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Cadmium Electrode
3.
Adjust the meter to the concentration of the cadmium standard and fix the value in the
memory according to the meter manufacturer's instructions after stabilization of the
reading.
4.
Rinse the electrodes with distilled water and blot dry.
5.
Place the more concentrated solution on the magnetic stirrer and begin stirring at a
constant rate. Lower the electrode tips into the solution
6.
Adjust the meter to the concentration of the cadmium standard and fix the value in the
memory according to the meter manufacturer's instructions after stabilization of the
reading.
7.
Place 100 ml of the sample and 2 ml of ISA into a 150 ml beaker. Place the beaker on the
magnetic stirrer and begin stirring at a constant rate.
8.
Immerse the rinsed, dried electrode tips in the solution and wait for the reading to stabilize.
Read the concentration directly from the meter display.
9.
The calibration should be checked every two hours. Assuming no change in ambient
temperature, immerse the electrode tips in the first cadmium standard. After the reading
has stabilized, compare it to the original reading recorded in Step 3 above. A reading
differing by more than ± 0.5 mV, or a change in ambient temperature will necessitate the
repetition of Steps 2-6 above. The meter should be re-calibrated daily.
Low Level Cadmium Determination (using a pH/mV meter)
This procedure is recommended for solutions with cadmium concentrations of less than 1.0X10
(1.1 ppm). If the solution is high in ionic strength, but low in cadmium ion, use the same procedure,
but prepare a calibration solution with a composition similar to the sample.
1.
Using 20 ml of standard ISA, dilute to 100 ml with distilled water. This low level ISA
(1.0M NaNO
background ionic strength will be 1.0X10
Dilute 1ml of 0.1M standard to one liter to prepare a 1.0X10 -4 M solution for
2.
measurements in moles per liter. Prepare a 10 ppm standard solution by diluting 1ml of the
1,000 ppm standard to 100 ml of solution for measurements in ppm. Standards should be
prepared fresh daily.
3.
To a 150 ml beaker add 100 ml of distilled water and 1 ml of low level ISA. Place the
beaker on the magnetic stirrer and begin stirring at a constant rate.
4.
Place the electrode tips in the solution. Assure that the meter in the mV mode.
5.
Add increments of the 1.0X10
6.
After the reading has stabilized, record the mV reading after each addition.
TABLE 2: Step-wise Calibration for Low Level Cadmium Measurements
) is added at the rate of 1 ml low level ISA to each 100 ml of solution. The
3
-4
M or 10 ppm standard as given in Table 2 below.
-2
M.
8
Instruction Manual
-5
M
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Troubleshooting
