How should I store the ISFET pH probe on my Navis BGC float? What should I do before testing and deploying it?
The pH sensor will be shipped dry but was pre-conditioned in seawater (generally from Pacific Ocean waters near Hawaii). While conditioning and evaluating the pH sensor, only expose it filtered, sterilized natural seawater. Do not use seawater CRMs (Certified Reference Material), synthetic seawater, deionized water, NaCl Solutions, or tap water.
Before pre-deployment testing, you will need to fill the plumbing around the pH sensor with natural seawater. The pH sensor needs time to acclimate to the ionic concentration of region specific waters. Once wet, the time to recondition the sensor so that it will report within its accuracy specification depends on several factors, including the ionic composition of the seawater used and the amount of time the pH sensor was stored dry. This time can range from several hours to up to three days.
When the seawater bridge between Counter Electrode and ISFET is broken for longer than 10 seconds, it will be necessary to re-condition the sensor. The sensor does not require recalibration after being re-conditioned.
To prepare the sensor for deployment, it is recommended that several days prior to deployment, the isolated battery is connected via the float interface and the pH sensor is stored in water that is similar to the deployment site. The sensor should be stored dry to avoid bio-fouling of the ISFET and the battery may be removed during storage. Seawater creates a half cell bridge between the Counter Electrode and ISFET, and power to that circuit is provided by the isolated 9V cell. Without seawater, the battery is unnecessary and may be disconnected.