晶体管振荡器的压电晶体在电解质溶液中的频移特性及其化学应用

野村等曾报告压电晶体在KCl溶液中的频移(至2mm)^[1]。对于电解质溶液中压电晶体振荡规律的定量研究,未见文献报道。     

Effects of salt concentration on analyte response using electrospray ionization mass spectrometry

The effect of salt concentration on analyte response using electrospray ionization mass spectrometry (ESI-MS) was measured and compared to that predicted by Enke's equilibrium partitioning model. The model predicts that analyte response will be proportional to concentration and that the response factor will decrease with increasing electrolyte concentration. The measured analyte response is proportional to concentration over four orders of magnitude when the electrolyte concentration is below 10(-3) M, as the model predicts. The concentration of excess charge ([Q]) generated by the ESI process increases significantly at 10(-3) M ionic concentration, but the response factor decreases at this concentration. Changes in shape of the spray that cause a loss of ion transmission efficiency may be the basis for the decrease in response. An increase in the analyte response factor with increasing electrolyte concentration is observed for electrolyte concentrations below 10(-3) M. An explanation for this based on the electrical double layer is proposed.     

Determination of Activation Energy for the Diffusion of Fe<Superscript>3+</Superscript> Ions in Agar Gel Medium Containing Various Transition Metal Sulfates

The study of the diffusion of ferric ions in agar gel containing transition metal sulfates was carried out. The effect of gel concentration, electrolyte concentration and temperature on the diffusion of Fe³⁺ ions in various transition metal sulfates was studied with a view to verify Wang’s model of diffusion and the applicability of transition state theory to diffusion in a gel medium. The diffusion coefficients were measured using the zone diffusion technique. For a given concentration of electrolyte the activation energy (E) is found to decrease with an increase in the charge density of the cation of the supporting electrolyte and for a given system it is found to decrease with increasing electrolyte concentration in agreement with Wang’s model. This observation is explained on the basis of the distortion in the water structure caused by ions and agar molecules. At a given electrolyte concentration the magnitude of the Arrhenius parameters, E and D _o, is found to decrease with increasing gel concentration in agreement with the transition state theory of diffusion.     

C.I. Reactive Orange 16-dodecylpyridinium chloride interactions in electrolytic solutions

The effect of electrolytes on the interaction between an anionic dye and a cationic surfactant was investigated spectrophotometrically in submicellar concentration range at certain temperature. The spectral change of the azo dye C.I. Reactive Orange 16 (RO16) exhibits a high sensitivity to the polarity of dye's environment. Dodecylpyridinium chloride (DPC) affects the electronic absorption spectra of dye solution that is dye-surfactant interaction results formation of complex and therefore a decrease in maximum absorption spectra (1.577 at 494 nm). The electrolyte cations cause an increase of the absorbance of DPC-RO16 ion-pair complex in the following order: Ca(2+)>Na(+)>NH(4)(+)>K(+)>Mg(2+), also for electrolyte anions Br(-)>Cl(-)>SO(4)(2-). Furthermore, this order can be changeable with increasing electrolyte concentration. The increase on absorbance value with increasing electrolyte concentration is explained as charge screening. The increase or decrease on absorption spectra of RO16-DPC solution depends on concentration range of the electrolyte added. As an increase on absorbance value with increasing electrolyte concentration is explained as charge screening, a decrease in this value for higher concentration of electrolyte is attributed as the charge of micelle shape.     

Frequency-dependent electroosmosis

This paper presents a theory for frequency-dependent electroosmosis. It is shown that for a closed capillary the electroosmosis frequency-dependent ratio of DeltaV/DeltaP is constant with increasing frequency until inertial effects become prevalent, at which time DeltaV/DeltaP starts to decrease with increasing frequency. The frequency response of the electroosmosis coupling coefficient is shown to be dependent on the capillary radius. As the capillary radius is made smaller, inertial effects start to occur at higher frequencies. As part of this paper, frequency-dependent electroosmosis is compared to frequency-dependent streaming potentials. In this comparison it is shown that inertial effects start to become more prevalent at higher frequencies for the closed capillary frequency-dependent electroosmosis case than for the frequency-dependent streaming potential case in the same capillary. It is also shown that this difference is due to a second viscosity (transverse) wave that emanates from the velocity zero within the capillary for the electroosmosis case. The second viscosity wave superposes with the viscosity wave that emanates from wall of the capillary to effectively reduce the hydraulic radius of the capillary. Data are presented for a 0.127-mm capillary to support the findings in this paper.     

毛细管反相电色谱法分离行为的研究

对乙睛-水-磷酸二氢销体系毛细管反相电色谱分离行为进行了研究。采用柱上紫外检测,在75μmi.d.×30cm的毛细管ODS（3μm）填充柱上获得了小于2.0的折合培板高度。同时还研究了乙睛的比例、电解质的浓度和电场强度等因素对电渗流和往效的影响。     

Buffer composition changes in background electrolyte during electrophoretic run in capillary zone electrophoresis

The electrophoretic behaviors of different analytes in capillary zone electrophoresis were studied by the Whole Column Imaging Detection (WCID). For capillary zone electrophoresis (CZE) in conventional buffer systems, non-constant sample plug movement characterized by progressive decrease of peak migration velocity was observed. The appropriate velocity decrease was correlated with a degree of ionization of the analyzed ion, thus the effect observed could be explained by fast buffer composition change resulting in the development of a non-linear pH gradient. To visualize the appropriate pH gradient, the concentration profile of initially uniformly distributed amphoteric substances was also monitored. The evolution of the concentration profile exhibited very complex dynamics. In addition, it was found that the nature of the electrode solutions strongly affect changes in the background electrolyte. In the case of traditional background electrolytes with an acid-base pair for electrode solutions a non-uniform ampholyte concentration developed quickly, leading finally to a quasi-stationary profile similar to those typical of IEF. Possible approaches to suppress a negative impact of the background electrolyte composition changes during electrophoretic run on CE-separation are presented herein. In particular it was observed that zwitterionic buffers are able to withstand prolonged electrolysis much better compared to traditional buffers.     

THE INFLUENCE OF COLLOIDAL STABILITY ON CRITICAL PIGMENT VOLUME CONCENTRATION (CPVC)

The level of colloidal stability of a latex coating formulation is governed by the hydrodynamic size of the pigment particle and its aggregates, along with the electrolyte concentration of the coating formulation. Model latex coating films were developed to investigate the effects of pigment aggregate size and the electrolyte concentration in the latex coating formulation on the critical pigment volume concentration (CPVC), as determined by mechanical optical and permeability properties.

The poly(styrene) pigment and poly(styrene-butadiene) (60:40) binder particles were characterized for their relative sizes, the surfactant surface coverage and the critical coagulation concentration, in dilute (1.8% solids) and concentrated (42% solids) dispersions, for sodium chloride and calcium chloride. The hydrodynamic diameter of the strong pigment aggregates formed as a function of aging time, after adjusting the electrolyte concentration of the pigment dispersion to the c.c.c. level were characterized by capillary chromatography technique.

The Increasing size of the pigment aggregates and the increasing electrolyte concentration of the latex coating formulation were shown to sharply decrease the CPVC values determined by mechanical and optical properties such as tensile strength and contrast ratio of the coating. Their influence on the permeability property of the films such as porosity was limited by the availability of the binder to form smooth surface below 35-40% PVC.

The morphological studies of the coating films showed that aggregates cause an increase in the degree of non-uniform distribution of the binder and pigment in the latex coating film     

温度和缓冲溶液对胶束电动毛细管色谱的迁移时间窗口的影响

以电渗淌度、胶束电泳淌度和淌度比这3个参数为考察对象,研究了毛细管温度、缓冲溶液种类和浓度对胶束电动毛细管色谱的迁移时间窗口的影响。电渗淌度和胶束电泳淌度均随毛细管温度的升高线性的增加,粘度是这一影响中的主要因素。理论上证明了管壁表面的局部粘度与主体粘度不同。当温度变化时,电渗淌度和胶束电泳淌度的变化幅度不同。降低温度可以扩展迁移时间窗口,虽然扩展幅度较小,但在商品化仪器上易于实现。推导出能统一描述电渗淌度和胶束电泳淌度与缓冲溶液浓度间的关系式。     

Inspection of the reversal of enantiomer migration order in ligand exchange micellar electrokinetic capillary chromatography

Enantiometers of D,L-phenylalanine were separated by capillary electrophoresis based on the principle of ligand exchange. Copper (II) complex of 4-hydroxy-L-proline was used as chiral selector. The separation and the migration order of D- and L-phenylalanine were strongly affected by adding an anion surfactant sodium dodecylsulfate (SDS). Without SDS in the electrolyte, the separation was also carried out but the resolution was very small. With SDS added into the electrolyte, the resolution decreased with increasing concentration of SDS until 5.0 mM. When the concentration of SDS in the electrolyte was over 5.0 mM, inversion of the migration order of DL-phenylalanine was observed and the resolution was also increased with increasing concentration up to 20 mM. It was interesting to find that the inversion of the migration order took place not only in the enantioscparation but also in the positional isomers. A family of a fluorinated amino acid, o-, m- and p-fluoro-D,L-phenylalanine was separated and the inversion of the migration order is discussed.     

Comparison of different capillary isoelectric focusing methods--use of "narrow pH cuts" of carrier ampholytes as original tools to improve resolution

Two capillary isoelectric focusing (CIEF) systems have first been optimized: one uses a bare silica capillary and 30% (v/v) of glycerol in the separation medium while the other uses a coated capillary and an aqueous background electrolyte. To perform permanent capillary coating, two neutral polymers have been compared: hydroxypropylcellulose (HPC) and polyvinylalcohol (PVA). HPC coating gave best results for electroosmotic flow (EOF) limitation on a wide pH range: as compared to a bare silica capillary, it allowed to decrease EOF by 96% at pH 7.2 after acidic and basic treatments, whereas PVA coating lead only to a 76% decrease. The glycerol CIEF system was more satisfying for the separation of model proteins classically used as pI markers. Finally, the use of "narrow pH cuts" of carrier ampholytes added to commercial ampholyte mixtures allowed increasing resolution up to a factor 2.4 at a chosen pH for the separation of pI markers and milk proteins.     

Direct Current Conductometry of Track Membranes

The electrical conductivity measured for a KCl solution in pores of poly(ethylene terephthalate) track membranes has been studied as depending on electrolyte concentration and pore diameter with the use of a direct-current source. The difference between the experimentally determined conductivity and the standard value has been shown to decrease with increasing electrolyte concentration and pore diameter. At the same time, its value is significantly lower than that determined by impedance spectroscopy. This result is related to a decrease in the contribution of a gel layer formed on the pore surface upon coming into the contact with the electrolyte to the electrical resistance of a membrane.     

Characteristic pH and electrolyte concentration dependences of 2-aminopyridine-derivatized oligosaccharides (N-glycans) in sonic-spray ionization mass spectrometry

The intensities of ion signals from neutral oligosaccharides (N-glycans) derivatized with 2-aminopyridine (PA) were analyzed by ion trap mass spectrometry with a sonic-spray ionization (SSI) source, in both positive- and negative-ion modes, while varying the pH and concentration of ammonium acetate buffer solution. Two characteristic results are reported and discussed. The first characteristic is the pH dependence of the ion intensities; on increasing the solution pH from 4.3 to 8.6, positive ion intensities increase and negative ion intensities decrease. The second characteristic concerns the dependence of ion intensities on electrolyte concentration; on increasing the electrolyte concentration, the SSI efficiency for the PA N-glycans first increases and then decreases. Assuming that the SSI mechanism essentially conforms to the statistical charging model and the charge residue model, a new model that focuses a great deal of attention on the counter (electrolyte) ion distribution surrounding the solvated analyte (PA N-glycan) is proposed, in particular to rationalize the characteristic pH dependence.     

Diffusioosmosis of electrolyte solutions in a fine capillary tube

A theoretical study is presented for the steady diffusioosmotic flow of an electrolyte solution in a fine capillary tube generated by a constant concentration gradient imposed in the axial direction. The capillary wall may have either a constant surface potential or a constant surface charge density of an arbitrary quantity. The electric double layer adjacent to the charged wall may have an arbitrary thickness, and its electrostatic potential distribution is determined by an analytical approximation to the solution of the Poisson-Boltzmann equation. Solving a modified Navier-Stokes equation with the constraint of no net electric current arising from the cocurrent diffusion, electric migration, and diffusioosmotic convection of the electrolyte ions, the macroscopic electric field and the fluid velocity along the axial direction induced by the imposed electrolyte concentration gradient are obtained semianalytically as a function of the radial position in a self-consistent way. The direction of the diffusioosmotic flow relative to the concentration gradient is determined by the combination of the zeta potential (or surface charge density) of the wall, the properties of the electrolyte solution, and other relevant factors. For a prescribed concentration gradient of an electrolyte, the magnitude of fluid velocity at a position in general increases with an increase in its distance from the capillary wall, but there are exceptions. The effect of the radial distribution of the induced tangential electric field and the relaxation effect due to ionic convection in the double layer on the diffusioosmotic flow are found to be very significant.     

Determining zeta Potential and Surface Conductance by Monitoring the Current in Electro-osmotic Flow

In this paper we have outlined a simple procedure for determining zeta potential, zeta(0), and surface conductance, lambda(s), based on current monitoring in electro-osmosis. In these experiments, the average velocity was determined by measuring the amount of time required to completely displace a solution by another solution in the capillary tube. The average velocity during electro-osmosis was found to be independent of capillary size, although it was dependent on the electrolyte concentration and applied electrical field. The measured values of the zeta potential, zeta(0), were found to be independent of capillary size and the applied field, while zeta(0) is strongly dependent on the electrolyte concentration. Calculations of the specific surface conductivity lambda(s) based on current measurements reveal a relationship between lambda(s) and capillary size, in agreement with the results reported in the literature. Copyright 2000 Academic Press.     

Simultaneous determination of low concentrations of ammonium and potassium ions by capillary type isotachophoresis

Low concentrations of ammonium and potassium ions (<2.0 mg/l.) were determined simultaneously by capillary type isotachophoresis based on the interaction between potassium and 18-crown-6 in the aqueous leading electrolyte. The PU value of potassium ion increased with increasing concentration of 18-crown-6 up to 3mM, whereas that of the ammonium ion remained almost constant. Thus complete separation of ammonium and potassium ions could be obtained by using 1-3mM 18-crown-6. The error in the analysis of mixtures containing ammonium and potassium ions (250-mul sample injection) was less than +/- 20% with a leading electrolyte containing 3mM 18-crown-6. The analysis time was 18 min.     

Dispersing phase viscometry and zeta potential in alumina dispersions

The stabilities of alumina dispersions were studied as a function of poly- and low molecular weight electrolyte concentration, using viscometry of the dispersing phase, and zeta potential measurements. The relation of polyelectrolyte adsorption to polymer concentration (at different low molecular weight electrolyte concentrations) was found to depend upon the dimensions of the polymer (which were a priori known to decrease with increasing poly- and low molecular weight electrolyte concentration). The occurrence of flocculation and bridging in the destabilization mechanism of the alumina dispersions was also characterized.     

毛细管电泳法分离测定芦丁、槲皮素和连翘苷

用毛细管电泳紫外检测法同时测定了芦丁、槲皮素和连翘苷，研究了各种条件的影响，得到了优化的实验条件，在20mmol/L的Na2B4O7(H3B03调节至pH8．40)-30mmol/L十二烷基硫酸钠-10％乙腈(1 9)的缓冲溶液中，分离电压为12kV时，芦丁、槲皮素和连翘苷在10min内得到了良好的分离，检测波长为254nm，芦丁、槲皮素和连翘苷分别在0．01-1．0mg/mL，0．01-1．0mg／mL和0．05-1．0mg/mL质量浓度范围内与电泳峰高呈现良好线性关系，检测下限分别为0．005mg/mL，0．005mg/mL和0．01mg／mL，应用于实际样品的测定。     

Method development approaches for capillary ion electrophoresis

Capillary ion electrophoresis (CIE) is a capillary electrophoretic technique optimized for rapid determination of low-molecular-mass inorganic and organic ions. CIE predominantly employs indirect UV detection since the majority of the analytes lack specific chromophores. Described are three methods for detection and electrolyte optimization. The first method discussed approaches for optimizing sensitivity, selectivity and peak confirmation using a chromate electrolyte and selected detection wavelengths. Peak confirmation is aided by using both direct detection of analytes. The second and third methods involve an unattended electrolyte development approach for instruments that only provide fresh electrolyte on the injection side of the capillary. The electrolyte composition is changed in both the injection side vial and in capillary before each sample injection while leaving the receiving side electrolyte vial constant at the initial electrolyte composition. In one mode, the concentration of the electroosmotic flow (EOF) modifier used to induce anodic flow is varied while keeping the background electrolyte composition constant. In a second experiment, the background electrolyte co-ion is sequentially changed from high mobility to low mobility while keeping the EOF modifier concentration constant. The end effect is to achieve a broad range of controlled peak symmetry for analytes in a simple matrix. The results are compared to separations obtained when the injection side and receiving side electrolytes are manually matched.     

Noncovalent coatings for the separation of synthetic polypeptides by nonaqueous capillary electrophoresis

Recently, we demonstrated the possibility to extend the range of capillary electrophoresis (CE) applications to the separation of non-water-soluble synthetic polymers. This work focuses on the control of the electro-osmotic flow (EOF) and on the limitation of the solute adsorption in nonaqueous electrolytes. For these purposes, different strategies were investigated. For the initial, a viscous additive (ethylene glycol or glycerol) was used in the electrolyte in order to decrease the EOF magnitude and, possibly, to compete with solute adsorption. A second strategy was to modify, before separation, the fused-silica capillary wall by the adsorption of poly(ethylene oxide) (PEO) via hydrogen bonding. The influence of the molecular mass of the adsorbed PEO on the EOF magnitude and direction was studied in electrolytes based on methanol/acetonitrile mixtures containing ammonium ions. For PEO molecular masses above 1000 g/mol, reversed (anodic) EOF were reported in accordance with previous results obtained with PEO covalently bonded capillaries. The influence of the nature and the concentration of the background electrolyte cation on the EOF magnitude and direction were also investigated. A third strategy consisted in modifying the capillary wall by the adsorption of a cationic polyelectrolyte layer. Advantageously, this polyelectrolyte layer suppressed the adsorption of the polymer solutes onto the capillary wall. The results obtained in this work confirm the high potential and the versatility of CE for the characterization of ionizable organic polymers in nonaqueous media.