Thermo Fisher Scientific Ion Selective Electrodes Lead - Manual (Page 5)

Instruction Manual Lead Electrode
3
Pb(ClO
4
)
2
·3H
2
O. Swirl the flask gently to dissolve the solid. Fill the flask to the mark with
distilled water, cap, and upend several times to thoroughly mix the solution.
5.
Eutech Lead Perchlorate Standard, 1,000 ppm Pb(ClO
4
)
2
, Code no. EC-SCS-PB2-BT. To
prepare this solution from your own laboratory stock, half fill a one liter volumetric flask
with distilled water and add 2.30 grams of reagent-grade lead perchlorate,
Pb(ClO
4
)
2
·3H
2
O. Swirl the flask to dissolve the solid. Fill the flask to the mark with
distilled water, cap, and upend several times to thoroughly 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 lead combination ion electrode or the reference electrode. Fill the reference electrode or the
combination 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 as recommended by the meter manufacturer.
Electrode Slope Check (with pH/mV meter)
(Check electrodes each day)
1. To a 150 ml beaker, add 50 ml of methanol-formaldehyde solution and 50 ml of distilled
water. Add 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 lead standard to the beaker. When the
reading has stabilized, record the mV reading.
3.
Using a pipet, add 10 ml the same lead standard used above to the beaker. When the
reading has stabilized, record the mV reading.
4.
Determine the difference between the two readings. The electrode is operating correctly if
the millivolt potential has changed by 25±2, assuming the temperature is between 20
o
and
25
o
C. See the
TROUBLESHOOTING
sections if the potential change is not within this range.
Slope is defined as the change in potential observed when the concentration changes by a factor of
10.
Electrode Slope Check (with ion meter)
(Check electrodes each day)
1. Prepare standard lead solutions whose concentrations vary by tenfold. Use either the 0.1M
or 1,000 ppm lead standard. Use the serial dilution method for this preparation.
2.
To a 150 ml beaker, add 50 ml of methanol-formaldehyde solution and 50 ml of the lower
value standard. Add 2 ml of ISA. Place the beaker on a 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.