Effect of DNA on the peroxidase based biosensor for phenol determination in waste waters

The influence of different additives, like bovine serum albumin (BSA), poly ethylenimine (PEI) and DNA, on the sensitivity and operational stability of a phenol biosensor based on peroxidase immobilized on silica-titanium and mixed in carbon was studied. The best results were found with electrodes co ntaining DNA in the paste, although with BSA better results were obtained, compared to the electrode without additives. The response of biosensor inco rporating DNA decayed ca. 50 % after 3 to ii days of use, but it then remai ned constant for 25 days of daily use, when stored in a phosphate buffer so lution under refrigeration between experiments. Original performance was re covered by simply substituting the used paste for a new portion of stock pa ste. The high sensitivity for phenol due to the immobilization of peroxidas e on silica-titanium and the increase of stability of the biosensor provide d by DNA addition were essential for the successful determination of phenol in real samples, with an average of 104.5 % recovery.