of an electrode was investigated in the concentration range from 1.0 × 10−2 to 1.0 × 10−6 mol L−1 for mercury(II) ion. The electrode displayed a good linearity (R2 = 0.9997) with the detection limit of 1.2 × 10−7 mol L−1 and showed a very high selectivity against Hg(II) ion without being affected by the presence of interfering ions. The electrode exhibited a potential change of 62.0 ± 2.0 mV for each ten-fold increase in concentration of mercury(II) ion. Potentiometric response of the electrode was investigated in the pH range from 3.0 to 10.0. In addition to this electrode being used to determine mercury(II) in different water samples, it can also be used with EDTA as an indicator electrode in the potentiometric titration of mercury(II) ion. Since the developed electrode displayed good potentiometric performance, it has potential to be used in environmental and biological samples for detection of mercury(II) ions.

All-solid-state potentiometric sensors with a multiwalled carbon nanotube inner transducing layer for anion detection in environmental samples.

While ion to electron transducing layers for the fabrication of potentiometric membrane electrodes for the detection of cations have been well established, similar progress for the sensing of anions has not yet been realized. We report for this reason on a novel approach for the development of all-solid-state anion selective electrodes using lipophilic multiwalled carbon nanotubes (f-MWCNTs) as the inner ion to electron transducing layer. This material can be solvent cast, as it conveniently dissolves in tetrahydrofuran (THF), an important advantage to develop uniform films without the need for using surfactants that might deteriorate the performance of the electrode. Solid contact sensors for carbonate, nitrate, nitrite, and dihydrogen phosphate are fabricated and characterized, and all exhibit comparable analytical characteristics to the inner liquid electrodes. For example, the carbonate sensor exhibits a Nernstian slope of 27.2 ± 0.8 mV·dec(-1), a LOD = 2.3 μM, a response time of 1 s, a linear range of four logarithmic units, and a medium-term stability of 0.04 mV·h(-1) is obtained in a pH 8.6 buffered solution. Water layer test, reversibility, and selectivity for chloride, nitrate, and hydroxide are also reported. The excellent properties of f-MWCNTs as a transducer are contrasted to the deficient performance of poly(3-octyl-thiophene) (POT) for carbonate detection. This is evidenced both with a significant drift in the potentiometric measures as well as a pronounced sensitivity to light (either sunlight or artificial light). This latter aspect may compromise its potential for environmental in situ measurements (night/day cycles). The concentration of carbonate is determined in a river sample (Arve river, Geneva) and compared to a reference method (automatic titrator with potentiometric pH detection). The results suggest that nanostructured materials such as f-MWCNTs are an attractive platform as a general ion-to-electron transducer for anion-selective electrodes.

Design of Potentiometric Sensors Based on Interaction of Cyclodextrins with the Enantiomer of Interest

Five enantioselective sensors based on α-, β-, carboxymethyl-β-(as sodium salt), 2-hydroxyl-3-trimethylammoniopropyl -β-(as chloride salt) and γ-cyclodextrins were designed based on results of their molecular interaction with the S- and R-enantiomers of ketoprofen obtained using SPR (surface plasmon resonance) based sensors. SPR proved to be an excellent technique for selecting the best chiral selectors. The best sensor was the one based on β-cyclodextrin. Low detection limits (of 10-8 to 10-9 magnitude orders) were recorded with the enantioselective, potentiometric membrane electrodes. Keywords: Cyclodextrin, enantioanalysis, enantioselective, potentiometric membrane electrode, S-ketoprofen, surface plasmon resonance.

Enantioselective, Potentiometric Membrane Electrodes Based on C70 Fullerenes for the Enantioanalysis of S-Clenbuterol in Serum

Two enantioselective, potentiometric membrane electrodes (EPMEs) based on carbon paste impregnated with [5-6] fullerene-C70 (I) and diethyl (1,2-methanofullerene C70)-71-71-dicarboxylate (II) for the enantioanalysis of S-clenbuterol are reported. The electrodes exhibited near-Nernstian (higher than 55.00 mV/decade of concentration) responses only over S-clenbuterol in the following concentration ranges: 10−10 – 10−5 and 10−9 – 10−4 mol/L, for (I) and (II), respectively. The limits of detection were of 10−11 and 10−10 mol/L magnitude order, for EPMEs based on (I) and (II), respectively. The proposed electrodes proved to be successful for the enantioanalysis of S-Clenbuterol as raw material and from serum samples: average recovery of S-Clen in serum samples being higher than 98.40%, with RSD values not exceeding 1.25%.

Synthesis of nano-sized arsenic-imprinted polymer and its use as As3+ selective ionophore in a potentiometric membrane electrode: Part 1

In this study, a new strategy was proposed for the preparation of As (III)-imprinted polymer by using arsenic (methacrylate)3 as template. Precipitation polymerization was utilized to synthesize nano-sized As (III)-imprinted polymer. Methacrylic acid and ethylene glycol dimethacrylate were used as the functional monomer and cross-linking agent, respectively. In order to assembly functional monomers around As (III) ion, sodium arsenite and methacrylic acid were heated in the presence of hydroquinone, leading to arsenic (methacrylate)3. The nano-sized As (III) selective polymer was characterized by FT-IR and scanning electron microscopy techniques (SEM). It was demonstrated that arsenic was recognized as As3+ by the selective cavities of the synthesized IIP. Based on the prepared polymer, the first arsenic cation selective membrane electrode was introduced. Membrane electrode was constructed by dispersion of As (III)-imprinted polymer nanoparticles in poly(vinyl chloride), plasticized with di-nonylphthalate. The IIP-modified electrode exhibited a Nernstian response (20.4±0.5mV decade−1) to arsenic ion over a wide concentration range (7.0×10−7 to 1.0×10−1molL−1) with a lower detection limit of 5.0×10−7molL−1. Unlike this, the non-imprinted polymer (NIP)-based membrane electrode was not sensitive to arsenic in aqueous solution. The selectivity of the developed sensor to As (III) was shown to be satisfactory. The sensor was used for arsenic determination in some real samples.

Determination of Salicylate ion by Potentiometric Membrane Electrode based on Zinc Aluminium Layered Double Hydroxides-4(2,4-dichlorophenoxy)Butyrate Nanocomposites

Determination of Salicylate ion by Potentiometric Membrane Electrode based on Zinc Aluminium Layered Double Hydroxides-4(2,4-dichlorophenoxy)Butyrate Nanocomposites

Quinine, Quinidine and Their Tert-butyl Carbomylated Derivatives as Chiral Selectors in the Enantioselective, Potentiometric Membrane Electrodes Design: Their Application for the Assay of (S) and (R) Enantiomers of 3,5-dinitrobenzoyl Leucine

Quinine, quinidine, tert-butyl carbomylated quinine and tert-butyl carbomylated quinidine are proposed as new chiral selectors in the construction of enantioselective, potentiometric membrane electrodes (EPMEs). A matrix based on carbon paste is used for the design of the electrodes. Electrodes revealed near-Nernstian values for the concentration range of the analytes ((S) and (R)-dinitrobenzoyl leucine (DNB-Leu)) situated in low magnitude order, with low limits of detection (lower than 10−7 mol/L). Quinine and quinide based EPMEs proved to be enantioselective for the (S)-DNB-Leu, while the tert-butyl carbomylated quinine based EPME was enantioselective for (R)-DNB-Leu. The tert-butyl carbamoyl quinidine based electrode was enantioselective only for specific ratios between the (S) and (R)- DNB-Leu enantiomers.

Enantioanalysis of ketoprofen based on its interaction with C60 fullerene and its derivatives

Three enantioselective, potentiometric membrane electrodes (EPMEs) based on C60 fullerene and its derivatives, (1,2-methanofullerene C60)-61-carboxylic acid and tert-butyl(1,2-methanofullerene C60)-61-carboxylate, were designed for the enantioanalysis of ketoprofen. Molecular modelling has been used to investigate the enantioselective binding between the enantiomers of ketoprofen and C60 fullerenes and to prove the mechanism of potential development for the proposed electrodes. The slopes obtained for these electrodes are near-Nernstain with detection limits of 10−8 and 10−7 mol L−1 magnitude order. The proposed electrodes can be reliably used for the enantioanalysis of ketoprofen raw material as well as from its pharmaceutical formulations. Electronic structures as well as molecular interaction have been investigated using Hartree–Fock theory, 3-21G(*) basis set. Stability and feasibility of all the generated structures were supported by their respective energy minima and fundamental frequencies. Molecular modeling calculations were in good agreement with the performances of the proposed electrodes.

Revisiting the Response Mechanism of Polymeric Membrane Based Heparin Electrodes

Potentiometric membrane electrodes that respond to heparin and other polyanions were introduced in the early 1990s. Herein, the mechanism of polymer membrane electrode type heparin sensors is revisited. The extraction/diffusion of heparin is studied via both potentiometric and impedance spectroscopic techniques using a pre-fractionated heparin preparation that contains polyanionic species > 10000 Daltons. The reversal in EMF response using this heparin preparation indicates diffusion of higher MW heparin fragments to the backside of the membrane. Diffusion coefficients are calculated using a novel formula derived from the phase boundary potential model and Fick's second law of diffusion. Impedance spectroscopy is also employed to show that high MW heparin species are extracted and diffuse across the PVC membranes.

Enantioselective, Potentiometric Membrane Electrodes (EPME) Based on Maltodextrins for the Determination of L-Vesamicol in Serum Samples

Three EPMEs based on maltodextrins with different dextrose equivalent (DE) values [I (4.0-7.0), II (13.0-17.0) and III (16.5-19.5)], were designed for the determination of L-vesamicol. The linear concentration ranges of the proposed electrodes were 10-4 - 10-2 mol/L for maltodextrin I-based electrode, 10-5 -10-3 mol/L for maltodextrin II-based electrode and 10-9 - 10-7 mol/L for maltodextrin III-based electrode. The detection limits of the proposed electrodes were 1.34x10-5, 5.0x10-6 and 3.33x10-10 mol/L for maltodextrin I, II and III based electrodes, respectively. The selectivity of EPMEs for L-vesamicol was tested over D-vesamicol, creatine, creatinine and some inorganic ions. The surfaces of the electrodes can be easily renewed by simply polishing on alumina. Keywords: Enantioselective, Potentiometric membrane electrode, Maltodextrins, L-vesamicol, Alzheimer's disease, Ag/AgCl electrode, Parkinson's disease, Down's Syndrome, Olivopontocerebellar atrophy, Electrophoresis

Cyclodextrins Based Enantioselective, Potentiometric Membrane Electrodes (EPME) and their Applications for Enantioanalysis of L-Cysteine in Urine

Four enantioselective, potentiometric membrane electrodes based on carbon paste impregnated with α-, β-, 2- hydroxyl-3-trimethylammoniopropyl -β- (as chloride salt) and γ-cyclodextrins are proposed for the enantioanalysis of Lcysteine. The proposed electrodes exhibited near-Nernstian slopes in a wide linear concentration range: 10-10 - 10-3 mol/L, with very low detection limits, near 10-11 mol/L. The surfaces of the electrodes are easily renewable by simply polishing on an alumina paper.

Advancing Membrane Electrodes and Optical Ion Sensors

While potentiometric sensors experienced a golden age in the 1970s that drove innovation and implementation in the clinical laboratory as sensors of choice, it has been only fairly recently that a theoretical understanding coupled with modern materials approaches transformed the area of membrane electrodes from a playful, yet empirical field to one firmly rooted in scientific understanding. This paper summarizes key progress in the field during the past two decades, emphasizing that the key impulses at the time originated from the emerging field of optical ion sensors. This simplified and transformed the underlying theory of their potentiometric membrane electrode counterparts, where subsequently substantial progress was made, including the realization of ultra-trace detection limits. The better understanding of zero-current ion fluxes and transport processes in turn allowed the development of approaches utilizing dynamic electrochemistry principles, thereby drastically expanding the field of membrane electrodes and making available a range of new methodologies that would have been difficult to predict only a few years ago. These significant developments are now starting to come back and influence the field of optical sensors, where the control and triggering of dynamic processes, away from simpler equilibrium principles, are becoming a highly promising field of research.

Enantioanalysis of L-Histidine Using Enantioselective, Potentiometric Membrane Electrodes Based on Maltodextrins

Three enantioselective, potentiometric electrodes (EPMEs) based on maltodextrins with different values of dextrose equivalent (DE) (maltodextrin I: DE 4.0–7.0; maltodextrin II: DE 13–17; maltodextrin III DE 16.5–19.5) were proposed for the assay of L-histidine in histidine raw materials and from its pharmaceutical formulation. The slopes of the electrodes were 58.3, 58.9, and 58.5 mV/decade of concentration for maltodextrin I, II, and III-based electrodes, respectively, and the detection limits were 1.97 × 10−12 mol/L, 1.72 × 10−12 mol/L, and 1.4 × 10−11 mol/L, respectively. All the electrodes are enantioselective and selective over polyvinylpyrrolidone, creatine, and creatinine. The L-histidine can be determined in the presence of D-histidine with recovery values higher than 99.10%. The proposed electrodes were successfully used for uniformity content tests of L-histidine in food supplements; the average recovery was higher than 97.30%. The surfaces of the electrodes were stable and easily renewable by simply polishing the alumina paper.

Enantioselective Potentiometric Membrane Electrodes Based on Antibiotics for the Determination of L- and D-Glyceric Acids

Glyceric acid (GA) is a human metabolite existing in L- and D-configurations, which are considered the markers for the diseases L- and D-glyceric aciduria/academia, respectively. Enantioselective, potentiometric membrane electrodes based on carbon paste modified with antibiotics as chiral selectors, vancomycin, and teicoplanin were designed for the assay of L- and D-GA, respectively, in the concentration ranges of 10−9–10−7and 10−4–10−2 moL/L with very low detection limits (1.5 × 10−10 moL/L for L-GA and 1.6 × 10−4 moL/L for D-GA, resp.). The surface of the electrodes can be regenerated simply by polishing in order to obtain a fresh surface ready to be used in a new assay. The proposed electrodes can be successfully applied for the enantioanalysis of L- and D-glyceric acids in serum samples.

Enantioselective Potentiometric Membrane Eectrodes Based on α-, β- and γ-Cyclodextrins as Chiral Selectors for the Assay of S-Deprenyl

Enantioselective, potentiometric membrane electrodes (EPMEs) based on � -, � - and � -cyclodextrins (CDs) as chiral selectors were proposed for the assay of S-deprenyl. The response characteristics proved that the proposed EPMEs could be reliably used in the assay of S-deprenyl. The best slope is exhibited by the EPME based on � -cyclodextrin. The limits of detection are very low: 10 -9 mol L -1 magnitude order for � -cyclodextrin based EPME, and 10 -11 mol L -1 magnitude order for � -, and � -cyclodextrins based EPMEs. The surfaces of the electrodes are stable and easily renewable by polishing on alumina paper.

Enantioanalysis of (-)Butaclamol Using Vancomycin and Teicoplanin as Chiral Selectors

Butaclamol is an antipsychotic drug used in the treatment of schizophrenia. The macrocyclic antibiotics, vancomycin and teicoplanin, are proposed as chiral selectors for the design of the enantioselective, potentiometric membrane electrodes (EPMEs) for the assay of (-)butaclamol. The slopes of the electrodes are near-Nernstian for the assay of (-) butaclamol with linear concentration ranges between 10(-10) and 10(-7) mol/L and between 10(-9) and 10(-7) mol/L for vancomycin and teicoplanin based EPMEs. Limits of detections varied. The electrodes were used reliably for the enantioanalysis of (-) butaclamol in serum samples.

Enantioanalysis of R-deprenyl based on its molecular interaction with C70 fullerenes

Two enantioselective, potentiometric membrane electrodes based on [5,6]fullerene-C(70) (1) and diethyl (1,2-methanofullerene C(70))-71-71-dicarboxylate (2) immobilized in carbon paste, were designed for the enantioanalysis of R-deprenyl. The electrodes exhibited near-Nernstian slopes: 57.90 (1) and 59.00mV/decade of concentration (2), respectively with low limits of detection 5.9x10(-11) (1) and 9.6x10(-11)mol/L (2), respectively. The linear concentration ranges are between 10(-10) and 10(-4)mol/L (1) and between 10(-9) and 10(-4)mol/L (2), respectively. The different characteristics involved in the molecular interaction between R-deprenyl and C(70) fullerenes were explained, namely (i) the stability of each molecule and (ii) the explanation of the molecular mechanism of interaction, using restricted Hartree-Fock theory, 3-21G(*) RHF-basis set. Furthermore, two intermolecular forces of interactions confer the stability of the electrodes; electrostatic interaction and moderate hydrogen bond interaction. Stability and feasibility of all the generated structures involved in this analysis were supported by their respective fundamental frequencies and energy minima. R-deprenyl can be recovered with average recoveries higher than 99.10% (RSD<0.03%) from synthetic mixtures between R- and S-deprenyl. The high selectivity and enantioselectivity made possible the enantioanalysis of R-deprenyl in its pharmaceutical formulations.

Enantioanalysis of S-Ibuprofen using [5–6] fullerene-C70and diethyl (1,2-methanofullerene C70)-71-71-dicarboxylate

[5–6] Fullerene-C70 and diethyl (1,2-methanofullerene C70)-71-71-dicarboxylate are used as chiral selectors for the construction of enantioselective, potentiometric membrane electrodes used in the enantioanalysis of S-Ibuprofen. The sensitivities (slopes) of the electrodes were 55.70 mV/pS-ibuprofen for [5–6] fullerene-C70 based electrode and 56.10 mV/pS-ibuprofen for diethyl (1,2-methanofullerene C70)-71-71-dicarboxylate based electrodes and the linear concentration ranges were between 10−10 and 10−3 mol L−1 (limit of detection 1 × 10−11 mol L−1), and between 10−10 and 10−4 mol L−1 (limit of detection 5.4 × 10−11 mol L−1), respectively. The recovery tests proved that these electrodes can be reliable used for the enantioanalysis of S-ibuprofen raw material (recovery higher than 99.00%) and from its pharmaceutical formulations (recovery higher than 98.40%).

Enantioanalysis of d-histidine based on its interaction with [5,6]fullerene-C70 and diethyl (1,2-methanofullerene-C70)-71,71-dicarboxylate

Enantioselective, potentiometric membrane electrodes based on [5,6]fullerene-C70 and diethyl (1,2-methanofullerene-C70)-71,71-dicarboxylate were proposed for the enantioanalysis of D-histidine in pharmaceutical compounds. Molecular modelling calculations were performed to support the experimental results. Electronic structures, as well as molecular interactions, have been investigated using Hartree–Fock theory, 3-21G(*) basis set. Stability and feasibility of all the generated structures were supported by their respective energy minima and fundamental frequencies. Molecular modelling calculations were in good agreement with the performances (e.g., response characteristics, enantioselectivity, recovery tests) of the proposed electrodes.

Enantioanalysis of S-deprenyl using enantioselective, potentiometric membrane electrodes based on C 60 derivatives

Enantioselective, potentiometric membrane electrodes based on (1,2-methanofullerene C 60)-61-carboxylic acid, diethyl (1,2-methanofullerene C 60)-61-61-dicarboxylate and tert-butyl (1,2-methanofullerene C 60)-61-carboxylic acid were proposed for the enantioanalysis of S-deprenyl in pharmaceutical compounds. Molecular modeling calculations were performed to prove the reliability of the proposed electrodes. The different characteristics involved in this analysis were explained, namely (i) the stability of each molecule using total energy, hardness and dipole moment, and (ii) the explanation of the mechanism of interaction using intermolecular forces (moderate hydrogen bond interactions), atomic charges and electrostatic potential. Electronic structures as well as molecular interaction have been investigated using Hartree–Fock theory, 3-21G(*) basis set. Stability and feasibility of all the generated structures were supported by their respective energy minima and fundamental frequencies.