Instruction Manual Fluoride Electrode EUTECH INSTRUMENTS PTE LTD.
Instruction Manual Fluoride Electrode TABLE OF CONTENTS GENERAL INSTRUCTIONS .......................................................................................................... 3 Introduction................................................................................................................................................................... 3 Required Equipment ...............................................................................................................................
Instruction Manual Fluoride Electrode EUTECH INSTRUMENTS PTE LTD. FLUORIDE ION ELECTRODE INSTRUCTION MANUAL GENERAL INSTRUCTIONS Introduction Eutech Instruments Fluoride Ion Electrode is used to measure fluoride 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.
Instruction Manual Fluoride Electrode 5. Eutech Total Ionic Strength Adjuster Buffer (TISAB 1), Code No. EC-ISA-FL1-BT. TISAB 1 is used to adjust the pH of the solution, de-complex fluoride and provide a constant background ionic strength. To prepare this solution from your own laboratory stock, half fill a four liter beaker with distilled water. Place the beaker on a magnetic stirrer, add a large stirring bar, and begin stirring.
Instruction Manual Fluoride Electrode Slope is defined as the change in potential observed when the concentration changes by a factor of 10. Electrode Slope Check (with ion meter) (Check electrodes each day) 1. Prepare standard fluoride solutions whose concentrations vary by tenfold. Use either the 0.1M, 1,000 ppm, or 100 ppm fluoride standard. Use the serial dilution method for this preparation. 2. To a 150 ml beaker, add 50 ml of the lower value standard and 50 ml of TISAB.
Instruction Manual Fluoride Electrode Sample Requirements All samples must be aqueous and not contain organics which can dissolve the epoxy electrode body and/or the cement bonding the sensing crystal to the electrode body. Inorganic solutions will not affect the electrode. Infrequent measurements in solutions containing methanol, acetone, or dioxane are permitted. Highly polar solvents, such as CHCl3 or DMF, should not be contained in the samples. Please check with Eutech Instruments Pte Ltd.
Instruction Manual Fluoride Electrode 3. Place the mid-range solution on the magnetic stirrer and begin stirring. After rinsing the electrodes with distilled water, blot dry, and immerse the electrodes in the solution. When the reading has stabilized, record the mV value. 4. Place the most concentrated solution on the magnetic stirrer and begin stirring. After rinsing the electrodes with distilled water, blot dry, and immerse the electrodes in the solution.
Instruction Manual Fluoride Electrode Direct Measurement of Fluoride (using an ion meter) 1. By serial dilution of the 0.1M, 1,000 ppm, or 100 ppm fluoride standard, prepare two fluoride standards whose concentration is near the expected sample concentration. Add 50 ml of TISAB 1 or TISAB 2, to each 50 ml of standard. When calibrating, assume that the added TISAB has no effect on the standard concentration. 2.
Instruction Manual Fluoride Electrode Prepare 2, 1, and 0.5 ppm fluoride standards by serial dilution of the 100 ppm fluoride standard. To each 50 ml of standard, add 50 ml of TISAB 1 or TISAB 2. Calibrate the meter as previously described by using the 2, 1, and 0.5 ppm standards. The calibration curve should be drawn on semilogarithmic 2-cycle graph paper or use an ion meter.
Instruction Manual 2. Fluoride Electrode Following the directions given in the preceding section (Determination of Fluoride in Acid Solutions), prepare standards, calibrate the electrodes and measure the unknown samples. Low Level Fluoride Measurements (using a pH/mV meter) Use the following low level fluoride measurement procedure in the non-linear portion of the calibration curve. (See Figure 1.) This procedure is used for fluoride samples containing less than 2X10-5M or 0.
Instruction Manual Fluoride Electrode Low Level Fluoride Determination (using an ion meter) Follow the previous procedure for fluoride measurements with an ion meter, except use low level TISAB 2 instead of TISAB 1. Always use the blank correction.
Instruction Manual Fluoride Electrode Titration Titration is a very accurate determination of fluoride. Eutech Fluoride Ion Electrodes can be used as highly sensitive endpoint detectors for titration of a fluoride-containing sample. Though titration are more time consuming than direct ion measurements, the results are more accurate and reproducible. Titration accurate to ±0.2% of the total fluoride concentration of the sample can be performed using lanthanum nitrate as the titrant.
Instruction Manual Cs o Cs x Vt Vt x Vf Vf Fluoride Electrode = concentration of sample = fluoride standard concentration (0.1M) = volume of titrant added to achieve the endpoint of unknown sample = volume of titrant added to achieve the endpoint in standardization = volume of sample used in sample titration = volume of standard used in standardization titration. A typical titration curve is shown in Figure 2.
Instruction Manual Fluoride Electrode Complexation Hydrogen ion, as well as some other multivalent cations, aluminum, silicon, iron+3, will form complexes with fluoride. The total ionic strength of the solution, the pH of the solution, the total fluoride concentration, and the concentration of the complexing agent all contribute to the degree of complexation. TISAB 1 and TISAB 2 complex about 5 ppm aluminum or iron in a 1 ppm fluoride solution.
Instruction Manual Fluoride 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 Fluoride Electrode When the level of hydroxide is greater than one-tenth the level of fluoride ion present, hydroxide ion interferes with electrode response to fluoride. As an example, no hydroxide interference with fluoride measurements take place at pH 7 when the hydroxide concentration is 1.0X10-7 or less. As the pH increases, the hydroxide interference becomes appreciable. At pH 10, hydroxide ion concentration is 1.0X10-4M and no error is found in measurements of 1.0X10-2M fluoride.
Instruction Manual Fluoride Electrode Electrode Storage The fluoride electrode may be stored for short periods of time in 1.0X10-2M fluoride solution with TISAB added. 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 Fluoride 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. All samples and standards containing fluoride ions have TISAB added so that the background ionic strength is high and constant relative to variable concentrations of fluoride.
Instruction Manual Fluoride Electrode 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 Standards and Reagents, Sample, and Technique sections below.) 5.
Instruction Manual Fluoride Electrode TROUBLESHOOTING HINTS Symptom Out of Range Reading Noisy or Unstable Readings (readings continuously or rapidly changing) Drift (reading slowly changing in one direction) Low Slope or No Slope 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 elect
Instruction Manual Fluoride Electrode Complexation to complexing agents 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.
Instruction Manual Fluoride Electrode SPECIFICATIONS Concentration Range: Saturated solutions to 1.0X10-6M (saturated solutions to 0.02 ppm) pH Range: 5 to 7 at 1.0X10-6M F-1 (0.02 ppm F-1) 5 to 11 at 1.0X10-1M F-1 (1900 ppm F-1) Temperature Range: 0o to 80oC (80o to 100oC intermittent use) Resistance: 150-200 kohm Reproducibility: ±2% Size: 110 mm length; 12 mm diameter; 1 m cable length Storage: Store in fluoride standard with TISAB added ORDERING INFORMATION CODE/NO.
