Chapter
4
|
pH, pH/ISE and pH/LogR Measurement Modules
12.
Enter the reaction ratio using the numeric keypad and
press the f2 (Accept) key.
13.
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.
a.
Follow all electrode rinsing and drying instructions or exceptions in the ISE user
manual. Do not wipe or rub the sensing element of the electrode.
14.
Wait for the mV value on the meter to stabilize and press the
f2 (Accept) key.
15.
Enter the standard volume using the numeric keypad and press the
f2 (Accept) key.
16.
Add the standard
to the sample and press the f2 (Yes) key.
17.
Wait for the mV value on the meter to stabilize and press the
f2 (Accept) key.
18.
The meter will display the calculated sample concentration and summary of the incremental
technique performed. Press the
f1 (Esc) key to proceed to the measurement mode or press
the
f2 (Next) key to perform another analysis.
Double Known Subtraction
Double Known Subtraction Recommendations
Ensure that the subtraction ability of the chosen standard concentration
and volume added does not
exceed the concentration of the sample.
The sample volume should be 100 mL.
The concentration of the standard in Molarity or Normality should be 50 times the expected sample
concentration when the reaction ratio is 1.
Calculate the volume of standard required to halve the initial sample concentration and divide by six.
The volume of the first addition should be 5/6 the total standard mL and the volume of the second
addition should be 1/6 the total standard mL.
If available, consult a printout from a previous analysis of a similar sample.
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.
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 measurement mode and use the
ISE Mode Menu
to set the Electrode Type.
3.
In the measurement mode, press the
setup key.
4.
Press the ◄ or ► key to highlight the channel setup menu that the ISE is connected with
(Channel 1, Channel 2, Channel 3 or Channel 4) and press the
f3 (Select) key.
5.
Press the ◄ or ►key to highlight Incremental Techniques and press the
f3 (Select) key.
6.
Press the
▲or
▼ key to highlight Double Known Subtraction and press the
f3 (Select) key.
7.
Enter the sample volume using the numeric keypad and press the
f2 (Accept) key.
8.
Enter the total volume (sample volume plus added ISA volume) using the numeric keypad
and press the
f2 (Accept) key.
52
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Orion V
ERSA
S
TAR
Meter User Manual
Thermo
Scientific
Chapter
4
|
pH, pH/ISE and pH/LogR Measurement Modules
9.
Enter the standard concentration in Molarity or Normality using the numeric keypad and
press the
f2 (Accept) key.
10.
Enter the reaction ratio using the numeric keypad and press the
f2 (Accept) key.
11.
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.
a.
Follow all electrode rinsing and drying instructions or exceptions in the ISE user
manual. Do not wipe or rub the sensing element of the electrode.
12.
Wait for the mV value on the meter to stabilize and press the
f2 (Accept) key.
13.
Enter the first standard volume using the numeric keypad and press the
f2 (Accept) key.
14.
Add the first specified volume of the standard to the sample and press the
f2 (Yes) key.
15.
Wait for the mV value on the meter to stabilize and press the
f2 (Accept) key.
16.
Enter the second standard volume using the numeric keypad and press the
f2 (Accept)
key.
17.
Add the second specified volume of the standard to the sample and press the
f2 (Yes) key.
18.
Wait for the mV value on the meter to stabilize and press the
f2 (Accept) key.
19.
The meter will display the calculated sample concentration and summary of the incremental
technique performed. Press the
f1 (Esc) key to proceed to the measurement mode or press
the
f2 (Next) key to perform another analysis.
Single Analate Addition
In single analate addition, the first measurement is in a known standard solution containing the
same type of analate of interest as the sample. The second measurement follows the addition
of the unknown sample. The concentration of the unknown sample is then calculated. Refer to
the following table to choose the correct standard concentration and volume of addition.
Amount of analate to be added per 100 mL
of standard
Standard concentration compared to expected
sample concentration
1 mL
100
times more concentrated
5 mL
20 times more concentrated
10 mL
10 times more concentrated
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 measurement mode and use the
ISE Mode Menu
to set the Electrode Type.
4.
In the measurement mode, press the
setup key.
Thermo Scientific
Orion V
ERSA
S
TAR
Meter User Manual
|
53