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1.
Summary A method based on a linear model enabling the efficient determination of the ionization constants (K
a) of saccharides by capillary zone electrophoresis with amperometric detection has been demonstrated. TheK
a values obtained from the plots of the reciprocal effective mobility against the inverse concentration of sodium hydroxide
were in agreement with literature values. 相似文献
2.
Ehala S Grishina AA Sheshenev AE Lyapkalo IM Kašička V 《Journal of chromatography. A》2010,1217(51):8048-8053
Thermodynamic acid-base dissociation (ionization) constants (pK(a)) of seven zwitterionic heterocyclic bases, first representatives of new heterocyclic family (2,3,5,7,8,9-hexahydro-1H-diimidazo[1,2-c:2',1'-f][1,3,2]diazaphosphinin-4-ium-5-olate 5-oxides), originally designed as chiral Lewis base catalysts for enantioselective reactions, were determined by capillary zone electrophoresis (CZE). The pK(a) values of the above very weak zwitterionic bases were determined from the dependence of their effective electrophoretic mobility on pH in strongly acidic background electrolytes (pH 0.85-2.80). Prior to pK(a) calculation by non-linear regression analysis, the CZE measured effective mobilities were corrected to reference temperature, 25°C, and constant ionic strength, 25 mM. Thermodynamic pK(a) values of the analyzed zwitterionic heterocyclic bases were found to be particularly low, in the range 0.04-0.32. Moreover, from the pH dependence of effective mobility of the bases, some other relevant characteristics, such as actual and absolute ionic mobilities and hydrodynamic radii of the acidic cationic forms of the bases were determined. 相似文献
3.
毛细管电泳电化学检测法同时测定三种氨基酸的电离常数 总被引:2,自引:1,他引:1
利用自制微圆盘铜电极,建立了一种毛细管电泳电化学检测同时测定色氨酸、丝氨酸和半胱氨酸pKα值的新方法。在不同pH条件下测定各氨基酸的有效淌度(μeff),利用Origin软件对μeff-[H^+]按理论关系式进行非线性拟合,得到其pKα值。该方法简便、快速,测定值与文献值符合良好。 相似文献
4.
5.
Geiser L Henchoz Y Galland A Carrupt PA Veuthey JL 《Journal of separation science》2005,28(17):2374-2380
CZE allows to measure the acidic dissociation constant (pKa) of many drug substances. However, determining the EOF intensity may be time-consuming, especially at a low pH. In order to overcome this drawback, a dynamic coating procedure of the capillary was carried out to increase microEOF, and thus to reduce the analysis time. In addition, this coating procedure enhanced migration time stability. The effective mobilities of 15 compounds were measured at different pH, producing pK'a values dependent on BGE ionic strength. The latter values were corrected with the activity coefficient to obtain a "true" pKa value. The 15 investigated compounds were (i) five acids: namely, salicylic acid, benzoic acid, ketoprofen, phenobarbital, and phenol, (ii) four bases: lidocaine, propafenone, propranolol, and quinine, (iii), five ampholytes: sulfanilamide, sulfabenzamide, sulfadimethoxine, sulfadoxine, and sulfisoxazole, and (iv) one zwitterion: cetirizine. The range of determined pKa values was between 1.2 and 11.2, and close to the pKa values available from the literature. 相似文献
6.
Yuki Tanikami Takuma Tagami Mayu Sakamoto Yukihiro Arakawa Hitoshi Mizuguchi Yasushi Imada Toshio Takayanagi 《Electrophoresis》2020,41(15):1316-1325
Acid dissociation constants (pKa) of nine kinds of flavin analogues as molecular catalyst candidates were determined by CZE. Although some of the analogues are instable and degradable under the light exposure or in alkaline aqueous solutions, the effective electrophoretic mobility of the flavin analogue of interest has been measured with the residual substance. The pKa values of the flavin analogues were analyzed through the changes in the effective electrophoretic mobility with varying pH of the separation buffer. One or two steps pKa values were determined by the analysis. One of the degraded species from the flavin analogues, lumichrome, was also detected in the CZE analysis, and its pKa values were also determined. While coexisting impurities generated over the storage conditions were found in some analogues, the pKa values of the target analogues were successfully determined with the help of the CZE separations. A pressure-assisted CZE was utilized for the determination or the estimation of the pKa values of such analogues as possessing carboxylic acid moiety. 相似文献
7.
Accurate determination of pK(a) values is important for proper characterization of newly synthesized molecules. In this work we have used CZE for determination of pK(a) values of new compounds prepared from intermediates, 2, 3 and 4-(2-chloro-acetylamino)-phenoxyacetic acids, by substituting chloride for 2-oxo-pyrrolidine, 2-oxo-piperidine or 2-oxo-azepane. These substances are expected to have a cognition enhancing activity and free radicals scavenging effect. Measurements were performed in a polyacrylamide-coated fused-silica capillary of 0.075 mm ID using direct UV detection at 254 nm. Three electrolyte systems were used for measurements to eliminate effects of potential interactions between tested compounds and components of the BGE. In the pH range 2.7-5.4, chloride, formate, acetate and phosphate were used as BGE co-ions, and sodium, beta-alanine and epsilon-aminocaproate as counterions. Mobility standards were measured simultaneously with the tested compounds for calculations of correct electrophoretic mobilities. Several approaches for the calculation of the pK(a) values were used. The values of pK(a) were determined by standard point-to-point calculation using Henderson-Hasselbach equation. Mobility and pH data were also evaluated by using nonlinear regression. Three parameter sigmoidal function fitted the experimental data with correlation coefficients higher than 0.99. Results from CZE measurements were compared with spectrophotometric measurements performed in sodium formate buffer solutions and evaluated at wavelength where the highest absorbance difference for varying pH was recorded. The experimental pK(a) values were compared with corresponding values calculated by the SPARC online calculator. Results of all three used methods were in good correlation. 相似文献
8.
Kvasnicka F 《Electrophoresis》2003,24(5):860-864
An on-line coupled capillary isotachophoresis - capillary zone electrophoresis method for the determination of lysozyme in selected food products is described. The optimized electrolyte system consisted of 10 mM NH(4)OH + 20 mM acetic acid (leading electrolyte), 5 mM epsilon -aminocaproic acid +5 mM acetic acid (terminating electrolyte), and 20 mM epsilon -aminocaproic acid +5 mM acetic acid +0.1% m/v hydroxypropylmethylcellulose (background electrolyte). A clear separation of lysozyme from other components of acidic sample extract was achieved within 15 min. Method characteristics, i.e., linearity (0-50 micrograms/mL), accuracy (recovery 96+/-5%), intra-assay (3.8%), quantification limit (1 microgram/ml), and detection limit (0.25 microgram/mL) were determined. Low laboriousness, sufficient sensitivity and low running costs are important attributes of this method. The developed method is suitable for the quantification of the egg content in egg pasta. 相似文献
9.
10.
Summary Capillary electrophoresis has been investigated as a novel experimental method for determination of the aggregation constants
of surfactants. The tendency of sodium cholate and sodium taurodeoxycholate to associate was studied in phosphate buffers
of pH 8.0 and pH 7.0, respectively. Stepwise aggregation equilibria of bile salt monomers has been described in terms of massbalance
equations. The Offord equation was used to model the electrophoretic mobility of the bile salt associates, and the experimental
mobility values could be fitted to the model. Interestingly, only even-membered aggregates-dimers and tetramers-besides the
monomers were proposed from the results of the curve-fitting for both bile salts. The aggregation constants calculated were
(in molar units): cholate logK
A2=1.37, logK
A4=4.98 taurodeoxycholate logK
A2=1.68, logK
A4=6.46. From these values, more pronounced aggregation of taurodeoxycholate starting at lower concentrations has been deduced,
supporting the back-to-back association model of bile salts. 相似文献
11.
In the complex neuronal network, chemical messengers like neuropeptides play a key role in signaling. To understand the mechanism of signaling, it is necessary to analyze the levels of neuropeptides from biological sources, which is important for neuroscience research. In the present work, a detailed investigation of the capillary zone electrophoresis (CZE) method was carried out to detect and quantify Substance P (SP), a bioactive neuropeptide, in rat brain tissues. The method involves specifically, a combination of solid phase extraction and immunoprecipitation prior to the CZE quantification. In this procedure, antibodies are used to capture the analyte of interest before the separation by CZE. Different separation parameters like buffer type, concentration, pH and applied voltage were the steps taken to study and achieve high efficiency CZE separation. CZE analysis was performed in an untreated fused-silica capillary column (35 cm×75 μm i.d.) and 185 nm wavelength using 100 mM phosphate buffer (pH 2.5) as a separation buffer. Electrophoresis in acidic mode and successive washing procedures solved the adsorption problem. The method provides a rapid analysis time of less than 15 min with 3.91% of RSD. Simultaneously, SP was quantified by Matrix Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry (MALDI-TOF-MS) and compared with CZE data. Starting from milligram amounts of brain tissue, the method allowed the detection of low picomole amounts of SP and the combined use of CZE and MALDI-TOF-MS was a success in quantification in this study. 相似文献
12.
建立了消毒剂中三氯新的毛细管电泳分析方法。探讨了缓冲介质和电泳参数对三氯新测定的影响。以15mmol/LNa2HPO4(pH6.0)-乙腈(V(Na2HPO4)∶V(乙腈)=50∶50)为电泳缓冲液,三氯新在12kV电压下电泳,于254nm检测波长处测定,6min可以完成分析。本方法的检出限为0.04mg/L,线性范围0.04~2.00mg/mL(r=0.997),加标回收率在90.9%~108.2%范围内,测定值的相对标准偏差分别为峰高7.7%,迁移时间5.5%。将本法与高效液相色谱法进行比较,样品测定结果的相对误差小于10%。将所建立的方法已用于消毒剂样品中三氯新的测定。 相似文献
13.
Nathan E. Ballou Gerald R. Ducatte Changyue Quang Vincent T. Remcho 《Journal of separation science》1996,19(4):183-188
A capillary electrophoretic method has been developed which achieves rapid quantitative separation and determination of ethylenediaminetetraacetic acid, N-(2-hydroxyethyl)ethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminediacetic acid, and nitrilotriacetic acid in Hanford tank waste simulant (TWS). Direct UV detection of Cu2+/chelator complexes is used to achieve enhanced sensitivity. The qualitative and quantitative reliability of the method and the quality of separations, as given by efficiency and resolution, is presented. In addition, the limits of detection and linearity of detector response with concentration are given for each chelator. The selection of Cu as the UV-absorbing species over other transition metals present in the waste is discussed. 相似文献
14.
15.
Phosphinic pseudopeptides (i.e., peptide isosteres with one peptide bond replaced by a phosphinic acid moiety) were analyzed and physicochemically characterized by capillary zone electrophoresis in the pH range of 1.1-3.2, employing phosphoric, phosphinic, oxalic and dichloroacetic acids as background electrolyte (BGE) constituents. The acid dissociation constant (pK(a)) of phosphinate group in phosphinic pseudopeptides and ionic mobilities of these analytes were determined from the pH dependence of their effective electrophoretic mobilities corrected to standard temperature and constant ionic strength of the BGEs. It was shown that these corrections are necessary whenever precise mobility data at very low pH are to be determined. Additionally, it was found that the ionic mobilities of the phosphinic pseudopeptides and pK(a) of their phosphinate group are affected by the BGE constituent used. The variability of migration behavior of the pseudopeptides can be attributed to their ion-pairing formation with the BGE components. 相似文献
16.
Separation of organic and inorganic arsenic species by capillary zone electrophoresis 总被引:1,自引:0,他引:1
Summary Capillary zone electrophoresis has been used to separate arsenite, arsenate, dimethylarsinic acid, and phenyl-,p-aminophenyl-, ando-aminophenylarsinic acids. Identification and quantification of the arsenic species at mg L−1 levels was possible by use of direct UV detection at 200 nm. The relative standard deviation (n=7) ranged from 0.97 to 1.52% for migration times and from 2.08 to 4.31% for peak areas. A method for rapid separation of
inorganic arsenic species was also developed; by use of this method arsenite and arsenate could be separated within 2 min.
Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999 相似文献
17.
A capillary electrophoretic method was explored to assay aromatic amines in food samples. With an inline-coupled transient isotachophoretic stacking approach, the method has yielded about 200-fold improvement of sensitivity in UV detection of three primary aromatic amines and melamine. By using K+ as a leading ion and Tris+ as a terminating ion, a plug of 10 cm (equivalent to 0.44 μL) sample solution was allowed to introduce into a 60 cm (50 cm effective) capillary for separation, giving limits of detection down to 2.0 × 10−8 M. Baseline separation was achieved within 10 min, with relative standard deviation of 0.41–0.75% (intra-day) or 1.2–1.5% (inter-day) for migration time and 3.8–4.3% (intra-day) or 5.2–6.7% (inter-day) for peak area. The method was directly applicable to assaying the melamine in powder milk samples, with recovery in between 92.0% and 107.1%. The method could also be applied to the analysis of trace primary aromatic amines migrating from composite food packaging bags after combination of a 10-fold off-line concentration step, with limit of detection down to less than 1 μg/L. By this method, 4,4′-diaminophenylmethane and 2,4-diaminotoluene were thus found in three types of composite food packaging bags. 相似文献
18.
Summary A novel method of separating and detecting trace aluminum by capillary zone electrophoresis is described. Aluminum is reacted with lumogallion [4-chloro-3-(2,4-dihydroxyphenylazo)-2-hydroxybenzen-1-sulphonic acid] so that the complex can be selectively and sensitively detected by a laser-induced fluorescence detector after capillary electrophoretic separation. Using the proposed method, limits of detection in the sub parts per billion range are achieved. The technique is applied to the determination of aluminum in human serum. 相似文献
19.
Michal Malý Milan Boublík Marijana Pocrnić Martin Ansorge Kateřina Lorinčíková Jana Svobodová Vlastimil Hruška Pavel Dubský Bohuslav Gaš 《Electrophoresis》2020,41(7-8):493-501
Thermodynamic acidity constants (acid or acid-base dissociation constants, sometimes called also as ionization constants) and limiting ionic mobilities (both of them at defined temperature, usually 25°C) are the fundamental physicochemical characteristics of a weak electrolyte, that is, weak acid or weak base or ampholyte. We introduce a novel method for determining the data of a weak electrolyte by the nonlinear regression of effective electrophoretic mobility versus buffer composition dependence when measured in a set of BGEs with various pH. To correct the experimental data for zero ionic strength we use the extended Debye-Hückel model and Onsager-Fuoss law with no simplifications. Contrary to contemporary approaches, the nonlinear regression is performed on limiting mobility data calculated by PeakMaster's correction engine, not on the raw experimental mobility data. Therefore, there is no requirement to perform all measurements at a constant ionic strength of the set of BGEs. We devised the computer program AnglerFish that performs the necessary calculations in a user-friendly fashion. All thermodynamic pKa values and limiting electrophoretic mobilities for arbitrarily charged substances having any number of ionic forms are calculated by one fit. The user input consists of the buffer composition of the set of BGEs and experimentally measured effective mobilities of the inspected weak electrolyte. 相似文献
20.
Summary Two modes of capillary electrophoresis (CE), capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography
(MEKC), were investigated for the separation of 12 aromatic sulphonate compounds. In CZE, although the voltage applied, the
buffer concentration and the pH were optimized for effective separation of the compounds studied, under the best conditions
four of the five amino compounds coeluted, as did naphthalene-1-sulphonic acid and naphthalene-2-sulphonic acid. In MEKC,
sodium dodecyl sulphate (SDS) and Brij 35 were chosen as the anionic and nonionic surfactants and the effect of the concentration
of micelles was examined. The effect of adding methanol as the organic modifier was also investigated with each of these micellar
systems. All the analytes, including the isomers, were completely separated by use of MEKC with Brij 35 but when SDS was used
only 11 compounds were separated because two amino compounds coeluted. 相似文献