User manual EUTECH INSTRUMENTS CARBON DIOXIDE GAS

[. . . ] Instruction Manual Carbon Dioxide Electrode EUTECH INSTRUMENTS PTE LTD. INSTRUCTION MANUAL CARBON DIOXIDE ION ELECTRODE 1 Instruction Manual Carbon Dioxide Electrode TABLE OF CONTENTS GENERAL INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Required Equipment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Required Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] The ionic strength of samples and standards should be made the same by adjustment with ISA for all carbon dioxide solutions. The temperature of both sample solutions and standard solutions should be the same. Direct Measurement of Carbon Dioxide (using a pH/mV meter) 1. By serial dilution, prepare three standard solutions from the 0. 1M or 1, 000 ppm stock standard. The resultant concentrations should be 10-2M, 10-3M, and 10-4M or 1, 000 ppm, 100 ppm, and 10 ppm. Place 100 ml of the 10-4M (10 ppm) standard into a 150 ml beaker on the magnetic stirrer, add 10 ml of carbon dioxide buffer, and begin stirring at a constant rate. After assuring that the meter is in the mV mode, lower the electrode tip into the solution. Place 100 ml of the 10-3M (100 ppm) standard into a 150 ml beaker on the magnetic stirrer, add 10 ml of carbon dioxide buffer, and begin stirring at a constant rate. After rinsing the electrode with distilled water, blot dry, and immerse the tip in the solution. Place 100 ml of the 10-2M (1, 000 ppm) standard into a 150 ml beaker on the magnetic stirrer, add 10 ml of carbon dioxide buffer, and begin stirring at a constant rate. After rinsing the electrode with distilled water, blot dry, and immerse the tip in the solution. Using the semi-logarithmic graph paper, plot the mV reading (linear axis) against the concentration (log axis). A typical calibration curve appears in Figure 1. 2. 3. 4. 5. 7 Instruction Manual Carbon Dioxide Electrode A calibration curve is constructed on semi-logarithmic paper when using the pH/mV meter in the millivolt mode. The measured electrode potential in mV (linear axis) is plotted against the standard concentration (log axis). In the linear region of the curve, only three standards are necessary to determine a calibration curve. The direct measurement procedures given are for the linear portion of the curve. To a clean, dry, 150 ml beaker add 100 ml of sample and add 10 ml of carbon dioxide buffer. Rinse the electrode with distilled water, blot dry, and lower the tip in the solution. Assuming no change in ambient temperature, place the electrode tips in the mid-range standard. After the reading has stabilized, compare it to the original reading recorded in Step 3 above. A reading differing by more than 0. 5 mV or a change in the ambient temperature will necessitate the repetition of Steps 2-5 above. A new calibration curve should be prepared daily. 7. Direct Measurement of Carbon Dioxide (using an ion meter) 1. By serial dilution of the 0. 1M or the 1, 000 ppm standards, prepare two standards whose concentration is near the expected sample concentration. When calibrating, assume that the added buffer has no effect on the standard concentration. Place the more dilute standard on the magnetic stirrer and begin stirring at a constant rate. [. . . ] Clean glassware will drain without leaving water droplets behind. Electrodes The electrodes may be checked by using the procedure found in the sections entitled Electrode Slope Check. 1. Be sure to use distilled or deionized water when following the procedures given in Electrode Slope Check. 2. If the electrode fails to response as expected, see the sections Measuring Hints and Electrode Response. If the electrode still does not perform as described, determine whether the carbon dioxide inner body is working properly as directed in Checking the Electrode Inner Body. If the stability and the slope check out properly, but measurement problems persist, the standards may be of poor quality, the sample may contain interferences or the technique may be in error. (See Standard, Sample and Technique sections below. ) Before replacing a "faulty" electrode, review the instruction manual and be sure to: - Clean and rinse the electrode thoroughly. [. . . ]