scholarly journals Electroanalysis with a single microbead of phosphate binding resin (FerrIX™) mounted in epoxy film

2021 ◽  
Author(s):  
Abigail K. Thompson ◽  
Klaus Mathwig ◽  
Philip J. Fletcher ◽  
Rémi Castaing ◽  
Frank Marken
Keyword(s):  
Impedance Spectroscopy ◽  
Electrolyte Concentration ◽  
Anion Transport ◽  
Phosphate Concentration ◽  
Phosphate Binding ◽  
Commercial Resin ◽  
Diffusion Migration ◽  
In Series ◽  
Electrode Membrane ◽  
Concentration Polarisation

AbstractCommercial resin microbeads are widely applied in ion exchange and extraction. Here, a single anion-selective and phosphate binding resin microbead (FerrIX™) is mounted into an epoxy membrane and investigated by 4-electrode membrane voltammetry and membrane impedance spectroscopy. Anion transport properties are observed to dominate associated with three distinct potential domains: (I) a low bias ohmic potential domain (dominant at high electrolyte concentration), (II) a concentration polarisation potential domain, and (III) an over-limiting potential domain. Voltammetric responses show transient diffusion-migration features at higher scan rates and quasi-steady state features at lower scan rates. Inherent microbead conductivity is shown to be linked to two resistive elements, electrolyte concentration dependent and independent, in series. The effects of phosphate binding are revealed as transient pattern in impedance spectroscopy data. Preliminary data suggest phosphate concentration-dependent peak features in the imaginary impedance versus frequency plot due to phosphate binding into the microbead. Graphical abstract

Visualizing Impedance Spectroscopy Response for Interpretation of Collected Data

2021 ◽  
Vol 105 (1) ◽  
pp. 109-118
Author(s):  
Petr Vanysek
Keyword(s):  
Impedance Spectroscopy ◽  
Complex Permittivity ◽  
Electrical Impedance ◽  
Complex Modulus ◽  
Physical Reality ◽  
Standard Part ◽  
In Series ◽  
As If

Measurements and interpretation of electrical impedance in electrochemistry and in related studies has become recently fairly commonplace as both the hardware and the interpretation software are more and more standard part of electrochemical potentiostats. With the interpretation software it is possible to model the studied system in any conceivable way, even if the physical reality may not follow the chosen model. An example is given where a circuit consisting of a capacitor with resistors in series and parallel are evaluated as if the circuit were just a pure capacitor. The method of plotting the results as complex permittivity and complex modulus is also shown.

scholarly journals Rapid Laser Reactive Sintering Synthesis of Colossal Dielectric CCTO Ceramics

2020 ◽  
Vol 10 (10) ◽  
pp. 3510
Author(s):  
Jiayang He ◽  
Yanwei Huang ◽  
Guang Feng ◽  
Si Shen ◽  
Ming Yan ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Dielectric Permittivity ◽  
Laser Power ◽  
Low Frequency ◽  
Reactive Sintering ◽  
Practical Applications ◽  
Dense Microstructure ◽  
Calcium Copper Titanate ◽  
Average Grain Size ◽  
In Series

Calcium copper titanate (CCTO) ceramics were successfully synthesized using a rapid laser reactive sintering method without conventional long heat treatment times. The microstructure, dielectric properties, and impedance spectroscopy results for CCTO sintered at laser power rates of 25–85 W were investigated in detail. The X-ray diffractometry results showed that prepared CCTO is polycrystalline in a cubic structure with high purity. Scanning electron microscopy showed that CCTO sintered at 85 W has a dense microstructure with an average grain size of 30 nm. The dielectric permittivity of CCTO ceramics increased with increasing laser power over the entire frequency range and achieved a value of almost 105 in the low-frequency region. The dielectric permittivity maintained almost constant values from 102 Hz to 107 Hz, with lower dielectric loss (~0.1) from 103 Hz to 106 Hz, demonstrating good frequency stability. The impedance spectroscopy study showed that grain and grain boundary resistance decreased with rising laser power based on two parallel Resistor-Capacitance (RC) equivalent circuits in series. The activation energies for the grain boundaries were calculated from the impedance using the slope of ln σ versus 1/T and were found to be in the range of 0.53–0.63 eV. CCTO synthesized by rapid laser reactive sintering is competitive for practical applications.

scholarly journals Influence of pH and phosphate concentration on the phosphate binding capacity of five contemporary binders. An in vitro study

Nephrology ◽  
2018 ◽  
Vol 24 (2) ◽  
pp. 221-226 ◽  
Author(s):  
Stefan P Schumacher ◽  
Leon J Schurgers ◽  
Marc G Vervloet ◽  
Aegida Neradova
Keyword(s):  
Binding Capacity ◽  
In Vitro Study ◽  
Phosphate Concentration ◽  
Vitro Study ◽  
Phosphate Binding ◽  
Influence Of Ph

scholarly journals Capacitive-Coupling Impedance Spectroscopy Using a Non-Sinusoidal Oscillator and Discrete-Time Fourier Transform: An Introductory Study

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6392
Author(s):  
Tomiharu Yamaguchi ◽  
Akinori Ueno
Keyword(s):  
Impedance Spectroscopy ◽  
Complex Impedance ◽  
Capacitive Coupling ◽  
Capacitively Coupled ◽  
Coupling Capacitance ◽  
Sinusoidal Oscillator ◽  
In Series ◽  
Multiple Frequencies ◽  
Short Time ◽  
Complex Impedance Spectra

In this study, we propose a new short-time impedance spectroscopy method with the following three features: (1) A frequency spectrum of complex impedance for the measured object can be obtained even when the measuring electrodes are capacitively coupled with the object and the precise capacitance of the coupling is unknown; (2) the spectrum can be obtained from only one cycle of the non-sinusoidal oscillation waveform without sweeping the oscillation frequency; and (3) a front-end measuring circuit can be built, simply and cheaply, without the need for a digital-to-analog (D-A) converter to synthesize elaborate waveforms comprising multiple frequencies. We built the measurement circuit using the proposed method and then measured the complex impedance spectra of 18 resistive elements connected in series with one of three respective capacitive couplings. With this method, each element’s resistance and each coupling’s capacitance were estimated independently and compared with their nominal values. When the coupling capacitance was set to 10 nF or 1.0 nF, estimated errors for the resistive elements in the range of 2.0–10.0 kΩ were less than 5%.

scholarly journals The origin of constant phase element in equivalent circuit of MIS (n) GaAs structures

2020 ◽  
Vol 31 (21) ◽  
pp. 19106-19118
Author(s):  
Łukasz Drewniak ◽  
Stanisław Kochowski
Keyword(s):  
Impedance Spectroscopy ◽  
Constant Phase Element ◽  
Deep Level ◽  
Frequency Dispersion ◽  
Interface States ◽  
Equivalent Circuits ◽  
Electrical Characteristics ◽  
In Series ◽  
Constant Phase Elements ◽  
Large Frequency

AbstractThe Au/Pd/Ti–SiO2-(n) GaAs properties have been analyzed via impedance spectroscopy (IS), as well as DLTS and ICTS, to identify the origin of electron processes responsible for existence of constant phase elements (CPE) in an equivalent circuits of that structure. We showed that CPEs connected in series with resistance represents the electron processes associated with deep levels in GaAs and/or interface states at SiO2-(n) GaAs interface, depending on the value of n of CPE parameter. CPE with n close to 1 characterize the electron processes associated with EL2 deep level, and CPE with n = 0.5–0.65 the complex electron processes associated with EL3 deep level and interface states together. We stated that constant phase elements in equivalent circuits of MIS-GaAs structures with large frequency dispersion of electrical characteristics can be the result of more than one electron process.

scholarly journals Fabrication of Phosphate-Imprinted PNIPAM/SiO2 Hybrid Particles and Their Phosphate Binding Property

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 253
Author(s):  
Zheng Cao ◽  
Yuyuan Chen ◽  
Dan Li ◽  
Junfeng Cheng ◽  
Chunlin Liu
Keyword(s):  
Adsorption Capacity ◽  
Phosphate Concentration ◽  
Solution Temperature ◽  
Maximum Adsorption Capacity ◽  
Template Molecule ◽  
Hybrid Particles ◽  
Phosphate Binding ◽  
Inorganic Hybrid ◽  
Phosphate Ions ◽  
Sio2 Microspheres

A SiO2 microsphere imprinted by phosphate ions was prepared with the use of phosphate ion as the template molecule and tetraethoxysilane as the precursor. Thereafter, the imprinted SiO2 microspheres were modified with 3-(trimethoxysilyl)propyl methacrylate (TMSPMA@SiO2), followed by introducing the double bond. In the presence of TMSPMA@SiO2, using N-isopropylacrylamide as monomer, and potassium persulfate as initiator, polymer/inorganic hybrid particles (PNIPAM/SiO2) were prepared. Fourier transform infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption-desorption test, and transmission electron microscope were employed for the characterization of molecular imprinted SiO2 microspheres and PNIPAM/SiO2 hybrid particles. The effects of phosphate concentration, pH value, and adsorption temperature on the phosphate binding properties of PNIPAM/SiO2 hybrid particles were studied by UV-vis spectrophotometer. The experimental results shed light on the fact that the PNIPAM structure is beneficial for the improvement of the adsorption ability of phosphate-imprinted SiO2 microspheres. With the increase in the initial phosphate concentration, the adsorption capacity of hybrid particles to phosphate ions increased to 274 mg/g at pH = 7 and 15 °C. The acid condition and the temperature below the low critical solution temperature (LCST) of PNIPAM are favorable to the adsorption of phosphate ions by PNIPAM/SiO2 hybrid particles, and the maximum adsorption capacity can reach 287 mg/g (at pH = 5 and 15 °C). The phosphate imprinted polymer/inorganic hybrid material is expected to be put to use in the fields of phosphate ions adsorption, separation, and recovery.

Urine Formation by the Malpighian Tubules of Calliphora

1969 ◽  
Vol 50 (1) ◽  
pp. 15-28
Author(s):  
M. J. BERRIDGE
Keyword(s):  
Chloride Transport ◽  
Phosphate Transport ◽  
Anion Transport ◽  
Phosphate Concentration ◽  
Malpighian Tubules ◽  
Large Size ◽  
Urine Production ◽  
Urine Formation ◽  
Pass Through

1. The ability of chloride and phosphate to support urine formation has been studied under different conditions. When sulphate is used as a balancing anion, rate of urine formation is linearly related to the external chloride or phosphate concentration. 2. Tubules can concentrate phosphate in the urine by a mechanism which is independent of other anions. Phosphate U/P declines with an increase in external phosphate concentration. 3. In the absence of phosphate, chloride is slightly concentrated in the urine. Chloride U/P is reduced by phosphate but unaffected by sulphate. 4. When an extensive series of anions was tested, rate of urine production was related to the size of the anions. Phosphate was the only exception because despite its large size it supported the highest rate of urine production. 5. Arsenate competitively inhibits phosphate transport, resulting in an augmentation of chloride transport. Copper, however, blocks urine formation in the presence of chloride but not in the presence of phosphate. 6. The experiments indicate two separate mechanisms for anion transport. Anions such as chloride probably pass through pores with an estimated radius of 3.6 Å., whereas phosphate is transported by a carrier.

scholarly journals Regulatory kinetics of wheat-germ aspartate transcarbamoylase. Adaptation of the concerted model to account for complex kinetic effects of uridine 5′-monophosphate

1984 ◽  
Vol 221 (2) ◽  
pp. 281-287 ◽  
Author(s):  
R J Yon
Keyword(s):  
Wheat Germ ◽  
Initial Rate ◽  
Dissociation Constants ◽  
Phosphate Concentration ◽  
Crude Enzyme ◽  
Aspartate Transcarbamoylase ◽  
Phosphate Binding ◽  
Carbamoyl Phosphate ◽  
Rate Versus ◽  
Kinetic Effects

The kinetic effects of the end-product inhibitor UMP on aspartate transcarbamoylase (EC 2.1.3.2) purified to homogeneity from wheat germ were studied. In agreement with an earlier study of the relatively crude enzyme [Yon (1972) Biochem. J. 128, 311-320], the half-saturating concentrations of UMP and of the first substrate, carbamoyl phosphate (but not of the second, L-aspartate), were found to be strongly interdependent. However, the kinetic behaviour of the pure enzyme differed from that of the crude enzyme in several important respects, namely: (a) the apparent affinity for UMP was lower with the pure enzyme; (b) sigmoidicity was absent from plots of initial rate versus carbamoyl phosphate concentration, each at a fixed UMP concentration; (c) sigmoidicity was greatly exaggerated in plots of initial rate versus UMP concentration, each at a fixed carbamoyl phosphate concentration, owing to the occurrence of a slight but definite maximum in each plot at low UMP concentration; (d) there was a relative increase in this maximum in the presence of N-phosphonacetyl-L-aspartate, an inhibitor competitive with carbamoyl phosphate. It is shown that a modified two-conformation concerted-transition model can be used to account for most of these features of the pure enzyme. The model treats carbamoyl phosphate and UMP as antagonistic allosteric ligands binding to alternative conformational states [Monod, Wyman & Changeux (1965) J. Mol. Biol. 12, 88-118], carbamoyl phosphate binding non-exclusively (dissociation constants 20 microM and 85 microM respectively) and UMP binding exclusively (dissociation constant 2.5 microM). The model postulates further that the conformation with lower affinity for carbamoyl phosphate has the higher value of kcat., and that it binds UMP in competition with carbamoyl phosphate. Parameters giving the best fit of experimental data to this model were found by a non-linear least-squares search procedure.

Sign in / Sign up

Export Citation Format

Share Document