A demonstration of acquiring specific concentration data by variations in the operating conditions of a non-specific sensor

A method for determining separate ion concentrations using a conductivity s ensor was developed and tested. While a single electrical conductivity meas urement in a solution does not give information on the present ion types, a range of measurements at various electrolyte temperatures does. Since the temperature dependency of the mobility of an ion is unique for that ion, it appeared to be possible to fit ion concentrations from a set of conductivi ty measurements while heating the electrolyte. For the calculation of the ion concentrations from conductivity vs, tempera ture sweep, an estimation algorithm is introduced based on the linear minim um mean square of the error. Errors in the measured conductivity will propa gate through the algorithm into errors in the fitted ion concentrations. Fo r the validation of the estimation method, this propagation of errors is al so evaluated. The example given merely shows the feasibility of obtaining s pecific concentration information from an intrinsically non-specific type o f measurement, electrolyte conductivity, by using the unique temperature de pendence of ionic mobility. (C) 2000 Elsevier Science B.V. All rights reser ved.