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Rapidlab 1200 Operator's Guide: System Overview and Intended Use
Rapidlab 1200 Systems Technology
The measurement technology used for the Rapidlab 1200 systems is based on
electrochemical, biochemical, and optical physics. Electrochemistry is the
measurement of current or voltage in an electrochemical cell. The cell has 2 or
more electrodes that interact with a chemical in solution and are connected to an
electrical system.
Electrodes used for measurement in the Rapidlab 1200 systems are called sensors.
Sensors are responsible for direct measurement of a specific substance of interest
in a sample. The Rapidlab 1200 systems sensors have the following
characteristics:
Molecular or ion-specific
recognition mechanism
Transducer mechanism
Signal processor system
The molecular recognition mechanism gives a sensor its identity. Each sensor is
designed to selectively measure the activity of a specific substance. Although
many elements in a sample may interact with a sensor, the sensor is highly
selective for 1 substance over others. The common recognition mechanism used
in many Rapidlab 1200 sensors is a membrane designed to be selective for a
specific substance.
The transducer mechanism converts the potential generated by the molecular
recognition mechanism to an electrical signal. In the Rapidlab 1200 systems, this
is accomplished through potentiometry or amperometry. For information about
Potentiometry, continue reading at the next section. For information about
Amperometry, refer to Amperometry‚ page 1-33.
Potentiometry
Potentiometry is the measurement of the voltage or potential generated between
2 electrodes in an electrochemical cell when no external current is applied and the
cell is in a state of equilibrium. The electrochemical cell consists of 2 electrodes (a
measuring or indicator electrode and a reference electrode), an electrolyte solution
(sample solution), and a measuring device such as a voltmeter. The
electrochemical cell is capable of measuring the concentration or activity of a
substance in a solution.
a membrane that is selective for a specific ion
converts the potential generated by the recognition
mechanism to an electrical signal using
potentiometry or amperometry
conditions the electronic signal from the sensor; the
electronic signals are then converted into a
concentration expressed in units of measure
1-27
02087462 Rev. V
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