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Courtie Mahamadi - One of the best experts on this subject based on the ideXlab platform.
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interference effects of excess lithium on the emission signal of the calcium and strontium ionic lines during inductively coupled plasma emission spectrometry simulation in terms of the simplified collisional radiative recombination rate model
Journal of analytical and bioanalytical techniques, 2014Co-Authors: Mark F. Zaranyika, Courtie MahamadiAbstract:ICP-AES Ca and Sr ion line signals were measured on 0-30 μg/mL Ca and Sr solutions, in the absence and presence of 1000 μg/mL Li as easily ionizable interferent, and the effect of the interferent on analyte calibration curve simulated using a simplified collisional radiative recombination rate model. Close agreement between experiment and theory was obtained for the full range of concentrations studied in the case of SrII, while the theoretical Ca ion line calibration curve exhibited close agreement below 10 μg/mL Ca concentration in the test solution, and a positive deviation of up to 18% from the experimental curve at higher Ca concentrations. The data obtained successfully demonstrates the potential of the simplified collisional radiative recombination rate model for simulating the effects of easily ionizable Interferents on high ionization potential analytes.
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departure from local thermal equilibrium during icp aes and faes characterization in terms of collisional radiative recombination activation energy
Pure and Applied Chemistry, 2013Co-Authors: Mark F. Zaranyika, Courtie MahamadiAbstract:A simplified rate model is presented showing that when analytes are determined by atomic spectroscopy first in the absence, and then in the presence, of easily ionizable ele- ments (EIEs) as Interferents, the change in collisional radiative recombination activation energy, ΔE a , is zero when the system conforms to local thermal equilibrium (LTE). ΔE a val- ues of -7.462, -7.925, and -8.898 eV were obtained when Ca(II), Mg(II), and Sr(II), respec- tively, were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) in the absence and presence of excess Li, while ΔE a values of -6.477 and -7.481 eV were obtained when Mg(II) and Sr(II), respectively, were determined in the absence and presence of excess K as interferent. A value of -2.223 eV for ΔE a was obtained when Mg(I) was determined by air-acetylene flame atomic emission spectrometry (FAES) in the absence and presence of excess K. The data confirm that all the systems studied were not in LTE, and suggest pre-LTE collisional radiative recombination in the absence of the interferent in all cases, and that collisional radiative recombination involving electrons from the interferent can occur from the ambipolar diffusion state or the LTE state. Possible causes for departure from LTE, and a possible collisional radiative recombination mechanism to account for the ΔE a values obtained, are discussed.
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plasma diagnostics through kinetic modelling characterization of matrix effects during icp and flame atomic spectrometry in terms of collisional radiative recombination activation energy a review
Journal of analytical and bioanalytical techniques, 2013Co-Authors: Mark F. Zaranyika, Courtie MahamadiAbstract:Inductively coupled plasma atomic emission spectrometry (ICP-AES) is one of the most widely used and extremely important tools for trace element analysis today. The technique however still suffers from matrix effects, especially those due to easily ionizable elements (EIEs). Current theory of atomic spectrometry assumes Local Thermal Equilibrium (LTE), and EIE interference effects cannot be explained fully as long as all the electrons in the plasma are regarded as equivalent in accordance with the LTE theory. If however it is assumed that electronic collisions with heavy particles can occur before or after thermal equilibration, then electrons can be expected to experience different activation energies depending on whether collisions occurred before or after thermal equilibration. This paper reviews recent work carried out to characterize EIE interference effects during ICP-AES, flame AAS and flame AES in terms of ion-electron collisional radiative recombination activation energy. The work is based on a simplified rate model showing that when analytes are determined by atomic spectrometry in the absence and then in the presence of EIEs as Interferents, the change in collisional radiative recombination activation energy, ΔEa, is zero when the system conforms to LTE. Several analyte-interferent systems have been studied, and results obtained so far lead to the conclusion that departure from LTE results from collisions involving electrons in the ambipolar diffusion state. Factors affecting both pre-LTE and LTE collisions, as well as a possible collisional radiative recombination mechanism designed to account for the ΔEa values obtained are discussed.
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interference effects of easily ionizable elements in icp aes and flame aas characterization in terms of the collisional radiative recombination activation energy
Spectroscopy Letters, 2012Co-Authors: Mark F. Zaranyika, Albert T Chirenje, Courtie MahamadiAbstract:ABSTRACT A simplified rate model for the interference effects of easily ionized elements on analyte absorbance and emission signals in Flame atomic absorption spectroscopy, FAAS, is presented showing that when the analyte is determined in the absence and presence of the interferent, the change in the collisional radiative recombination activation energy, ΔE a, is zero when the systems conform to local thermal equilibrium. The proposed model also shows that ΔE a can be calculated from the slope of the plot of A′/A or I′/I versus the interferent-to-analyte ion number density ratio, where A and I denote absorbance and emission signal intensities, respectively, and the prime denotes presence of the interferent. ΔE a values of −1.5168 and −1.6924 eV where obtained when Mg was determined by FAAS in the presence of excess Ca and Sr respectively, and values of −6.62, −9.83, and −13.52 eV were obtained when CaI, CaII, and MgII respectively were determined in the presence of excess Li, confirming that these systems...
Cuili Xiang - One of the best experts on this subject based on the ideXlab platform.
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glucose biosensor based on electrodeposition of platinum nanoparticles onto carbon nanotubes and immobilizing enzyme with chitosan sio2 sol gel
Biosensors and Bioelectronics, 2008Co-Authors: Cuili Xiang, Fen XuAbstract:A novel amperometric biosensor, based on electrodeposition of platinum nanoparticles onto multi-walled carbon nanotube (MWNTs) and immobilizing enzyme with chitosan-SiO2 Sol-gel, is presented in this article. MWNTs were cast on the glass carbon (GC) substrate directly. An extra Nafion coating was used to eliminate common Interferents such as acetaminophen and ascorbic acids. The morphologies and electrochemical performance of the modified electrodes have been investigated by scanning electron microscopy (SEM) and amperometrie methods, respectively. The synergistic action of Pt and MWNTs and the biocompatibility of chitosan-SiO2 sol-gel made the biosensor have excellent electrocatalytic activity and high stability. The resulting biosensor exhibits good response performance to glucose with a wide linear range from 1 mu M to 23 mM and a low detection limit 1 mu M. The biosensor also shows a short response time (within 5 s), and a high sensitivity (58.9 mu Am M-1 cm(-2)). In addition, effects of pH value, applied potential, rotating rate, electrode construction and electroactive Interferents on the amperometric response of the sensor were investigated and discussed in detail. (C) 2007 Elsevier B.V. All rights reserved.
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glucose biosensor based on electrodeposition of platinum nanoparticles onto carbon nanotubes and immobilizing enzyme with chitosan sio2 sol gel
Biosensors and Bioelectronics, 2008Co-Authors: Cuili Xiang, Yongjin Zou, Lixian SunAbstract:A novel amperometric biosensor, based on electrodeposition of platinum nanoparticles onto multi-walled carbon nanotube (MWNTs) and immobilizing enzyme with chitosan-SiO(2) sol-gel, is presented in this article. MWNTs were cast on the glass carbon (GC) substrate directly. An extra Nafion coating was used to eliminate common Interferents such as acetaminophen and ascorbic acids. The morphologies and electrochemical performance of the modified electrodes have been investigated by scanning electron microscopy (SEM) and amperometric methods, respectively. The synergistic action of Pt and MWNTs and the biocompatibility of chitosan-SiO(2) sol-gel made the biosensor have excellent electrocatalytic activity and high stability. The resulting biosensor exhibits good response performance to glucose with a wide linear range from 1 microM to 23 mM and a low detection limit 1 microM. The biosensor also shows a short response time (within 5s), and a high sensitivity (58.9 microAm M(-1)cm(-2)). In addition, effects of pH value, applied potential, rotating rate, electrode construction and electroactive Interferents on the amperometric response of the sensor were investigated and discussed in detail.
Mark F. Zaranyika - One of the best experts on this subject based on the ideXlab platform.
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interference effects of excess lithium on the emission signal of the calcium and strontium ionic lines during inductively coupled plasma emission spectrometry simulation in terms of the simplified collisional radiative recombination rate model
Journal of analytical and bioanalytical techniques, 2014Co-Authors: Mark F. Zaranyika, Courtie MahamadiAbstract:ICP-AES Ca and Sr ion line signals were measured on 0-30 μg/mL Ca and Sr solutions, in the absence and presence of 1000 μg/mL Li as easily ionizable interferent, and the effect of the interferent on analyte calibration curve simulated using a simplified collisional radiative recombination rate model. Close agreement between experiment and theory was obtained for the full range of concentrations studied in the case of SrII, while the theoretical Ca ion line calibration curve exhibited close agreement below 10 μg/mL Ca concentration in the test solution, and a positive deviation of up to 18% from the experimental curve at higher Ca concentrations. The data obtained successfully demonstrates the potential of the simplified collisional radiative recombination rate model for simulating the effects of easily ionizable Interferents on high ionization potential analytes.
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departure from local thermal equilibrium during icp aes and faes characterization in terms of collisional radiative recombination activation energy
Pure and Applied Chemistry, 2013Co-Authors: Mark F. Zaranyika, Courtie MahamadiAbstract:A simplified rate model is presented showing that when analytes are determined by atomic spectroscopy first in the absence, and then in the presence, of easily ionizable ele- ments (EIEs) as Interferents, the change in collisional radiative recombination activation energy, ΔE a , is zero when the system conforms to local thermal equilibrium (LTE). ΔE a val- ues of -7.462, -7.925, and -8.898 eV were obtained when Ca(II), Mg(II), and Sr(II), respec- tively, were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) in the absence and presence of excess Li, while ΔE a values of -6.477 and -7.481 eV were obtained when Mg(II) and Sr(II), respectively, were determined in the absence and presence of excess K as interferent. A value of -2.223 eV for ΔE a was obtained when Mg(I) was determined by air-acetylene flame atomic emission spectrometry (FAES) in the absence and presence of excess K. The data confirm that all the systems studied were not in LTE, and suggest pre-LTE collisional radiative recombination in the absence of the interferent in all cases, and that collisional radiative recombination involving electrons from the interferent can occur from the ambipolar diffusion state or the LTE state. Possible causes for departure from LTE, and a possible collisional radiative recombination mechanism to account for the ΔE a values obtained, are discussed.
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plasma diagnostics through kinetic modelling characterization of matrix effects during icp and flame atomic spectrometry in terms of collisional radiative recombination activation energy a review
Journal of analytical and bioanalytical techniques, 2013Co-Authors: Mark F. Zaranyika, Courtie MahamadiAbstract:Inductively coupled plasma atomic emission spectrometry (ICP-AES) is one of the most widely used and extremely important tools for trace element analysis today. The technique however still suffers from matrix effects, especially those due to easily ionizable elements (EIEs). Current theory of atomic spectrometry assumes Local Thermal Equilibrium (LTE), and EIE interference effects cannot be explained fully as long as all the electrons in the plasma are regarded as equivalent in accordance with the LTE theory. If however it is assumed that electronic collisions with heavy particles can occur before or after thermal equilibration, then electrons can be expected to experience different activation energies depending on whether collisions occurred before or after thermal equilibration. This paper reviews recent work carried out to characterize EIE interference effects during ICP-AES, flame AAS and flame AES in terms of ion-electron collisional radiative recombination activation energy. The work is based on a simplified rate model showing that when analytes are determined by atomic spectrometry in the absence and then in the presence of EIEs as Interferents, the change in collisional radiative recombination activation energy, ΔEa, is zero when the system conforms to LTE. Several analyte-interferent systems have been studied, and results obtained so far lead to the conclusion that departure from LTE results from collisions involving electrons in the ambipolar diffusion state. Factors affecting both pre-LTE and LTE collisions, as well as a possible collisional radiative recombination mechanism designed to account for the ΔEa values obtained are discussed.
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interference effects of easily ionizable elements in icp aes and flame aas characterization in terms of the collisional radiative recombination activation energy
Spectroscopy Letters, 2012Co-Authors: Mark F. Zaranyika, Albert T Chirenje, Courtie MahamadiAbstract:ABSTRACT A simplified rate model for the interference effects of easily ionized elements on analyte absorbance and emission signals in Flame atomic absorption spectroscopy, FAAS, is presented showing that when the analyte is determined in the absence and presence of the interferent, the change in the collisional radiative recombination activation energy, ΔE a, is zero when the systems conform to local thermal equilibrium. The proposed model also shows that ΔE a can be calculated from the slope of the plot of A′/A or I′/I versus the interferent-to-analyte ion number density ratio, where A and I denote absorbance and emission signal intensities, respectively, and the prime denotes presence of the interferent. ΔE a values of −1.5168 and −1.6924 eV where obtained when Mg was determined by FAAS in the presence of excess Ca and Sr respectively, and values of −6.62, −9.83, and −13.52 eV were obtained when CaI, CaII, and MgII respectively were determined in the presence of excess Li, confirming that these systems...
Bruns R.e. - One of the best experts on this subject based on the ideXlab platform.
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Comparative Study Of The Selectivity Of A Kinetic-catalytic Method: The Determination Of Cr(vi) By Oxidation Of The O-dianisidine By Hydrogen Peroxide [estudo Comparativo Da Seletividade De Um Método Cinético-catalítico: A Determinação De Cr(vi) Pela
2015Co-Authors: Reis C., De Andrade J.c., Bruns R.e.Abstract:Selectivity studies for the determination of Cr(VI) using the catalytic oxidation of the o-dianisidine by hydrogen peroxide showed two distincts situations. In the first, when Interferents were studied by a univariate procedure, Cr(III) and Cu(II) cause serious interferences even at the 2:1 proportion, relative to Cr(VI), while Fe(III) interfered at the 15:1 ratio and EDTA at the 10:1 ratio. On the other hand, when a multivariate investigation was performed, Cr(III) did not present any significant principal effects and its significant interaction effects were negative, in contrast to EDTA, that presented positive interaction effects although, like Cr(III), did not show significant interaction effects. In view of the interferent's action it become necessary to separate Cr(VI) by extraction with methylisobutylketone in a chloridric acid medium before its determination in vegetals and in wastewater from a cellulose industry samples. Using this procedure, the method precision is ±0,5% at the 10 ng/mL Cr(VI) concentration level. The detection and quantification limits, calculated by means of absorbance measurements of ten replicates of blank reagents were 1,1 and 3,2 ng/mL, respectively. The results obtained with real samples showed a relative standard deviation between 1,2% and 3,0% relative to their reference values
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Comparative Study Of The Selectivity Of A Kinetic-catalytic Method: The Determination Of Cr(vi) By Oxidation Of The O-dianisidine By Hydrogen Peroxide [estudo Comparativo Da Seletividade De Um Método Cinético-catalítico: A Determinação De Cr(vi) Pela
2015Co-Authors: Reis C., De Andrade J.c., Bruns R.e.Abstract:Selectivity studies for the determination of Cr(VI) using the catalytic oxidation of the o-dianisidine by hydrogen peroxide showed two distincts situations. In the first, when Interferents were studied by a univariate procedure, Cr(III) and Cu(II) cause serious interferences even at the 2:1 proportion, relative to Cr(VI), while Fe(III) interfered at the 15:1 ratio and EDTA at the 10:1 ratio. On the other hand, when a multivariate investigation was performed, Cr(III) did not present any significant principal effects and its significant interaction effects were negative, in contrast to EDTA, that presented positive interaction effects although, like Cr(III), did not show significant interaction effects. In view of the interferent's action it become necessary to separate Cr(VI) by extraction with methylisobutylketone in a chloridric acid medium before its determination in vegetals and in wastewater from a cellulose industry samples. Using this procedure, the method precision is ±0,5% at the 10 ng/mL Cr(VI) concentration level. The detection and quantification limits, calculated by means of absorbance measurements of ten replicates of blank reagents were 1,1 and 3,2 ng/mL, respectively. The results obtained with real samples showed a relative standard deviation between 1,2% and 3,0% relative to their reference values.222189193Den Boef, G., Hulanicki, A., (1983) Pure Appl. Chem., 55, p. 553Muller, H., (1982) Crit. Rev. Anal. Chem., 13, p. 312Buscaróns, F., Artigas, J., (1957) Anal. Chim. Acta, 16, p. 452Kneebone, B.M., Freiser, H., (1975) Anal. Chem., 47, p. 595Legret, M., Divet, L., (1988) Analusis, 16, p. 97Dolmanova, I.F., Shekhovtsova, T.N., Peshkova, V., (1972) Zh. Analit. Khim, 27, p. 1981Dolmanova, I.F., Shekhovtsova, T.N., (1977) Zh. Analit. Khim., 32, p. 1546Montgomery, D.C., (1991) Design and Analysis of Experiments, p. 293. , John Wiley & Sons, Inc.SingaporeKatz, S.A., McNabb, W.M., Hazel, J.F., (1962) Anal. Chim. Acta, 27, p. 405Pilkington, E.S., Smith, P.R., (1967) Anal. Chim. Acta, 39, p. 321(1980) Anal. Chem., 52, p. 2242(1991) Bimontly Report 91.1, , January/February OIC Dr. V. Houba, P. O. Box 8005, 6700 EC, Wageningen, Holand
Fen Xu - One of the best experts on this subject based on the ideXlab platform.
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glucose biosensor based on electrodeposition of platinum nanoparticles onto carbon nanotubes and immobilizing enzyme with chitosan sio2 sol gel
Biosensors and Bioelectronics, 2008Co-Authors: Cuili Xiang, Fen XuAbstract:A novel amperometric biosensor, based on electrodeposition of platinum nanoparticles onto multi-walled carbon nanotube (MWNTs) and immobilizing enzyme with chitosan-SiO2 Sol-gel, is presented in this article. MWNTs were cast on the glass carbon (GC) substrate directly. An extra Nafion coating was used to eliminate common Interferents such as acetaminophen and ascorbic acids. The morphologies and electrochemical performance of the modified electrodes have been investigated by scanning electron microscopy (SEM) and amperometrie methods, respectively. The synergistic action of Pt and MWNTs and the biocompatibility of chitosan-SiO2 sol-gel made the biosensor have excellent electrocatalytic activity and high stability. The resulting biosensor exhibits good response performance to glucose with a wide linear range from 1 mu M to 23 mM and a low detection limit 1 mu M. The biosensor also shows a short response time (within 5 s), and a high sensitivity (58.9 mu Am M-1 cm(-2)). In addition, effects of pH value, applied potential, rotating rate, electrode construction and electroactive Interferents on the amperometric response of the sensor were investigated and discussed in detail. (C) 2007 Elsevier B.V. All rights reserved.