Introduction: Only vindication of a nasal continuous positive airway pressure (CPAP) retitration procedure will be an actual change in the optimal CPAP pressure after that test. The purpose of this study was to identi...Introduction: Only vindication of a nasal continuous positive airway pressure (CPAP) retitration procedure will be an actual change in the optimal CPAP pressure after that test. The purpose of this study was to identify any items in patient characteristics, clinical features, baseline PSG and initial CPAP titration as predictors of change in optimal pressure on CPAP retitration. Methods: 46 patients with obstructive sleep apnea (OSA) were divided in two groups: Group I (optimal pressure was changed on CPAP retitration): N = 30, M 22 and F 8, age 31-72, BMI 26-50 Kg/m2, neck size 15 – 20', tonsillectomy in 8, narrow oropharynx in 15, uvuvlopalatopharyngoplasty (UP3) in 2, abnormal chin in 3, deviated nasal septum (DNS) and prior nose surgery in 1 each, initial CPAP pressure 6-19 cm, sleep efficiency 65%-98%, REM latency 0-304 minutes and residual apnea hypopnea index (AHI) 0-23/hour. Group II (optimal pressure unchanged after CPAP retitration): N = 16, M 11 and 5 F, age 32-69, BMI 23-62 Kg/m2, neck size 14.5-20', tonsillectomy in 6, narrow oropharynx in 5, abnormal chin in 4, corrective nasal surgery in 2, DNS in 1, initial CPAP pressure 8-13 cm of H2O, sleep efficiency 69%-95%, REM latency 0-270 minutes and residual AHI 0-19/hour. The statistical analyses were performed using two-tailed Fisher’s t test and unpaired t test. A p value of <0.05 was considered statistically significant. Results: Patient characteristics (age, gender, neck size, and BMI), clinical features (tonsillar status, oropharyngeal narrowing, chin abnormality, DNS/nasal surgery or UP3), baseline PSG or initial CPAP titration (sleep efficiency, REM latency, residual AHI and initial CPAP pressure) did not differ significantly between the 2 groups (p = 0.09-0.99). Conclusion: Patient characteristics, clinical features or variables on baseline PSG and initial CPAP titration do not predict a change in optimal pressure on CPAP retitration. The results suggest that 1) Significant weight change;2) Patient’s subjective feeling of pressure being too high or insufficient;3) Residual or recurrent daytime sleepiness uncorrected by interface readjustments;4)展开更多
A new method for the determination of aniline in environmental water based on oscillopolarographic titration was presented in this paper. Several factors including the kind, concentration, and volume of acid, the dosa...A new method for the determination of aniline in environmental water based on oscillopolarographic titration was presented in this paper. Several factors including the kind, concentration, and volume of acid, the dosage of potassium bromide, the temperature and concentration of concomitant substances were investigated in detail. The experimental results indicated that this method was simple, rapid, and sensitive. The linear range was 8.367×10-4 to 2.789×10-2 mol L-1, the relative standard deviation (R.S.D.) was lower than 0.96%, and the spiked recoveries of aniline in environmental water samples were in the range of 99.4-106.9% under the optimal conditions. The results indicated that the present method could be used as an alternative method for aniline determination in realworld water samples.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
The stability constants and thermodynamic functions for complexes of lanthanum with eight kind of amino acids according to 1 : 1 and 1 : 2 in proportion have been determined by titration calorimeter at 298. 15 K. The ...The stability constants and thermodynamic functions for complexes of lanthanum with eight kind of amino acids according to 1 : 1 and 1 : 2 in proportion have been determined by titration calorimeter at 298. 15 K. The enthalpy change makes a predominant contribution to the stability of these complexes. The ring in amino acid associated with lanthanum ion helps to enhance the stability of complexes. Steric effects between rings in complexes leads to that the equilibrium constants of reaction of the complexes (1 : 2) is much less than that of the complexes (1 : 1).展开更多
By using calcium ion selective elatrode (Ca ISE) as indicating electrode, saturated calomel electrode (SCE) as reference electrode and EGTA as titrant, calcium in seawater was determined by potentiometric titration in...By using calcium ion selective elatrode (Ca ISE) as indicating electrode, saturated calomel electrode (SCE) as reference electrode and EGTA as titrant, calcium in seawater was determined by potentiometric titration in borate buffer solution. This method can reduce observation errors in the determination of the endpoint, and thus provide better analytical precision(<0.08%) than present complexometric titration.展开更多
Rocky desertification has become a major environmental issue in the karst region of southwestern China.Karst rocky desertification was more severe in regions of limestone soil than in adjacent regions of other soils,d...Rocky desertification has become a major environmental issue in the karst region of southwestern China.Karst rocky desertification was more severe in regions of limestone soil than in adjacent regions of other soils,despite the relatively higher soil organic matter(SOM)content in limestone soil.The underlying mechanism remains ambiguous.We speculated that the geochemical characteristics of limestone soils in the karst region plays an essential role,especially the high calcium content of limestone soil.To test this hypothesis,we collected limestone soil samples from a limestone soil profile in the southwestern China karst region and extracted humic acid(HA)from these limestone soil samples.We investigated the interaction of Ca^(2+)and three HA samples on a joint experimental platform,which consists of an automatic potentiometric titrator,a UV–visible spectrometer,and a Fluorescence spectrometer.HA solutions were titrated by Ca^(2+)and optical spectra of the HA solutions were monitored during the titration experiments.The results indicated that:(1)the interaction of Ca^(2+)and HA is a combined process of adsorption and complexation.Adsorption dominated the overall distribution behavior of Ca^(2+),which could be fit by Langmuir and Freundlich isotherm models.Complexation was distinguished only when the concentration of Ca2+is low;(2)the changes of UV–visible spectroscopy and excitation–emission matrix fluorescencespectroscopy spectra of HA samples when they were binding with Ca^(2+)implied the apparent molecular size and structure of HA became larger and more complex;(3)the combination of Ca^(2+)and HA plays an important role in the SOM preservation of limestone soils but the stability of the Ca–HA association was relatively weak.The present study draws attention to maintaining the relatively higher Ca^(2+)concentration in limestone soils in ecologic restoration attempts in karst regions.展开更多
The analytical technique of conductometric titration is used to characterize polymeric materials.This technique allows obtaining the polymer dry weight capacity(DWC) and the extent of reaction and establishing the opt...The analytical technique of conductometric titration is used to characterize polymeric materials.This technique allows obtaining the polymer dry weight capacity(DWC) and the extent of reaction and establishing the optimal number of water molecules per sulfonic groups.In this particular case the polymer material under study was Nafion~? 117.Two different reactions were made: Neutralization and exchange.Both of them allow obtaining the same result.Conductometric titrations could be considered as a good method to study the neutralization and exchange reactions for polymeric materials used in fuel cells or electrolyzers.The implementation of this analytical technique allows reducing operation time of those types of materials.The waiting time between determinations permits to say that the amount of reactant consumed and products obtained were the same after each addition of titrant.展开更多
The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitatio...The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the "mix effect" while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.展开更多
Amount and properties of roots surface charge are important for nutrient uptake and balance in plants. Roots surface charge markedly varies at different rizosphere conditions (particularly pH and ionic strength), whic...Amount and properties of roots surface charge are important for nutrient uptake and balance in plants. Roots surface charge markedly varies at different rizosphere conditions (particularly pH and ionic strength), which can markedly alter during vegetation season. Among recently available measuring methods, surface charge-pH dependence of roots (as well as other biological objects) is most easily evaluated by potentiometric titration. Use of this method is also easy at different ionic strengths. Potentiometric titration also allows for estimation of the distribution of charge generating surface groups. However, many applications of this method seem to be based either on incorrect methodical or theoretical approaches. In this paper we discuss the methodical and theoretical backgrounds of the titration method. Basing on experimental titration curves of roots of barley grown in nutrient solution, we show inconsistency of surface charge results obtained at different measuring conditions. Limitations of theoretical interpretations of the results are outlined also.展开更多
In water treatment processes and conditioning drinking water, PEs are widely used;however, their environmental impact is still doubtful, since residual concentrations increase organic matter content and represents a p...In water treatment processes and conditioning drinking water, PEs are widely used;however, their environmental impact is still doubtful, since residual concentrations increase organic matter content and represents a potential health hazard. This paper demonstrates a multiparametric study of two colloidal titration methods: spectrophotometric and zeta potential end point detection. The first one was optimized to guarantee the accuracy of cationic commercial PE quantification. It includes the indicator dose optimization using analytical criteria for competing equilibria, a calibration curve for two ranges of CPE concentration (1 - 5 ppm and 5 - 100 ppm) and the interference study of flocculant and Sn in the CPE quantification. The second method provides a physicochemical validation of the electric surface phenomena occurring during the colloidal titration and the end point detection. As an additional contribution the zeta potential titration was discussed and proposed as an alternative method for quantifying CPE when the sample is metal free.展开更多
A potentiometric study on the complexes of His,Gly-His,ALa-His,Gly-Gly andGly—Gly—Gly with Zn（Ⅱ）and Cd（Ⅱ）has been reported.Small-scale potentiometric titrations were car-ried out to determine stabil ity consta...A potentiometric study on the complexes of His,Gly-His,ALa-His,Gly-Gly andGly—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<sup>-3</sup>（KNO<sub>3</sub>）.The com-puter programs SUPERQUAD were applied for data treatment with satisfactory results.展开更多
A new method called differential reciprocal oscillographic chronopotentiometrictitration is presented.It makes use of appearance or disappearance of a peak of depolarizer ondifferential reciprocal oscillogram indicati...A new method called differential reciprocal oscillographic chronopotentiometrictitration is presented.It makes use of appearance or disappearance of a peak of depolarizer ondifferential reciprocal oscillogram indicating the end point of titration.This method was appliedto titration of Pb<sup>2+</sup>,Cd<sup>2+</sup>,Ni<sup>2+</sup>,Co<sup>3+</sup>,Zn<sup>2+</sup>,Ga<sup>3+</sup> and Cu<sup>2+</sup>by EDTA or EGTA.The end point oftitration is very easy to observe and the sensibility of the method is higher than that ofdiffcrcntial oscillographic chronopotcntiometric titration.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<sup>-3</sup>（KNO<sub>3</sub>）.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 GCONDECON 300 software.A considerably larger ligand:metal ratio（e,g.50:1）was possible usingvoltammetry.Evaluation of results from the two techniques suggests that stability constants for thespecies[CdL<sub>2</sub>]and[CdL<sub>3</sub>]are reliable when calculated fromvoltammetry while those for[CdL]are morereliable when determined by pH-metric titration.展开更多
A novel method was established to determine the H2-storage capacity in carbon nanotubes. According to 2NO+2H2 (or 4H) = N2+2H2O reaction, the H2-storage capacity in carbon nanotubes could be calculated. The H2-storage...A novel method was established to determine the H2-storage capacity in carbon nanotubes. According to 2NO+2H2 (or 4H) = N2+2H2O reaction, the H2-storage capacity in carbon nanotubes could be calculated. The H2-storage capacity in carbon nanotubes is at least 2.89 wt%.展开更多
This paper reports a new method of titration for very weak acids andbases using the appearance of incisions on oscillopolarogram to indicate theend-point.This method has the advantages of rapidity,simplicity,no indica...This paper reports a new method of titration for very weak acids andbases using the appearance of incisions on oscillopolarogram to indicate theend-point.This method has the advantages of rapidity,simplicity,no indicatorneeded as well as good precision.展开更多
The use of K<sub>2</sub>NbF<sub>7</sub> as a probe solute for the cyclic voltammetric determination of oxide in FLINAKmelts was studied and demonstrated.This method is based on a complex reacti...The use of K<sub>2</sub>NbF<sub>7</sub> as a probe solute for the cyclic voltammetric determination of oxide in FLINAKmelts was studied and demonstrated.This method is based on a complex reaction and the peak current densityof NbF<sub>7</sub><sup>2-</sup>reduction.The reaction constant was determined to be very large at 973 K.A cyclic voltammetricstandard addition experiment is also employed to determine the amount of oxide in FLINAK melt.The oxidecontent of FLINAK melts is equal to the amount of Nb（V）added minus the amount of NbF<sub>7</sub><sup>2-</sup>which is ob-tained from the voltammogram.展开更多
pH-fixed titration method for the determination of weak acids andbases has been studied in this paper.It is not necessary to know theionization constant of weak acid or base and the concentration of titrant.This metho...pH-fixed titration method for the determination of weak acids andbases has been studied in this paper.It is not necessary to know theionization constant of weak acid or base and the concentration of titrant.This method had been applied to determine phenol,4-aminoantipyrine andglycine,whose ionization constants range from 10<sup>-10</sup>to 10<sup>-12</sup>.Theresults were satisfactory.展开更多
An equation describing the state of weak acid mixtures was derived from the relationships between mole balance and charge balance. The equation was solved with numerical method and the compositions of the acid mixture...An equation describing the state of weak acid mixtures was derived from the relationships between mole balance and charge balance. The equation was solved with numerical method and the compositions of the acid mixtures were determined. The advantages of this treatment were demonstrated by analyzing binary mixtures of chloroacetic, formic and acetic acids.展开更多
The adsorption behavior of heparin and fibronectin was studied by quartz crystal microbalance with dissipation(QCM-D), and the interaction between heparin and fibronectin was evaluated using immunochemistry and isothe...The adsorption behavior of heparin and fibronectin was studied by quartz crystal microbalance with dissipation(QCM-D), and the interaction between heparin and fibronectin was evaluated using immunochemistry and isothermal titration calorimetry(ITC) measurement. The results showed that there was competitive adsorption between heparin and fibronectin, and the preadsorption of fibronectin could prevent subsequent heparin adsorption to some extent, and the adsorbed Hep/Fn complex on the surface was in a rigid form. The bioactivity of heparin and fibronectin could be affected by the bulk concentration of each, and both heparin and fibronectin in Hep/Fn complex formed under p H 4 condition displayed larger bioactivity than that formed under p H 7 condition. Moreover, the fibronectin showed more exposed cell-binding sites at the p H value lower than physiological condition. The results of ITC further suggested that the interaction between heparin and fibronectin under p H 4 was stronger than under p H 7, and the complex was also more stable. The study brings forth the detailed interaction between heparin and fibronectin, which will be helpful for better understanding the interaction mechanism of the two biomolecules. The results may be potentially useful for the development of new generation of cardiovascular biomaterials.展开更多
文摘Introduction: Only vindication of a nasal continuous positive airway pressure (CPAP) retitration procedure will be an actual change in the optimal CPAP pressure after that test. The purpose of this study was to identify any items in patient characteristics, clinical features, baseline PSG and initial CPAP titration as predictors of change in optimal pressure on CPAP retitration. Methods: 46 patients with obstructive sleep apnea (OSA) were divided in two groups: Group I (optimal pressure was changed on CPAP retitration): N = 30, M 22 and F 8, age 31-72, BMI 26-50 Kg/m2, neck size 15 – 20', tonsillectomy in 8, narrow oropharynx in 15, uvuvlopalatopharyngoplasty (UP3) in 2, abnormal chin in 3, deviated nasal septum (DNS) and prior nose surgery in 1 each, initial CPAP pressure 6-19 cm, sleep efficiency 65%-98%, REM latency 0-304 minutes and residual apnea hypopnea index (AHI) 0-23/hour. Group II (optimal pressure unchanged after CPAP retitration): N = 16, M 11 and 5 F, age 32-69, BMI 23-62 Kg/m2, neck size 14.5-20', tonsillectomy in 6, narrow oropharynx in 5, abnormal chin in 4, corrective nasal surgery in 2, DNS in 1, initial CPAP pressure 8-13 cm of H2O, sleep efficiency 69%-95%, REM latency 0-270 minutes and residual AHI 0-19/hour. The statistical analyses were performed using two-tailed Fisher’s t test and unpaired t test. A p value of <0.05 was considered statistically significant. Results: Patient characteristics (age, gender, neck size, and BMI), clinical features (tonsillar status, oropharyngeal narrowing, chin abnormality, DNS/nasal surgery or UP3), baseline PSG or initial CPAP titration (sleep efficiency, REM latency, residual AHI and initial CPAP pressure) did not differ significantly between the 2 groups (p = 0.09-0.99). Conclusion: Patient characteristics, clinical features or variables on baseline PSG and initial CPAP titration do not predict a change in optimal pressure on CPAP retitration. The results suggest that 1) Significant weight change;2) Patient’s subjective feeling of pressure being too high or insufficient;3) Residual or recurrent daytime sleepiness uncorrected by interface readjustments;4)
文摘A new method for the determination of aniline in environmental water based on oscillopolarographic titration was presented in this paper. Several factors including the kind, concentration, and volume of acid, the dosage of potassium bromide, the temperature and concentration of concomitant substances were investigated in detail. The experimental results indicated that this method was simple, rapid, and sensitive. The linear range was 8.367×10-4 to 2.789×10-2 mol L-1, the relative standard deviation (R.S.D.) was lower than 0.96%, and the spiked recoveries of aniline in environmental water samples were in the range of 99.4-106.9% under the optimal conditions. The results indicated that the present method could be used as an alternative method for aniline determination in realworld water samples.
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.
基金Supported by the National Nature Science Foundation of China(29873036)
文摘The stability constants and thermodynamic functions for complexes of lanthanum with eight kind of amino acids according to 1 : 1 and 1 : 2 in proportion have been determined by titration calorimeter at 298. 15 K. The enthalpy change makes a predominant contribution to the stability of these complexes. The ring in amino acid associated with lanthanum ion helps to enhance the stability of complexes. Steric effects between rings in complexes leads to that the equilibrium constants of reaction of the complexes (1 : 2) is much less than that of the complexes (1 : 1).
文摘By using calcium ion selective elatrode (Ca ISE) as indicating electrode, saturated calomel electrode (SCE) as reference electrode and EGTA as titrant, calcium in seawater was determined by potentiometric titration in borate buffer solution. This method can reduce observation errors in the determination of the endpoint, and thus provide better analytical precision(<0.08%) than present complexometric titration.
基金supported by the National Natural Science Foundation of China (U1701241, U1612441,41773147, and 41273149)the Science Foundation of Guizhou(20113109) 。
文摘Rocky desertification has become a major environmental issue in the karst region of southwestern China.Karst rocky desertification was more severe in regions of limestone soil than in adjacent regions of other soils,despite the relatively higher soil organic matter(SOM)content in limestone soil.The underlying mechanism remains ambiguous.We speculated that the geochemical characteristics of limestone soils in the karst region plays an essential role,especially the high calcium content of limestone soil.To test this hypothesis,we collected limestone soil samples from a limestone soil profile in the southwestern China karst region and extracted humic acid(HA)from these limestone soil samples.We investigated the interaction of Ca^(2+)and three HA samples on a joint experimental platform,which consists of an automatic potentiometric titrator,a UV–visible spectrometer,and a Fluorescence spectrometer.HA solutions were titrated by Ca^(2+)and optical spectra of the HA solutions were monitored during the titration experiments.The results indicated that:(1)the interaction of Ca^(2+)and HA is a combined process of adsorption and complexation.Adsorption dominated the overall distribution behavior of Ca^(2+),which could be fit by Langmuir and Freundlich isotherm models.Complexation was distinguished only when the concentration of Ca2+is low;(2)the changes of UV–visible spectroscopy and excitation–emission matrix fluorescencespectroscopy spectra of HA samples when they were binding with Ca^(2+)implied the apparent molecular size and structure of HA became larger and more complex;(3)the combination of Ca^(2+)and HA plays an important role in the SOM preservation of limestone soils but the stability of the Ca–HA association was relatively weak.The present study draws attention to maintaining the relatively higher Ca^(2+)concentration in limestone soils in ecologic restoration attempts in karst regions.
基金supported by the Defense Ministry of Argentina under Grant PIDDEF No.22/11
文摘The analytical technique of conductometric titration is used to characterize polymeric materials.This technique allows obtaining the polymer dry weight capacity(DWC) and the extent of reaction and establishing the optimal number of water molecules per sulfonic groups.In this particular case the polymer material under study was Nafion~? 117.Two different reactions were made: Neutralization and exchange.Both of them allow obtaining the same result.Conductometric titrations could be considered as a good method to study the neutralization and exchange reactions for polymeric materials used in fuel cells or electrolyzers.The implementation of this analytical technique allows reducing operation time of those types of materials.The waiting time between determinations permits to say that the amount of reactant consumed and products obtained were the same after each addition of titrant.
基金the National High-Tech Development Plan (2006AA05Z417)the Natural Science Foundation of Lia-oning Province (20062145)the Education department of Liaoning Province (05L073)
文摘The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the "mix effect" while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.
文摘Amount and properties of roots surface charge are important for nutrient uptake and balance in plants. Roots surface charge markedly varies at different rizosphere conditions (particularly pH and ionic strength), which can markedly alter during vegetation season. Among recently available measuring methods, surface charge-pH dependence of roots (as well as other biological objects) is most easily evaluated by potentiometric titration. Use of this method is also easy at different ionic strengths. Potentiometric titration also allows for estimation of the distribution of charge generating surface groups. However, many applications of this method seem to be based either on incorrect methodical or theoretical approaches. In this paper we discuss the methodical and theoretical backgrounds of the titration method. Basing on experimental titration curves of roots of barley grown in nutrient solution, we show inconsistency of surface charge results obtained at different measuring conditions. Limitations of theoretical interpretations of the results are outlined also.
文摘In water treatment processes and conditioning drinking water, PEs are widely used;however, their environmental impact is still doubtful, since residual concentrations increase organic matter content and represents a potential health hazard. This paper demonstrates a multiparametric study of two colloidal titration methods: spectrophotometric and zeta potential end point detection. The first one was optimized to guarantee the accuracy of cationic commercial PE quantification. It includes the indicator dose optimization using analytical criteria for competing equilibria, a calibration curve for two ranges of CPE concentration (1 - 5 ppm and 5 - 100 ppm) and the interference study of flocculant and Sn in the CPE quantification. The second method provides a physicochemical validation of the electric surface phenomena occurring during the colloidal titration and the end point detection. As an additional contribution the zeta potential titration was discussed and proposed as an alternative method for quantifying CPE when the sample is metal free.
文摘A potentiometric study on the complexes of His,Gly-His,ALa-His,Gly-Gly andGly—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<sup>-3</sup>（KNO<sub>3</sub>）.The com-puter programs SUPERQUAD were applied for data treatment with satisfactory results.
文摘A new method called differential reciprocal oscillographic chronopotentiometrictitration is presented.It makes use of appearance or disappearance of a peak of depolarizer ondifferential reciprocal oscillogram indicating the end point of titration.This method was appliedto titration of Pb<sup>2+</sup>,Cd<sup>2+</sup>,Ni<sup>2+</sup>,Co<sup>3+</sup>,Zn<sup>2+</sup>,Ga<sup>3+</sup> and Cu<sup>2+</sup>by EDTA or EGTA.The end point oftitration is very easy to observe and the sensibility of the method is higher than that ofdiffcrcntial oscillographic chronopotcntiometric titration.
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<sup>-3</sup>（KNO<sub>3</sub>）.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 GCONDECON 300 software.A considerably larger ligand:metal ratio（e,g.50:1）was possible usingvoltammetry.Evaluation of results from the two techniques suggests that stability constants for thespecies[CdL<sub>2</sub>]and[CdL<sub>3</sub>]are reliable when calculated fromvoltammetry while those for[CdL]are morereliable when determined by pH-metric titration.
文摘A novel method was established to determine the H2-storage capacity in carbon nanotubes. According to 2NO+2H2 (or 4H) = N2+2H2O reaction, the H2-storage capacity in carbon nanotubes could be calculated. The H2-storage capacity in carbon nanotubes is at least 2.89 wt%.
文摘This paper reports a new method of titration for very weak acids andbases using the appearance of incisions on oscillopolarogram to indicate theend-point.This method has the advantages of rapidity,simplicity,no indicatorneeded as well as good precision.
文摘The use of K<sub>2</sub>NbF<sub>7</sub> as a probe solute for the cyclic voltammetric determination of oxide in FLINAKmelts was studied and demonstrated.This method is based on a complex reaction and the peak current densityof NbF<sub>7</sub><sup>2-</sup>reduction.The reaction constant was determined to be very large at 973 K.A cyclic voltammetricstandard addition experiment is also employed to determine the amount of oxide in FLINAK melt.The oxidecontent of FLINAK melts is equal to the amount of Nb（V）added minus the amount of NbF<sub>7</sub><sup>2-</sup>which is ob-tained from the voltammogram.
文摘pH-fixed titration method for the determination of weak acids andbases has been studied in this paper.It is not necessary to know theionization constant of weak acid or base and the concentration of titrant.This method had been applied to determine phenol,4-aminoantipyrine andglycine,whose ionization constants range from 10<sup>-10</sup>to 10<sup>-12</sup>.Theresults were satisfactory.
文摘An equation describing the state of weak acid mixtures was derived from the relationships between mole balance and charge balance. The equation was solved with numerical method and the compositions of the acid mixtures were determined. The advantages of this treatment were demonstrated by analyzing binary mixtures of chloroacetic, formic and acetic acids.
基金Funded by the Natural Science Research Program of Jiangsu Education Department(No.13KJB310014)Natural Science Research Program of Jiangsu Province(No.BK20140429)
文摘The adsorption behavior of heparin and fibronectin was studied by quartz crystal microbalance with dissipation(QCM-D), and the interaction between heparin and fibronectin was evaluated using immunochemistry and isothermal titration calorimetry(ITC) measurement. The results showed that there was competitive adsorption between heparin and fibronectin, and the preadsorption of fibronectin could prevent subsequent heparin adsorption to some extent, and the adsorbed Hep/Fn complex on the surface was in a rigid form. The bioactivity of heparin and fibronectin could be affected by the bulk concentration of each, and both heparin and fibronectin in Hep/Fn complex formed under p H 4 condition displayed larger bioactivity than that formed under p H 7 condition. Moreover, the fibronectin showed more exposed cell-binding sites at the p H value lower than physiological condition. The results of ITC further suggested that the interaction between heparin and fibronectin under p H 4 was stronger than under p H 7, and the complex was also more stable. The study brings forth the detailed interaction between heparin and fibronectin, which will be helpful for better understanding the interaction mechanism of the two biomolecules. The results may be potentially useful for the development of new generation of cardiovascular biomaterials.
