User manual EUTECH INSTRUMENTS FLUORIDE EPOXY

[. . . ] Instruction Manual Fluoride Electrode EUTECH INSTRUMENTS PTE LTD. INSTRUCTION MANUAL FLUORIDE ION ELECTRODE 1 Instruction Manual Fluoride Electrode TABLE OF CONTENTS GENERAL INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Required Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Required Solutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] When calibrating, assume that the added TISAB has no effect on the standard concentration. Place the more dilute solution on the magnetic stirrer and begin stirring at a constant rate. Adjust the meter to the concentration of the fluoride standard and fix the value in the memory according to the meter manufacturer's instructions after stabilization of the reading. Place the more concentrated solution on the magnetic stirrer and begin stirring at a constant rate. Adjust the meter to the concentration of the fluoride standard and fix the value in the memory according to the manufacturer's instructions after stabilization of the reading. For low level measurements, place the rinsed, dried electrodes into a solution containing equal volumes of distilled water and TISAB 1 or TISAB 2 (or add 10 ml of TISAB 2 to each 100 ml of distilled water). After stabilization, fix the blank value in the meter according to the meter manufacturer's instructions. After rinsing the electrodes and blotting dry, place the electrode tips into the sample diluted with an equal volume of TISAB 1 or TISAB 2. After stabilization, read the concentration directly from the meter display. Assuming no change in ambient temperature, place the electrode tips in the first fluoride standard. After the reading has stabilized, compare it to the original reading in Step 4 above. A reading differing by more than 0. 5 mV or a change in ambient temperature will necessitate repetition of Steps 2-8 (29) above. 8. 9. 10. 11. Direct Measurement of Fluoride in Water (ASTM D1179, METHOD B) The procedure is used to determine total fluoride concentration in water in ppm. TISAB is added to standards and to samples in order to break fluoride complexes of iron and aluminum, adjust the pH, and provide a constant ionic strength. Fluoride sample concentration is determined, using this method, independent of the level or nature of dissolved minerals. 8 Instruction Manual Fluoride Electrode Prepare 2, 1, and 0. 5 ppm fluoride standards by serial dilution of the 100 ppm fluoride standard. 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. Direct Measurement of Fluoride in Acid Solutions Hydrogen ion complexes a portion of the fluoride ion in solutions with a pH below 5, forming HF or HF2-1, which cannot be detected by the electrodes. Adjustment to weakly acidic/weakly basic range before making the fluoride determination is necessary, but not with strongly basic solutions. The use of sodium acetate buffers the pH above 5 and helps fix the total ionic strength of standards and samples to the same level. Dissolve reagent grade sodium acetate (CH3COONa) in distilled water to prepare a 15% solution. Prepare a blank solution containing all components of the sample except fluoride. Add fluoride to the blank solution to prepare standards in the concentration range of the unknown solutions. [. . . ] The recommended ISA for the fluoride electrode is TISAB though similar solutions can be used as long as they do not contain ions that would interfere with the electrode's response to fluoride. 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. [. . . ]