Chromatographic studies on the effect of exposure of polypyrrole coated stationary phases to redox reagents have been carried out. Polypyrrole containing chloride or dodecylsulfate as counterion was chemically synthesized and coated onto silica particles and packed into a chromatographic column. A series of standard compounds was used as the molecular probes. Changes in the chromatographic properties of polypyrrole as the result of the exposure to redox reagents were compared with those obtained by electrochemical treatment.