Microelectrophoretic techniques

Model particle mobility has been determinated with the Tiselius method (Tiselius, 1937, 1938). This method also allows the integration of the mobility of a large number of particles even if the refractive index is very close to that of the electrolyte medium, allowing to minimize the experimental errors inherent to the classical microelectrophoretic techniques. The electrophoretic mobilities will not be transformed into surface charges because the theoretical relationship between these parameters is highly dependant on the particle radius of curvature and the electrolyte concentration in the vicinity of the particle (Hunter and Wright, 1971). For both methods, the analytical error falls below 5 %, however, it increases up to 10 % for natural composite samples and/or low mobilities. 

Recent advances made in measuring particle charge and mobility in nonaqueous suspensions are reviewed. Microelectrophoretic techniques have been used to determine zeta potential and the measurements related to particle stability. 

A dsorption studies of ionic species at the solid-liquid or liquid-liquid interfaces can be carried out using data obtained from electrokinetic measurements (1, 6, 7, 12, 13, 14, 26, 27, 29, 30, 37, 41,44). In the case of solid-water most of the measurements have been obtained by using either the streaming potential technique or microelectrophoresis. Since the hydrocarbons investigated previously were liquid, the microelectrophoretic technique was used (7, 37, 41,44). It is not an easy task to obtain precise results on f potentials of oil droplets from mobility measurements unless a certain number of corrections are introduced (4, 5, 20, 21, 22). 

Recently, the microelectrophoretic technique received two improvements [21]. First, electrodes were designed in such a manner that micrometer-sized bubbles are produced over the entire cross-section of the electrophoresis cell, which allows to select a bubble easily in the stationary plane. Second, a motorized vertical translation stage controlled by a computer is implemented. Thus, when bubbles rise, the electrophoresis cell mounted on the translation stage is made to move downward so that the bubbles can be kept in the field of view of the microscope. As a result, the movement of bubbles with diameters up to 80 p-m can be readily followed and bubble trajectory can be traced for 4-8 sec. 

Since our last review, an interesting work has been published by Phianmongkhol and Varley on the measurement of I potential of air bubbles in solutions of various proteins, BSA, 3-casein, and lysozyme [47]. They used a microelectrophoretic technique with a cylindrical cell coated according to the procedme described in our first paper on potential measurement [30]. They found that the average value of the potential of the bubbles immersed in phosphate buffer of pH 7.0 (ionic strength... 

Nuclear magnetic resonance spectroscopy has been used to study self-ossociation in promethazine hydrochloride, in 2-butyl-3-benzofuranyl 4-[2-(diethylamino) ethoxy]-3,5-diiodo-phenyl ketone hydrochloride (SKF 33134A),40ond in d-propoxyphene hydrochloride. Florence has measured the properties of p-diethylaminoethyl diphenylpropylacetate hydrochloride (SKF 525-A) by light scattering, surface tension, and microelectrophoretic techniques. He suggests that caution should be exercised in the interpretation of enzyme inhibition results obtained with a compound of this type since it exhibits surface activity, and surfactants are known to exert an appreciable effect on certain enzyme systems. 

Electrokinetic phenomena involve the combined effects of motion and an electric field. When an electric field is applied to a colloidal suspension, the particles move with a velocity that is proportional to the applied field strength. The motion is called electrophoresis. It is a valuable source of information on the sign and magnitude of the charge and on the potential associated with the double layer. The measured potential, called the I potential, is an important guide to the stability of lyophobic colloids (25). The most widely used method for measuring the potential is the microelectrophoretic technique, in which the motion of individual particles is followed in a microscope. The technique is used with very dilute suspensions. Modern instrumentation provides for automated, rapid measurements and for the use of concentrated suspensions. 

HT has also the properties of a neurotransmitter at some synapses in the CNS of mammals (1) 5-HT neurons are located in specific areas 5-HT is found in nerve endings in subcellular fractions identical with synaptosomes (2) all the biosynthetic equipment for making 5-HT is present in the brain along with the inactivating machinery (uptake and MAO) (3) 5-HT is released from spinal-cord neurons and brain slices by electrical stimulation (4) 5-HT or iproniazid when applied by microelectrophoretic technique to isolated neurons alters the firing pattern (5) drugs which alter the metabolism of 5-HT in the brain (reserpine, p-chlorophenylalanine) produce pronounced behavioural effects. 

In our laboratory a variation of microelectrophoretic technique was developed. This method, in contrast to other microelectrophoretic methods (Alexidze and Chaglid, 1970 Rosenberg, 1970), makes possible the determination of LDH isozymes in any size cell, not only in large cells but in small cells as well (Korochkin, 1972b,c Korochkin et al., 1972b). The principles of this technique are demon-... 

Thomas, G., et al., Capillary and microelectrophoretic separations of ligase detection reaction products produced from low-abundant point mutations in genomic DNA, Electrophoresis, 25,1668, 2004. BraziU, S.A. and Kuhr, W.G., A single base extension technique for the analysis of known mutations utilizing capillary gel electrophoresis with electrochemical detection. Anal Chem, 74, 3421, 2002. 

The aforementioned general approach is schematized in Figure 2.6. It involves the application of several methodologies based on macroscopic adsorption data and potentiometric titrations as well as microelectrophoretic mobility or streaming potential measurements, the appKcation of spectroscopic techniques as well as the application of electrochemical (equilibrium) modeling, quantum-mechanical calculations and dynamic simulations. 

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