The ion selective microelectrodes (ISME) have been applied to observe the continuous profiles of NO3-N and NH4-N in bulk solutions or biofilms. In order to evaluate the performance and applicability of ion concentration measuring system, the characteristics, such as slope of calibration curve, detection limit and potentiometric selectivity coefficient were investigated. The slopes of calibration curve showed high degree of correspondence for each target ion concentrations. And the detection limits of nitrate and ammonia ion selective microelectrode were 10-4.7 M and 10-4.4 M, respectively. These ion selective microelectrodes were proved that their own performance could be maintained for 16 days after making. NO3-N and NH4-N selective microelectrodes were also adapted to detect the continuous ion profiles of cilia media packed MLE (Modified Ludzack-Ettinger) process. And the monitored nitrate and ammonia ion profiles with the ion selective microelectrode were stable and well corresponded to the results with conventional ion chromatograph. However, the electric potential was unstable until 8 hr because of the unknown noise. The tip shape and performance of the ion selective microelectrode was stably kept over 2 days continuous monitoring.

Abstract
 1. Introduction
 2. Materials and Methods
  2.1. Fabrication of ion selective microelectrode
  2.2. Characteristics of fabricated ion selective microelectrode
  2.3. Monitoring of ion compounds in cilia media packed MLE reactor with ISME
 3. Results and Discussion
  3.1. Calibration curves and detection limits
  3.2. Variation of ammonia and nitrate ion microelectrode calibration curves according to elapsed time
  3.3. Potentiometric selectivity coefficient to interfering ions
  3.4. Evaluation of continuous monitoring with ion selective microelectrode
 4. Conclusions
 References

• Im-Gyu Byun(Institute for Environmental Technology and Industry, Pusan National University) Corresponding author