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Analytical potentiometry is a powerful technique to investigate multiple species in solution and their formation constants. However, there have been some difficulties in this method resulting primarily from the theoretical approach. In... more
Analytical potentiometry is a powerful technique to investigate multiple species in solution and their formation constants. However, there have been some difficulties in this method resulting primarily from the theoretical approach. In this paper we critically examined them ...
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Evidence is given for an acid-base dissociation reaction of tris (ethylenediamine) cobalt (III) ion in basic aqueous solutions. The evidence is based on the nmr chemical shifts of the methylene protons and on the u.v. absorption spectra... more
Evidence is given for an acid-base dissociation reaction of tris (ethylenediamine) cobalt (III) ion in basic aqueous solutions. The evidence is based on the nmr chemical shifts of the methylene protons and on the u.v. absorption spectra of Co(en)33+ ion in basic solution. The equilibrium constant of the deprotonation reaction is estimated by each of the two methods.
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High-level yeast inocula was investigated as a means of overcoming the toxicity problem in ethanol fermentation of acid hydrolyzate of wood cellulose. When the inoculum level exceeded 108 initial cells/mL, 50% of the yeast cells survived... more
High-level yeast inocula was investigated as a means of overcoming the toxicity problem in ethanol fermentation of acid hydrolyzate of wood cellulose. When the inoculum level exceeded 108 initial cells/mL, 50% of the yeast cells survived the initial cell death period during which furfural and HMF were depleted. The fermentation thus proceeded to completion by virtue of cell regrowth. The specific ethanol productivity in batch fermentation on the basis of viable cells was comparable to that of pure glucose fermentation. Continuous fermentation with cell recycle was superior to batch fermentation in that there was no overall cell decline and the ethanol yield was substantially higher. The maximum ethanol productivity in continuous fermentation was 4.9 g/L h and it occurred at a dilution rate of 0.24 hr−1.
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The inhibitory effects of six lignocellulose degradation products on glucose fermentation by Saccharomyces cerevisiae and Zymomonas mobilis on xylose fermentation by Pichia stipitis and Candida shehatae were studied in batch cultures.... more
The inhibitory effects of six lignocellulose degradation products on glucose fermentation by Saccharomyces cerevisiae and Zymomonas mobilis on xylose fermentation by Pichia stipitis and Candida shehatae were studied in batch cultures. Toxic compounds were added in varying concentrations and subsequent inhibitions on growth and ethanol production were quantified. Vanillin was shown to be a strong inhibitor of both growth and ethanol production by xylose fermenting yeasts and S. cerevisiae when it was added to the culture media at a concentration of 1 g l−1. Fermentative activities of Z. mobilis were greatly sensitive to the presence of hydroxybenzaldehyde (0.5 g l−1). Analysis of culture media extracts showed that some of the inhibitors, particularly vanillin and furaldehyde, could be assimilated by the tested microbial strains which resulted in the partial recovery in both growth and ethanol production processes on prolonged incubation.
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Xylose, the dominant sugar in red oak acid prehydrolysate, was fermented to ethanol. In batch cultures of xylose concentrations ranging from 10 to 100 g l−1, Pichia stipitis CBS 5776 yielded 0.50–0.40 g ethanol per g xylose consumed.... more
Xylose, the dominant sugar in red oak acid prehydrolysate, was fermented to ethanol. In batch cultures of xylose concentrations ranging from 10 to 100 g l−1, Pichia stipitis CBS 5776 yielded 0.50–0.40 g ethanol per g xylose consumed. Model compounds of inhibitors generated in the acid prehydrolysis of red oak hemicelluloses, lignin and extractives, hindered the fermentation. Recycled yeasts and treatments with molecular sieve or mixed bed ionresins facilitated the ethanol fermentation of red oak acid prehydrolysate. A maximal ethanol concentration of 9.9 g l−1 was obtained from an acid prehydrolysate containing 21.7 g l−1 of xylose. Fermentation inhibitors derived from red oak lignin and extractives were identified.
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Economic optimization of the production of ethanol by simultaneous saccharification and fermentation (SSF) requires knowledge about the influence of substrate and enzyme concentration on yield and productivity. Although SSF has been... more
Economic optimization of the production of ethanol by simultaneous saccharification and fermentation (SSF) requires knowledge about the influence of substrate and enzyme concentration on yield and productivity. Although SSF has been investigated extensively, the optimal conditions for SSF of softwoods have yet not been determined. In this study, SO2-impregnated and steam-pretreated spruce was used as substrate for the production of ethanol by SSF. Commercial enzymes were used in combination with the yeast Saccharomyces cerevisiae. The effects of the concentration of substrate (2% to 10% w/w) and of cellulases (5 to 32 FPU/g cellulose) were investigated. SSF was found to be sensitive to contamination because lactic acid was produced. The ethanol yield increased with increasing cellulase loading. The highest ethanol yield, 68% of the theoretical based on the glucose and mannose present in the original wood, was obtained at 5% substrate concentration. This yield corresponds to 82% of the theoretical based on the cellulose and soluble glucose and mannose present at the start of SSF. A higher substrate concentration caused inefficient fermentation, whereas a lower substrate concentration, 2%, resulted in increased formation of lactic acid, which lowered the yield. Compared with separate hydrolysis and fermentation, SSF gave a higher yield and doubled the productivity.
Research Interests: Production, Biotechnology, Multidisciplinary, Cellulose, Cellulase, and 16 moreOptimization, Saccharomyces cerevisiae, Glucose, Wood, Biofuel, Ethanol Production, Ethanol, Lignin, Fermentation, Carbohydrate metabolism, STEAM, Ethanol Fermentation, Softwood, Mannose, Water Vapor, and Simultaneous Saccharification and Fermentation
High concentrations of both ethanol and sugar in the fermentation broth inhibit the growth of yeast cells and the rate of product formation. Inhibitory effects of ethanol on the yeast strain Saccharomyces cerevisiae NRRL-Y-132 were... more
High concentrations of both ethanol and sugar in the fermentation broth inhibit the growth of yeast cells and the rate of product formation. Inhibitory effects of ethanol on the yeast strain Saccharomyces cerevisiae NRRL-Y-132 were studied in batch and continuous chemostat cultures. Growth was limited by either glucose or ethanol. Feed medium was supplemented with different ethanol concentrations. Ethanol was found to inhibit growth and the activity of yeast to produce ethanol in a noncompetitive manner. A linear kinetic pattern for growth and product formation was observed according to μ = μm (1 – P/Pm) and v = vm (1 – P/Pm′), where μm is the maximum specific growth rate at P = 0 (hr−1); Pm is the maximum specific product formation rate at P = 0 (hr−1); Pm is the maximum ethanol concentration above which cells do not grow (g/liter); Pm′ is the maximum ethanol concentration above which cells do not produce ethanol (g/liter). Substrate inhibition studies were carried out using short-time experimental techniques under aerobic and anaerobic condition. The degree of substrate inhibition was found to be higher than that has been reported for ethanol fermentation of pure sugar. The kinetic relationships thus obtained were used to compute growth, substrate utilization, and alcohol production patterns and have been discussed with reference to batch and continuous fermentation of enzymatically produced bagasse hydrolysate.
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Rapid fermentation of bagasse hydrolysate to ethanol under anaerobic conditions by a strain of Saccharomyces cerevisiae has been studied in batch and continuous cultures at pH 4.0 and 30°C temperature with cell recycle. By using a 23.6... more
Rapid fermentation of bagasse hydrolysate to ethanol under anaerobic conditions by a strain of Saccharomyces cerevisiae has been studied in batch and continuous cultures at pH 4.0 and 30°C temperature with cell recycle. By using a 23.6 g/liter cell concentration, a concentation of 9.7% (w/v)ethanol was developed in a period of 6 hr. The rate of fermentation was found to increase with supplementation of yeast vitamins in the hydrolysate. In continuous culture employing cell recycle and a 0.127 v/v/m air flow rate, a cell mass concentration of 48.5 g/liter has been achieved. The maximum fermentor productivity of ethanol obtained under these conditions was 32.0 g/liter/hr, which is nearly 7.5 times higher than the normal continuous process without cell recycle and air sparging. The ethanol productivity was found to decrease linearly with ethanol concentration. Conversion of glucose in the hydrolysate to ethanol was achieved with a yield of 95 to 97% of theoretical.
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The inhibitory effect of ethanol on yeast growth and fermentation has been studied for the strain Saccharomyces cerevisiae ATCC No. 4126 under anaerobic batch conditions. The results obtained reveal that there is no striking difference... more
The inhibitory effect of ethanol on yeast growth and fermentation has been studied for the strain Saccharomyces cerevisiae ATCC No. 4126 under anaerobic batch conditions. The results obtained reveal that there is no striking difference between the response of growth and ethanol fermentation. Two kinetic models are also proposed to describe the kinetic pattern of ethanol inhibition on the specific rates of growth and ethanol fermentation: microi/micro0 = 1 - (P/Pm)alpha (for growth) nui/nu0 = 1 - (P/P'm)beta (for ethanol production). The maximum allowable ethanol concentration above which cells do not grow was predicted to be 112 g/L. The ethanol-producing capability of the cells was completely inhibited at 115 g/L ethanol. The proposed models appear to accurately represent the experimental data obtained in this study and the literature data.
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Inhibition by secondary fermentation products may limit the ultimate productivity of new glucose to ethanol fermentation processes. New processes are under development whereby ethanol is selectively removed from the fermenting broth to... more
Inhibition by secondary fermentation products may limit the ultimate productivity of new glucose to ethanol fermentation processes. New processes are under development whereby ethanol is selectively removed from the fermenting broth to eliminate ethanol inhibition effects. These processes can concentrate minor secondary products to the point where they become toxic to the yeast. Vacuum fermentation selectively concentrates nonvolatile products in the fermentation broth. Membrane fermentation systems may concentrate large molecules which are sterically blocked from membrane transport. Extractive fermentation systems, employing nonpolar solvents, may concentrate small organic acids. By-product production rates and inhibition levels in continuous fermentation with Saccharomyces cerevisiae have been determined for acetaldehyde, glycerol, formic, lactic, and acetic acids, 1-propanol, 2-methyl-1-butanol, and 2,3-butanediol to assess the potential effects of these by-products on new fermentation processes. Mechanisms are proposed for the various inhibition effects observed.
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Inhibition by secondary fermentation products may limit the ultimate productivity of new glucose to ethanol fermentation processes. New processes are under development whereby ethanol is selectively removed from the fermenting broth to... more
Inhibition by secondary fermentation products may limit the ultimate productivity of new glucose to ethanol fermentation processes. New processes are under development whereby ethanol is selectively removed from the fermenting broth to eliminate ethanol inhibition effects. These processes can concentrate minor secondary products to the point where they become toxic to the yeast. Vacuum fermentation selectively concentrates nonvolatile products in the fermentation broth. Membrane fermentation systems may concentrate large molecules which are sterically blocked from membrane transport. Extractive fermentation systems, employing nonpolar solvents, may concentrate small organic acids. By-product production rates and inhibition levels in continuous fermentation with Saccharomyces cerevisiae have been determined for acetaldehyde, glycerol, formic, lactic, and acetic acids, 1-propanol, 2-methyl-1-butanol, and 2,3-butanediol to assess the potential effects of these by-products on new fermentation processes. Mechanisms are proposed for the various inhibition effects observed.
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Cell recycle and vacuum fermentation systems were developed for continuous ethanol production. Cell recycle was employed in both atmospheric pressure and vacuum fermentations to achieve high cell densities and rapid ethanol fermentation... more
Cell recycle and vacuum fermentation systems were developed for continuous ethanol production. Cell recycle was employed in both atmospheric pressure and vacuum fermentations to achieve high cell densities and rapid ethanol fermentation rates. Studies were conducted with Saccharomyces cerevisiae (ATCC No. 4126) at a fermentation temperature of 35°C. Employing a 10% glucose feed, a cell density of 50 g dry wt/liter was obtained in atmospheric-cell recycle fermentations which produced a fermentor ethanol productivity of 29.0 g/liter-hr. The vacuum fermentor eliminated ethanol inhibition by boiling away ethanol from the fermenting beer as it was formed. This permitted the rapid and complete fermentation of concentrated sugar solutions. At a total pressure of 50 mmHg and using a 33.4% glucose feed, ethanol productivities of 82 and 40 g/liter-hr were achieved with the vacuum system with and without cell recycle, respectively. Fermentor ethanol productivities were thus increased as much as twelvefold over conventional continuous fermentations. In order to maintain a viable yeast culture in the vacuum fermentor, a bleed of fermented broth had to be continuously withdrawn to remove nonvolatile compounds. It was also necessary to sparge the vacuum fermentor with pure oxygen to satisfy the trace oxygen requirement of the fermenting yeast.
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... Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (30). 8. AA El-Bindary, AZ El-Sonbati and HM Kera Pol J Chem 74 (2000), p. 2399. 9. LG Van Uitert and CG Hass J Am Chem Soc 75 (1953), p. 451. ... 14. HM Irving and... more
... Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (30). 8. AA El-Bindary, AZ El-Sonbati and HM Kera Pol J Chem 74 (2000), p. 2399. 9. LG Van Uitert and CG Hass J Am Chem Soc 75 (1953), p. 451. ... 14. HM Irving and RJP Williams Nature 162 (1948), p. 746. ...
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The complexation equilibria for the boric acid–d-glucosaminic acid and d-glucosaminic acid–metal(II) ion binary systems, the boric acid–d-glucosaminic acid–metal(II) ion ternary system, and the corresponding binary and ternary systems... more
The complexation equilibria for the boric acid–d-glucosaminic acid and d-glucosaminic acid–metal(II) ion binary systems, the boric acid–d-glucosaminic acid–metal(II) ion ternary system, and the corresponding binary and ternary systems with germanic acid instead of boric acid involving nickel(II), zinc(II), cadmium(II) and lead(II) as the metal(II) ion have been investigated in aqueous solution at 25°C and I=0.1 mol dm−3 (NaClO4) by potentiometric measurements (d-glucosaminic acid is 2-amino-2-deoxy-d-gluconic acid). The complexes have been characterized in aqueous solution by 13C NMR spectra and the pKa values. The 1:2 ester of borate and d-glucosaminate shows a selectivity for metal(II) ions different from the free d-glucosaminate ligand. It has been demonstrated that the coordination site of the 1:2 ester can distinguish the difference in metal ion size. Such selectivity for metal(II) ions in the boric acid system is discussed by comparison with the germanic acid system.
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Speciation in the aqueous V(III)–carnosine system has been determined from potentiometric and spectroscopic (UV-Vis absorption and CD) data. Application of the Hyperquad program to the experimental potentiometric data indicates that under... more
Speciation in the aqueous V(III)–carnosine system has been determined from potentiometric and spectroscopic (UV-Vis absorption and CD) data. Application of the Hyperquad program to the experimental potentiometric data indicates that under our experimental conditions (I=0.5 mol⋅L−1 NaClO4, pH=2 to 6.5, and L/M>5) only ML2H4, ML2H3, ML2H2 and ML2H form. These potentiometric results prove that stable complexes form and, with use of the spectroscopic methods, the binding sites are identified.
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A nonlinear curve fitting using Microsoft Excel Solver and user-defined function is described for the evaluation of formation constants and molar absorptivities of metal complexes from spectrophotometric data and evaluation of protonation... more
A nonlinear curve fitting using Microsoft Excel Solver and user-defined function is described for the evaluation of formation constants and molar absorptivities of metal complexes from spectrophotometric data and evaluation of protonation constants of acids from potentiometric data. The procedure was applied to the spectrophotometric data of ML and ML2complexes and potentiometric data of HL and H2L acids. The obtained
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The stability constants of the complexes formed by three tetra-aza macrocyclic complexones (DOTA, TRITA and TETA) with Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+) were determined with an automated titration... more
The stability constants of the complexes formed by three tetra-aza macrocyclic complexones (DOTA, TRITA and TETA) with Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+) were determined with an automated titration instrument with data acquisition and the calculations were performed with the Superquad program, confirming and extending the range of values previously available. Both 1:1 and 2:1 metal-to-ligand complexes were now considered including their protonated species. The results show that DOTA is a powerful but unselective ligand whereas TETA, although not so powerful as DOTA, is an interesting selective ligand for pairs of metal ions, e.g., Cd(2+) and Pb(2+).
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Abstract Techniques of data reduction and methods of calculation have been given for the determination of equilibrium constants by titration calorimetry. It has been shown how, starting with typical titration calorimetry data, the... more
Abstract Techniques of data reduction and methods of calculation have been given for the determination of equilibrium constants by titration calorimetry. It has been shown how, starting with typical titration calorimetry data, the apparent heat liberated in the reaction ...
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Page 1. 2904 Irving and Rossotti : Calculation of Formation Curves of Metal The Calculation of Formation Curves of Metal Complexes from pH Titration Curves in Mixed Solvents. By HM IRVING and (MRs.) H. S. ROSSOTTI. [Reprint Order No. ...
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Single-ion activity coefficient equations were determined for the calculation of the molality-scale dissociation constants, Km, for acetic acid in aqueous NaCl or KCl solutions at 298.15 K. The salt alone determines the ionic strength,... more
Single-ion activity coefficient equations were determined for the calculation of the molality-scale dissociation constants, Km, for acetic acid in aqueous NaCl or KCl solutions at 298.15 K. The salt alone determines the ionic strength, Im, of the solutions considered in this study. The activity coefficient equations are of the Hückel type, and Km can be calculated by those for a
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In order to have more information about the thermodynamic properties of the complexes formed by Cobalt(II) and DPKBH (di-2-pyridyl ketone benzoylhydrazone) and for the development of speciation methods for cobalt, the respective stepwise... more
In order to have more information about the thermodynamic properties of the complexes formed by Cobalt(II) and DPKBH (di-2-pyridyl ketone benzoylhydrazone) and for the development of speciation methods for cobalt, the respective stepwise formation constants were determined in ethanolic solution 50% (V/V), at pH 5.3 and 25.0°C. The spectrophotometric method of corresponding solutions was used and the following overall formation
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The stability of molybdenum(VI) complex formed by iminodiacetic acid(IDA) has been studied at 25°C, pH = 6.0, and different ionic strengths ranging from (0.3 to 1.0) mol dm−3 of sodium perchlorate. A combination of potentiometric and... more
The stability of molybdenum(VI) complex formed by iminodiacetic acid(IDA) has been studied at 25°C, pH = 6.0, and different ionic strengths ranging from (0.3 to 1.0) mol dm−3 of sodium perchlorate. A combination of potentiometric and spectrophotometric techniques have been used based on the continuous variations method. According to our investigations, the metal-to-ligand ratio is 1: 1. The Solver, Microsoft Excel 2000 powerful optimization package, has been used to perform non-linear least-squares curve fitting. In order to obtain better consistency between the experimental and calculated results, two empirical parameters have been introduced in a Debye-Huckel-type equation. This equation enables us to calculate the values of stability constants in the desired range of ionic strength.
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The interaction of the antitumor agent chlorambucil (CHL) with three different cyclodextrins (CD), namely methyl-βCD (MeβCD) polymer-βCD (poly-βCD) and γCD, is examined kinetically and spectrophotometrically, monitoring the hydrolysis and... more
The interaction of the antitumor agent chlorambucil (CHL) with three different cyclodextrins (CD), namely methyl-βCD (MeβCD) polymer-βCD (poly-βCD) and γCD, is examined kinetically and spectrophotometrically, monitoring the hydrolysis and the changes in the UV absorbance of CHL respectively, in the presence of increasing concentrations of the examined CD. The stoichiometry coefficient for all the CHL–CD complexes was calculated and found to be 1:1, using the continuous variation method based on the UV data. Also, the stability constant Kst for the CHL–CD complexes was calculated and evaluated using the above mentioned two methods, each one based on linear and nonlinear mathematical models. All studies demonstrate that the interaction of CHL with the methylated derivative (MeβCD) is stronger (the highest Kst value), probably due to the enhanced hydrophobic character of this derivative.
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The values of the stability constants of the Ca(II) and lanthanide(III) complexes of murexide reported in the literature were determined without proper correction for binding of buffer ions to the metal ion. The constants are best... more
The values of the stability constants of the Ca(II) and lanthanide(III) complexes of murexide reported in the literature were determined without proper correction for binding of buffer ions to the metal ion. The constants are best determined without a buffer present. Accurate values of conditional stability constants for the Eu(III)-murexide complex (relative standard deviation better than 3%), of the differential molar absorptivity of the Eu(III)-murexide complex with respect to murexide at 480 nm (relative standard deviation better than 0.5%) and of the molar absorptivity of murexide at 520 and at 506 nm (precision better than 0.4%) at pH 5.0 and 6.5 at 15, 25 and 35 degrees are reported. The accuracy and precision of the concentration of metal ion solution determined by using these conditional stability constants are discussed.
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Stability constants of n-butyrato (B) and 2-, 3- and 4-hydroxybutyrato complexes (abbreviated 2-OH-B, 3-OH-B and 4-OH-B respectively) of Co(II), Ni(II) and Cu(II) were obtained from spectrophotometric data, using Bjerrum's method of... more
Stability constants of n-butyrato (B) and 2-, 3- and 4-hydroxybutyrato complexes (abbreviated 2-OH-B, 3-OH-B and 4-OH-B respectively) of Co(II), Ni(II) and Cu(II) were obtained from spectrophotometric data, using Bjerrum's method of corresponding solutions. The constants and their ±95 per cent confidence intervals were calculated with a digital computer and had the following values:
An improved slope-intercept method has been developed for determining the stability constant of a 1:1 complex, using spectrophotometric data. Applying this method the stability constant of Fe(III)-5 chlorosalicylate complex was... more
An improved slope-intercept method has been developed for determining the stability constant of a 1:1 complex, using spectrophotometric data. Applying this method the stability constant of Fe(III)-5 chlorosalicylate complex was determined. The log k1 value at room temperature (25 ± 2°C) and at I = 0·1 is 15·42. The effect of ionic strength and pH has also been studied. Extrapolation of concentration quotient values to zero ionic strength results in a thermodynamic value of 16·38, whereas taking the concentration quotient at I = 0·1 and making activity corrections based on Davies equation it is 16·76.
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The stability constants of Ni(II) complexes with 2-methylhydrazinedithio-carboxylic and 3,3-dimethylhydrazinedithiocarboxylic acids and Ni(II) and Cu(II) complexes with 3-methyl-3-phenylhydrazinedithiocarboxylic acid have been determined... more
The stability constants of Ni(II) complexes with 2-methylhydrazinedithio-carboxylic and 3,3-dimethylhydrazinedithiocarboxylic acids and Ni(II) and Cu(II) complexes with 3-methyl-3-phenylhydrazinedithiocarboxylic acid have been determined in aqueous solution at 25°C and I = 0.01 M. The Bjerrum method of corresponding solutions has been applied, revealing the simultaneous presence of 1:1 and 1:2 complexes in solution.
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Multivariate curve resolution, alternating least-squares is applied to spectra data obtained in the study of Cu(II) complexation by l-histidine. The combination of several chemometric techniques based on factor analysis (FA), singular... more
Multivariate curve resolution, alternating least-squares is applied to spectra data obtained in the study of Cu(II) complexation by l-histidine. The combination of several chemometric techniques based on factor analysis (FA), singular value decomposition (SVD), evolving factor analysis (EFA), and multivariate curve resolution with constrained alternating least-squares (ALS) is used to determine the number of species and their distribution diagram. This multivariate analysis data treatment simultaneously reveals the species Cu, CuL, CuLH, CuL2, CuL2H, and CuLOH, through the calculated concentration profiles and allows the assignment of numerically obtained pure individual spectra. Formation constants of these species were calculated by hard-modeling methods applied potentiometric and spectrophotometric measurements.