The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
Yoshinobu Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Limiting Current Density
Ion Exchange Membranes, 2015Co-Authors: Yoshinobu TanakaAbstract:When an electric current passes through an ion exchange membrane, salt concentration on the desalting surface of the membrane decreases because of concentration polarization and reduces to zero at the limiting current density. In this circumstance, there are no more salt ions available to carry the electric current; as a result, the voltage drop across the boundary layer increases drastically and causes higher energy consumption and the generation of water dissociation. The limiting current density of an ion exchange membrane i lim is measured using the current–voltage relationship. The mechanism of i lim can be understood from the Nernst diffusion model and analyzed with chemical engineering techniques. When the current density reaches i lim at the outlet of a desalting cell at its lowest linear velocity and electrolyte concentration, the average current density applied to an Electrodialyzer is defined as limiting current density ( I / S ) lim . The solution velocity distribution in an Electrodialyzer strongly influences ( I / S ) lim .
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Development of a computer simulation program of batch ion-exchange membrane electrodialysis for saline water desalination
Desalination, 2013Co-Authors: Yoshinobu TanakaAbstract:Abstract A computer simulation program is developed to predict the desalinating performance of a constant voltage feed-and-bleed electrodialysis process, inputting membrane characteristics, Electrodialyzer specifications and electrodialytic conditions. A salt solution is supplied to a one-stage or a two-stage process to produce drinking water. Energy consumption for ion transport and limiting cell voltage in both processes are equivalent. In order to operate the two-stage process effectively, the cell pair number in the first stage should be the same to that in the second stage. Current density in the two-stage process becomes larger than that in the one-stage process because salt concentration in the first stage in the two-stage process is increased. Thus, the cell pair number integrated in the two-stage process is reduced compared to that in the one-stage process for producing the same amount of drinking water. Water recovery of the two-stage process is larger than that in the one-stage process because the cell pair number (thus solution feed to concentrating cells in the two-stage process) is reduced compared to that in the one-stage process.
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Ion-exchange membrane electrodialysis program and its application to multi-stage continuous saline water desalination
Desalination, 2012Co-Authors: Yoshinobu TanakaAbstract:Abstract The first part of this article describes the program of a one-stage continuous electrodialysis process operating at a constant current mode. The full continuous electrodialysis program is developed and explained definitely by arranging equations systematically with the following supplementary steps. For preventing scale formation in concentrating cells, salt solutions supplied to the desalting cells are also fed to the concentrating cells. Influence of temperature to the performance of the Electrodialyzer is taken into account. Pressure drop in the Electrodialyzer is evaluated by incorporating the functions of hydrodynamic diameters of desalting and concentrating cells and slots. An electric current screening effect of a spacer is determined by the volume ratio of spacer rods in a desalting and concentrating cell. In the second part of this article, saline water is desalinated with the multi-stage electrodialysis program by operating the process at a constant concentration mode. Changing salt concentration of a feeding solution in each stage incrementally, the performances of the Electrodialyzer such as; ion and solution flux across a membrane pair; cell voltage; current density; salt concentration in concentrating cells; energy consumption; water recovery; limiting current density; pressure drop in the cells and slots are computed in each stage. Energy consumption, water recovery, pressure drop and membrane area are computed in the total stages to produce drinking water.
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ion exchange membrane electrodialysis for saline water desalination and its application to seawater concentration
Industrial & Engineering Chemistry Research, 2011Co-Authors: Yoshinobu TanakaAbstract:Membrane pair characteristics of commercially available ion-exchange membranes are measured by changing current density and seawater temperature supplied to the Electrodialyzer. The hydraulic permeabilities (leading parameter) for three types of commercially available membranes are almost the same, and their averages are expressed by the empirical function of temperature. Hydraulic osmosis is predominant at lower current density and electro-osmosis is predominant at larger current density. The influence of temperature and salt concentration on the physical properties of saline water, such as solution density, specific conductance, and NaCl activity coefficient, is expressed by empirical equations. Ionic constituents in a concentrated solution are expressed by empirical equations. Electric current screening ratio of a spacer is defined and calculated. Direct current electric resistance of a membrane pair is calculated, and it is predominant over that of a desalting cell and a concentrating cell. It is nece...
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a computer simulation of batch ion exchange membrane electrodialysis for desalination of saline water
Desalination, 2009Co-Authors: Yoshinobu TanakaAbstract:Abstract A computer simulation program including the principle of ① mass transport, ② current density distribution, ③ energy consumption and ④ limiting current density is developed for predicting desalinating performance of a continuous (one-pass flow) electrodialysis process. In this simulation the following parameters are inputted; ① membrane characteristics such as overall transport number, overall solute permeability, overall electro-osmotic permeability, overall hydraulic permeability, direct current electric resistance etc. ② Electrodialyzer specifications such as flow-pass thickness, flow-pass width and flow-pass length of a desalting cell etc. and ③ electrodialytic conditions such as current density, electrolyte concentration in a feeding solution, linear velocity in desalting cells, standard deviation of normal distribution of solution velocity ratio etc. In a practical-scale Electrodialyzer, electrolyte concentration in a desalting cell is decreased along a flow-pass and it gives rise to electrolyte concentration distribution. It causes electric resistance distribution and current density distribution. Solution velocities in desalting cells vary between the cells, and give rise to solution velocity distribution. In this simulation, these distributions are taken into account assuming that the frequency distribution of solution velocity ratio is equated by the normal distribution. Further, the influences of Electrodialyzer specifications and elctrodialysis conditions described above on the performances of an Electrodialyzer (desalting ratio, current efficiency, electrolyte concentration at the outlets of desalting cells, cell voltage, energy consumption, electrolyte concentration distribution, current density distribution, and limiting current density) are predicted. The simulation model is developed on the basis of the experiments and its reasonability is supported by the performance of Electrodialyzers operating in salt-manufacturing plants.
Desmond F Lawler - One of the best experts on this subject based on the ideXlab platform.
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treatment of model inland brackish groundwater reverse osmosis concentrate with electrodialysis part ii sensitivity to voltage application and membranes
Desalination, 2014Co-Authors: Shane W Walker, Desmond F LawlerAbstract:Abstract The objective of this research was to investigate the sensitivity of electrodialysis performance to variations in voltage application and membranes when treating brackish water reverse osmosis concentrate waste. Synthetic BWRO concentrates from Arizona and Texas of 7890–14,800 mg/L total dissolved solids were prepared with poly-phosphonate antiscalants. Experimentation was performed using a laboratory-scale Electrodialyzer with two sets of membranes (AMV-CMV and PCSA-PCSK) with a nominal transfer area of 64 cm 2 per membrane. Flow, pressure, conductivity, temperature, and pH were measured continuously, and periodic samples were analyzed for specific anion and cation concentrations. The BWRO concentrates were successfully treated with stack voltage applications of 0.5–1.5 V/cell-pair for salinity removal ratios up to 99% with current density less than 500 A/m 2 . This paper highlights that (1) the specific energy consumption was proportional to the applied voltage and equivalent concentration separated ( i.e. , approximately 0.03 kW h/m 3 per Volt/cell-pair applied per meq/L separated); (2) lower voltage applications decreased the relative separation rate of sulfate compared to chloride; and (3) water transport by electro-osmosis was independent of voltage application or resulting current densities, while it is affected by the ion exchange membranes.
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treatment of model inland brackish groundwater reverse osmosis concentrate with electrodialysis part i sensitivity to superficial velocity
Desalination, 2014Co-Authors: Shane W Walker, Desmond F LawlerAbstract:Abstract The objective of this research was to investigate the sensitivity of electrodialysis performance to variations in hydraulic flow when treating brackish water reverse osmosis (BWRO) concentrate waste. A synthetic BWRO concentrate from Arizona of 7890 mg/L total dissolved solids was prepared with poly-phosphonate antiscalants, and desalinated with a laboratory-scale Electrodialyzer with 10 cell-pairs and a transfer area of 64 cm 2 per membrane. Flow, pressure, conductivity, temperature, and pH were measured continuously, and periodic process samples were analyzed by ion chromatography and inductively coupled plasma-optical emission spectrometry for anion and cation concentrations, respectively. The BWRO concentrate was successfully treated with a stack voltage application of 1.0 V/cell-pair and current densities less than 280 A/m 2 for salinity removal ratios up to 99% (without precipitation). The superficial velocities were controlled in a range of 1.2 to 4.8 cm/s, which corresponded to Reynolds numbers of 10 to 40. This paper shows the polarization parameter (ranging from 2.0 to 3.6 A/m 2 per meq/L) as a function of Reynolds number and removal ratio, and, at maximum sensitivity, the polarization parameter was proportional to Reynolds number raised to the 0.132 power.
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competitive separation of di vs mono valent cations in electrodialysis effects of the boundary layer properties
Water Research, 2012Co-Authors: Younggy Kim, Shane W Walker, Desmond F LawlerAbstract:Abstract In electrodialysis desalination, the boundary layer near ion-exchange membranes is the limiting region for the overall rate of ionic separation due to concentration polarization over tens of micrometers in that layer. Under high current conditions, this sharp concentration gradient, creating substantial ionic diffusion, can drive a preferential separation for certain ions depending on their concentration and diffusivity in the solution. Thus, this study tested a hypothesis that the boundary layer affects the competitive transport between di- and mono-valent cations, which is known to be governed primarily by the partitioning with cation-exchange membranes. A laboratory-scale Electrodialyzer was operated at steady state with a mixture of 10 mM KCl and 10 mM CaCl 2 at various flow rates. Increased flows increased the relative calcium transport. A two-dimensional model was built with analytical solutions of the Nernst–Planck equation. In the model, the boundary layer thickness was considered as a random variable defined with three statistical parameters: mean, standard deviation, and correlation coefficient between the thicknesses of the two boundary layers facing across a spacer. Model simulations with the Monte Carlo method found that a greater calcium separation was achieved with a smaller mean, greater standard deviation, or more negative correlation coefficient. The model and experimental results were compared for the cationic transport number as well as the current and potential relationship. The mean boundary layer thickness was found to decrease from 40 to less than 10 μm as the superficial water velocity increased from 1.06 to 4.24 cm/s. The standard deviation was greater than the mean thickness at slower water velocities and smaller at faster water velocities.
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electrodialysis with spacers effects of variation and correlation of boundary layer thickness
Desalination, 2011Co-Authors: Shane W Walker, Younggy Kim, Desmond F LawlerAbstract:The performance of electrodialysis is strongly dependent on the boundary layer thickness near an ion-exchange membrane. While a thinner boundary layer is known to enhance the ionic separation, the effects of statistical properties of the boundary layer thickness, such as the variation of the thickness and the correlation between the two boundary layers facing across the spacer, have not been elucidated. These effects were estimated by the Monte Carlo method incorporated into an analytical model. The analytical model simulates the binary ionic transport in four distinct regions of an electrodialysis cell pair: the bulk solution, boundary layer, ion-exchange membrane, and interface between the aqueous solution and ion-exchange membrane. The model current and potential relationships found that a greater variation or more positive correlation improves the ionic separation in the non-Ohmic regime. A bench-scale Electrodialyzer was operated in a batch recycle system to develop steady-state current and potential relationships. Comparison between the model and experimental results found that the mean boundary layer thickness was tens of micrometers and the standard deviation of the thickness was similar to or greater than the mean thickness with the sheet-flow type mesh spacer.
Shane W Walker - One of the best experts on this subject based on the ideXlab platform.
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treatment of model inland brackish groundwater reverse osmosis concentrate with electrodialysis part ii sensitivity to voltage application and membranes
Desalination, 2014Co-Authors: Shane W Walker, Desmond F LawlerAbstract:Abstract The objective of this research was to investigate the sensitivity of electrodialysis performance to variations in voltage application and membranes when treating brackish water reverse osmosis concentrate waste. Synthetic BWRO concentrates from Arizona and Texas of 7890–14,800 mg/L total dissolved solids were prepared with poly-phosphonate antiscalants. Experimentation was performed using a laboratory-scale Electrodialyzer with two sets of membranes (AMV-CMV and PCSA-PCSK) with a nominal transfer area of 64 cm 2 per membrane. Flow, pressure, conductivity, temperature, and pH were measured continuously, and periodic samples were analyzed for specific anion and cation concentrations. The BWRO concentrates were successfully treated with stack voltage applications of 0.5–1.5 V/cell-pair for salinity removal ratios up to 99% with current density less than 500 A/m 2 . This paper highlights that (1) the specific energy consumption was proportional to the applied voltage and equivalent concentration separated ( i.e. , approximately 0.03 kW h/m 3 per Volt/cell-pair applied per meq/L separated); (2) lower voltage applications decreased the relative separation rate of sulfate compared to chloride; and (3) water transport by electro-osmosis was independent of voltage application or resulting current densities, while it is affected by the ion exchange membranes.
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treatment of model inland brackish groundwater reverse osmosis concentrate with electrodialysis part i sensitivity to superficial velocity
Desalination, 2014Co-Authors: Shane W Walker, Desmond F LawlerAbstract:Abstract The objective of this research was to investigate the sensitivity of electrodialysis performance to variations in hydraulic flow when treating brackish water reverse osmosis (BWRO) concentrate waste. A synthetic BWRO concentrate from Arizona of 7890 mg/L total dissolved solids was prepared with poly-phosphonate antiscalants, and desalinated with a laboratory-scale Electrodialyzer with 10 cell-pairs and a transfer area of 64 cm 2 per membrane. Flow, pressure, conductivity, temperature, and pH were measured continuously, and periodic process samples were analyzed by ion chromatography and inductively coupled plasma-optical emission spectrometry for anion and cation concentrations, respectively. The BWRO concentrate was successfully treated with a stack voltage application of 1.0 V/cell-pair and current densities less than 280 A/m 2 for salinity removal ratios up to 99% (without precipitation). The superficial velocities were controlled in a range of 1.2 to 4.8 cm/s, which corresponded to Reynolds numbers of 10 to 40. This paper shows the polarization parameter (ranging from 2.0 to 3.6 A/m 2 per meq/L) as a function of Reynolds number and removal ratio, and, at maximum sensitivity, the polarization parameter was proportional to Reynolds number raised to the 0.132 power.
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competitive separation of di vs mono valent cations in electrodialysis effects of the boundary layer properties
Water Research, 2012Co-Authors: Younggy Kim, Shane W Walker, Desmond F LawlerAbstract:Abstract In electrodialysis desalination, the boundary layer near ion-exchange membranes is the limiting region for the overall rate of ionic separation due to concentration polarization over tens of micrometers in that layer. Under high current conditions, this sharp concentration gradient, creating substantial ionic diffusion, can drive a preferential separation for certain ions depending on their concentration and diffusivity in the solution. Thus, this study tested a hypothesis that the boundary layer affects the competitive transport between di- and mono-valent cations, which is known to be governed primarily by the partitioning with cation-exchange membranes. A laboratory-scale Electrodialyzer was operated at steady state with a mixture of 10 mM KCl and 10 mM CaCl 2 at various flow rates. Increased flows increased the relative calcium transport. A two-dimensional model was built with analytical solutions of the Nernst–Planck equation. In the model, the boundary layer thickness was considered as a random variable defined with three statistical parameters: mean, standard deviation, and correlation coefficient between the thicknesses of the two boundary layers facing across a spacer. Model simulations with the Monte Carlo method found that a greater calcium separation was achieved with a smaller mean, greater standard deviation, or more negative correlation coefficient. The model and experimental results were compared for the cationic transport number as well as the current and potential relationship. The mean boundary layer thickness was found to decrease from 40 to less than 10 μm as the superficial water velocity increased from 1.06 to 4.24 cm/s. The standard deviation was greater than the mean thickness at slower water velocities and smaller at faster water velocities.
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electrodialysis with spacers effects of variation and correlation of boundary layer thickness
Desalination, 2011Co-Authors: Shane W Walker, Younggy Kim, Desmond F LawlerAbstract:The performance of electrodialysis is strongly dependent on the boundary layer thickness near an ion-exchange membrane. While a thinner boundary layer is known to enhance the ionic separation, the effects of statistical properties of the boundary layer thickness, such as the variation of the thickness and the correlation between the two boundary layers facing across the spacer, have not been elucidated. These effects were estimated by the Monte Carlo method incorporated into an analytical model. The analytical model simulates the binary ionic transport in four distinct regions of an electrodialysis cell pair: the bulk solution, boundary layer, ion-exchange membrane, and interface between the aqueous solution and ion-exchange membrane. The model current and potential relationships found that a greater variation or more positive correlation improves the ionic separation in the non-Ohmic regime. A bench-scale Electrodialyzer was operated in a batch recycle system to develop steady-state current and potential relationships. Comparison between the model and experimental results found that the mean boundary layer thickness was tens of micrometers and the standard deviation of the thickness was similar to or greater than the mean thickness with the sheet-flow type mesh spacer.
Antonio Aldaz - One of the best experts on this subject based on the ideXlab platform.
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electrodialysis of brackish water powered by photovoltaic energy without batteries direct connection behaviour
Desalination, 2007Co-Authors: Juan Manuel Ortiz, Vicente Garciagarcia, Eduardo Expósito, F. Gallud, Vicente Montiel, Antonio AldazAbstract:Abstract The shortage of drinking water is a major problem in the South East of Spain. In these areas, it is essential to make use of water from underground reservoirs, most of which are over exploited and suffer from saline contamination given their proximity to the sea. The desalination of brackish water by electrodialysis is a useful method for obtaining low cost drinking water. Photovoltaic energy can be used to power the electrodialysis system in remote areas in a reliable and autonomous way. Moreover, the photovoltaic array can be connected directly to the Electrodialyzer, that is without batteries. Thus, the environmental threat of improper battery disposal is eliminated and increases the sustainability of the process. The aim of our paper is i) to demonstrate the feasibility of the desalination of brackish water by means of an electrodialysis system powered directly by photovoltaic solar panels, and ii) to explain theoretically the interaction between the photovoltaic generator and the electrodialysis system during the process. These systems are appropriate for small applications in isolated locations with lack of electric grid, where it is not necessary to produce water continuously and the volume of daily treated water required is small — about 1–10 m3.
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photovoltaic electrodialysis system for brackish water desalination modeling of global process
Journal of Membrane Science, 2006Co-Authors: Juan Manuel Ortiz, Vicente Garciagarcia, Eduardo Expósito, F. Gallud, Vicente Montiel, Antonio AldazAbstract:Abstract The shortage of drinking water is a major problem in the South East of Spain. In these areas, it is essential to make use of water from underground reservoirs, most of which are over exploited and suffer from saline contamination given their proximity to the sea. The desalination of brackish water is a means of obtaining low cost drinking water. The method of desalination designed in this paper uses an electrodialysis system fed by photovoltaic modules that is simple, reliable, and low cost because it does not include battery storage or a battery regulator. These systems are of particular interest for isolated zones with access to wells of brackish water where connection to the electric grid is not possible. In this paper, the feasibility of the desalination of brackish water using an electrodialysis system powered by photovoltaic energy and the influence of experimental parameters has been studied. Likewise, a mathematical simulation model that allows predicting and simulating the functioning of a system of these characteristics under different meteorological conditions has been developed. The model has been applied with satisfactory results to the desalination of a NaCl solution in different experimental conditions. Data given by the mathematical simulation model was contrasted with experimental results in order to compare the reliability of the model, and good agreement was obtained. The application of this model allows the design of an electrodialysis system powered by photovoltaic energy (Electrodialyzer size and the number and configuration of the PV modules), for the desalination of brackish water, as well as the study of its behaviour in different geographical locations.
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brackish water desalination by electrodialysis batch recirculation operation modeling
Journal of Membrane Science, 2005Co-Authors: Juan Manuel Ortiz, J A Sotoca, Vicente Garciagarcia, Eduardo Expósito, F. Gallud, Vicente Montiel, Antonio AldazAbstract:Abstract The shortage of drinking water is a major problem in the South East of Spain. In these areas, it is essential to make use of water from underground reservoirs, most of which are over exploited and suffer from saline contamination given their proximity to the sea. The desalination of brackish water is a means of obtaining low cost drinking water. Electrodialysis is a technique based in the transport of ions through selective membranes under the influence of an electrical field. This technique has proved its feasibility and high performance in the desalination of brackish water, the desalting of amino acids and other organic solutions, effluent treatment and or recycling of industrial process streams and salt production. In this paper, a mathematical model for the desalination of brackish water through controlled potential electrodialysis has been developed. The application of this model allows: (i) to predict the behaviour of the system, (ii) to calculate the electrical energy consumption and (iii) to calculate the necessary time for successful desalination. The model has been applied with satisfactory results to the desalination of a NaCl solution in different experimental conditions. The model developed could be applied to commercial Electrodialyzers (pilot/industrial plant) working in batches with recirculation and controlled potential, which is the usual mode of operation of such equipment when the requirements for treated water are moderated.
Sekwon Kim - One of the best experts on this subject based on the ideXlab platform.
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angiotensin i converting enzyme ace inhibitory peptide derived from the sauce of fermented blue mussel mytilus edulis
Bioresource Technology, 2005Co-Authors: Pyojam Park, Wonkyo Jung, Heeguk Byun, Sekwon KimAbstract:Abstract The angiotensin I converting enzyme (ACE) inhibitory activity of fermented blue mussel sauce (FBMS) was investigated. Blue mussels were fermented with 25% NaCl (w/w) at 20 °C for 6 months and the resultant mixture was passed through a 40-mesh sieve, desalted using an Electrodialyzer and then lyophilized. The IC50 value of FBMS for ACE activity was 1.01 mg/ml. An ACE inhibitory peptide was purified from FBMS using Sephadex G-75 gel chromatography, SP-Sephadex C-25 ion exchange chromatography and reversed-phase high-performance liquid chromatography on a C18 column. The IC50 value of purified ACE inhibitory peptide was 19.34 μg/ml, and 10 amino acid residues of the N-terminal sequence was EVMAGNLYPG. The purified peptide was evaluated for antihypertensive effect in spontaneously hypertensive rats (SHR) following oral administration. Blood pressure significantly decreased after peptide ingestion. This result suggested that FBMS may have beneficial effects on hypertension.
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antioxidative activity of a low molecular weight peptide derived from the sauce of fermented blue mussel mytilus edulis
European Food Research and Technology, 2005Co-Authors: Wonkyo Jung, Niranjan Rajapakse, Sekwon KimAbstract:In order to identify nutraceutical functions of fermented fish and shellfish sauces, which are highly appreciated in food products in South-East Asia, the antioxidative activity of fermented blue mussel sauce (FBMS) was investigated. The blue mussel was fermented with 25% NaCl (w/w) at 20±0.5 °C for 12 months and the fermented sauce was passed bimonthly through a 40-mesh sieve, desalted using an Electrodialyzer, and then lyophilized. The antioxidative activity of FBMSs was investigated and compared with that of a natural antioxidant, α-tocopherol standing as a reference. Using consecutive chromatographic methods, the antioxidative peptide with a molecular mass of 620 Da was purified from 6-month-fermented sauce, and its sequence of the peptide was FGHPY. In addition, 64.8 μM of the purified peptide could scavenge 89.5% of hydroxyl radical in radical scavenging assay using electron spin resonance spectroscopy.