1ISE25NO3Nitrate Ion-selective ElectrodeIntroductionThe ISE25NO3 electrode is a PVC membrane electrode with anitrate ion carrier. The electrode is used for direct measurement ofnitrate ions in aqueous solutions. It is characterised by near theo-retical sensitivity, fast response, a high degree of selectivity fornitrate ions against a background of other ions and requires aminimum maintenance level.ApplicationsThe electrode is primarily intended for the determination of nitratesin water (ground, surface, drinking and waste water) in foodstuffs,plants and soil samples.English2Preparing the electrodeRemove one of the three tubes from the ISE-K-NO3 kit. Fill the tubewith 1 ml of nitrate inner solution (S41M004) using the 1 ml plasticsyringe, making sure that no air bubbles are present. To release airbubbles, tap the electrode with your finger.Screw on the electrode insert M27Ag-9 (E34M001) and connect theappropriate cable. Condition the electrode for two hours in0.01 mol/l KNO3.Measuring hintsFor precise measurements, all samples and standards should havethe same temperature, preferably ambient temperature. The elec-trode should not be used above 50°C.Note: always rinse the electrode with distilled water betweenmeasurements. Never touch the membrane!The samples and the solutions must be of equal ionic strength inorder to correct the difference between the concentration and theactivity; refer to “Theory” page 10. Finally, it is generally recom-mended to add an indifferent salt to the solution, for example0.2 mol/l NaH2PO4. Stir the solution with a magnetic stirrer atmedium speed.3CalibrationPreparing the standards:Dilute each solution 1:1 using the indifferent salt 0.2 mol/l NaH2PO4and calibrate using an ion meter. It is recommen...
