PASCO CI-6735 - Manual

Nitrate Ion Selective Electrode 012–06616A 2 where: C X = concentration of ion X Z X = charge of ion X Σ = sum of all of the types of ions in the solution In the case of high and constant ionic strength relative to the sensed ion concentration, the activity coefficient, γ , is constant and the activ...

012–06616A Nitrate Ion Selective Electrode 3 RO O1013 SAMPL E 4MKCI Refe rence Fill Solutio n Figure 1.Included Equipment to ISEAmplifier Sodium Ion SelectiveElectrode filling pipette fillingsolution Equipment • Nitrate Ion Selective Electrode • Nitrate Ion Selective Electrode fill solution • Pipett...

Nitrate Ion Selective Electrode 012–06616A 4 Figure 2Equipment Setup. a: filling the electrodewith filling solution; b & c: connecting theelectrode to the ISE Amplifier and to thecomputer interface b c Rotate ringone-quarterturn to secure electrodeconnector ISE Amplifier Insert DINconnector into...

012–06616A Nitrate Ion Selective Electrode 5 Measurement Measuring Hints • All samples and standards should be at the same temperature for precise measurement. A difference of 1 °C in temperature will result in a 2% measurement error. • The sensing membrane is normally subject to water uptake and mi...

Nitrate Ion Selective Electrode 012–06616A 6 Measurement Procedure Direct Measurement Direct measurement is a simple procedure for measuring a large number of samples. A single reading is all that is required for each sample. The ionic strength of samples and standards should be made the same by adj...

012–06616A Nitrate Ion Selective Electrode 7 10 -6 10 -5 10 - 4 10 -3 10 -2 0.1 +230 +190 +150 +30 1 10 100 1,000 0.1 1 10 100 1,000 10 -1 10 - fold change ~ 56mV (ppm as N) (ppm as NO 3 ) +70 +110 Figure 3Typical nitrate electrode calibration curve ä Note: A calibration curve is constructed on semi...

Nitrate Ion Selective Electrode 012–06616A 8 2. Dilute 1 ml of 0.l M standard to 100 ml to prepare a l.0Xl0 -3 M NO 3 -1 solution for measurements in moles per liter. Use the 1,000 ppm standard for preparing a 100 ppm NO 3 -1 standard by diluting 10 ml of the 1,000 ppm standard to 100 ml. Standards ...

012–06616A Nitrate Ion Selective Electrode 9 Electrode Characteristics Reproducibility Electrode measurements reproducible to +2% can be obtained if the electrode is calibrated every hour. Factors such as temperature fluctuations, drift, and noise limit reproducibility. Reproducibility is independen...

Nitrate Ion Selective Electrode 012–06616A 10 The above interference removal procedures require similar treatment of standards as well as samples. If the electrode is exposed to high levels of interfering ions which cannot be removed, the electrode reading may drift and the response may become slugg...

012–06616A Nitrate Ion Selective Electrode 11 Figure 4Typical electrode time response to step changes in NaNO3 Limits of Detection The upper limit of detection in pure sodium nitrate solutions is 1 M. In the presence of other ions, the upper limit of detection is above l0 -1 M nitrate, but two facto...

Nitrate Ion Selective Electrode 012–06616A 12 Maintenance Electrode Storage The nitrate electrode may be stored for short periods of time in l0 -2 M nitrate solution. For longer storage (longer than two weeks), rinse and dry the nitrate membrane and cover the tip with any protective cap shipped with...

012–06616A Nitrate Ion Selective Electrode 13 4. If the problem persists, the standards or reagent may be of poor quality, interferences in the sample may be present or the technique may be faulty. (See Standards Reagents, Sample, and Technique sections below.) 5. If another electrode is not availab...

Nitrate Ion Selective Electrode 012–06616A 14 Troubleshooting Hints Symptom Possible Causes Next Step Out of Range Reading defective electrode check electrode operation electrodes not plugged in unplug electrodes and reseat electrodes properly reference electrode not filled be sure reference electro...

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