User manual EUTECH INSTRUMENTS NITRATE EPOXY

[. . . ] Instruction Manual Nitrate Electrode EUTECH INSTRUMENTS PTE LTD. INSTRUCTION MANUAL NITRATE ION ELECTRODE 1 Nitrate Electrode Instruction Manual TABLE OF CONTENTS GENERAL INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Required Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Required Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 GENERAL PREPARATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrode Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrode Slope Check (with pH/mV meter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrode Slope Check (with ion meter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 MEASUREMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Measuring Hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Sample Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Units of Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 MEASUREMENT PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] Place the more concentrated solution on the magnetic stirrer and begin stirring at a constant rate. Adjust the meter to the concentration of the nitrate standard and fix the value in the memory according to the meter manufacturer's instructions after stabilization of the reading. For low level measurements, place the rinsed, dried electrodes into a solution containing 100 ml of distilled water and 2 ml of ISA. After stabilization, fix the blank value in the meter according to the meter manufacturer's instructions. Immerse the electrode tips in the solution and wait for the reading to stabilize. Assuming no change in ambient temperature, place the electrode tips in the first nitrate standard. After the reading has stabilized, compare it to the original reading in Step 3 above. A reading differing by more than 0. 5 mV or a change in ambient temperature will necessitate the repetition of Steps 2-6 above. 5. 6. 7. 8. 9. 10. Low Level Nitrate Measurements (using a pH/mV meter) This procedure is recommended for solutions with ionic strengths less than 1. 0X10-2M. If the solution is high in ionic strength, but low in nitrate, use the same procedure, but prepare a calibration solution with a composition similar to the sample. This low level ISA [0. 4M (NH4)2SO4] is added at the rate of 1 ml low level ISA to each 100 ml of sample. Dilute 1 ml of 0. 1M standard to 100 ml to prepare a 1. 0X10-3M NO3-1 solution for measurements in moles per liter. Use the 1, 000 ppm standard for preparing a 100 ppm NO3-1 standard by diluting 10 ml of the 1, 000 ppm standard to 100 ml. Standards should be prepared fresh daily. 8 2. Instruction Manual Nitrate Electrode 3. Add 1 ml of the low level ISA to a 100 ml volumetric flask and fill to the mark with distilled water. Pour this solution into a 150 ml beaker and place the beaker on the magnetic stirrer. Add increments of the 1. 0X10-3M or 100 ppm standards as given in Table 2 below. After the reading has stabilized, record the mV reading after each addition. TABLE 2: Step-wise Calibration for Low Level Nitrate Measurements Added Concentration Step Pipet Volume (ml) M NO3-1 ppm NO3-1 1 A 0. 1 1. 0X10-6 0. 1 -6 2 A 0. 1 2. 0X10 0. 2 3 A 0. 2 4. 0X10-6 0. 4 4 A 0. 2 6. 0X10 0. 6 5 A 0. 4 9. 9X10-6 1. 0 2. 9 6 B 2. 0 2. 9X10-5 -5 7 B 2. 0 4. 8X10 4. 8 4. 6. Pipet A = 1 ml graduated pipet Pipet B = 2 ml pipet Solutions: additions of 1. 0X10-3M or 100 ppm standard to 100 ml of ISA as prepared in Step 3 above. On semi-logarithmic graph paper, plot the millivolt reading (linear axis) against the concentration (log axis) as in Figure 1. Measure out 100 ml of the sample into a 150 ml beaker, add 1 ml of low level ISA. After the reading has stabilized, record the mV reading and determine the concentration from the low level calibration curve. [. . . ] 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. The composition of the liquid junction filling solution in the reference electrode is most important. The speed with which the positive and negative ions in the filling solutions diffuse into the samples should be as nearly equal as possible, that is, the filling solution should be equitransferent. No junction potential can result if the rate at which positive and negative charge carried into the sample is equal. [. . . ]