Enhancing the Selectivity of Amperometric Nitric Oxide Sensor over Ammonia and Nitrite by Modifying Gas-Permeable Membrane with Teflon AF~R

摘要

A planar amperometric nitric oxide (NO_((g))) sensor based on a platinized platinum (pPt) working electrode (as anode) is one of the most sensitive NO detection methods reported to date with sub-nmol L~(-1) detection limits.The use of an outer gas permeable membrane (porous polytetrafluoroethylene (PTFE) membrane) in this sensor design has been shown to impart superiorNO selectivity over common interfering species present in biological samples,such as nitrite and ascorbate.Recently,however,it has been recognized that ammonia (NH_(3(g))) present in biological samples,e.g.,cell culture medium or blood,can interfere with NO detection using this sensor configuration owing to the concomitant oxidation capability of ammonia at the surface of the inner platinized platinum electrode.Herein,the selectivity of such an amperometric NO sensor is investigated in detail over both ammonia and nitrite and these results are compared to experimental data obtained with other types of amperometric NO sensors (including commercial WPI,Inc.device).Further,it is demonstrated that the NO selectivity of the planar-type NO sensor can be enhanced significantly by treating the porous PTFE gas permeable outer membrane with a Teflon AF~R solution.By filling the pores of the outer membrane with Teflon AF~R,the flux of ammonia and nitrite to the internal working electrode is greatly reduced,while maintaining good permeability toward NO_((g)) .