Amperometric sensing system for the detection of urea by a combination of the pH-stat method and flow injection analysis

A new type of amperometric sensing system for urea was constructed based on combining the pH-stat method and the Bow injection analysis (EIA) to solve the problem of potentiometry of dependency on the buffer concentration to the response of urea and moreover to eliminate the response to interfering substances. In the new system, the response to urea was independent of the buffer concentration and the relation between current response and urea con centration became linear. The possibility of automatic operation of this sy stem with a potentiostatic feed back circuit was also confirmed. In this sy stem, the relationship between urea concentration and current response was found to be linear up to 600 muM (=6.0 x 10(-4) mol dm(-3)). Since the samp le path was separated from the electrolysis path, no current response of in terfering substances such as ascorbic acid and uric acid occurred at the ph ysiological level. Thus, the possibility of amperometric sensing of urea wh ich has a merit of no dependency on the buffer concentration and moreover n o influence of interfering substances was demonstrated. (C) 2001 Elsevier S cience B.V. All rights reserved.