Miniature Clark-type oxygen electrode arrays were fabricated
using thin film technology. Each oxygen electrode comprised a silver
cathode and a Ag/AgCl anode. The use of a dry electrolyte containing
polyvinylpyrrolidone (PVP) permitted the use of solid state
fabrication processes. The electrolyte was left dry until it was
used, when the water essential for oxygen reduction was introduced
through a gas-permeable membrane and absorbed by the PVP. The
miniature oxygen electrode arrays showed good characteristics for
monitoring dissolved oxygen concentrations and could be mass
produced with assured quality. The yeast Trichosporon cutaneum
was immobilized onto the cathode of an oxygen electrode using a
photo-crosslinkable resin and the response of the sensor was the
difference between the output of a yeast-immobilized electrode and
that of a bare oxygen electrode. Measurements using the dual-type
sensor for biochemical oxygen demand (BOD) were markedly simplified
as air-saturated samples were not required, so air pumps and
stirrers can be omitted from the sensing system. The BOD sensor was
used for the analysis of real samples and the results agreed well
with those determined using the conventional 5-day BOD determination
method. This is a significant step toward the development of a
portable BOD measuring system incorporating disposable electrodes
and containing no mechanical parts.
Author Keywords: Oxygen electrode arrays;
Sensors; Biochemical oxygen demand
