Figure ić8.āăelectrolyte sensor components, Electrolyte solution membrane electrode – Bayer HealthCare Rapidlab 800 User Manual
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IĆ14
800 Series Operator's Manual
Figure IĆ8.āăElectrolyte Sensor Components
Potassium, Chloride, and
Calcium Sensor
Sample Path
Silver/Silver Chloride
Wire
Electrolyte
Solution
Silver/Silver Chloride
Wire
Electrolyte Solution
Sample Path
Sodium Sensor
The recognition mechanism in the ISE is the membrane. Each sensor has a
membrane selective for the specific substance that it measures. To understand this
concept more clearly, take the case of the potassium sensor. The potassium sensor
membrane is designed as a charge separator. As shown in Figure I-9, the
positively-charged potassium ions selectively interact with the membrane when the
sample interfaces with the membrane. The negatively-charged chloride ions do not
interact with the membrane. The charge separation causes the membrane potential
that is measured by the electrochemical cell.
Figure IĆ9.āăSample Membrane Interface Interaction
Electrolyte
Solution
Membrane
Electrode
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Cl-
Na+
Na+
Na+
Cl-
Cl-
Cl-
Cl-
K+
Cl-
K+
Na+
Cl-
Randomly
Oriented Ions
Internal Electrolyte
Solution
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+
K+