Strong interaction between natural dissolved organic matter (DOM) and Hg(Ⅱ) may influence the trans- port, conversion, toxicity and bio-validity of mercury in the environment. In this paper ultraviolet (UV) absorbanc...Strong interaction between natural dissolved organic matter (DOM) and Hg(Ⅱ) may influence the trans- port, conversion, toxicity and bio-validity of mercury in the environment. In this paper ultraviolet (UV) absorbance titration was employed for the first time for the determination of the conditional stability constants of Hg(Ⅱ) and (DOM). With increasing Hg(Ⅱ) concentrations, the UV absorbance of fulvic acid, humic acid, and DOM in river increases progressively. By linear and non-linear model fitting, the conditional stability constants (lgK) of Hg(Ⅱ) and DOM were worked out to be 3.54?4.93 and 3.64?4.85, respectively. The results are consistent with those acquired by the typical fluorescence quenching titration method, with the maximum relative error of lgK being 2.6% and the average relative error being 0.2%. The UV absorbance titration method has the advantages of rapid determination, simple performance, and it will probably become a new approach to studying interactions between DOM and trace metallic ions.展开更多
The formation constants of Co￣(2+), Ni￣(2+), Cu￣(2+) and Zn￣(2+) complexes with humic acid (HA) and fulvicacid (FA) in red soil were determined by the potentiometric titration method. The constants as a functionof...The formation constants of Co￣(2+), Ni￣(2+), Cu￣(2+) and Zn￣(2+) complexes with humic acid (HA) and fulvicacid (FA) in red soil were determined by the potentiometric titration method. The constants as a functionof composition of the complexation solutions were obtained by two graphical approaches respectively Theformation constants decreased with increasing concentration of metal in the solution. The results provideunambiguous evidence for the heterogeneity of the function groups of humic substances. The formationconstants of FA were much smaller than those of HA, and the formation constants of Cu￣(2+) were muchgreater than those of Co￣(2+) , Ni￣(2+) and Zn￣(2+) . The potentiometric titration method for determining formationconstants are also discussed in the article.展开更多
A potentiometric study on the complexes of His,Gly-His,ALa-His,Gly-Gly and Gly—Gly—Gly with Zn(Ⅱ)and Cd(Ⅱ)has been reported.Small-scale potentiometric titrations were car- ried out to determine stabil ity constant...A potentiometric study on the complexes of His,Gly-His,ALa-His,Gly-Gly and Gly—Gly—Gly with Zn(Ⅱ)and Cd(Ⅱ)has been reported.Small-scale potentiometric titrations were car- ried out to determine stabil ity constants of complexes at 25℃ with I=0.10 mol dm^(-3)(KNO_3).The com- puter programs SUPERQUAD were applied for data treatment with satisfactory results.展开更多
This paper reports the determination of stability constants for complexes of Cd(Ⅱ)with Gly, Ala,Val,Asp,Gly—Asp,Asp Gly,Gly—Gly and Gly—Gly—Gly using both micro—pH—metric titra- tions and the application of con...This paper reports the determination of stability constants for complexes of Cd(Ⅱ)with Gly, Ala,Val,Asp,Gly—Asp,Asp Gly,Gly—Gly and Gly—Gly—Gly using both micro—pH—metric titra- tions and the application of convolution—deconvolution cyclic voltammetry at 25℃ and I=0.10 mol· dm^(-3)(KNO_3).Stability constants were calculated from pH—metric data using the SUPERQUAD com- puter program and cyclic voltammograms were collected,stored and manipulated using the EG and G CONDECON 300 software.A considerably larger ligand:metal ratio(e,g.50:1)was possible using voltammetry.Evaluation of results from the two techniques suggests that stability constants for the species[CdL_2]and[CdL_3]are reliable when calculated fromvoltammetry while those for[CdL]are more reliable when determined by pH-metric titration.展开更多
The mixed dissociation constant of azathioprine—chemically 6-(3-methyl-5-nitroimidazol-4-yl)sulfanyl-7H- purine at various ionic strengths I of range 0.01-0.2, and at temperatures of 25℃ and 37℃, was determined wit...The mixed dissociation constant of azathioprine—chemically 6-(3-methyl-5-nitroimidazol-4-yl)sulfanyl-7H- purine at various ionic strengths I of range 0.01-0.2, and at temperatures of 25℃ and 37℃, was determined with the use of two different multiwavelength and multivariate treatments of spectral data, SPECFIT32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis according to a general rule. First, the number of components is determined, and then the spectral responses and concentrations of the components are calculated. Concurrently, the experimental determination of the thermodynamic dissociation constant was in agreement with its computational prediction of the PALLAS programme based on knowledge of the chemical structures of the drug. The factor analysis in the INDICES programme predicts the correct number of two light-absorbing species L- and HL. The thermodynamic dissociation constant of azathioprine was estimated by nonlinear regression of {pKa, I} data, = 8.07(1) at 25℃ and 7.84(1) at 37℃, where the figure in brackets is the standard deviation in last significant digits. The reliability of the dissociation constants of azathioprine was proven with goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration data.展开更多
As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in thi...As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and p H value based on acidbase potentiometric titration reaction.The distribution curves of alendronate sodium were drawn according to the determined p Ka values.There were 4 dissociation constants(pKa_1=2.43,pKa_2=7.55,pKa_3=10.80,pKa_4=11.99,respectively) of alendronate sodium,and 12 existing forms,of which 4 could be ignored,existing in different p H environments.展开更多
This paper proposes a new method for determining the intrinsic acidity constants K and K The new method is a great improvement over the modified Langmuir plot method generally adopted in that determination of these co...This paper proposes a new method for determining the intrinsic acidity constants K and K The new method is a great improvement over the modified Langmuir plot method generally adopted in that determination of these constants is not dependent on the specific surface area S of the marine solid particles. The new method was used to determine K, K and S for the main inorganic components of marine solid particles, including illite, montmorillonite, kaolinite, goethite, y-AlOOH. amorphous ferric oxide, MnO2, manganite, SiO 2 and calcium carbonate, and can facilitate the study on the effect of solution constituents, solution temperature, ionic strength, etc. on the value展开更多
This is the novel measurement of the apparent formation constants of trivalent lanthanide with humic substances by potentiometric titration using an ion selective electrode (ISE) consisting of bis(diphenylphosphoryl)m...This is the novel measurement of the apparent formation constants of trivalent lanthanide with humic substances by potentiometric titration using an ion selective electrode (ISE) consisting of bis(diphenylphosphoryl)methane as an ionophore. The ISE prepared exhibited a Nernstian response to the Eu3+ concentration in the test solutions in the presence of humic acid and fulvic acid. The effect of the solution conditions, including the pH, initial metal and humic substance concentrations, and ionic strength, on the formation constants was examined. The present formation constants were compared with the reported data using solvent extraction method.展开更多
This paper reports the determination of stability constants for complexes of Pb(Ⅱ) with Gly, Ala, Asp and Gly-Gly using both micro-pH-metric titrations and the application of convolution-de- convolution cyclic voltam...This paper reports the determination of stability constants for complexes of Pb(Ⅱ) with Gly, Ala, Asp and Gly-Gly using both micro-pH-metric titrations and the application of convolution-de- convolution cyclic voltammetry at 25℃ and I = 0.10 mol.dm^(-3)(KNO_3). Stability constants were calculated from pH-metric data using the SUPERQUAD computer program and cyclic voltammograms were collected, stored and manipulated using the E G and G CONDECON 300 software. A consider- ably larger ligand: metal ratio (e.g. 50:1) was possible using voltammetry. Under these conditions, hydroxy complex formation was minimised and the formation of bis-complexes optimised. Computer based calculations were carried out on PC-compatible microcomputers fitted with mathematics co- processors. Evaluation of results from the two techniques suggests that stability constants for the species [PbL_2] are reliable when calculated from voltammetry while those for [PbL] are mote reliable when determined by pH-metric titration.展开更多
N,N-Bis(2-pyridylmethyl)-amine-N-ethyl-2-pyridine-2-carboxamide was synthesized and characterized according to the literature. At 25 ℃, I=0.1 mol/L KNO 3, the stability constants of the binary system formed by the li...N,N-Bis(2-pyridylmethyl)-amine-N-ethyl-2-pyridine-2-carboxamide was synthesized and characterized according to the literature. At 25 ℃, I=0.1 mol/L KNO 3, the stability constants of the binary system formed by the ligand with metal ions in ethanol aqueous solution were studied by pH potentiometric titration and the appropriate structures with respect to the titration species were proposed. The results show that the stability order of divalent metals binding to the ligand is Co<Ni>Cu<Zn which does not conform to the order of the Irving-Williams series. Then the abnormal property of copper complex is discussed.展开更多
目的测定水不溶弱碱性药物葡萄内酯的解离常数(pKb)。方法采用Benet法和Chtten and Harris法。利用葡萄内酯易溶于丙酮的性质,选用不同比例丙酮-水混合物为溶剂进行滴定,然后利用Benet法进行pKb的计算。结果葡萄内酯pKb为9.7527,为弱碱...目的测定水不溶弱碱性药物葡萄内酯的解离常数(pKb)。方法采用Benet法和Chtten and Harris法。利用葡萄内酯易溶于丙酮的性质,选用不同比例丙酮-水混合物为溶剂进行滴定,然后利用Benet法进行pKb的计算。结果葡萄内酯pKb为9.7527,为弱碱性药物。结论 Benet法和Chtten and Harris法可有效测定难溶于水的弱碱性药物的pKb。展开更多
基金the National Natural Science Foundation of China（Grant Nos.40525011,40632011）；the International Cooperation Project of the Chinese Academy of Sciences.
文摘Strong interaction between natural dissolved organic matter (DOM) and Hg(Ⅱ) may influence the trans- port, conversion, toxicity and bio-validity of mercury in the environment. In this paper ultraviolet (UV) absorbance titration was employed for the first time for the determination of the conditional stability constants of Hg(Ⅱ) and (DOM). With increasing Hg(Ⅱ) concentrations, the UV absorbance of fulvic acid, humic acid, and DOM in river increases progressively. By linear and non-linear model fitting, the conditional stability constants (lgK) of Hg(Ⅱ) and DOM were worked out to be 3.54?4.93 and 3.64?4.85, respectively. The results are consistent with those acquired by the typical fluorescence quenching titration method, with the maximum relative error of lgK being 2.6% and the average relative error being 0.2%. The UV absorbance titration method has the advantages of rapid determination, simple performance, and it will probably become a new approach to studying interactions between DOM and trace metallic ions.
文摘The formation constants of Co￣(2+), Ni￣(2+), Cu￣(2+) and Zn￣(2+) complexes with humic acid (HA) and fulvicacid (FA) in red soil were determined by the potentiometric titration method. The constants as a functionof composition of the complexation solutions were obtained by two graphical approaches respectively Theformation constants decreased with increasing concentration of metal in the solution. The results provideunambiguous evidence for the heterogeneity of the function groups of humic substances. The formationconstants of FA were much smaller than those of HA, and the formation constants of Cu￣(2+) were muchgreater than those of Co￣(2+) , Ni￣(2+) and Zn￣(2+) . The potentiometric titration method for determining formationconstants are also discussed in the article.
文摘A potentiometric study on the complexes of His,Gly-His,ALa-His,Gly-Gly and Gly—Gly—Gly with Zn(Ⅱ)and Cd(Ⅱ)has been reported.Small-scale potentiometric titrations were car- ried out to determine stabil ity constants of complexes at 25℃ with I=0.10 mol dm^(-3)(KNO_3).The com- puter programs SUPERQUAD were applied for data treatment with satisfactory results.
文摘This paper reports the determination of stability constants for complexes of Cd(Ⅱ)with Gly, Ala,Val,Asp,Gly—Asp,Asp Gly,Gly—Gly and Gly—Gly—Gly using both micro—pH—metric titra- tions and the application of convolution—deconvolution cyclic voltammetry at 25℃ and I=0.10 mol· dm^(-3)(KNO_3).Stability constants were calculated from pH—metric data using the SUPERQUAD com- puter program and cyclic voltammograms were collected,stored and manipulated using the EG and G CONDECON 300 software.A considerably larger ligand:metal ratio(e,g.50:1)was possible using voltammetry.Evaluation of results from the two techniques suggests that stability constants for the species[CdL_2]and[CdL_3]are reliable when calculated fromvoltammetry while those for[CdL]are more reliable when determined by pH-metric titration.
基金financial support of the Grant Agency IGA MZCR(Grant No NS9831-4/2008)the Czech Ministry of Education(Grant No MSM0021627502)
文摘The mixed dissociation constant of azathioprine—chemically 6-(3-methyl-5-nitroimidazol-4-yl)sulfanyl-7H- purine at various ionic strengths I of range 0.01-0.2, and at temperatures of 25℃ and 37℃, was determined with the use of two different multiwavelength and multivariate treatments of spectral data, SPECFIT32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis according to a general rule. First, the number of components is determined, and then the spectral responses and concentrations of the components are calculated. Concurrently, the experimental determination of the thermodynamic dissociation constant was in agreement with its computational prediction of the PALLAS programme based on knowledge of the chemical structures of the drug. The factor analysis in the INDICES programme predicts the correct number of two light-absorbing species L- and HL. The thermodynamic dissociation constant of azathioprine was estimated by nonlinear regression of {pKa, I} data, = 8.07(1) at 25℃ and 7.84(1) at 37℃, where the figure in brackets is the standard deviation in last significant digits. The reliability of the dissociation constants of azathioprine was proven with goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration data.
基金the support of Key Laboratory of Chinese Medicine Preparation of Solid Dispersion,Gansu Longshenrongfa Pharmaceutical Industry Co.,Ltd.,Gansu Province,China
文摘As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and p H value based on acidbase potentiometric titration reaction.The distribution curves of alendronate sodium were drawn according to the determined p Ka values.There were 4 dissociation constants(pKa_1=2.43,pKa_2=7.55,pKa_3=10.80,pKa_4=11.99,respectively) of alendronate sodium,and 12 existing forms,of which 4 could be ignored,existing in different p H environments.
文摘This paper proposes a new method for determining the intrinsic acidity constants K and K The new method is a great improvement over the modified Langmuir plot method generally adopted in that determination of these constants is not dependent on the specific surface area S of the marine solid particles. The new method was used to determine K, K and S for the main inorganic components of marine solid particles, including illite, montmorillonite, kaolinite, goethite, y-AlOOH. amorphous ferric oxide, MnO2, manganite, SiO 2 and calcium carbonate, and can facilitate the study on the effect of solution constituents, solution temperature, ionic strength, etc. on the value
文摘This is the novel measurement of the apparent formation constants of trivalent lanthanide with humic substances by potentiometric titration using an ion selective electrode (ISE) consisting of bis(diphenylphosphoryl)methane as an ionophore. The ISE prepared exhibited a Nernstian response to the Eu3+ concentration in the test solutions in the presence of humic acid and fulvic acid. The effect of the solution conditions, including the pH, initial metal and humic substance concentrations, and ionic strength, on the formation constants was examined. The present formation constants were compared with the reported data using solvent extraction method.
文摘This paper reports the determination of stability constants for complexes of Pb(Ⅱ) with Gly, Ala, Asp and Gly-Gly using both micro-pH-metric titrations and the application of convolution-de- convolution cyclic voltammetry at 25℃ and I = 0.10 mol.dm^(-3)(KNO_3). Stability constants were calculated from pH-metric data using the SUPERQUAD computer program and cyclic voltammograms were collected, stored and manipulated using the E G and G CONDECON 300 software. A consider- ably larger ligand: metal ratio (e.g. 50:1) was possible using voltammetry. Under these conditions, hydroxy complex formation was minimised and the formation of bis-complexes optimised. Computer based calculations were carried out on PC-compatible microcomputers fitted with mathematics co- processors. Evaluation of results from the two techniques suggests that stability constants for the species [PbL_2] are reliable when calculated from voltammetry while those for [PbL] are mote reliable when determined by pH-metric titration.
文摘N,N-Bis(2-pyridylmethyl)-amine-N-ethyl-2-pyridine-2-carboxamide was synthesized and characterized according to the literature. At 25 ℃, I=0.1 mol/L KNO 3, the stability constants of the binary system formed by the ligand with metal ions in ethanol aqueous solution were studied by pH potentiometric titration and the appropriate structures with respect to the titration species were proposed. The results show that the stability order of divalent metals binding to the ligand is Co<Ni>Cu<Zn which does not conform to the order of the Irving-Williams series. Then the abnormal property of copper complex is discussed.
文摘目的测定水不溶弱碱性药物葡萄内酯的解离常数(pKb)。方法采用Benet法和Chtten and Harris法。利用葡萄内酯易溶于丙酮的性质,选用不同比例丙酮-水混合物为溶剂进行滴定,然后利用Benet法进行pKb的计算。结果葡萄内酯pKb为9.7527,为弱碱性药物。结论 Benet法和Chtten and Harris法可有效测定难溶于水的弱碱性药物的pKb。
