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Top Tips for dissolved oxygen measurements

15/2/2019

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As with all electrodes maintenance is key to keeping your readings stable and accurate. The TRUEscience Dissolved Oxygen probe is a galvanic sensor with a fixed membrane cap. This galvanic probe provides good performance without the problem of membrane replacement associated with polorgraphic electrodes. It offers good sensitivity and response but the sample must be stirred during readings. Take care not to introduce oxygen into the sample by over-stirring when reading.

Taking measurements
Prior to sample measurement ensure that the electrode is thoroughly rinsed with de-ionised water. It is worth performing this rinse twice given the possibility of carryover being greatest in high concentration solutions. Before taking a sample measurement it is a good idea to rinse the electrode with your sample in a separate beaker. 

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Using a magnetic stirrer for laboratory analysis is recommended but not essential. It is however important to ensure the solution is homogeneous and a stirrer will help to achieve this. NOTE: You must continue stirring during measurements as Oxygen is consumed at the membrane surface.

​Required Solutions
Distilled or deionised water will be required to prepare Standards, for storage and to rinse the electrode between measurements.
Zero Oxygen Solution is used to carry out a calibration zero point. This will need to made fresh as they will absorb oxygen.

Short term electrode storage 
Simply reattach the soaker bottle in reverse order of removal. Ensure the soaker bottle has sufficient DI water in it.

Electrode cleaning 
​The TRUEscience galvanic oxygen electrode has no customer serviceable parts. Cleaning is important however, and the electrodes should be rinsed thoroughly in de-ionised water between and after measurements are made, never allow the sample to dry on the electrode. If dirt or any of the sample does dry on the membrane on the tip of the electrode it can be immersed in DI water and ultrasonically cleaned for 30 seconds.
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​The TRUEscience Galvanic Dissolved Oxygen electrode offers a fast response and rugged construction ensuring that calibration and measurement are both rapid and consistent. The Galvanic DO cell is very simple in its operation and basically works as a battery which generates a voltage. This voltage is directly proportional to the Oxygen concentration which permeates through the membrane into the galvanic cell. 

​The cell comes complete and ready for operation without the need for awkward membrane installation and manual filling with hazardous solution. Bubble removal from the membrane/cell interface is not required which allows calibration to be performed quickly and easily by any operator regardless of experience. 


The TRUEscience bluetooth system allows you to connect the SMART Cap and dissolved oxygen electrode to the free TRUEscience app on an Android tablet or phone to create easily sharable, enriched readings. Grab an Android device and use the TRUEscience dissolved oxygen starter kit to get started with dissolved oxygen measurement.
For more information on dissolved oxygen measurement or the TRUEscience system please get in touch with the team by calling +44 1954 233 144 or send us an email info@truescience.co.uk
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How's best to store a Redox electrode?

15/2/2019

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Like pH electrodes, redox electrodes are stored with the electrode tip submerged in 3.0 Molar KCL (potassium chloride). The TRUEscience redox electrodes are shipped with a soaker bottle around the tip of the electrode, keep this for long term storage and make sure it is topped up with electrode storage solution when in use.

For electrode storage on a laboratory bench whilst attached to the TRUEscience SMART Cap, use the electrode storage stand to keep the electrode well conditioned when not in use. The SMART Clip will hang the Cap and electrode on the stand, and suspend the tip of the probe in the storage solution. This ensures the electrode does not get damaged by hitting the bottom of the container. The unique stand will keep the glass bulb in conditioned use with minimal storage solution wastage. 
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Dirty, contaminated electrodes will slow down the response rate and may cause the readings to drift. Make sure your redox electrodes are thoroughly rinsed before and after use to make sure no contamination accumulates. There are a range of different cleaning solutions which can be applied to the electrode based on contaminant for example 0.1 molar HCL can be used for oil and grease deposits, pepsin or HCL can be used for blockage due to proteins. ORP/Redox electrode tips (Platinum rods or discs) may need additional cleaning from time to time with Crocus (mild abrasive) paper.

For more help on cleaning electrodes for your specific application or redox measurements in general please get in touch with us by ringing +44 1954 233 144 or send us an email using info@truescience.co.uk. 
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How do you measure the pH of deionised water?

15/2/2019

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Measuring the pH of deionised water is about the most difficult application to handle. Most results are incorrect and very few ever endpoint. The issue is there is no conductivity and therefore the two half cells (pH and reference) cannot effectively communicate. One potential is basically subtracted from the other. If any one or both are unstable, so is the result.

The TRUEscience low ionic strength pH electrode, part number 1222328, has been specially designed for low ionic strength solutions. They are made with the following features:
  1. The pH bulb has a low resistance glass with a large surface area
  2. The reference is refillable with a large junction surface area and a high leak rate
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A little trick you can do to accelerate the endpoint is to add a drop of 4M KCl to the sample. It doesn’t affect the pH but it will speed up the endpoint.  This is essentially what reference electrodes do anyway, they leak 4M KCl slowly into the sample. The longer you leave electrodes in DI water the worse it gets.  You will often get a downwards drift and you can never really see the endpoint.

For more information about our range of electrodes or further application support give us a ring on +44 1954 233 144 or send us an email info@truescience.co.uk

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    Posts by the TRUEscience team! We want to explore questions around pH testing in the real world, as well as impart our favourite tips and tricks to make your testing SMART!

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