eutech-instruments iodide epoxy User Manual
Instruction Manual
Iodide Electrode
8
5.
Place the more concentrated solution on the magnetic stirrer and begin stirring at a
constant rate. Lower the electrode tips into the solution.
constant rate. Lower the electrode tips into the solution.
6.
Adjust the meter to the concentration of the standard and fix the value in the memory
according to the meter manufacturer's instructions after stabilization of the reading.
according to the meter manufacturer's instructions after stabilization of the reading.
7.
For low level iodide measurements, place the rinsed, dried electrodes into a solution
containing 100 ml of distilled water and 2 ml of ISA. After stabilization, fix the blank
value into the meter according to the meter manufacturer's instructions.
containing 100 ml of distilled water and 2 ml of ISA. After stabilization, fix the blank
value into the meter according to the meter manufacturer's instructions.
8.
Place 100 ml of the sample and 2 ml of ISA in a 150 ml beaker, place it on the magnetic
stirrer, and begin stirring.
stirrer, and begin stirring.
9.
Immerse the electrode tips in the solution and wait for the reading to stabilize. Read the
concentration directly from the meter display.
concentration directly from the meter display.
10. The calibration should be checked every two hours. Assuming no change in ambient
temperature, place the electrode tips in the first iodide standard. After the reading has
stabilized, compare it to the original reading in Step 3 above. A reading differing by more
than 0.5 mV or a change in the ambient temperature will necessitate the repetition of steps
2-6 above. The meter should be re-calibrated daily.
stabilized, compare it to the original reading in Step 3 above. A reading differing by more
than 0.5 mV or a change in the ambient temperature will necessitate the repetition of steps
2-6 above. The meter should be re-calibrated daily.
Low Level Iodide Determinations (using a pH/mV meter)
For the iodide electrodes, no special low level determination is necessary. Linear response is
possible down to 2.0X10
-8
M.
ELECTRODE CHARACTERISTICS
Reproducibility
Electrode measurements reproducible to ±2% can be obtained if the electrode is calibrated every
hour. Factors such as temperature fluctuations, drift, and noise limit reproducibility. Reproducibility
is independent of concentration within the electrode's operating range.
Interferences
A layer of silver may form on the electrode surface in the presence of strong reducing agents.
Insoluble salts of silver may be deposited on the membrane, causing electrode malfunction if high
levels of ions forming these salts are present in the sample. Proper performance can be restored by
polishing. See the section
Electrode Response
for proper polishing procedure.
Solutions containing oxidizing agents such as MnO
4
-1
, Fe
+3
, and Cu
+2
, may be measured without
problem. All samples must be free of mercury.
The maximum allowable ratio of interfering ion to iodide ion is given in Table 2. This ratio is
expressed as the ratio of the interfering ion molarity to the iodide molarity. Readings will be in error
if this ratio is exceeded. Neither accuracy of the measurement nor surface of the electrode
membrane will be affected if the ratio is less than that listed in the table.
The maximum allowable ratio of interfering ion to iodide ion is given in Table 2. This ratio is
expressed as the ratio of the interfering ion molarity to the iodide molarity. Readings will be in error
if this ratio is exceeded. Neither accuracy of the measurement nor surface of the electrode
membrane will be affected if the ratio is less than that listed in the table.