EXO Calibration - Ammonium ISE

EXO Calibration - Ammonium ISE

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EXO Calibration - Ammonium ISE

This video covers the calibration of the EXO Ammonium Ion Selective Electrode in mg/L using Kor Software.

Timestamps of specific moments of the video

  • 0:00 – Overview
  • 1:16 – Calibration Point 1
  • 3:11 – Calibration Point 2

Video Transcript

In this video, we are calibrating the EXO Ammonium Ion Selective Electrode – or ISE. These sensors are shipped dry. So before calibrating a new sensor, we want to make sure we soak it overnight in a 100 mg/L solution. This will help hydrate new sensors. It is also a good idea to soak sensors that have been used in the field because this soaking can help remove interfering ions from the sensor that might have been picked up during use. 

After soaking, rinse and dry the sensor before proceeding with the calibration.

As a best practice, make sure all the sensors, probe guard, calibration cup and wiper are clean. For efficiency, it may be helpful to have a dedicated probe guard and cal cup just for calibration.

We will perform a 2-point calibration for this sensor. We’re going to use 1 mg/L ammonium standard as the first point, and a 100 mg/L standard as the second point. These solutions can be purchased from YSI. If you expect significant temperature variation during your deployment, you can do a 3-point calibration. And you can find those instructions in the EXO manual.  

Fill the cal cup to the first line with the 1 mg/L ammonium standard and insert the sonde into the calibration cup.

Using Kor software, select the ammonium calibration.

Kor will indicate when the readings are stable in real time on this graph. Note the Ammonium mV value or raw sensor signal coming from the sensor, which should be around 0 mV +/- 20 for a brand-new sensor.

Click apply and remove the sonde from the standard. We’re now going to rinse and dry the sonde, sensors, and sensor guard. I do this by having another cal cup filled with de-ionized water. I’m going to go ahead and place the sonde in there, tighten down the calibration cup, and go ahead and shake it up and give it a good rinse with my DI water; if you have access to DI water, or you can also use a squirt bottle. So I’ve rinsed my sonde from the 1 mg/L standard. I’m going to remove the sensor guard and make sure I wipe off the sensors. And for best practices, use a Kimwipe for the sensor tips. And now I’m going to thoroughly dry off my probe guard.

For the second calibration point, we’re going to move to our 100 mg/L standard. 

Again, we’re going to fill our cal cup to the first line and immerse the sensors in the standard solution. Click to add another cal point. Wait for the readings to stabilize before applying this calibration point. You should see millivolt values around 90 and 130 greater than what you saw in the first calibration point.

Once readings are stable, go ahead and click apply. Now you will see the calibration summary screen where you can choose to redo the calibration or complete the calibration. I’ll go ahead and choose to complete the calibration. 

Our EXO ammonium ISE sensor is now calibrated and ready to go! Please check out our other EXO University videos, and thanks for watching.

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