Single Known Addition - Thermo Scientific Orion Versa Star Pro User Manual

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Chapter 4 pH, pH/ISE and pH/LogR Measurement Modules
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62 Orion Versa Star Pro Meter User Manual

Single Known Addition

In known addition, a standard of known concentration is added to a sample of unknown
concentration. The total concentration should approximately double upon the addition of the
standard, therefore sample concentration should be known within an order of magnitude. Refer
to the following table to choose the correct standard concentration and volume of addition.
Amount of standard to be added per
100 mL of sample
1 mL
5 mL
10 mL
1. Prepare the ion selective electrode (ISE) according to the instructions in the electrode user
manual. Prepare all required solutions (ionic strength adjusters, standards, etc) and review
any special requirements outlined in the electrode user manual. Connect the ISE, and any
other electrodes to be used, to the module inputs on the selected channel.
2. Determine the ISE slope as directed in the electrode user manual.
3. In the measurement mode, press the channel key until the channel with the pH/ISE
module with ISE connected is shown. If needed, press the mode key until ISE
Measurement is shown as the measure mode and use the
Electrode Type.
4. In the measurement mode, press the setup key.
5. Press the ,,  or  key to highlight Channel 1, Channel 2, Channel 3 or Channel 4
and press the f3 (Select) key.
a. Select the appropriate channel number that the ISE is connected.
6. Press the  or  key to highlight Incremental Techniques and press the f3 (Select) key.
7. Press the  or  key to highlight Single Known Addition and press the f3 (Select) key.
8. Press the f3 (Clear) key as needed to delete the displayed slope value. Use the numeric
keypad to enter the ISE slope value determined in step 2 and press the f2 (Accept) key.
9. Enter the sample volume using the numeric keypad and press the f2 (Accept) key.
10. Enter the total volume (sample volume plus added ISA volume) using the numeric keypad
and press the f2 (Accept) key.
11. Enter the standard concentration using the numeric keypad and press the f2 (Accept) key.
12. Rinse the ISE and any other electrodes in use with distilled water or rinse solution required
for that electrode. Blot the electrode dry with a lint-free tissue or shake the electrode, place
into the prepared sample and press the f2 (Next) key.
Standard concentration compared to expected sample
concentration
100 times more concentrated
20 times more concentrated
10 times more concentrated
ISE Mode Menu to set the
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