Optimization of an electrolyte conductivity detector for measuring low ion concentrations.
The optimization process of a planar interdigitated conductivity detector for measuring very low electrolyte concentrations for use in a lab-on-chip gas detection system is described. An electrical equivalent of the sensor is given, which includes the double layer capacitance dependency on the electrolyte concentration, resulting in a better description of the impedance of the sensor. The cell constant of the sensor is minimized to reduce the cell resistance in low specific conductivity solutions under the restriction of a small electrode area (> or = 0.1 cm(2)) for fast measurement, prescribed by the ammonia detection system. The small size makes it suitable for integration in micro channels. The developed sensor has a cell constant of 7.9 m(-1) resulting in a maximum resistance for deionized water of 177 k Omega at a frequency of 1 kHz.
Timmer
Björan
B
MESA+ Research Institute, University of Twente, Enschede, P O Box 217, 7500AE, Enschede, The Netherlands. B.H.Timmer@el.utwente.nl
Sparreboom
Wouter
W
Olthuis
Wouter
W
Bergveld
Piet
P
van den Berg
Albert
A