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

Cyanide Electrode Instruction Manual
4
3.
Cyanide Standard, 1X10
-2
M. To prepare this solution from your own laboratory stock, add
10 ml of ISA and about 500 ml of distilled water to a one liter volumetric flask. Add 0.49
grams of dry, reagent-grade sodium cyanide, NaCN, to the solution and swirl the flask
gently to dissolve the solid. Dilute to the mark with distilled water, cap, and upend the
flask several times to thoroughly mix the contents. Store all standards in plastic bottles and
prepare weekly.
4.
Cyanide Standard, 1,000 ppm. To prepare this solution from your own laboratory stock,
add 10 ml of ISA and about 500 ml of distilled water to a one liter volumetric flask. Add
1.88 grams of dry, reagent-grade NaCN and swirl the flask gently to dissolve the solid.
Dilute to the mark with distilled water, cap, and upend the flask several times to
thoroughly mix the contents. Store all standards in plastic bottles and prepare weekly.
GENERAL PREPARATION
Electrode Preparation
Remove the rubber caps covering the electrode tips and the rubber insert covering the filling hole of
the cyanide 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 100 ml of distilled water and 1 ml of 10M NaOH 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 1.0X10
-2
M or 1,000 ppm standard to the beaker. When the
reading is stable, record the mV reading.
3.
Using a pipet, add 10 ml of the same standard used above to the beaker. After the reading
has stabilized, record the mV reading.
4.
The electrode is operating correctly if the mV potential has changed by 57±2 mV,
assuming the solution 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 an ion meter)
(Check electrodes each day)