User manual EUTECH INSTRUMENTS LEAD EPOXY

[. . . ] EUTECH INSTRUMENTS PTE LTD. INSTRUCTION MANUAL LEAD ION ELECTRODE TABLE OF CONTENTS GENERAL INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Required Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Required Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 GENERAL PREPARATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Electrode Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Electrode Slope Check (with pH/mV meter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Electrode Slope Check (with ion meter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 MEASUREMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Measuring Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Sample Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Units of Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 MEASUREMENT PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] Place the beaker on the magnetic stirrer and begin stirring at a constant rate. After rinsing the electrodes, blot dry, and lower the electrode tips into the solution. After stabilization, read the concentration directly from the meter display. Assuming no change in ambient temperature, immerse the electrode tips in the more dilute standard. After the reading has stabilized, compare it to the original reading recorded in Step 4 above. A reading differing by more than 0. 5 units or a change in ambient temperature will necessitate repetition of Steps 2-8 (2-9) above. 8. 9. 10. 11. 7 Low Level Lead Determination (using a pH/mV meter) This procedure is recommended for solutions with lead concentrations of less than 1. 0X10-6M. If the solution is high in ionic strength, but low in lead ion concentration, use the same procedure, but prepare a calibration solution with a composition similar to the sample. This low level ISA (1. 0M NaClO4) is added at the rate of 1 ml low level ISA to each 100 ml of solution. Dilute 1ml of 0. 1M standard to one liter to prepare a 1. 0X10-4M solution for measurements in moles per liter. Prepare a 10 ppm standard solution by diluting 1 ml of the 1, 000 ppm standard to 100 ml for measurements in ppm. Plastic lab-ware is recommended to avoid absorption of lead on the beaker walls. Add 50 ml of distilled water, 50 ml of methanol-formaldehyde solution, and 1 ml of low level ISA to a 150 ml plastic beaker. Place the beaker on the magnetic stirrer and begin stirring at a constant rate. Add increments of the 1. 0X10-4M or 10 ppm standard as given in Table 2 below. TABLE 2: Step-wise Calibration For Low Level Lead Measurements Added Volume (ml) 0. 1 0. 1 0. 2 0. 2 0. 4 2. 0 2. 0 Concentration ppm M 1. 0X10-2 1. 0X10-7 2. 0X10-2 2. 0X10-7 4. 0X10-7 4. 0X10-2 -2 6. 0X10-7 6. 0X10 1. 0X10-1 9. 9X10-7 -1 2. 9X10 2. 9X10-6 4. 8X10-1 4. 8X10-6 2. 3. 4. 6. Step 1 2 3 4 5 6 7 Pipet A A A A A B B Pipet A = 1 ml graduated pipet Pipet B = 2 ml pipet Solutions: additions of 10 ppm or 1. 0X10-4M standard to 100 ml of solution prepared in Step 3 above 7. On a semi-logarithmic graph paper, plot the mV reading (linear axis) against the concentration (log axis) as in Figure 1. Place the beaker on the magnetic stirrer and begin stirring at a constant rate. 9. Instruction Manual Lead Electrode reading has stabilized, record the mV reading and determine the concentration from the low level calibration curve. Check the calibration curve every two hours by repeating Steps 3- 7 above. Low Level Lead Determination (using an ion meter) 1. Using 20 ml of standard ISA, dilute to 100 ml with distilled water. This low level (1. 0M NaClO4) is added at a the rate of 1 ml low level ISA to each 100 ml of solution. [. . . ] 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. When making measurements, it is important to remember that this potential be the same when the reference is in the standardizing solution as well as in the sample solution or the change in liquid junction potential will appear as an error in the measured electrode potential. [. . . ]