Incremental Methods - Accumet XL 20 User Manual

The incremental methods which include known addition, known subtraction, analate addition and
analate subtraction are particularly useful with samples containing complex ionic backgrounds
which cannot be matched in standards. They are also useful with occasional samples whose
temperatures vary. More information on these methods is available in the ISE Theory Section
(see 'Appendix: ISE Theory' section).
Standardizing the meter for all incremental methods
Prior to conducting an analysis using any of the incremental methods, it is necessary to
standardize the meter with at least two standards. This will establish a slope value for the
electrode in use. The slope value is required in the incremental method calculations which yield
the ion concentration of the sample. See ISE Theory on 'Appendix: ISE Theory' section.
Make sure you have selected one of the incremental methods (known addition, known
subtraction, analate addition, or analate subtraction) in the Ion Setup screen.
1. Add ionic strength adjuster to the standards.
2. Immerse the ion selective electrode in the stirring standard. Always begin standardization
with the least concentrated ion standard.
3. Touch Standardize to initiate standardization.
4. Use the keypad to enter value of the standard.
5. Touch Enter on the keypad to accept this value. If you have entered a value in error, touch
BS to clear the value and key in a new value.
6. The meter accepts the value and the standard icon starts blinking. When the Stable icon
appears on the screen, press the Confirm icon to confirm the standardization.
7. Repeat with additional standards (up to five).
Ion Operation: Incremental Methods
XL25, 50 and 60 meters
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