User manual EUTECH INSTRUMENTS CADMIUM EPOXY

[. . . ] Instruction Manual Cadmium Electrode EUTECH INSTRUMENTS PTE LTD. INSTRUCTION MANUAL CADMIUM ION ELECTRODE 1 Cadmium 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 a 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] On a semi-logarithmic graph paper, plot the mV reading (linear axis) against the concentration (log axis) as in Figure 1. Measure out 100 ml of the sample into a 150 ml beaker and add 1ml of low level ISA. Place the beaker on the magnetic stirrer and begin stirring at a constant rate. After the 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. 8. 9. 10. Low Level Cadmium Determination (using an ion meter) 1. Using 20 ml of standard ISA, dilute to 100 ml with distilled water. This low level ISA (1. 0M NaNO3) is added at the rate of 1ml low level ISA to each 100 ml of solution. Follow the steps given in Direct Measurement of Cadmium (using an ion meter) to the end of Step 6. To a 150 ml beaker, add 100 ml of distilled water and 1 ml of low level ISA. Place the beaker on the magnetic stirrer and begin stirring at a constant rate. When the reading has stabilized, fix the blank value in the meter according to the meter manufacturer's instructions. Continue with Steps 7-9 in Direct Measurement of Cadmium (using an ion meter), remembering to use the low level ISA described in Step 1 above. 2. 3. 4. 5. Titration Titration is a very accurate determination of total cadmium ion concentration. This method makes use of the electrode as an endpoint detector when EDTA is used as a titrant. 9 Cadmium Electrode Instruction Manual Titration of Cadmium The method outlined in this section makes use of the cadmium ion electrode as a highly sensitive endpoint detector for cadmium-containing samples. The sample pH can be adjusted to pH 10 by adding ammonia to eliminate unwanted ion complexes. Prepare the stock EDTA titrant as given in the section Required Solutions. Dilute the EDTA to 10 to 20 times as concentrated as the suspected sample concentration. The sample should contain at least 1. 0X10-4M cadmium for a good detection of the endpoint. Pipet 100 ml of the sample into a 150 ml beaker, place the beaker on the magnetic stirrer and begin stirring at a constant rate. Position the burette tip in the beaker, slightly above the liquid level in the beaker and slightly off center. Position the electrode tips in the solution about halfway between the center of the beaker and the beaker wall. Begin adding the EDTA in 0. 5 ml to 1. 0 ml increments and about 0. 1 ml to 0. 2 ml increments as the potential begins to change more rapidly. Continue the additions several milliliters past the endpoint until little change is noted in the mV reading even when adding 0. 5 - 1. 0 ml increments. [. . . ] 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 solution diffuse into the sample 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. Strongly acidic (pH = 0-2) and strongly basic (pH = 12-14) solutions are particularly troublesome to measure. [. . . ]