A. Steinschaden et al., MINIATURIZED THIN-FILM CONDUCTOMETRIC BIOSENSORS WITH HIGH DYNAMIC-RANGE AND HIGH-SENSITIVITY, Sensors and actuators. B, Chemical, 44(1-3), 1997, pp. 365-369
Conductometric measurements are of interest in analytical chemistry. T
hey provide an overall-sight of the ionic strength in electrolytes and
can be used for analytical purposes if they are provided with a selec
tivity factor, e.g. enzyme membranes. Miniaturised transducers were fo
rmed by means of photolithography, thin film, and plasma technologies.
Two-and 4-electrode measurements were taken to characterise sensitivi
ty and dynamic range. However, using 4-electrode measurements expands
the dynamic range from deionised water up to 1 mol KCl-solution and in
creases the sensitivity at high background conductivity. Such measurem
ents were taken out with electrodes which had an interdigital distance
of 50 mu m and an area of 0.04 mm(2). Additionally, interdigital stru
ctures with interdigital distances of 5 mu m were investigated. Coated
with a poly-HEMA membrane wherein urease was immobilised, a urea sens
or was constructed. The concentration-range of urea was 1-30 mmol urea
in 20 mmol HEPES-buffer. (C) 1997 Elsevier Science S.A.