YSI 2700 SELECT, User Manual

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With normal use, enzyme sensors may become fouled and cease to operate in a normal mode.
A fouled sensor’s output current will decrease and calibration may become unstable. Since the
severity of fouling will vary, listed below are methods of cleaning which should be matched to
the cleaning needs. Follow the steps carefully and in order.
Sensor Maintenance
It is necessary to maintenance the enzyme sensor when the 2788 PM kit is installed and
periodically as needed.
1. Remove the enzyme membrane and hold the probe with the electrodes facing up.
2. Wad a small portion of a lint free tissue and wet it with 70% isopropyl alcohol.
3. Using your thumb, press the alcohol soaked wad against the probe’s surface and rotate the
probe back and forth.
4. Rinse the sensor with reagent grade water and return the sensor to normal service.
Sensor Cleaning and Reconditioning
The following procedure is recommended to be used only when the enzyme sensor stops
operating normally and the above maintenance procedure is ineffective. This is not a routine
maintenance procedure.
1. With the membrane removed, immerse the sensor in a 14% solution of ammonia for 3
minutes.
2. Immediately after soaking, rinse the sensor with reagent grade water for 3-5 minutes. It is
important that all the residual ammonia is removed.
3. Prepare a small amount of 0.5% sodium hypochlorite solution.
4. Immerse the sensor in the solution for 30 - 45 seconds. Check periodically...sensor should
darken, but do not allow it to become black.
5. Remove the sensor and immediately rinse it with reagent water for at least 2 minutes.
6. Install a new membrane and return the probe to service.
The procedure below is only recommended as a last resort for revitalizing a sensor after the
above cleaning procedure has been unsuccessfully attempted.
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1. Using a clean new pencil eraser, carefully, rub the center electrode (platinum) of the sensor.
Do not rub the epoxy between the two electrodes or the outer silver electrode.
2. To remove any eraser dust or residual, rinse sensor with 70% isopropyl alcohol and then
reagent grade water.
3. Prepare a small amount of 0.5% sodium hypochlorite solution.
4. Immerse the sensor in the solution for about 45 seconds.
5. Remove the sensor and immediately rinse it with reagent grade water for at least 2 minutes.
6. Install a new membrane and return the probe to service.
Note: Several hours may be required for the sensor to stabilize after cleaning.