Macro 900 Operation Manual V3© 2013 Palintest Ltd. www.palintest.com Page 147 of 1475. During long term deployment of ion selective electrodes, the user shouldobtain grab samples during the course of the deployment for analysis in thelaboratory by chemical means and use the results to apply post calibration tothe recorded results.6. Accuracy in the field is dependent upon full three-point calibration andminimal time between calibration and use.7. In order to achieve accurate readings with ISE electrodes, the Probe needsto be either placed in flowing water, or needs to be stirred or raised andlowered continuously to ensure a minimum flow rate of 0.3m/s over theelectrode. If there is no water flow across the ISE electrode, the ionsin the immediate area of the electrode will be depleted and thereading will start to fall. This also applies to calibration, where theprobe should be stirred at all times.26.1. Special Notes Concerning ISE Electrodes during pH CalibrationThe high ionic concentration of pHcalibration solutions (buffers), includingMacroCal, can cause significant offsets inISE electrodes.These offsets are temporary, but bestavoided because they can causesignificant errors during both calibrationand normal operation.For this reason all ISE electrodes aresupplied with a red rubber sealing cap.The caps should be fitted to all ISEElectrodes during pH calibration orwhen using MacroCal in order to protect the ISE electrodes from the effectsof the buffer solution.At all other times, the ISE electrodes should be left uncovered.
