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5 5 5 5----1 1 1 1
5. Principles of Operation
5.1 Sensor Technology
The sensor technology of the YSI SPORT is based on the principles conceived
by Dr. Leland Clark, formerly of Children's Hospital Foundation, Cincinnati,
Ohio. The immobilized enzyme membrane was invented by YSI and is covered
by U.S. Patent 4,073,713. This sensor technology has been used successfully
since 1975 in the YSI 23A Blood Glucose Analyzer; then later in the YSI 27
Industrial Analyzer, the YSI 23L Blood Lactate Analyzer, the YSI 2300 STAT
Glucose/L- Lactate Analyzer, and the YSI 2700 SELECT Chemistry Analyzer.
Figure Figure Figure Figure 5 5 5 5....1 1 1 1 Sensor Probe and Enzyme Membrane Sensor Probe and Enzyme Membrane Sensor Probe and Enzyme Membrane Sensor Probe and Enzyme Membrane
The probe is fitted with a three-layer membrane containing immobilized lactate
oxidase in the middle layer. Figure 5.1 shows an exploded view of the
membrane and its relationship to the face of the probe. The face of the probe,
covered by the membrane, is situated in a buffer-filled sample chamber into
which a sample is injected. Some of the substrate diffuses through the
membrane. When it contacts the immobilized enzyme (lactate oxidase), it is
rapidly oxidized, producing hydrogen peroxide (Reaction 1). The hydrogen
peroxide (H
2
O
2
) is, in turn, oxidized at the platinum anode, producing electrons
(Reaction 2). A dynamic equilibrium is achieved when the rate of H
2
O
2
production and the rate at which H
2
O
2
leaves the immobilized enzyme layer
become constant. Equilibrium is indicated by a steady state response. The
electron flow is linearly proportional to the steady state H
2
O
2
concentration and,
therefore, to the concentration of lactate.