Direct injection of organic solvent extracts for capillary electrophoresis

It is demonstrated here that organic solvents immiscible in water used in sample extraction, such as chloroform, can be injected directly and successfully on the capillary without the need for evaporation and reconstitution. Current continuity was maintained all the time during the run. In order to avoid the rapid evaporation of the organic solvent during the analysis, the aqueous layer was left over the chloroform. This simplified the extraction step, and enabled the injection from the same vial over several hours without dealing with problem of evaporation. The relative peak heights in the electropherograms can be modified by the inclusion in the chloroform of a more polar solvent, by adjusting the pH, or adjusting the salt content of the sample. Addition of a polar solvent to the chloroform improved greatly the precision of the analysis for both the peak height and migration time.