The detection of small biological molecules as antigens is always an interesting challenge as environmental controls in our society are more and more necessary. The coupling between electrochemical/gravimetric techniques appears very attractive for examining biosensitive films based on conducting polymers. The electrochemical performance of modified polypyrrole films was examined in this work by using the couple anti-human serum albumin (HSA)/HSA. Electrochemical quartz crystal microbalance used in the ac regime and electrochemical impedance allow the electrochemical subleties to be discovered, in particular the insertion law of the ions present in the electrolyte.