Orion Benchtop pH/ISE Meter Instruction Manual
Calibration and Measurement of Concentration
31
Chapter VI
Calibration and Measurement of
Concentration
Orion 710Aplus, 720Aplus, 920Aplus
A. General Information
A one, two, or multipoint calibration should be performed before
concentration is measured. It is recommended that a two point standard
calibration be performed at the beginning of each day and every time
electrodes are changed to determine the slope of the electrode. This serves a
dual purpose, determining if the electrode is working properly and storing
the slope value into memory. Perform a calibration with one standard every
two hours to compensate for possible electrode drift. Use a fresh aliquot
from one of the standards used in the initial calibration. During calibration,
always use the most dilute standard first, the meter will automatically
recognize slope direction (i.e. will recognize anion or cation electrodes).
Standards should bracket the sample range and be in the same
concentration units.
Units
Any convenient units of concentration units can be used. For example:
molarity, ppm, %, etc.
Temperature
Allow all samples and standards to reach the same temperature before
measurement, or use temperature compensation if the electrode isopotential
point is known. (Orion 920Aplus only)
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