Thermo Fisher Scientific Ion Selective Electrodes Sodium - Manual (Page 4)

Sodium Electrode Instruction Manual
2
6.
Eutech Sodium Standard, 100 ppm Na
+
, Code no. EC-SCS-LNA3-BT. To prepare this
solution from your own laboratory stock, half fill a one liter volumetric flask with
distilled water and add 0.254 grams of reagent grade NaCl. Swirl the flask to dissolve the
solid. Fill the flask to the mark with distilled water, cap, and upend several times to mix
the solution.
GENERAL PREPARATION
Electrode Preparation
Remove the rubber caps covering the electrode tips and the rubber insert covering the filling hole of
the reference electrode. Fill the combination electrode or the reference electrode with the filling
solution shipped with the electrode to a level just below the fill hole. No preparation is required
with a sealed reference electrode. Connect the electrodes to the proper terminals of the meter as
recommended by the meter manufacturer. Soak the sodium electrode tip overnight in the electrode
storage solution.
Electrode Slope Check (with pH/mV meter)
(Check electrodes each day)
1. To a 150 ml glass beaker, add 100 ml of distilled water and 2 ml of ISA. Place the beaker
on a magnetic stirrer and begin stirring at a constant rate. After assuring that the meter is
in the millivolt mode, lower the electrode tips into the solution.
2.
Using a pipet, add 1 ml of 0.1M or 1,000 ppm sodium standard to the beaker. When the
reading has stabilized, record the mV reading.
3.
Using a pipet, add 10 ml of the same sodium standard used above to the beaker. When
the reading has stabilized, record the mV reading.
4.
Determine the difference between the two readings. A difference of 56
±2 mV indicates
correct electrode operation assuming the solution temperature is between 20
o
and 25
o
C.
See the
TROUBLESHOOTING
section if the potential change is not within this range.
Slope is defined as the change in potential observed when the concentration changes be a factor of
10.
Electrode Slope Check (with ion meter)
(Check electrodes each day)
1. Prepare standard sodium solutions whose concentrations vary by tenfold. Use either the
0.1M NaCl or the 1,000 ppm sodium standard. Use the serial dilution method for this
preparation.
2.
To a 150 ml beaker, add 100 ml of the lower value standard and 2 ml of ISA. Place the
beaker on the magnetic stirrer and begin stirring at a constant rate. Lower the electrode
tips into the solution. Assure that the meter is in the concentration mode.
3.
Adjust the meter to the concentration of the standard and fix the value in the memory
according to the meter manufacturer's instructions.