Ions, inorganic electrophoretic

Separations of anions are based on differences in electrophoretic flow. Inorganic ions are generally smaller and therefore more mobile than organic ions. The electrophoretic mobilities of inorganic ions are an inverse function of their hydrated ionic radii. Electrophoretic mobility is also affected by the charge on an ion and by the solvent medium. Tables of limiting ionic conductance are a convenient source for estimating electric mobilities of ions. 

Once an electrophoretic separation has been accomplished, the paper or gel is sprayed or dipped in a visualizing solution similar to that used in the visualization of components on a thin-layer plate. Detection methods similar to those used in HPLC are used in CE. The type of analytes (e.g., inorganic ions, organic ions, and ionic biomolecules) will determine which detection method is best. 

Swartz, M. E. (1993). Capillary electrophoretic determination of inorganic ions in a prenatal vitamin formulation./. Chromatogr. 640, 441—444. 

In the case of high-mobility analytes such as inorganic anions,, e values are comparable or even greater than that of xe0. For instance, common anions such as chloride, bromide, and sulfate have electrophoretic mobilities of 7.92, 8.09, and 8.29 x 1CT4 cm2/(V s), respectively. Thus, these anions migrate faster than the EOF but in the opposite direction. As a consequence, they would not be detected in the normal configuration described above (detector at cathode). Rather one would need to inject at the cathode and place the detector at the anode to detect these ions. 

High performance capillary electrophoresis is one form of free-solution electrophoresis. CE is useful to researchers and analysts working in areas in which traditional electrophoresis is customarily applied (e.g., biopolymer analysis) and also in disciplines not usually associated with electrophoretic analysis, such as inorganic ion analysis. The potential application areas of CE are vast, because this technique can separate a variety of ligates, from inorganic ions up to intact cells, using the same instrumental hardware designed for separations based on different physical-chemical mechanisms. 

Mbuna, J. et al. Capillary zone electrophoretic studies of ion association between inorganic anions and tetraalkylammonium ions in aqueous dioxane media. J. Chromatogr. A. 2005, 1069, 261-270. 

Overby, L.R., Bocchieri, S.F., and Frederickson, R.L. Chromatographic, electrophoretic, and ion exchange identification of radioactive organic and inorganic arsenicals,... 

A certain inorganic cation has an electrophoretic mobility of 4.31 X 10 " cm-s V . This same ion has a diffusion coefficient of 9.8 X 10 cm-s. If this ion is separated by capillary zone electrophoresis with a. 50.0-cm capillary, what is the expected plate count N at applied voltages of... 

Doss, S.K.. Surface properties of hydroxyapatite. I. The effect of various inorganic ions on the electrophoretic behavior, J. Dent. Res., 55, 1067, 1976. 

Separations of common inorganic anions are quite fast, as indicated by the migration times in Table 10.5. It is also possible to obtain a baseline because of the greater ion-exchange affinity for iodide the electrophoretic mobilities of bromide and iodide are almost identical. A separation of several inorganic anions is illustrated in Fig. 10.15. 

Capillary electrophoresis has become an attractive alternative to ion chromatography and atomic absorption spectrometry for measuring inorganic ions because of its multi-ion capability, high speed, high resolution and sensitivity, and relatively low cost. Because of their relatively high electrophoretic mobility, analysis times can be shortened for small ions by having them move electrophoretically in the... 

The possibility to use ion exchange papers like CM-, DEAE- and ECTEOLA-cel-lulose for electrophoretic separations was demonstrated by Yaron and Sober [38]. Huens and Jakubovic [39] used CM cellulose for the separation of haemoglobin variants. Several studies using paper impregnated with inorganic ion exchangers were reported. 

Photometric detectors are the most popular in CE instruments including diode array detectors. Laser-induced fluorescence (LIE) detection and electric conductivity detectors are also popular. LIE is particularly sensitive and powerful for detecting low concentration analytes. However, most analytes are not natively fluorescent and some derivatizations are necessary. Conductivity detector is useful for the detection of non-ultraviolet (non-UV) absorbing analytes such as inorganic ions or fatty acids. Both LIE detection and conductivity detectors are commercially available and easy to interface with conventional CE instruments. Electrochemical detectors are also useful for selective high-sensitivity detection. Several techniques have been developed to circumvent the problem of strong effects of electrophoretic field on electrochemical detection, but despite this, commercial electrochemical detectors are not used extensively. 

Electrospray ionization works best with preformed ions in solution and when preformed ions are separated from their counterions. In 1991 Blades et al. reported on the electrophoretic nature of electrospray, in which the charge balance requires the conversion of ions into electrons. Therefore, oxidation occurs at the needle (Fig. 8.5) and the interface of the mass spectrometer acts as a counterelectrode. Electrospray is particularly suitable for the analysis of inorganic ions and molecules, which have acidic or basic functional groups. Organic molecules are generally observed as protonated or deprotonated... 

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