Capillary electrophoresis of anions at high salt concentrations

Abstract

It is commonly thought that even a moderately high ionic concentration in the background electrolyte (BGE) would lead to Joule heating and serious peak distortion. However, we obtained very satisfactory separations of both inorganic and organic anions in electrolyte solutions as high as 5 M sodium chloride using direct photometric detection. Samples containing a 0.5 M concentration of a salt can be analyzed directly by making the BGE concentration of the same salt even higher to obtain electrostacking. The temperature in the center of the capillary was calculated to be 49 degrees C when the current is at its maximum of 280 microA. The effect of various salts on electrophoretic and electroosmotic mobility is discussed. Several examples are given of capillary electrophoresis under high-salt conditions.

Trace ion analysis of seawater by capillary electrophoresis: Determination of iodide using transient isotachophoretic preconcentration

“…As was demonstrated in a study by Fritz and co-workers [5], an electrolyte solution of 0.5 M sodium chloride at pH 2.4 (adjusted with HCl) offers the possibility of circumventing interference from seawater matrix salinity. Furthermore, the acidic pH value selected in combination with high concentration of sodium cations greatly reduced the electroosmotic flow so that no use of a flow modifier was required.…”

“…In this context, the CE method has attracted even more attention from environmental scientists than ion chromatography (IC), an established technique in the area. A great deal of effort from several research groups was directed toward elimination of the interfering role of matrix salts, and this problem has principally been solved by performing anion separations in background electrolytes (BGEs) containing high chloride concentrations [5][6][7]. Another challenge that still requires a proper solution is behind the analysis of seawater, a typical sample with an even distribution of concentrations, for trace-level ions.…”

Recent advances of transient isotachophoresis‐capillary electrophoresis in the analysis of small ions from high‐conductivity matrices

“…A viable modification of anionic tITP-CE configuration with regard to the BGE composition consists also in using a high salt (co-ion) concentration, such as 500 mM NaCl [63,64,[66][67][68][69] or artificial seawater [72][73][74][75][76][77][78][79]. This is a welldocumented approach for reduction of the matrix interferences and minimization of electrodispersion for CE separation of inorganic ions from loaded samples [87], and even 1500 mM sodium chloride can be tolerated in such systems without excessive Joule heating [88,89]. The character of the BGE counterion should also be taken into account when selecting the proper BGE composition for tITP stacking of samples containing an excess of chloride [61].…”

Capillary electrophoresis of trace metals in highly saline physiological sample matrices

“…Although the use of very high concentration BGE (. 1 M) to achieve field-amplification stacking of high ionic strength samples has been reported [25], they usually suffer from the Joule heating problem and long analysis times [15]. Therefore, on-line preconcentration techniques in CE suitable for high salt samples have been of much interest [26][27][28][29][30].…”