TROLL 9500 Operator's Manual - Geotech Environmental Equipment

Section 14: orpUsage Recommendations and Cautions• ORP readings vary slightly with temperature, but are not easily correctedbecause, unlike pH, the ORP value depends on the activityof many ions in solution. pH values are more easily correctedbecause they are due to the activity of one ion, H + .Sensor Care and HandlingSensor RemovalUse the sensor removal tool to pop the sensor out.Maintenance/Inspection/CleaningsensorremovaltoolIf the platinum ORP sensor appears dull or fouled, it may be cleanedwith a swab dipped in alcohol. Rub gently until the platinum appearsshiny. Rinse in clean water.If a film develops on the glass electrode, or if the sensing glass orjunction become dehydrated, the response may be sluggish or erratic,or the sensor may fail to calibrate. In these cases, rinse the sensorin 90% isopropyl alcohol, then soak in storage solution (Catalog No.0065370) for at least an hour, overnight if needed. If this does not restorethe response, try soaking in 0.1 M HCl solution for 5-10 minutes,followed by a thorough rinse in clean water. If the response has stillnot improved, replace the filling solution, or the junction.Note: The following maintenance instructions apply to In-Situ’s newestpH/ORP sensor (cat. no. 0059520). Older sensors (cat. no. 0032010& 0032020, now discontinued) are not user-serviceable.Replacing the Filling SolutionReplace the filling solution every 5-6 months, or when:• The sensor fails to calibrate with reasonable slope and offset• Readings drift• Readings during calibration at pH 7 are outside the range 0±20 mV1. Unscrew the reference junction as shown.2. Holding the sensor at an angle, shake out the old filling solution.3. Protect the connector end of the sensor with the soft cap it shippedwith, or wrap the sensor in a paper towel toprevent solution from entering the connector.5. Screw in the reference junction, and hand-tighten until snug. Somefilling solution will overflow. Wipe the excess off the sensor body.6. Soak the sensor in tap water for at least 15 minutes.7. Recalibrate the sensor.If necessary, thoroughly clean the electrical connector toremove filling solution: Using a disposable pipette, fill theconnector with isopropyl alcohol (70% to 100%). Shake todry. Repeat 3 times. Dry overnight. When thoroughly dry, recalibrate.Replacing the JunctionReplace the junction when the sensor fails to calibrate, even afterreplacing the filling solution.1. Unscrew the reference junction and discard.2. Replace the filling solution and screw in a new reference junctionas described above.3. Soak for 15 minutes in tap water, then recalibrate the sensor.StorageTIP: Keep the junction damp at all times to avoid a lengthyrewetting process.Short-Term Storage (several days)Store in the Cal Cup in tap water.Long-Term Storage (up to several weeks)Remove the sensor and store in the electrode storage bottle with10-20 mL of storage solution (Catalog No. 0065370). Tighten the capto prevent drying. Prior to use, condition the sensor by rinsing withdeionized or tap water and soaking for 15 minutes.ReferencesEaton, A.D., L.S. Clesceri, E.W. Rice, and A.E. Greenberg, eds.,Standard Methods for the Examination of Water and Wastewater,21st edition, Washington, D.C.: American Public Health Association,American Water Works Association, and Water EnvironmentFederation, 2005. Section 2580, Oxidation-Reduction Potential.4. Using the dispenser cap on the filling solution bottle,insert the tube into the bottom of the empty reservoir.Squeeze a steady stream of solution into the reservoir untilit overflows and no bubbles are observed.Continue to add solution while withdrawing the tube.TROLL 9500 Operator’s Manual 1010095110 rev. 007 01/09