Instruction Manual Sodium Electrode EUTECH INSTRUMENTS PTE LTD.
Sodium Electrode Instruction Manual TABLE OF CONTENTS GENERAL INSTRUCTIONS .......................................................................................................... 1 REQUIRED EQUIPMENT ..................................................................................................................................1 REQUIRED SOLUTIONS ..................................................................................................................................1 GENERAL PREPARATION....
Instruction Manual Sodium Electrode EUTECH INSTRUMENTS PTE LTD. SODIUM ION ELECTRODE INSTRUCTION MANUAL GENERAL INSTRUCTIONS Eutech Instruments Sodium Ion Electrode is used to measure sodium ions in aqueous solutions quickly, simply, accurately, and economically. 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. 4.
Sodium Electrode 6. Instruction Manual Eutech Sodium Standard, 100 ppm Na+, Code no. EC-SCS-LNA3-BT. To prepare this solution from your own laboratory stock, half fill a one liter volumetric flask with distilled water and add 0.254 grams of reagent grade NaCl. Swirl the flask to dissolve the solid. Fill the flask to the mark with distilled water, cap, and upend several times to mix the solution.
Instruction Manual Sodium Electrode 4. 5. Rinse the electrodes with the electrode rinse solution and blot dry. To another 150 ml beaker, add 100 ml of the higher value standard and 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. 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.
Sodium Electrode Instruction Manual TABLE 1: Concentration Unit Conversion Factors ppm Na+ 229.90 22.99 2.30 moles/liter Na+ 1.0 x 10-2 1.0 x 10-3 1.0 x 10-4 MEASUREMENT PROCEDURE Direct Measurement Direct measurement is a simple procedure for measuring a large number of samples. A single meter reading is all that is required for each sample. The ionic strength of samples and standards should be made the same by adjustment with ISA for all sodium solutions.
Instruction Manual Sodium 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 are for the linear portion of the curve.
Sodium Electrode Instruction Manual 9. After rinsing the electrodes and blotting dry, place the electrode tips in the solution and wait for the reading to stabilize. Read the 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 sodium standard. After the reading has stabilized, compare it to the original reading recorded in Step 4 above. A reading difference by more than 0.
Instruction Manual Sodium Electrode 8. On semi-logarithmic graph paper, plot the millivolt reading (linear axis) against the concentration (log axis) as in Figure 1. 9. Rinse the electrodes with electrode rinse solution and blot dry. 10. To a 150 ml plastic beaker add 100 ml of sample and 1 ml of low level ISA. Place the beaker on the magnetic stirrer and begin stirring. Adjust the pH, if necessary, to above 9. Lower the electrode tips into the solution.
Sodium Electrode Instruction Manual Rb+1 NH4+1 Ag+1 Tl+1 1.1X104 ppm 1.8X103 ppm 0.0001 ppm 4.5X103 ppm 1.1X105 ppm 1.8X104 ppm 0.001 ppm 4.5X104 ppm --0.01 ppm -- 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 10-3M level.
Instruction Manual Sodium Electrode Limits of Detection The upper limit of detection in pure sodium solutions is 1M. In the presence of other ions, the upper limit of detection is above 10-1M sodium, but two factors influence this upper limit. Both the possibility of a liquid junction potential developing at the reference electrode and the salt extraction effect influence this upper limit.
Sodium Electrode Instruction Manual The edge of the shaded area (the straight line) shown in Figure 3 indicates a minimum pH at which dilute sodium measurements can be made with less than 10% hydrogen ion interference. The pH should be adjusted to a pH greater than 9 by the addition of ISA to all standards and samples for optimal results over the entire concentration range of sodium. Additional ammonium hydroxide may be necessary to adjust the pH to the desired level in some cases.
Instruction Manual Sodium Electrode In the case of high and constant ionic strength relative to the sensed ion concentration, the activity coefficient, γ , is constant and the activity, X, is directly proportional to the concentration. To adjust the background ionic strength to a high and constant value, ionic strength adjuster is added to samples and standards. The recommended ISA for sodium is an ammonium chloride/ammonium hydroxide buffer.
Sodium Electrode Instruction Manual persists and you are using an electrode pair, try the same routine with a working reference electrode. 4. If the problem persists, the reagent may be of poor quality, interference in the sample may be present or the technique may be faulty. (See the Standards and Reagents, Sample, and Technique sections below.) 5.
Instruction Manual Sodium Electrode TROUBLESHOOTING HINTS Symptom Out of Range Reading "Incorrect Answer" (but calibration curve is good) Possible Causes defective meter defective electrode electrodes not plugged in properly reference electrode not filled electrodes not in solution air bubble on redipping electrode incorrect scaling of semi-log paper incorrect sign incorrect standards wrong units used Drift (reading changing in one direction) Low Slope or No Slope Noisy or Unstable Readings (reading
Sodium Electrode Instruction Manual SPECIFICATIONS Concentration Range: Saturated to 1.0 x 10-6M (0.02 ppm) pH Range: 5 to 12 (depending on Na+ level) Temperature Range: -5o to 70oC Resistance: < 200 Mohm Reproducibility: ±2% Size: 110 mm length; 12 mm diameter; 1 m cable length Storage: Store in 5M NaCl with added ISA ORDERING INFORMATION Code No. Description EC-NA02 Sodium Ion Combination Electrode, epoxy body EC-SCS-LNA1-BT Sodium Standard, 0.
