Accumet XL 20 User Manual page 143

Ion Operation: Analate Subtraction Method
Measuring Concentration in Samples Using the Analate Subtraction Method
The analate subtraction method is useful when no ion specific electrode is available to measure
the ion of interest directly. Like known subtraction the sample and the standard contain different
ionic species. However, the ion being measured is in the standard and not in the sample. The
reduction of free ions in the standard solution is proportional to the concentration of the ion of
interest in the sample. See ISE Theory on 'Appendix: ISE Theory' section.
Taking an Analate Subtraction Measurement
1. Immerse the ion selective electrode in a known volume of the standard solution.
2. Stir the standard.
3. Wait for the reading to stabilize (STABLE will appear). Touch AS to take the first reading.
4. Add a known volume of sample solution to the standard.
5. Wait for the reading to stabilize (STABLE will appear). Touch AS to take the second
reading.
6. Use the keypad to enter the sample volume.
7. Touch Enter to accept the value.
8. Use the keypad to enter the standard volume.
9. Touch Enter to accept the value.
10. Use the keypad to enter the volume of ionic strength adjuster used. If no ISA was used,
enter a value of zero.
11. Touch Enter to accept the value.
12. Use the keypad to enter the concentration of the standard solution.
13. Touch Enter to accept the value. Your Analate Subtraction result is now displayed.
14. Touch Print to send the data to a printer
OR
Touch OK to return to the Measure screen for a new measurement.
XL25, 50 and 60 meters
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