PASCO CI-6727 - Manual

Calcium Ion Selective Electrode 012–06601A 2 RO O1013 SAMPL E 4MKCI Refe rence Fill Solutio n The reference electrode must also be considered. When two solutions of different composition are brought into contactwith one another, liquid junction potentials arise. Millivolt potentials occur from the i...

012–06601A Calcium Ion Selective Electrode 3 • Ionic Strength Adjuster (ISE), 4 M KCL To prepare this solution, half fill a 1000 ml volumetric flask with distilled water and add 298 grams ofreagent-grade potassium chloride (KCl). Swirl the flask gently to dissolve the solid. Fill to the mark withdis...

Calcium Ion Selective Electrode 012–06601A 4 3. Using a pipette, add 10 ml of the same calcium standard used above to the beaker. When the reading hasstabilized, record the voltage reading indicated in the Digits display. 4. Determine the difference between the two readings. The electrode is operati...

012–06601A Calcium Ion Selective Electrode 5 TABLE 1 Concentration Unit Conversion Factors ppm Ca +2 ppm CaCO 3 moles/liter 4.01 10.0 1.0 X 10 -4 10.00 24.9 2.5 X 10 -4 40.10 100.1 1.0X10 -3 400.80 1000.9 1.0 X 10 -2 Measurement Procedure Direct Measurement Direct measurement is a simple procedure f...

Calcium Ion Selective Electrode 012–06601A 6 6. To a clean, dry, 150 ml beaker, add 100 ml of the sample, 2 ml of ISA, and 2 ml of ISA. Place the beakeron the magnetic stirrer and begin stirring at a constant rate. Rinse the electrode with distilled water, blotdry, and lower the electrode tip into t...

012–06601A Calcium Ion Selective Electrode 7 5. Add increments of the l.0 X 10 -3 M or 10 ppm standard as given in Table 2 below. 6. After the reading has stabilized, record the voltage reading indicated in the Digits display after each addition. Titration The progressive and quantitative addition o...

012–06601A Calcium Ion Selective Electrode 9 Electrode Characteristics Reproducibility Electrode measurements reproducible to ±4 % can be obtained if the electrode is calibrated every hour. Factors suchas temperature fluctuations, drift, and noise limit reproducibility. Reproducibility is independen...

012–06601A Calcium Ion Selective Electrode 11 Electrode Response Plotting the electrode potential against the calcium concentration on semi-logarithmic paper results in a straight linewith a slope of about 26 mV per decade. (Refer to Figure 3) The time needed to reach 99% of the stable electrode pot...

Calcium Ion Selective Electrode 012–06601A 12 Troubleshooting Guide The goal of troubleshooting is the isolation of a problem through checking each of the system components in turn:the glassware, the electrodes, the standards and reagents, the sample, and the technique. Glassware/Plastic-ware Clean ...

012–06601A Calcium Ion Selective Electrode 13 Technique Be sure that the electrode’s limit of detection has not been exceeded. Be sure that the analysis method is clearlyunderstood and is compatible with the sample. Refer to the instruction manual again, particularly the General Preparation and Elec...

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