1. Rapid Lab Systems measuring principle

2. Agenda Sensor/Electrode Location Measuring principles
The potentiometric measuring principle
Reference electrode
pH electrode
Electrolyte electrodes
pCO2 electrode
The amperometric measuring principle
pO2 electrode
Metabolite electrodes

3. Location
The Sensors are placed in the sensor modules easily accessible under a window on the front of the analyzer

4. Two measuring principles
The potentiometric measuring principle is used for
The amperometric measuring principle is used for
pH, pCO2, cK+, cNa+, cCa2+, cCl–
pO2, cGlucose, cLactate

5. The potentiometric measuring principle
Electrodes measure a change in voltage due to a change in ion concentration across a membrane
pH, pCO2, cK+, cNa+, cCa2+, cCl– V
Voltmeter
Reference electrode
Electrode
Electrolyte solution
Electrolyte solution
Electrode
Electrode
Sample
Liquid junction
Membrane

6. ( ) E = E - E + E Measuring a potential
Each link in the circuit exhibits a potential
The only unknown potential is the one between the membrane and the sample, ESample
The potential of the whole circuit is measured, Evoltmeter, and the unknown potential can be calculated: ( ) E = E - E + E
Sample
voltmeter
Ref pH

7. pH-sensitive glass membrane
Inner buffer solution with known and constant pH
air bubble
Ag/AgCl H+
Sample
Glass membrane
Constant exchange of H+ ions
Varying exchange of H+ ions – dependent on sample pH
The difference in potential across the glass membrane arises when there is a change in charge balance at the membrane.
A difference in ion exchange on either side of the membrane occurs if the H+ concentrations (and therefore pH) on both sides are unequal. The number of positive and negative ions are no longer equal, so the potential difference across the membrane changes.
In other words, the sample concentration of H+ will trigger the difference in ion exchange and cause a change in the potential across the membrane.

8. The amperometric measuring principle
Electrodes measure the current produced during an electrochemical reaction at an electrode
pO2, cGlucose, cLactate
Applied voltage
Ammeter - measures current
Cathode - reduction
Anode - oxidation
Electrolyte solution - buffered
Sample

9. pO2 and metabolite electrodes
The pO2 and metabolite electrodes are designed to measure the current produced during an electrochemical reaction
The flow of electrons (the current) is proportional to the concentration of the substrate (the pO2/Glu/Lac)
A+ + e-  A
An electrochemical reaction: - a reaction where electrons are transferred

10. THANK YOU