The Experts below are selected from a list of 36372 Experts worldwide ranked by ideXlab platform
Wei Qin - One of the best experts on this subject based on the ideXlab platform.
-
Self-Sterilizing Polymeric Membrane Sensors Based on 6-Chloroindole Release for Prevention of Marine Biofouling.
Analytical chemistry, 2020Co-Authors: Tian-jia Jiang, Chao Hou, Shengtao Fang, Wei QinAbstract:A self-sterilizing strategy based on antimicrobial organic agent release is proposed for Polymeric Membrane sensors to prevent marine biofouling. A solid-contact Polymeric Membrane calcium ion-sele...
-
improving the biocompatibility of Polymeric Membrane potentiometric ion sensors by using a mussel inspired polydopamine coating
Analytical Chemistry, 2019Co-Authors: Xiaojing Jiang, Rongning Liang, Peng Wang, Wei QinAbstract:Polymeric Membrane potentiometric ion sensors have been widely used in clinical diagnosis for the detection of electrolyte ions and account for billions of measurements every year throughout the world. However, in many cases of practical relevance, biofouling, which might lead to sensor failure, usually occurs due to the lack of biocompatibility of these sensors. Herein, we describe a simple and robust approach for improving the biocompatibility of the Polymeric ion-selective Membranes. A marine mussel-inspired polydopamine polymer is used as a hydrophilic coating on the surface of conventional potentiometric ion sensors. Such a coating can be easily formed by self-polymerization of dopamine and robustly deposited on the sensor surface mimicking the adhesion mechanism of mussels. The classical poly(vinyl chloride) Membrane-based calcium ion-selective electrode (ISE) is chosen as a model. Compared to the unmodified Ca2+ ISE, the polydopamine modified electrode shows a significantly reduced blood platelet a...
-
Soluble Molecularly Imprinted Polymer-Based Potentiometric Sensor for Determination of Bisphenol AF
Analytical chemistry, 2017Co-Authors: Huan Zhang, Wei Qin, Ruiqing Yao, Ning Wang, Rongning LiangAbstract:Molecularly imprinted polymer (MIP)-based Polymeric Membrane potentiometric sensors have been successfully developed for determination of organic compounds in their ionic and neutral forms. However, most of the MIP receptors in potentiometric sensors developed so far are insoluble and cannot be well dissolved in the Polymeric Membranes. The heterogeneous molecular recognitions between the analytes and MIPs in the Membranes are inefficient due to the less available binding sites of the MIPs. Herein we describe a novel Polymeric Membrane potentiometric sensor using a soluble MIP (s-MIP) as a receptor. The s-MIP is synthesized by the swelling of the traditional MIP at a high temperature. The obtained MIP can be dissolved in the plasticized Polymeric Membrane for homogeneous binding of the imprinted polymer to the target molecules. By using neutral bisphenol AF as a model, the proposed method exhibits an improved sensitivity compared to the conventional MIP-based sensor with a lower detection limit of 60 nM. ...
-
an effective solid contact for an all solid state Polymeric Membrane cd2 selective electrode three dimensional porous graphene mesoporous platinum nanoparticle composite
Sensors and Actuators B-chemical, 2017Co-Authors: Tanji Yin, Wei QinAbstract:Abstract The three-dimensional porous graphene-mesoporous platinum nanoparticle (3D PGR-MPN) composite is used as solid contact for developing an all-solid-state Polymeric Membrane Cd2+ ion-selective electrode (Cd2+-ISE). The 3D PGR with MPNs as cross-linking sites can be synthesized by a facile hydrothermal co-assembly method. The obtained 3D PGR-MPN composite is promising for acting as solid contact due to its unique characteristics such as high interfacial area, superior double layer capacitance, excellent conductivity and high hydrophobicity. The ISE exhibits a stable Nernstian response in the range of 10−8–10−4 M and the detection limit is 10−8.8 M. The 3D PGR-MPN-based Cd2+-ISE shows good potential response and no water layer exists between the Polymeric Membrane and the 3D PGR-MPN layer. Additionally, the proposed Cd2+-ISE is robust to O2, CO2 and light interferences. This work provides a versatile method for preparing an effective solid contact to develop a stable and reliable all-solid-state ISE.
-
Soluble Molecularly Imprinted Polymer-Based Potentiometric Sensor for Determination of Bisphenol AF
2017Co-Authors: Huan Zhang, Wei Qin, Ruiqing Yao, Ning Wang, Rongning LiangAbstract:Molecularly imprinted polymer (MIP)-based Polymeric Membrane potentiometric sensors have been successfully developed for determination of organic compounds in their ionic and neutral forms. However, most of the MIP receptors in potentiometric sensors developed so far are insoluble and cannot be well dissolved in the Polymeric Membranes. The heterogeneous molecular recognitions between the analytes and MIPs in the Membranes are inefficient due to the less available binding sites of the MIPs. Herein we describe a novel Polymeric Membrane potentiometric sensor using a soluble MIP (s-MIP) as a receptor. The s-MIP is synthesized by the swelling of the traditional MIP at a high temperature. The obtained MIP can be dissolved in the plasticized Polymeric Membrane for homogeneous binding of the imprinted polymer to the target molecules. By using neutral bisphenol AF as a model, the proposed method exhibits an improved sensitivity compared to the conventional MIP-based sensor with a lower detection limit of 60 nM. Moreover, the present sensor exhibits an excellent selectivity over other phenols. We believe that s-MIPs can provide an appealing substitute for the traditional insoluble MIP receptors in the development of Polymeric Membrane-based electrochemical and optical sensors
Tanji Yin - One of the best experts on this subject based on the ideXlab platform.
-
an effective solid contact for an all solid state Polymeric Membrane cd2 selective electrode three dimensional porous graphene mesoporous platinum nanoparticle composite
Sensors and Actuators B-chemical, 2017Co-Authors: Tanji Yin, Wei QinAbstract:Abstract The three-dimensional porous graphene-mesoporous platinum nanoparticle (3D PGR-MPN) composite is used as solid contact for developing an all-solid-state Polymeric Membrane Cd2+ ion-selective electrode (Cd2+-ISE). The 3D PGR with MPNs as cross-linking sites can be synthesized by a facile hydrothermal co-assembly method. The obtained 3D PGR-MPN composite is promising for acting as solid contact due to its unique characteristics such as high interfacial area, superior double layer capacitance, excellent conductivity and high hydrophobicity. The ISE exhibits a stable Nernstian response in the range of 10−8–10−4 M and the detection limit is 10−8.8 M. The 3D PGR-MPN-based Cd2+-ISE shows good potential response and no water layer exists between the Polymeric Membrane and the 3D PGR-MPN layer. Additionally, the proposed Cd2+-ISE is robust to O2, CO2 and light interferences. This work provides a versatile method for preparing an effective solid contact to develop a stable and reliable all-solid-state ISE.
-
an all solid state Polymeric Membrane pb2 selective electrode with bimodal pore c 60 as solid contact
Analytica Chimica Acta, 2015Co-Authors: Tanji Yin, Wei QinAbstract:An all-solid-state Polymeric Membrane Pb2+ ion-selective electrode (Pb2+-ISE) based on bimodal pore C-60 (BP-C-60) as solid contact has been developed. A BP-C-60 film can be readily formed on the surface of a glassy carbon electrode by electrochemical deposition. Cyclic voltammetry and electrochemical impedance spectroscopy have been employed to characterize the BP-C-60 film. The large double layer capacitance and fast charge-transfer capability make BP-C-60 favorable to be used as solid contact for developing all-solid-state ISEs. The all-solid-state BP-C-60-based Pb2+-ISE shows a Nernstian response in the range from 1.0 x 10 (9) to 1.0 x 10 (3) M with a detection limit of 5.0 x 10 (10) M. The Membrane electrode not only displays an excellent potential stability with the absence of a water layer between the ion-selective Membrane and the underlying BP-C-60 solid contact, but also is insensitive to interferences from O-2, CO2 and light. The proposed solid-contact Pb2+-ISE has been applied to determine Pb2+ in real water samples and the results agree well with those obtained by anodic stripping voltammetry. (C) 2015 Elsevier B.V. All rights reserved.
-
all solid state Polymeric Membrane ion selective miniaturized electrodes based on a nanoporous gold film as solid contact
Analytical Chemistry, 2014Co-Authors: Tanji Yin, Dawei Pan, Wei QinAbstract:A new type of all-solid-state Polymeric Membrane ion-selective electrodes (ISEs) is developed by using a nanoporous gold (NPG) film as solid contact. The NPG film is in situ formed on the surface of a gold wire electrode by the multicyclic electrochemical alloying/dealloying method. The characteristics of the NPG film, such as the large surface area, high double layer capacitance, and good conductivity, have been demonstrated by cyclic voltammetry and electrochemical impedance spectroscopy. The NPG film offers a well-defined interface between the electronic conductor and the ion-selective Membrane. The NPG film-based all-solid-state K+ ISE shows a stable Nernstian response within the concentration range from 10–6 to 10–2 M, and the detection limit is 4.0 × 10–7 M. The proposed electrode exhibits an improved potential stability with a reduced water layer in comparison with the coated-wire K+-ISE, which is due to the bicontinuous electron- and ion-conducting properties of the ionophore-doped Polymeric membr...
Elzbieta Malinowska - One of the best experts on this subject based on the ideXlab platform.
-
polyion selective Polymeric Membrane based pulstrode as a detector in flow injection analysis
Analytical Chemistry, 2014Co-Authors: Andrea K Bellvlasov, Joanna Zajda, Ayman S Eldourghamy, Elzbieta Malinowska, Mark E. MeyerhoffAbstract:A method for the detection of polyions using fully reversible polyion selective Polymeric Membrane type pulstrodes as detectors in a flow-injection analysis (FIA) system is examined. The detection electrode consists of a plasticized Polymeric Membrane doped with 10 wt % of tridodecylmethylammonium-dinonylnaphthalene sulfonate (TDMA/DNNS) ion-exchanger salt. The pulse sequence used involves a short (1 s) galvanostatic pulse, an open-circuit pulse (0.5 s) during which the EMF of the cell is measured, and a longer (15 s) potentiostatic pulse to return the Membrane to its original chemical composition. It is shown that total pulse sequence times can be optimized to yield reproducible real-time detection of injected samples of protamine and heparin at up to 20 samples/h. Further, it is shown that the same Membrane detector can be employed for FIA detection of both polycations at levels ≥10 μg/mL and polyanions at levels of ≥40 μg/mL by changing the direction of the galvanostatic pulse. The methodology describe...
-
fluoride selective Polymeric Membrane electrodes based on zr iv and al iii salen ionophores of various structures
Analytica Chimica Acta, 2010Co-Authors: łukasz Gorski, Alexey Matusevich, Pawel G Parzuchowski, Iwona łuciuk, Elzbieta MalinowskaAbstract:Abstract Al(III)- and Zr(IV)-salophens of novel structures were tested as anion-selective ionophores. It was shown that these compounds are highly selective to fluoride and give selectivity greatly deviating from classical Hofmeister pattern, when doped into the Polymeric Membrane of ion-selective electrode (ISE). The following selectivity sequence has been recorded for both ionophores: F − > ClO 4 − > SCN − > NO 3 − ≈ Br − ≈ Cl − . The results of potentiometric and spectrophotometric measurements allow to conclude that the nature and structure of salophen ligands influence stability of ISE working parameters. An increase in salophen ligands lipophilicity results in prolongation of the ISE lifetime, most likely due to slower ionophore decomposition caused by the hydrolysis of imine bonds in salophen structure. Ion-selective electrodes (ISEs) with the most successful Al(III)-salophen exhibited a stable, fast and near-Nernstian fluoride response and a functional lifetime near 3 weeks and selectivity coefficients with log K F − , Y − pot . as follows: −2.8 (Y − = Br − ), −2.7 (Cl − ), −2.8 (NO 3 − ), −1.5 (SCN − ), −1.3 (ClO 4 − ), which is better than for other ones based on Zr(IV)- and Al(III)-salophens and salens described to date.
-
Polymeric Membrane electrodes with improved fluoride selectivity and lifetime based on zr iv and al iii tetraphenylporphyrin derivatives
Analytica Chimica Acta, 2007Co-Authors: Mariusz Pietrzak, Mark E. Meyerhoff, Elzbieta MalinowskaAbstract:Abstract Novel aluminum(III)- and zirconium(IV)-tetraphenylporhyrin (TPP) derivatives are examined as fluoride-selective ionophores for preparing polymer Membrane-based ion-selective electrodes (ISEs). The influence of t -butyl- or dichloro-phenyl ring substituents as well as the nature of the metal ion center (Al(III) versus Zr(IV)) on the anion complexation constants of TPP derivative ionophores are reported. The anion binding stability constants of the ionophores are characterized by the so-called “sandwich Membrane” method. All of the metalloporphyrins examined form their strongest anion complexes with fluoride. The influence of plasticizer as well as the type of lipophilic ionic site additive and their amounts in the sensing Membrane are discussed. It is shown that Membrane electrodes formulated with the metalloporphyrin derivatives and appropriate anionic or cationic additives exhibit enhanced potentiometric response toward fluoride over all other anions tested. Since selectivity toward fluoride is enhanced in the presence of both anionic and cationic additives, the metalloporphyrins can function as either charged or neutral carriers within the organic Membrane phase. In contrast to previously reported fluoride-selective Polymeric Membrane electrodes based on metalloporphyrins, nernstian or near-nernstian (−51.2 to −60.1 mV decade −1 ) as well as rapid ( t t -butyltetraphenylporphyrin as the ionophore provides fluoride sensors with prolonged (7 months) functional lifetime.
-
aluminum iii porphyrins as ionophores for fluoride selective Polymeric Membrane electrodes
Electroanalysis, 2006Co-Authors: Jeremy T Mitchellkoch, Mariusz Pietrzak, Elzbieta Malinowska, Mark E. MeyerhoffAbstract:Aluminum(III) porphyrins are examined as potential fluoride selective ionophores in Polymeric Membrane type ionselective electrodes. Membranes formulated with Al(III) tetraphenyl (TPP) or octaethyl (OEP) porphyrins are shown to exhibit enhanced potentiometric selectivity for fluoride over more lipophilic anions, including perchlorate and thiocyanate. However, such Membrane electrodes display undesirable super-Nernstian behavior, with concomitant slow response and recovery times. By employing a sterically hindered Al(III) picket fence porphyrin (PFP) complex as the Membrane active species, fully reversible and Nernstian response toward fluoride is achieved. This finding suggests that the super-Nernstian behavior observed with the nonpicket fence metalloporphyrins is due to the formation of aggregate porphyrin species (likely dimers) within the Membrane phase. The steric hindrance of the PFP ligand structure eliminates such chemistry, thus leading to theoretical response slopes toward fluoride. Addition of lipophilic anionic sites into the organic Membranes enhances response and selectivity, indicating that the Al(III) porphyrin ionophores function as charged carrier type ionophores. Optimized Membranes formulated with Al(III)PFP in an o-nitrophenyloctyl ether plasticized PVC film exhibit fast response to fluoride down to 40 mM, with very high selectivity over SCN � , ClO4 � ,C l � ,B r � and NO3 � (k pot < 10 � 3 for all anions tested). With further refinements in the Membrane chemistry, it is anticipated that Al(III) porphyrin-based Membrane electrodes can exhibit potentiometric fluoride response and selectivity that approaches that of the classical solid-state LaF3 crystal-based fluoride sensor.
-
zirconium iv porphyrins as novel ionophores for fluoride selective Polymeric Membrane electrodes
Analytica Chimica Acta, 2002Co-Authors: Elzbieta Malinowska, łukasz Gorski, Mark E. MeyerhoffAbstract:Abstract The feasibility of using Zr(IV)-porphyrins as novel ionophores for preparing anion-selective Polymeric Membrane electrodes is examined. Electrodes constructed using o-nitrophenyl octyl ether plasticized poly(vinyl chloride) Membranes containing Zr(IV)-octaethylporphyrin (OEP) dichloride (Zr(IV)[OEP]Cl2) or Zr(IV)-tetraphenylporphyrin (TPP) dichloride (Zr(IV)[TPP]Cl2) were found to exhibit enhanced potentiometric selectivity toward fluoride compared to electrodes based on a typical anion-exchanger (e.g. tridodecylmethylammonium chloride). At pH 5.5, the electrodes displayed the following selectivity sequences: ClO4− > SCN− > I− > F− > NO3− > Br− > NO2− > Cl− and F− > ClO4− > SCN− > I− > NO2− > NO3− > Br− > Cl− for Membranes doped with Zr(IV)[OEP]Cl2) and Zr(IV)[TPP]Cl2, respectively. Both ionophores are shown to operate via a charged carrier mechanism, with 10 mol% of lipophilic tetraphenylborate derivative in the Membrane phase required to achieve optimal selectivity. Electrodes prepared with both metalloporphyrin species display super-Nernstian response toward fluoride with slopes typically greater than −100 mV per decade. It is shown, via UV–VIS spectroscopy of the Membrane phase, that this behavior occurs due to spontaneous formation of hydroxide ion bridged porphyrin dimers in the Membrane in the presence of the lipophilic anionic additive. The dimers are easily converted to monomeric species upon increasing the concentration of fluoride in the sample solution. Decreasing the pH of sample buffer background solution (from pH 5.5 to pH 3) decreases the lower detection limit (DL) of the electrode response toward fluoride (by two-order of magnitude) and improves the electrodes’ selectivity.
Mark E. Meyerhoff - One of the best experts on this subject based on the ideXlab platform.
-
detecting levels of polyquaternium 10 pq 10 via potentiometric titration with dextran sulphate and monitoring the equivalence point with a Polymeric Membrane based polyion sensor
Analytical Methods, 2016Co-Authors: Stephen A Ferguson, Xuewei Wang, Mark E. MeyerhoffAbstract:Polymeric quaternary ammonium salts (polyquaterniums) have found increasing use in industrial and cosmetic applications in recent years. More specifically, polyquaternium-10 (PQ-10) is routinely used in cosmetic applications as a conditioner in personal care product formulations. Herein, we demonstrate the use of potentiometric polyion-sensitive Polymeric Membrane-based electrodes to quantify PQ-10 levels. Mixtures containing both PQ-10 and sodium lauryl sulfate (SLS) are used as model samples to illustrate this new method. SLS is often present in cosmetic samples that contain PQ-10 (e.g., shampoos, etc.) and this surfactant species interferes with the polyion sensor detection chemistry. However, it is shown here that SLS can be readily separated from the PQ-10/SLS mixture by use of an anion-exchange resin and that the PQ-10 can then be titrated with dextran sulphate (DS). This titration is monitored by potentiometric polyanion sensors to provide equivalence points that are directly proportional to PQ-10 concentrations.
-
polyion selective Polymeric Membrane based pulstrode as a detector in flow injection analysis
Analytical Chemistry, 2014Co-Authors: Andrea K Bellvlasov, Joanna Zajda, Ayman S Eldourghamy, Elzbieta Malinowska, Mark E. MeyerhoffAbstract:A method for the detection of polyions using fully reversible polyion selective Polymeric Membrane type pulstrodes as detectors in a flow-injection analysis (FIA) system is examined. The detection electrode consists of a plasticized Polymeric Membrane doped with 10 wt % of tridodecylmethylammonium-dinonylnaphthalene sulfonate (TDMA/DNNS) ion-exchanger salt. The pulse sequence used involves a short (1 s) galvanostatic pulse, an open-circuit pulse (0.5 s) during which the EMF of the cell is measured, and a longer (15 s) potentiostatic pulse to return the Membrane to its original chemical composition. It is shown that total pulse sequence times can be optimized to yield reproducible real-time detection of injected samples of protamine and heparin at up to 20 samples/h. Further, it is shown that the same Membrane detector can be employed for FIA detection of both polycations at levels ≥10 μg/mL and polyanions at levels of ≥40 μg/mL by changing the direction of the galvanostatic pulse. The methodology describe...
-
Polymeric Membrane electrodes with high nitrite selectivity based on rhodium iii porphyrins and salophens as ionophores
Analytical Chemistry, 2009Co-Authors: Mariusz Pietrzak, Mark E. MeyerhoffAbstract:Several porphyrin and salophen complexes with Rh(III) are examined as ionophores to prepare nitrite selective Polymeric Membrane electrodes. All ionophores tested exhibit preferred selectivity toward nitrite anion. Enhanced potentiometric nitrite selectivity is observed in the presence of either lipophilic anionic as well as cationic sites within the Membranes, suggesting that the ionophores can function via either a charged or a neutral carrier response mechanism. Among a range of complexes and Membrane formulations examined, optimal nitrite selectivity and reversible response down to 5 × 10−6 M is achieved using Rh(III)-tetra(t-butylphenylporphyrin) as the ionophore in the presence of lipophilic cationic sites in plasticized poly(vinyl chloride) Membrane. Response times are substantially longer than typical Membrane electrodes apparently because of a slow nitrite ligation reaction with Rh(III); however, a significant improvement in dynamic EMF response can be realized by optimizing the Membrane formulat...
-
Polymeric Membrane electrodes with improved fluoride selectivity and lifetime based on zr iv and al iii tetraphenylporphyrin derivatives
Analytica Chimica Acta, 2007Co-Authors: Mariusz Pietrzak, Mark E. Meyerhoff, Elzbieta MalinowskaAbstract:Abstract Novel aluminum(III)- and zirconium(IV)-tetraphenylporhyrin (TPP) derivatives are examined as fluoride-selective ionophores for preparing polymer Membrane-based ion-selective electrodes (ISEs). The influence of t -butyl- or dichloro-phenyl ring substituents as well as the nature of the metal ion center (Al(III) versus Zr(IV)) on the anion complexation constants of TPP derivative ionophores are reported. The anion binding stability constants of the ionophores are characterized by the so-called “sandwich Membrane” method. All of the metalloporphyrins examined form their strongest anion complexes with fluoride. The influence of plasticizer as well as the type of lipophilic ionic site additive and their amounts in the sensing Membrane are discussed. It is shown that Membrane electrodes formulated with the metalloporphyrin derivatives and appropriate anionic or cationic additives exhibit enhanced potentiometric response toward fluoride over all other anions tested. Since selectivity toward fluoride is enhanced in the presence of both anionic and cationic additives, the metalloporphyrins can function as either charged or neutral carriers within the organic Membrane phase. In contrast to previously reported fluoride-selective Polymeric Membrane electrodes based on metalloporphyrins, nernstian or near-nernstian (−51.2 to −60.1 mV decade −1 ) as well as rapid ( t t -butyltetraphenylporphyrin as the ionophore provides fluoride sensors with prolonged (7 months) functional lifetime.
-
aluminum iii porphyrins as ionophores for fluoride selective Polymeric Membrane electrodes
Electroanalysis, 2006Co-Authors: Jeremy T Mitchellkoch, Mariusz Pietrzak, Elzbieta Malinowska, Mark E. MeyerhoffAbstract:Aluminum(III) porphyrins are examined as potential fluoride selective ionophores in Polymeric Membrane type ionselective electrodes. Membranes formulated with Al(III) tetraphenyl (TPP) or octaethyl (OEP) porphyrins are shown to exhibit enhanced potentiometric selectivity for fluoride over more lipophilic anions, including perchlorate and thiocyanate. However, such Membrane electrodes display undesirable super-Nernstian behavior, with concomitant slow response and recovery times. By employing a sterically hindered Al(III) picket fence porphyrin (PFP) complex as the Membrane active species, fully reversible and Nernstian response toward fluoride is achieved. This finding suggests that the super-Nernstian behavior observed with the nonpicket fence metalloporphyrins is due to the formation of aggregate porphyrin species (likely dimers) within the Membrane phase. The steric hindrance of the PFP ligand structure eliminates such chemistry, thus leading to theoretical response slopes toward fluoride. Addition of lipophilic anionic sites into the organic Membranes enhances response and selectivity, indicating that the Al(III) porphyrin ionophores function as charged carrier type ionophores. Optimized Membranes formulated with Al(III)PFP in an o-nitrophenyloctyl ether plasticized PVC film exhibit fast response to fluoride down to 40 mM, with very high selectivity over SCN � , ClO4 � ,C l � ,B r � and NO3 � (k pot < 10 � 3 for all anions tested). With further refinements in the Membrane chemistry, it is anticipated that Al(III) porphyrin-based Membrane electrodes can exhibit potentiometric fluoride response and selectivity that approaches that of the classical solid-state LaF3 crystal-based fluoride sensor.
Jiawang Ding - One of the best experts on this subject based on the ideXlab platform.
-
Polymeric Membrane Fluoride-Selective Electrodes Using Lewis Acidic Organo-Antimony(V) Compounds as Ionophores.
ACS sensors, 2020Co-Authors: Yihao Zhang, Yinghui Duan, Yi Qian, Peidong Zhang, Qingjie Guo, Jiawang DingAbstract:Four Lewis acidic organo-antimony(V) compounds with strong binding affinity to fluoride were used for the first time as ionophores to fabricate Polymeric Membrane fluoride-selective electrodes. Improved detection limits and significant anti-Hofmeister selectivity could be achieved by optimizing ionophores, lipophilic additives, and plasticizers. Membrane electrodes fabricated with tetrakis-(pentafluorophenyl)stibonium (ionophore 2) performed best in detection limit, sensitivity, and selectivity. Optimal performance was obtained by fluoride with a slope of -59.5 mV/decade in the linear range of 1 × 10-5 to 4 × 10-2 M and a detection limit of 5 × 10-6 M. Studies on the influence of sample solution pH demonstrate that the best pH for fluoride determination is pH 3.0. All of the electrodes studied respond rapidly (in 1 min) in different concentrations of fluoride solutions. The anion-ionophore complex constants in the Membrane phase determined using the segmented sandwich Membrane method correlate well with the solution-phase binding data and determined selectivity sequence of the ion-selective electrodes. The possibility of real life application of the optimized electrodes was assessed by determination of fluoride concentrations in tap water.
-
potentiometric aptasensing based on target induced conformational switch of a dna probe using a Polymeric Membrane silver ion selective electrode
Biosensors and Bioelectronics, 2013Co-Authors: Jiawang Ding, Wei Qin, Yan Zhang, Xuewei WangAbstract:In this article, we introduce a general, sensitive, facile, and label-free potentiometric assay based on metal-mediated DNA base pairs. A nucleic acid with one adenosine-5'-triphosphate (ATP) binding sequence (aptamer) in the middle and two cytosine(C)-rich sequences at the lateral portions was employed as a model. A rigid hairpin structure can be formed in the presence of Ag+ ions, in which the C residues of the spatially separated nucleotides are linked by the ions. The strong interaction between Ag+ ions and cytosines forms a stable C-Ag+-C structure, which could reduce the concentration of silver ions released from the Polymeric Membrane silver ion-selective electrode (ISE) at the sample-Membrane interface and decrease the potential response. In the presence of its target, the aptamer (the loop sequence of the probe) binds specifically to the target via reaction incubation. Such target-binding induced aptamer conformational change prevents the formation of C-Ag+-C structure, leaving more silver ions at the sample-Membrane interface, which can be detected by the silver ISE. ATP can be quantified in the range of 0.5-3.0 mu M with a detection limit of 0.37 mu M. The relative standard deviation for 5 mu M ATP is 5.5%. For the proposed method, the combination of using ion fluxes of silver ions as modulating reagents and as signal reporters greatly simplifies the detection procedures. In addition, by changing the binding sequence in the middle of the probe, the present detection method will be able to explore new applications of ISE for the detection of a large variety of targets. (C) 2013 Elsevier B.V. All rights reserved.
-
potentiometric determination of trypsin using a Polymeric Membrane polycation sensitive electrode based on current controlled reagent delivery
Bioelectrochemistry, 2012Co-Authors: Y Chen, Jiawang Ding, Wei QinAbstract:A potentiometric biosensor for the determination of trypsin is described based on current-controlled reagent delivery. A Polymeric Membrane protamine-sensitive electrode with dinonylnaphthalene sulfonate as cation exchanger is used for in situ generation of protamine. Diffusion of protamine across the Polymeric Membrane can be controlled precisely by applying an external current. The hydrolysis catalyzed with trypsin in sample solution decreases the concentration of free protamine released at the sample-Membrane interface and facilitates the stripping of protamine out of the Membrane surface via the ion-exchange process with sodium ions from the sample solution, thus decreasing the Membrane potential, by which the protease can be sensed potentiometrically. The influences of anodic current amplitude, current pulse duration and protamine concentration in the inner filling solution on the Membrane potential response have been studied. Under optimum conditions, the proposed protamine-sensitive electrode is useful for continuous and reversible detection of trypsin over the concentration range of 0.5-5 U mL(-1) with a detection limit of 0.3 U mL(-1). The proposed detection strategy provides a rapid and reagentless way for the detection of protease activities and offers great potential in the homogeneous immunoassays using proteases as labels. (C) 2012 Elsevier B.V. All rights reserved.
-
primary ion conditioned Polymeric Membrane electrodes for sensitive detection of polyions
Sensors and Actuators B-chemical, 2012Co-Authors: Xuewei Wang, Jiawang Ding, Wenjing SongAbstract:A novel operation mode for development of sensitive and renewable Polymeric Membrane polyion-sensitive electrodes has been explored in this paper. In contrast to the traditional polyion sensors which are conditioned with highly discriminated ions, the proposed polycation-sensitive Membrane electrode with dinonylnaphthalene sulfonate as the ion-exchanger is conditioned with the primary ion (protamine), and activated with the discriminated ion (Na+) before measurement. Using this protocol, the Membrane with protamine in the Membrane bulk but with discriminated ions rich at the Membrane outer surface can be prepared. The protamine inside the Membrane efficiently suppresses the fluxes of protamine from the sample-Membrane interface into the Membrane bulk, thus decreasing the detection limit toward protamine by one order of magnitude. With the reproducible protamine fluxes obtained by the conditioning and activation steps, the protamine-sensitive electrode could be reused without significant signal deterioration. Titrimetric analysis of heparin with this novel technique has been demonstrated. The proposed polyion sensing platform offers much promise in the detection of polyions as well as in other polyion-involved bioanalyses.
-
potentiometric flow injection system for determination of reductants using a Polymeric Membrane permanganate ion selective electrode based on current controlled reagent delivery
Analytica Chimica Acta, 2011Co-Authors: Wenjing Song, Jiawang Ding, Rongning Liang, Wei QinAbstract:A Polymeric Membrane permanganate-selective electrode has been developed as a current-controlled reagent release system for potentiometric detection of reductants in flow injection analysis. By applying an external current, diffusion of permanganate ions across the Polymeric Membrane can be controlled precisely. The permanganate ions released at the sample-Membrane interface from the inner filling solution of the electrode are consumed by reaction with a reductant in the sample solution thus changing the measured Membrane potential, by which the reductant can be sensed potentiometrically. Ascotbate, dopamine and norepinephrine have been employed as the model reductants. Under the optimized conditions, the potential peak heights are proportional to the reductant concentrations in the ranges of 1.0 x 10(-5) to 2.5 x 10(-7) M for ascorbate, of 1.0 x 10(-5) to 5.0 x 10(-7) M for dopamine, and of 1.0 x 10(-5) to 5.0 x 10(-7) M for norepinephrine, respectively with the corresponding detection limits of 7.8 x 10(-8), 1.0 x 10(-7) and 1.0 x 10(-7) M. The proposed system has been successfully applied to the determination of reductants in pharmaceutical preparations and vegetables, and the results agree well with those of iodimetric analysis. (C) 2011 Elsevier B.V. All rights reserved.
