Electrokinetic removal of charged species from small sample volumes

•Simple sample preparation technique for microliter volume samples.•Solventless micropurification using a commercial capillary electrophoresis instrument.•Selective extraction of cationic or anionic charged species.•Extraction of cationic and analysis of neutral species.

Cationic or anionic molecules can be selectively injected from an aqueous mixture of charged and neutral species into a capillary by electrophoresis. Under stacking conditions, this selective field enhanced sample injection was studied here as a potential sample preparation technique for the clean-up or purification of microliter samples. As a simple demonstration, cationic small molecules were removed or extracted from a 100 μL sample mixture using a commercial capillary electrophoresis instrument. The extraction was monitored using an on-line UV detector. Results from the micellar electrokinetic chromatography analysis of treated and untreated sample revealed significant reduction of cationic species in the treated sample. The technique is essentially a sequence of field enhanced sample injection experiments in capillary electrophoresis.