Instruction Manual Iodide Electrode EUTECH INSTRUMENTS PTE LTD.
Instruction Manual Iodide Electrode TABLE OF CONTENTS GENERAL INSTRUCTIONS .......................................................................................................... 3 Introduction ..............................................................................................................................................3 Required Equipment.................................................................................................................................3 Required Solutions .
Instruction Manual Iodide Electrode EUTECH INSTRUMENTS PTE LTD. IODIDE ION ELECTRODE INSTRUCTION MANUAL GENERAL INSTRUCTIONS Introduction Eutech Instruments Iodide Ion Electrode is used to quickly, simply, accurately, and economically measure free iodide ion in aqueous solutions. Required Equipment 1. A pH/mV meter or an ion meter, either line operated or portable. 2. Semi-logarithmic 4-cycle graph paper for preparing calibration curves when using the meter in the mV mode. 3. A magnetic stirrer.
Instruction Manual Iodide Electrode GENERAL PREPARATION Electrode Preparation Remove the rubber caps covering the electrode tips and the rubber insert covering the filling hole of the combination electrode or of 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.
Instruction Manual Iodide Electrode 6. Adjust the meter to the concentration of the standard and fix the value in the memory. 7. Read the electrode slope according to the meter manufacturer's instructions. Correct electrode operation is indicated by a slope of 93-100%. See the TROUBLESHOOTING sections if the slope is not within this range. MEASUREMENT Measuring Hints All samples and standards should be at the same temperature for precise measurement.
Instruction Manual Iodide Electrode Iodide ions can be measured in units of moles/liter, parts/million, or any other convenient concentration unit. Table 1 indicates some of the concentration units. TABLE 1: Concentration Unit Conversion Factors moles/liter 1.0X10-4 1.0X10-3 1.0X10-2 1.0X10-1 ppm I-1 12.7 127.0 1,270.0 12,770.0 MEASUREMENT PROCEDURE Direct Measurement Direct measurement is a simple procedure for measuring a large number of samples.
Instruction Manual Iodide Electrode A calibration curve is constructed on semi-logarithmic paper when using a pH/mV meter in the millivolt mode. The measured electrode potential in mV (linear axis) is plotted against the standard concentration (log axis). In the linear region of the curve, only three standards are necessary to determine a calibration curve. In the non-linear region, additional points must be measured. The direct measurement procedures given are for the linear portion of the curve.
Instruction Manual Iodide Electrode 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 standard and fix the value in the memory 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.
Instruction Manual Iodide Electrode TABLE 2: Maximum Allowable Ratio of Interfering Ion to Iodide Ion Interference Cl-1 (1) S2O3-2(2) Br-1 (1) CN-1 (3) S-2 (3) Maximum Ratio 1.0X106 1.0X105 5.0X103 4.0X10-1 1.0X10-6 (1) Gran's plot titration can be used to measure mixed halides in solution. (2) These substances represent complexing species whose maximum level can be exceeded without electrode damage. Values shown represents a 1% error. (3) Add Ni+2 to remove sulfide or cyanide interferences.
Instruction Manual Iodide Electrode Temperature Influences Samples and standards should be at the same temperature since electrode potentials are influenced by changes in temperature. A 1oC difference in temperature results in a 2% error at the 1.0X10-3M concentration level. Because of solubility equilibrium on which the electrode depends, the absolute potential of the reference electrode changes slowly with the temperature.
Instruction Manual Iodide Electrode A drifting potential reading or a decrease in electrode slope may mean that the electrode membrane needs polishing. To polish the membrane: 1. If using polishing paper, cut off a 1-2" piece and place it face up on the lab bench. 2. Put a few drops of distilled or deionized water in the center of the paper. 3.
Instruction Manual Iodide Electrode Electrode Storage The iodide ion electrode may be stored for short periods of time in 1.0x10-2M iodide solution. For longer storage (longer than two weeks), rinse and dry the sensing pellet and cover the membrane tip with any protective cap shipped with the electrode.
Instruction Manual Iodide Electrode The reference electrode must also be considered. When two solutions of different composition are brought into contact with one another, liquid junction potentials arise. Millivolt potentials occur from the inter-diffusion of ions in the two solutions. Electrode charge will be carried unequally across the solution boundary resulting in a potential difference between the two solutions, since ions diffuse at different rates.
Instruction Manual 4. 5. Iodide Electrode persists and you are using an electrode pair, try the same routine with a working reference electrode. If the problem persists, the standards and/or reagents may be of poor quality, interferences in the sample may be present or the technique may be faulty. (See Standards and Reagents, Sample, and Technique sections below.
Instruction Manual Iodide Electrode TROUBLESHOOTING HINTS Symptom Out of Range Reading Possible Causes defective meter Next Step check meter with shorting strap (see meter instruction manual) defective electrode check electrode operation electrodes not plugged in properly unplug electrodes and reset reference electrode not filled be sure reference electrode is filled air bubble on membrane remove bubble by redipping electrode Noisy or Unstable Readings (readings continuously or rapidly changin
Instruction Manual Iodide Electrode standard used as ISA use ISA electrode exposed to complexing agents check section entitled Complexation air bubble on membrane remove bubble by re-dipping probe "Incorrect Answer" (but calibration curve is good) incorrect scaling of semi-log paper plot millivolts on the linear axis. On the log axis, be sure that concentration numbers within each decade are increasing with increasing concentration.
Instruction Manual Iodide Electrode SPECIFICATIONS Concentration Range: 1M to 1.0X10-8M 127,000 ppm to 0.4 ppm pH Range: 0-14 Temperature Range: 0° to 80°C Resistance: <1 Mohm Reproducibility: ±2% Samples: Aqueous solutions only; avoid organic solvents Size: 110 mm in length; 12 mm in diameter; 1 m cable length Storage: Store in iodide solution ORDERING INFORMATION CODE/NO. DESCRIPTION EC-IO-03 Iodide Ion Combination Electrode, epoxy body EC-SCS-IO1-BT Iodide Standard, 0.
