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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] 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. In the non-linear region, additional points must be measured. 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. Place the beaker on the magnetic stirrer and begin stirring. Rinse the electrode with distilled water, blot dry, and lower the tip in the solution. When the reading has stabilized record the mV value. Using the calibration curve, determine the sample concentration. The calibration should be checked every 1-2 hours. 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. Add 10 ml of carbon dioxide buffer to each 100 ml of standard. 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. Assure that the meter is in the concentration mode. Lower the electrode tip into the solution. Adjust the meter to the concentration of the CO2 standard and fix the value in the memory according to the meter manufacturer's instructions after stabilization of the reading. Rinse the electrode with distilled water and blot dry. [. . . ] See Sample Requirements and Interferences. Technique Be sure that the electrode's limit of detection has not been exceeded. Be sure that the analysis method is clearly understood and is compatible with the sample. Reread sections on GENERAL PREPARATION and ELECTRODE CHARACTERISTICS. If trouble still persists, call Eutech Instruments Pte Ltd. at (65) 6778-6876 and ask for the Customer Services Department. 16 Instruction Manual Carbon Dioxide Electrode TROUBLESHOOTING HINTS Symptom Out of Range Reading Possible Causes defective meter Next Step perform meter checkout procedure (see meter instruction manual) refer to Checking the Electrode Inner Body unplug electrode and reset defective inner body electrode not plugged in properly internal filling solution not added fill outer body of electrode with proper amount of internal filling solution remove bubble by re-dipping electrode put electrode in solution air bubble on membrane electrode not in solution Noisy or Unstable Reading (readings continuously or random changing. ) insufficient internal filling solution fill outer body of electrode with proper amount of internal filling solution perform meter checkout procedure (see meter instruction manual) ensure that bottom cap is screwed on tight enough to close gap between bottom cap and body refer to Checking the Electrode Inner Body defective meter bottom cap loose defective inner body air bubbles on membrane remove bubbles by redipping electrode check meter and stirrer for grounding meter or stirrer improperly grounded Drift (reading slowly changing in one direction) internal filling solution leakage ensure that membrane is installed properly 17 Instruction Manual Carbon Dioxide Electrode incorrect internal filling solution refill outer body of electrode using filling solution shipped with electrode dilute sample of dissolved species above 1M reduce surface area-tovolume ratio, slow down rate of stirring, avoid high temperatures replace membrane total sample level electrode in sample too long; CO2 loss membrane failure (wet, perforation, discoloration) samples and standards not at constant temperature heat generated by magnetic stirrer defective inner body allow samples and standards to come to room temperature before use place insulating material between stirrer and beaker refer to Checking the Electrode Inner Body electrode exposed to air for extended period hold electrode by outer body and pull on electrode cable. 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