The limitations of author's modification of the well-known method for determination of water cont... more The limitations of author's modification of the well-known method for determination of water content inorganic solvents with chloranilic acid (CAA) [Anal. Chim. Acta 16 (1962) 494] are illustrated. An insight into the CAA solvatochromism at the molecular level is proposed on the basis of quantum-chemical calculations. The bathochromic shift is explained by CAA anion formation in an interaction with the solvent. Deprotonation of CAAdepends substantially on the solvent, bothon the first solvation shell microstructure and on the bulk solvent phase. The deprotonation equilibrium, responsible for the long-wavelength absorption, limits applicability of the analytical method.
The optimal condition of water content determination in a-AI203, including sample mixing with met... more The optimal condition of water content determination in a-AI203, including sample mixing with methanol followed by titration of the suspension with K.Fisher reagent in the presence of methylene-blue background dye have been found. We have proved the absence of any significant systematic errors by variation of weighed. The determination limit, corre¬sponding to standard deviation of single result 0.3, of the methodic developed is 9-10-2 mass %. Thermogravimetric and mass-spectrometric data show that a-AI203 contains not only water, but also significant amounts of CO and C02, which, apparently, is the main reason of blowhole-like defects in those single crystals. We assume that material degassing by heating it in vacuum can allow a more effective elimination of such defects in the crystals, than the widely used thermal treatment of the material at atmospheric pressure.
The possibility of determining the total water content in inorganic salts and their crystal hydra... more The possibility of determining the total water content in inorganic salts and their crystal hydrates using a EuroEAA3000 elemental analyzer (EuroVector, Italy), designed for CHNS analysis of organic commpounds, is shown, and the metrological characteristics of such determination are assessed. To confirm the correctness, the results obtained are compared to independent data obtained by Fisher titrimetric and gravii metric analyses. The accuracy of determination with the elemental analyzer is comparable with that of the titrimetric method. The essential advantages of the method suggested over the conventional techniques are its high speed (only 5–6 min), use of milligram charges, and simplicity of performance. The simultaneous assessment of sulfate sulfur that is part of the analyzed salt is also possible
The papers takes stock of different methods for evaluating the detection (cmin) and determination... more The papers takes stock of different methods for evaluating the detection (cmin) and determination (c lim) limits of components described in the literature and presents a comparative analysis of the results of such evaluations. It is shown that use of the data on the fluctuations of the blank experiment, in spite of their wide application for such evaluations, gives ambiguous estimates for cmin and clim. The most correct method for evaluating the specified parameters is the experimental determination of the actual analyte concentration (content) from the empirical concentration dependence of the relative standard deviation. In case when this estimation method cannot be used, it is recommended to evaluate clim by the lower boundary of the calibration graph. The article may be useful for inexperienced analysts experimenters in choosing a method for evalluating the results obtained.
Conditions for eliminating systematic errors and minimizing random errors in the determination of... more Conditions for eliminating systematic errors and minimizing random errors in the determination of water in methanol and α-alumina using Karl Fisher reagent with visual end-point detection are studied. The concentration dependence of the relative standard deviation of the determination of water by the Karl Fisher method is found to be linear in RSD–1/c coordinates. To exclude the effect of moisture contained in the titration flask, it is suggested to bind water with a titrant in the presence of a small amount of methanol. The methanol effect (that is, the dependence of the titration results on the water : methanol ratio and the total amount of the titrated water–methanol mixture) is shown to be eliminated in the presence of the products of water interaction with Karl Fisher reagent that form on the water binding stage. It is found that the use of a background dye, methylene blue, eliminates significant systematic errors in the determination of water by the Karl Fisher method,
particularly, at low concentrations. It is noted that the visual detection of the titration end-point has some advantages over the automated electrometric versions of the method; in particular, it is characterized by a better reproducibility of the determination of low concentrations of water.
The limitations of author's modification of the well-known method for determination of water cont... more The limitations of author's modification of the well-known method for determination of water content inorganic solvents with chloranilic acid (CAA) [Anal. Chim. Acta 16 (1962) 494] are illustrated. An insight into the CAA solvatochromism at the molecular level is proposed on the basis of quantum-chemical calculations. The bathochromic shift is explained by CAA anion formation in an interaction with the solvent. Deprotonation of CAAdepends substantially on the solvent, bothon the first solvation shell microstructure and on the bulk solvent phase. The deprotonation equilibrium, responsible for the long-wavelength absorption, limits applicability of the analytical method.
The optimal condition of water content determination in a-AI203, including sample mixing with met... more The optimal condition of water content determination in a-AI203, including sample mixing with methanol followed by titration of the suspension with K.Fisher reagent in the presence of methylene-blue background dye have been found. We have proved the absence of any significant systematic errors by variation of weighed. The determination limit, corre¬sponding to standard deviation of single result 0.3, of the methodic developed is 9-10-2 mass %. Thermogravimetric and mass-spectrometric data show that a-AI203 contains not only water, but also significant amounts of CO and C02, which, apparently, is the main reason of blowhole-like defects in those single crystals. We assume that material degassing by heating it in vacuum can allow a more effective elimination of such defects in the crystals, than the widely used thermal treatment of the material at atmospheric pressure.
The possibility of determining the total water content in inorganic salts and their crystal hydra... more The possibility of determining the total water content in inorganic salts and their crystal hydrates using a EuroEAA3000 elemental analyzer (EuroVector, Italy), designed for CHNS analysis of organic commpounds, is shown, and the metrological characteristics of such determination are assessed. To confirm the correctness, the results obtained are compared to independent data obtained by Fisher titrimetric and gravii metric analyses. The accuracy of determination with the elemental analyzer is comparable with that of the titrimetric method. The essential advantages of the method suggested over the conventional techniques are its high speed (only 5–6 min), use of milligram charges, and simplicity of performance. The simultaneous assessment of sulfate sulfur that is part of the analyzed salt is also possible
The papers takes stock of different methods for evaluating the detection (cmin) and determination... more The papers takes stock of different methods for evaluating the detection (cmin) and determination (c lim) limits of components described in the literature and presents a comparative analysis of the results of such evaluations. It is shown that use of the data on the fluctuations of the blank experiment, in spite of their wide application for such evaluations, gives ambiguous estimates for cmin and clim. The most correct method for evaluating the specified parameters is the experimental determination of the actual analyte concentration (content) from the empirical concentration dependence of the relative standard deviation. In case when this estimation method cannot be used, it is recommended to evaluate clim by the lower boundary of the calibration graph. The article may be useful for inexperienced analysts experimenters in choosing a method for evalluating the results obtained.
Conditions for eliminating systematic errors and minimizing random errors in the determination of... more Conditions for eliminating systematic errors and minimizing random errors in the determination of water in methanol and α-alumina using Karl Fisher reagent with visual end-point detection are studied. The concentration dependence of the relative standard deviation of the determination of water by the Karl Fisher method is found to be linear in RSD–1/c coordinates. To exclude the effect of moisture contained in the titration flask, it is suggested to bind water with a titrant in the presence of a small amount of methanol. The methanol effect (that is, the dependence of the titration results on the water : methanol ratio and the total amount of the titrated water–methanol mixture) is shown to be eliminated in the presence of the products of water interaction with Karl Fisher reagent that form on the water binding stage. It is found that the use of a background dye, methylene blue, eliminates significant systematic errors in the determination of water by the Karl Fisher method,
particularly, at low concentrations. It is noted that the visual detection of the titration end-point has some advantages over the automated electrometric versions of the method; in particular, it is characterized by a better reproducibility of the determination of low concentrations of water.
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Papers by Тамара A Бланк
solvents with chloranilic acid (CAA) [Anal. Chim. Acta 16 (1962) 494] are illustrated. An insight into the CAA
solvatochromism at the molecular level is proposed on the basis of quantum-chemical calculations. The
bathochromic shift is explained by CAA anion formation in an interaction with the solvent. Deprotonation of
CAAdepends substantially on the solvent, bothon the first solvation shell microstructure and on the bulk solvent
phase. The deprotonation equilibrium, responsible for the long-wavelength absorption, limits applicability of the
analytical method.
assessment of sulfate sulfur that is part of the analyzed salt is also possible
particularly, at low concentrations. It is noted that the visual detection of the titration end-point has some advantages over the automated electrometric versions of the method; in particular, it is characterized by a better reproducibility of the determination of low concentrations of water.
solvents with chloranilic acid (CAA) [Anal. Chim. Acta 16 (1962) 494] are illustrated. An insight into the CAA
solvatochromism at the molecular level is proposed on the basis of quantum-chemical calculations. The
bathochromic shift is explained by CAA anion formation in an interaction with the solvent. Deprotonation of
CAAdepends substantially on the solvent, bothon the first solvation shell microstructure and on the bulk solvent
phase. The deprotonation equilibrium, responsible for the long-wavelength absorption, limits applicability of the
analytical method.
assessment of sulfate sulfur that is part of the analyzed salt is also possible
particularly, at low concentrations. It is noted that the visual detection of the titration end-point has some advantages over the automated electrometric versions of the method; in particular, it is characterized by a better reproducibility of the determination of low concentrations of water.