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Electrically controlled electrofocusing of ampholytes between two zones of modified electrolyte with two different values of pH

1993; Elsevier BV; Volume: 638; Issue: 2 Linguagem: Inglês

10.1016/0021-9673(93)83426-s

1873-3778

Jan Pospı́chal, Mirko Deml, Petr Boček,

Analytical Chemistry and Sensors

A method is described for the separation and concentration of ampholytes from their mixtures with other ionic species. In a quadrupole electromigration column, two zones of different pHs are created by using controlled flows of the solvolytic ions (H+ and OH−) from appropriate electrode chambers at opposite sides of the column. Thus, a time-variable interface is created between two zones with a sharp change of pH. The position of the interface in the column, the direction and velocity of its movement and the difference in pH across the interface-pH gap can be adjusted by electric currents. This arrested interface is reasonably stable with time and has the following separation properties: ampholytes with pI values between the pHs of both zones are focused into a zone at interface; and other types of ampholytes and other weak or strong ions are not trapped at the interface. The basic properties of the above system are described and experiments showing the effects of the type of sample (ampholyte, weak ion), time, the concentration of primary electrolyte and the additives changing the viscosity, solubility or pI of ampholyte are given. The method proposed offers the following advantages: the ampholytes in the sample may be concentrated several hundred-fold; the focused zones have sharp boundaries (zones 0.1 mm in length were prepared) and high concentrations of the trapped species; the zone of a trapped ampholyte contains the ampholyte proper and simple ions of primary electrolyte (KCI) only; and the zones can be shifted to any selected position in the column (potentially to the location of a detector cell or a collection device).