Background electrolyte analysis

In CZE, the capillary, inlet reservoir, and outlet reservoir are filled with the same electrolyte solution. This solution is variously termed background electrolyte, analysis buffer, or run buffer. In CZE, the sample is injected at the inlet end of the capillary, and components migrate toward the detection point according to their mass-to-charge ratio by the electrophoretic mobility and separations principles outlined in the preceding text. It is the simplest form of CE and the most widely used, particularly for protein separations. CZE is described in Capillary Zone Electrophoresis. ... 

Capillary electrophoresis (CE) or capillary zone electrophoresis (CZE) is the technique most often employed in pesticide residue analysis. In its most basic form, free zone electrophoresis, a fused-silica capillary is filled with electrolyte (running buffer or background electrolyte). A potential is applied across the capillary and the cations... 

Matrix effects in the analysis of nutrients in seawater are caused by differences in background electrolyte composition and concentration (salinity) between the standard solutions and samples. This effect causes several methodological difficulties. First, the effect of ionic strength on the kinetics of colorimetric reactions results in color intensity changes with matrix composition and electrolyte concentration. In practice, analytical sensitivity depends upon the actual sample matrix. This effect is most serious in silicate analysis using the molybdenum blue method. Second, matrix differences can also cause refractive index interference in automated continuous flow analysis, the most popular technique for routine nutrient measurement. To deal with these matrix effects, seawater of... 

Many applications for ion analysis use a UV detector with indirect detection, though other electrochemical, laser-induced fluorescence (LIE), or mass spectrometry detectors have been described. The main advantage of UV detection is its availability on commercial instruments and that both UV-absorbing and non-UV-absorbing analytes may be detected. Nowadays, electrochemical detectors are also available specific background electrolytes (BGEs) must be used and the detector has to be adapted to existing CE instruments. 

Concerning more general application of mercury electrode in the studies on com-plexation equilibria, one should mention the paper by Jaworski et al. [59], who have investigated oxidation of mercury microelectrode in solutions with thiocyanates without any background electrolyte added. In the experiments, normal pulse voltammetry and staircase voltammetry were used. The authors have developed a general procedure for the determination of the stability constants, based on the data taken from the voltammograms. They have applied it to the analysis of Hg(II)-SCN complexes. 

E Electrochromatography. It is defined by Heftmann(Ref 78,p 14) as "a method of analysis in which direct current electrical potential promotes the separation of substances by differential migration from a narrow zone in a stabilized background electrolytic solution . 

Post-column reactions have also been used for polarographic analysis [61 ]. If the column effluent does not contain sufficient background electrolyte, the electrolyte may be added after the sample components have passed through the column. This tech-... 

Berzas Nevado et al. [138] developed a new capillary zone electrophoresis method for the separation of omeprazole enantiomers. Methyl-/ -cyclodextrin was chosen as the chiral selector, and several parameters, such as cyclodextrin structure and concentration, buffer concentration, pH, and capillary temperature were investigated to optimize separation and run times. Analysis time, shorter than 8 min was found using a background electrolyte solution consisting of 40 mM phosphate buffer adjusted to pH 2.2, 30 mM /1-cyclodextrin and 5 mM sodium disulfide, hydrodynamic injection, and 15 kV separation voltage. Detection limits were evaluated on the basis of baseline noise and were established 0.31 mg/1 for the omeprazole enantiomers. The method was applied to pharmaceutical preparations with recoveries between 84% and 104% of the labeled contents. 

The samples taken to the experiments were not purified with the method advised by Parfitt [165]. The Parfit s opinion on acidity or alkalinity of the hydroxyl group of both form of the titania comes from the position of the pHpzc. This value is determined by the adsorption/desorption reactions of the proton and adsorption of the background electrolyte ions. The oxide surface charge depends on the alkali-acid properties of the hydroxyl groups and confine only to the analysis of the acid properties of the oxide surface group, do not allow to predict the shift of pHpzc properly. 

Chee and Wan (1993) believe that CZE offers some advantages over MEKC for drug screening, particularly, simple background electrolyte preparation and shorter analysis times. They see the main limitation as the inability to analyze acidic, neutral, and basic drugs together. An additional advantage offered by CZE is that a peculiar separation mechanism, poorly correlated with MEKC, allows the use of this technique in parallel with MEKC for confirmation purposes, with the same instrumental hardware. 

A more extensive analysis was carried out using the dependence of AG (log k ) on the free energy of transfer of a cationic reactant from the reference solvent to other solvents using Eq. (56 a) and results obtained in an identical or similar background electrolyte these data are given in Table 8. 

The above presentation shows that the detailed analysis of the dependence of AGfr on the mixed solvent composition and on the stability and concentration of various solvated reactant species may be quite complicated, especially in the case of labile ions. The free energy of ions is dependent not only on their interaction with the solvent and with other components of the mixture [252] (for instance, ions of background electrolyte), but also on the change in solution structure [252] and on the change in hydrogen bond formation [253]. 

As in the case of chromatography, a chiral selector is also required in CE for enantiomeric resolution. Generally, suitable chiral compounds are used in the background electrolyte (BGE) as additives and hence are called chiral selectors or chiral BGE additives. There are only a few publications available that deal with the chiral resolution on a capillary coated with the chiral selector in CE. The analysis of the chiral pollutants discussed in this chapter is restricted only to using chiral selectors in the BGE. The most commonly used chiral BGE additives are cyclo-dextrins, macrocyclic glycopeptide antibiotics, proteins, crown ethers, ligand exchangers, and alkaloids.A list of these chiral BGE additives is presented in Table 1. 

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