ANALYSIS OF OLIGONUCLEOTIDES BY ON-COLUMN TRANSIENT CAPILLARY ISOTACHOPHORESIS AND CAPILLARY ELECTROPHORESIS IN POLY(ETHYLENE GLYCOL)-FILLED COLUMNS

Capillary electrophoresis in poly(ethylene glycol) (PEG) solution-fill ed uncoated silica capillaries was demonstrated to be suitable for sep aration of oligonucleotides in 100 mM ammonium formate (pH 4.5) buffer s. Reversed polarity (-30 kV at the injector end) was used, because th e electroosmotic now (EOF) at 4.5 was considerably lower than the mobi lity of the anionic analytes. On-column transient isotachophoresis (IT P) was developed for preconcentration of oligonucleotide samples in PE G solution-filled capillaries, The ITP focusing step allows injection of 20% of column length without loss of peak resolution. The detection limit of the method was 100 ng/mL of 16-mer oligonucleotide by using UV detection at wavelength 254 nm (signal-to-noise ratio 10).