Accumet XL 20, User Manual, Page: 134 / 199

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Ion Operation:
Direct Reading Methods
XL25, 50 and 60 meters
Direct Reading with Blank Offset
This method presents you with the ability to measure samples with low level concentrations of the
ion of interest. It eliminates background interference by subtracting the value of a blank
concentration from the value for the sample.
See ISE Theory on ‘Appendix: ISE Theory’ section.
To Standardize the Meter Using Direct reading with Blank Offset
You will need to standardize the meter with one blank and a minimum of two standards. Make
sure that you have selected “Direct Reading with Blank Offset” on the Ion Setup screen.
1. Add ionic strength adjuster to the
standards and the blank.
2. Immerse the ion selective
electrode in the blank or standard
containing the lowest
concentration of the ion of interest.
3. Stir the standard or blank.
4. Touch
Standardize to initiate the
standardization process. At this
point, the meter will display the
question “Is this reading standard
or blank?”
5. Touch STANDARD if the sample
that the electrode is immersed in
is an Ion standard solution.
OR
Touch BLANK if the sample that
the electrode is immersed in is
the blank solution.
If you touched STANDARD
6. The Meter goes to the
Standardization screen. The
screen will flash each standard
icon once, then a numeric keypad
will appear. Using the
displayed keypad input the value
of the standard that you are using to standardize the meter. Touch
Enter to accept this
value.
The meter accepts the value and starts blinking. When the Stable icon appears on the
screen, press the Confirm icon to confirm the standardization.
If you touched BLANK
7. The meter will return to the Ion Measure screen and a beaker icon labeled blank will be
displayed. The blank value will be displayed on the bottom display panel.
Repeat if the meter has not been standardized with at least 2 standards of known ion
concentration.