Isotachophoretic System Research Articles

Concept of the effective mobility of the hydrogen ion and its use in cationic isotachophoresis

The concept of the effective mobility of the terminating H+ ion for cationic isotachophoresis in an acidic medium is introduced and its application to the selection of the electrolyte system for a required separation is discussed. Based on the theoretical description of the migrating reaction boundary, a relationship is derived for the calculation of the effective mobility of the H+ ion. Further, a rule is defined for the selection of a terminating cation such that the loss of the control of the migration of H+ ions through the isotachophoretic system is avoided. The method for the calculation and the rule mentioned above have been verified experimentally for model systems.

Isotachophoresis of urinary purines and pyrimidines : The use of spacers and enzymes for identification

An isotachophoretic system is described for the separation and identification of urinary purine and pyrimidine bases and nucleosides. For a better discrimination and interpretation of the UV profiles, well-defined non-UV-absorbing substances were introduced as spacers. Treatment of urine samples with purified enzymes before analysis resulted in specific shifts in the metabolite profiles, providing a sensitive and specific means of identifying a number of metabolites. With an injected volume of 3 μl (untreated urine diluted 1:5) the present method allows reproducible separations within 20 min of at least twenty different nucleosides and bases.

Capillary isotachophoresis: continuous sampling technique in the analyses of low-concentration samples

A method has been developed for sampling that permits an increase in the total amounts of sample components in an isotachophoretic system so that the zones which originate can be detected and evaluated. This method is based on the simultaneous pumping of the leading electrolyte and the sample in an isotachophoretic column. It is shown that the continuous sampling technique is quantitative and that it increases the operational capability of isotachophoresis at least by 1/2-2 orders of magnitude towards lower concentrations. As an illustration, the simultaneous analysis of chlorides and sulphates in a mineral water is reported and the results are compared with those of titrimetric, gravimetric and previous isotachophoresis analyses.