Measure. Analyze. Learn.
Hello. I'm here today to introduce how to use
ion selective electrodes (ISE).
Vernier Ion Selective Electrodes can be used to measure
the concentration of specific ions in aqueous solutions.
Vernier offers four different types of electrodes:
nitrate, ammonium, calcium, and chloride.
Each sensor requires a calibration before use,
and a high and low standard are provided with each sensor.
To prepare the sensor for calibration,
soak the tip in the high standard for at least 30 minutes.
This nitrate ISE has been soaking in the high standard,
the 100 milligrams per liter, for at least 30 minutes.
Then connect the sensor to LabQuest 2.
The data collection software will
automatically identify the sensor.
Tap on the red box, and choose 'Calibrate'.
Tap on 'Calibrate Now' to start the calibration process.
Your sensor will have been in the high standard
for at least 30 minutes.
Enter the high standard value into the 'Value 1' box.
And again, for the nitrate ISE this value is 100 mg/L.
And then, tap on 'Keep'.
Remove the sensor from your high standard.
Thoroughly rinse the tip with distilled water,
to prevent contamination of your low standard.
Then gently blot dry, using a paper towel or a lab wipe.
Then place the tip of the electrode in the low standard.
For the nitrate ISE this is 1 milligram per liter.
And, make sure the tip is not touching
the bottom of the container,
and your small white reference contacts are immersed.
Wait 60 seconds for your sensor to equilibrate.
In the 'Value 2' box,
enter the low standard samples concentration.
For the nitrate ISE this is 1 mg/L.
And then, tap on 'Keep'.
To save this custom calibration onto your sensor:
tap on the 'Storage' tab;
choose 'Save Calibration to Sensor';
Then, tap on 'OK';
and tap on 'OK' again to complete this process.
This calibration will be good only for several hours.
Frequent calibrations will only improve your data.
Remove the tip from the low standard,
and thoroughly rinse before measuring your sample.
You may see some strange readings on the screen.
When the sensor is placed in aqueous solutions,
the proper reading will appear.
Gently blot dry with a paper towel, or chemwipe.
And here, I have sample of stream water.
Again, make sure the tip is not resting at the bottom of
the container, and your white reference contacts are immersed.
Wait 60 seconds before data collection,
or recording your data.
Upon completion of your experiment,
remove the sensor from the solution.
Again, thoroughly rinse with distilled water.
Gently blot dry.
And, place the sensor in the long term storage bottle
containing damp sponge.
Make sure the tip does not rest against the sponge.
The ISE sensor booklet contains additional information
on the proper care and storage.
It also contains information on preparing
the high and low standards.
For additional information on the ISEs, please visit our website.