If the response time and/or quality of data collected by a WQSensor decrease, try cleaning and reconditioning the probe. If these steps do not resolve the problem, consider replacing the sensing module to boost performance.


The sensor can be cleaned using distilled or deionized water. Rinse thoroughly as necessary but avoid using any detergent or other cleaning products.


A good working ISE response stabilizes within one or two minutes. However, the ISE can become sluggish if the membrane becomes dirty from grease or particles in the sample.

The WQ-NO3 is a PVC ISE, and as such it should not be polished in an attempt to recondition the electrode. Instead, rinse the electrode thoroughly with deionized water and soak for 2-4 hours in the lowest standard used for calibration.

Nitrate electrodes can be soaked for too long (e.g. overnight) and effectively become numb to water quality variations. If this occurs, dry the electrode for at least 12 to 24 hours in air. Soak the probe in the lowest standard used for calibration for 10 to 20 minutes before recalibrating after the drying period.

Replacing the Sensing Module

NexSens recommends replacing the sensing module every six months for all ISE WQSensors to maximize measurement accuracy and sensor performance.

The sensing modules are user replaceable. Removal and installation is quick and easy and can be done in just a few minutes with no tools.

Follow the procedure outlined below to replace the sensing module:

  1. Remove the existing sensor module by unthreading the connection between the module and the probe body. This can be done by hand, although a 7/16” wrench can be used to get started if necessary.
  2. Screw the new module onto the probe body until it is hand tight. Do not over tighten the connection.


Exploded View of Sensing Module Assembly

Figure 1: Exploded view of sensing module assembly



Short Term

For short term storage (1-3 days), rinse the electrode thoroughly with distilled or deionized water and then place the sensor tip in a solution of ISA and distilled or deionized water. ISA should be added to the water in a 1:50 ratio. For example, add 2 mL of ISA for each 100 mL of water.

Long Term

The sensor electrode should be stored completely dry for any amount of time longer than three days. Rinse the tip thoroughly with distilled or deionized water, blot dry, and allow to completely dry out. Then place the ISE sensor storage cap over the end of the probe.


REV: 13H21

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