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14.
Ion Standardization
The AB250 can measure ion concentration such as ammonia or fluoride when
using an ion selective electrode (ISE) for the specific ion of interest.
Ion standardization is required with at least two calibration standards in order for
the instrument to calculate the measurement.
Prepare ion standards that bracket your measurement range. Follow the ion
selective electrode instruction manual for the appropriate ionic strength
adjustment and sample preparation.
For best results always begin with your lowest standard value, followed by the
next lowest, and so on.
1)
Connect the ISE and press
MODE
as needed for concentration mode.
2)
Rinse the ISE with clean water then dip into your lowest calibration standard
and stir. Observe the lower display which contains the mV reading of the ISE.
3)
Press STD. Use
▼
/
▲
keys to match the upper display to your ISE calibration
standard value.
4)
After ‘Stable’ appears, press
STD
to accept the standardization value.
5)
Rinse the ISE with clean water and dip into your next lowest calibration
standard and stir. Press
STD
after “Stable” appears to accept the next
standardization value.
6)
The mV/decade slope value will be displayed upon a successful calibration.
“Slope Error” indicates that the calibration for the current point was not
successful. This occurs when the slope (mV difference between two
consecutive points) is <15 mV/decade or >90 mV/decade.
7)
Repeat steps 4 & 5 with additional ISE standards if desired.
8)
To view the Ion Standardization Report at any time from the measure screen,
press REPORT.
The primary display will show “- - - -” when ion calibration is
required for ion measurement.
Refer to your Ion Selective Electrode instruction manual for
details on conditioning, storage, maintenance, calibration
standard preparation, Ionic Strength Adjustment,
troubleshooting, etc. Each ISE is unique and requires care and
operation that is specific to the electrode and ion of interest.
