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Analysis of the electron transfer pathway in small laccase by EPR and UV-vis spectroscopy coupled with redox titration
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作者 Lu Yu Aokun Liu +3 位作者 Jian Kuang Ruotong Wei Zhiwen Wang Changlin Tian 《Magnetic Resonance Letters》 2024年第3期52-59,共8页
Bacterial small laccases(SLAC) are promising industrial biocatalysts due to their ability to oxidize a broad range of substrates with exceptional thermostability and tolerance for alkaline p H. Electron transfer betwe... Bacterial small laccases(SLAC) are promising industrial biocatalysts due to their ability to oxidize a broad range of substrates with exceptional thermostability and tolerance for alkaline p H. Electron transfer between substrate, copper centers, and O2is one of the key steps in the catalytic turnover of SLAC. However, limited research has been conducted on the electron transfer pathway of SLAC and SLAC-catalyzed reactions, hindering further engineering of SLAC to produce tunable biocatalysts for novel applications. Herein, the combinational use of electron paramagnetic resonance(EPR) and ultraviolet-visible(UV-vis) spectroscopic methods coupled with redox titration were employed to monitor the electron transfer processes and obtain further insights into the electron transfer pathway in SLAC. The reduction potentials for type 1 copper(T1Cu), type 2 copper(T2Cu) and type 3copper(T3Cu) were determined to be 367 ± 2 mV, 378 ± 5 m V and 403 ± 2 mV,respectively. Moreover, the reduction potential of a selected substrate of SLAC, hydroquinone(HQ), was determined to be 288 mV using cyclic voltammetry(CV). In this way, an electron transfer pathway was identified based on the reduction potentials. Specifically,electrons are transferred from HQ to T1Cu, then to T2Cu and T3Cu, and finally to O2.Furthermore, superhyperfine splitting observed via EPR during redox titration indicated a modification in the covalency of T2Cu upon electron uptake, suggesting a conformational alteration in the protein environment surrounding the copper sites, which could potentially influence the reduction potential of the copper sites during catalytic processes. The results presented here not only provide a comprehensive method for analyzing the electron transfer pathway in metalloenzymes through reduction potential measurements, but also offer valuable insights for further engineering and directed evolution studies of SLAC in the aim for biotechnological and industrial applications. 展开更多
关键词 Electron paramagnetic resonance Redox titration Electron transfer Reduction Potential Small laccase
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Study and Application of a New On-Line Titration Technique
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作者 朱建育 施利毅 《Journal of Shanghai University(English Edition)》 CAS 2002年第2期181-184,共4页
A new on line titration method and device based on a new technique continuous flow titration is described. By the means of electronically controlled switching of a solenoid valve, the main component of the system, t... A new on line titration method and device based on a new technique continuous flow titration is described. By the means of electronically controlled switching of a solenoid valve, the main component of the system, the equivalent point of the titration is easily determined. Several kinds of mixing tools were examined, whereby a self made mixing chamber with minimum volume gave best results and was therefore used in the device. The error of the titration is within 0.2% and the relative standard deviation (RSD) is below 1.2%. The results show no difference compared with a commercial device, meanwhile the new on line titration system is cheaper and fully automated and thus easy to hand and less solvent consumption. 展开更多
关键词 continuous flow titration on line system automated titration conductimetric detection.
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Does Patient’s Initial Evaluation Predict a Change in Optimal Pressure on CPAP Retitration?
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作者 Narayan P. Verma 《International Journal of Clinical Medicine》 2014年第4期138-142,共5页
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
关键词 OBSTRUCTIVE SLEEP APNEA CPAP titration CPAP Retitration
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“Titration”软件在分析化学教学中的应用 被引量:1
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作者 余菁 屠婕红 《化学教育》 CAS 2000年第9期37-38,共2页
关键词 分析化学教学 titration 软件 酸碱滴定
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Determination of aniline in environmental water samples by alternating-current oscillopolarographic titration 被引量:6
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作者 Jun Ping Xiao Qing Xiang Zhou +2 位作者 Xiao Ke Tian Hua Hua Bai Xian Fa Su 《Chinese Chemical Letters》 SCIE CAS CSCD 2007年第6期730-733,共4页
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
关键词 Alternating-current oscillopolarographic titration ANILINE Potassium bromide
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Determination of pKa values of alendronate sodium in aqueous solution by piecewise linear regression based on acid-base potentiometric titration 被引量:2
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作者 Jing Ke Hanfei Dou +3 位作者 Ximin Zhang Dushimabararezi Serge Uhagaze Xiali Ding Yuming Dong 《Journal of Pharmaceutical Analysis》 SCIE CAS 2016年第6期404-409,共6页
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
关键词 Dissociation CONSTANTS ALENDRONATE SODIUM Distribution curve Piecewise linear regression ACID-BASE POTENTIOMETRIC titration
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Study of Complexes of Lanthanum with Amino Acids by Titration Calorimeter 被引量:2
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作者 Ye Gang, Wang Cun-xin, Qu Song-sheng College of Chemistry and Environment Science, Wuhan University, Wuhan 430072, China 《Wuhan University Journal of Natural Sciences》 EI CAS 2000年第4期479-484,共6页
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 ent... 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
关键词 titration calorimeter rare earth amino acid COMPLEXES steric effects
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POTENTIOMETRIC TITRATION OF CALCIUM IN SEAWATER 被引量:1
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作者 谢式南 纪红 +1 位作者 吴爱琴 陈国华 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 1997年第1期32-35,共4页
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
关键词 CALCIUM ION SELECTIVE elatrode CALCIUM seawater POTENTIOMETRIC titration
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Interaction of Ca^(2+) and soil humic acid characterized by a joint experimental platform of potentiometric titration, UV–visible spectroscopy, and fluorescence spectroscopy 被引量:1
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作者 Haiming Tang Baohua Xiao Peiwen Xiao 《Acta Geochimica》 EI CAS CSCD 2021年第3期300-311,共12页
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
关键词 Limestone soil Humic acid Calcium INTERACTION titration UV–Vis EEM
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Extraction Mechanism of Rare Earths with Sec-Octylphenoxy Acetic Acid by Two-Phase Titration Technique 被引量:1
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作者 乐善堂 廖伍平 +1 位作者 李德谦 苏锵 《Journal of Rare Earths》 SCIE EI CAS CSCD 2002年第5期416-419,共4页
The compositions of the extracted complexes of La, Gd, Er and Y with sec octyl phenoxy acetic acid in heptane and the related apparent extraction equilibrium constants K M were determined using two phase titration... The compositions of the extracted complexes of La, Gd, Er and Y with sec octyl phenoxy acetic acid in heptane and the related apparent extraction equilibrium constants K M were determined using two phase titration technique. The stoichiometric compounds for La, Gd, Er and Y should be LaA 3·2.5HA, GdA 3·3HA, ErA 3·3.1HA and YA 3·4.3HA respectively. And their p K M are 3.43, 3.46, 3.08 and 2.58 respectively. 展开更多
关键词 rare earths two phase titration sec octylphenoxy acetic acid EXTRACTION
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Determination of Dimethylallylamine by Titration in Nonaqueous Solvent 被引量:2
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作者 刘立华 龚竹青 郑雅杰 《Journal of Donghua University(English Edition)》 EI CAS 2004年第5期124-127,共4页
The content of dimethylallylamine was determined using glacial acetic acid as solvent, acetic-formic mixture as an anhydrite, perchloric acid-glacial acetic acid as titrant, and 1% crystal violet in acetic acid as ind... The content of dimethylallylamine was determined using glacial acetic acid as solvent, acetic-formic mixture as an anhydrite, perchloric acid-glacial acetic acid as titrant, and 1% crystal violet in acetic acid as indicator in the presence of methylamine and dimethylamine The influences of inert constituents and water on the titration were investigated, and a complete analytical method was determined. The results showed that the determination error of total amines increased with water increasing, while the effect of water on the determination of dimethylallylamine was little when the amount of water was within 5%, the relative error was generally within 1%, and that the end-point was acutely when about 10% chloroform was added. Compared with gas chromatography, this method is simple, convenient and accurate. 展开更多
关键词 Dimethylallylamine(DMAA) Non-aqueous titration acetic acid Acetic-formic mixed anhydrite Perchloric glacial acetic acid Crystal violet
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Determination of Formation Constants of Co ̄(2+), Ni ̄(2+),Cu ̄(2+) and Zn ̄(2+) Complexes with Humic and Fulvic Acidsby Potentiometric Titration Method 被引量:1
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作者 DUJIN-ZHOU LUCHANG-QING 《Pedosphere》 SCIE CAS CSCD 1994年第4期289-296,共8页
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
关键词 formation constants of complexes humic and fulvic acids potentiometric titration red soil
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Conductometric Titration for the Prediction of Conductivity in Solutions with Polymeric Membranes 被引量:1
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作者 María José Lavorante Juan Isidro Franco 《Journal of Electronic Science and Technology》 CAS CSCD 2017年第4期342-350,共9页
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
关键词 CONDUCTIVITY conductometric titration polymeric membranes
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Preparation and Characterization of Cathode Materials La_(0.7)Sr_(0.3-x)Ca_xCo_(0.9)Fe_(0.1)O_(3-δ) by Reverse Titration Co-Precipitation Method for ITSOFC 被引量:1
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作者 高文元 胡志强 +5 位作者 李长敏 唐乃岭 孙福禄 唐旭 魏蔷薇 孙永平 《Journal of Rare Earths》 SCIE EI CAS CSCD 2007年第S1期358-363,共6页
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
关键词 intermediate temperature solid oxide fuel cell La_(0.7)Sr_(0.3-x)Ca_xCo(1-y)Fe_yO_(3-δ) reverse titration co-precipitation property rare earths
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Rapid determination of phenolic compounds in water samples by alternating-current oscillopolarographic titration 被引量:1
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作者 XIAO Jun-ping WANG Xue-feng +4 位作者 ZHOU Qing-xiang FAN Xiao-yuan SU Xian-fa Bai Hua-hua DUAN Hai-jing 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2007年第5期622-627,共6页
A rapid, simple and sensitive method was demonstrated for the determination of phenolic compounds in water samples by alternating-current oscillopolarographic titration. With the presence of sulfuric acid, phenol coul... A rapid, simple and sensitive method was demonstrated for the determination of phenolic compounds in water samples by alternating-current oscillopolarographic titration. With the presence of sulfuric acid, phenol could be transferred into a nitroso-compound by reacting with NaNO2. The titration end-point was obtained by the formation of a sharp cut in the oscillopolarographic with infinitesimal NaNO2 on double platinum electrodes. The results showed that phenol had an excellent linear relationship over the range of 4.82×10^-6 -9.65×10^-3 mol/L, the RSD of the proposed method was lower than 1.5%, and the spiked recoveries of three real water samples were in the range of 95.6%-106.9%. 展开更多
关键词 alternating-current oscillopolarographic titration phenolic compounds
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Pitfalls and Uncertainties of Using Potentiometric Titration for Estimation of Plant Roots Surface Charge and Acid-Base Properties 被引量:1
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作者 Grzegorz Jozefaciuk Alicja Szatanik-Kloc +1 位作者 Malgorzata Lukowska Justyna Szerement 《American Journal of Plant Sciences》 2014年第13期1862-1876,共15页
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
关键词 CHARGE Density DISSOCIATION Method Plant ROOT Surface titration
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A Multiparameter Colloidal Titrations for the Determination of Cationic Polyelectrolytes 被引量:1
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作者 Eduardo A. López Maldonado Adrián O. Terán Mercedes T. O. Guzmán 《Journal of Environmental Protection》 2012年第11期1559-1570,共12页
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
关键词 POLYELECTROLYTE Quantification COLLOIDAL titration ZETA Potential Polydadmac O-TOLUIDINE Blue Indicator Wastewater Treatment
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Modified Titration Intratympanic Gentamicin Injection for Unilateral Intractable Ménière's Disease 被引量:1
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作者 刘波 冷杨名 +5 位作者 师洪 周任红 刘晶晶 张文娟 张甦琳 孔维佳 《Journal of Huazhong University of Science and Technology(Medical Sciences)》 SCIE CAS 2015年第5期747-751,共5页
This study looked into the efficacy of a modified titration protocol of intratympanic gentamicin injection(ITG) in the patients with unilateral intractable Ménière's disease(MD). Modified titration prot... This study looked into the efficacy of a modified titration protocol of intratympanic gentamicin injection(ITG) in the patients with unilateral intractable Ménière's disease(MD). Modified titration protocol of ITG at a low dose(20 mg/m L) was administered to 10 patients with definite unilateral intractable MD. After initial first two fixed ITGs on weekly basis,the patients might or might not be given any more injections,depending on the appearance of unilateral vestibular loss(UVL). ITG was terminated if the patients satisfied the criteria of UVL. All patients were followed-up for at least two years. The effects of ITG on the vertigo attack,functional level scores and postural balance were evaluated. Of the 10 cases,8 showed the sign of UVL after receiving initial two ITGs and were not given any more intratympanic injections,and the other 2 patients were administered three ITGs. A two-year follow-up revealed that complete and substantial vertigo control was achieved in 9 cases,and limited vertigo control in 1 patient. Hearing level was lowered in 2 patients. The posture stability and functional level scores were improved. Our study showed that the modified titration protocol of ITG at a low dose could effectively control vertigo in patients with unilateral intractable MD. 展开更多
关键词 vertigo intractable vestibular unilateral hearing ni re's Disease titration appearance auditory
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Determination of Oxide in FLINAK Melt by Electrochemical Titration Technique
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作者 王新东 段淑贞 +2 位作者 Christensen E. Von Barner J.H. Bjerrum N.J. 《Rare Metals》 SCIE EI CAS CSCD 1993年第2期97-102,共6页
The use of K2NbF7 as a probe solute for the cyclic voltammetric determination of oxide in FLINAK melts was studied and demonstrated. This method is based on a complex reaction and the peak current density of NbF72- re... The use of K2NbF7 as a probe solute for the cyclic voltammetric determination of oxide in FLINAK melts was studied and demonstrated. This method is based on a complex reaction and the peak current density of NbF72- reduction. The reaction constant was determined to be very large at 973 K. A cyclic voltammetric standard addition experiment was also employed to determine the amount of oxide in FLNAK melt. The oxide content of FLINAK melts is equal to the amount of Nb(V) added minus the amount of NbF72- which is obtained from the voltammogram. 展开更多
关键词 ELECTROCHEMISTRY Liquid metals NIOBIUM OXIDES titration
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Spectroscopic study on variations in illite surface properties after acid-base titration
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作者 LIUWen-xin COVENEYR.M. TANGHong-xiao 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2003年第4期456-463,共8页
FT IR, Raman microscopy, XRD, 29 Si and 27 Al MAS NMR, were used to investigate changes in surface properties of a natural illite sample after acid base potentiometric titration. The characteristic ... FT IR, Raman microscopy, XRD, 29 Si and 27 Al MAS NMR, were used to investigate changes in surface properties of a natural illite sample after acid base potentiometric titration. The characteristic XRD lines indicated the presence of surface Al Si complexes, preferable to Al(OH) 3 precipitates. In the microscopic Raman spectra, the vibration peaks of Si O and Al O bonds diminished as a result of treatment with acid, then increased after hydroxide back titration. The varied ratio of signal intensity between IV Al and VI Al species in 27 Al MAS NMR spectra, together with the stable BET surface area after acidimetric titration, suggested that edge faces and basal planes in the layer structure of illite participated in dissolution of structural components. The combined spectroscopic evidence demonstrated that the reactions between illite surfaces and acid leaching silicic acid and aluminum ions should be considered in the model description of surface acid base properties of the aqueous illite. 展开更多
关键词 natural illite acid base titration spectroscopic information surface Al Si species surface complexation
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