pH/ORP Electrode Maintenance and Use

Proper use and maintenance of the electrode will ensure maximum performance.

Contents:

1. pH Electrode Instruction Guide
2. Using pH Electrodes
3. Calibration of the pH meter with a pH Electrode
4. ORP Electrode Instruction Guide

pH Electrode Instruction Guide

Preparation

• Remove the protective cap. DO NOT BE ALARMED IF ANY SALT DEPOSITS ARE PRESENT. This is normal with electrodes and they will disappear when rinsed with water.
• Shake the electrode down as with a glass thermometer to eliminate any air bubbles inside the electrode.
• If the bulb and/or junction are dry, soak the tip of the electrode in a Storage Solution (HI 70300M) or pH 7 (HI 7007M) or pH 4 (HI 7004M) buffer for at least an hour prior to using it.

Measurement:

• Rinse the electrode tip with distilled or deionized water.
• Immerse the tip in the sample, stir gently and wait for the reading to stabilize. For a faster response and to avoid cross contamination, rinse the tip with a few drops of the solution to be tested, before taking measurements.

Storage:

• To minimize clogging and ensure a quick response time, the glass bulb of the pH electrode and the junction should be kept moist. Replace protective cap with a few drops of a Storage Solution (HI 70300M), or in its absence, pH 7 (HI 7007M) or pH 4 (HI 7004M) buffers.
• NEVER STORE THE ELECTRODE IN DISTILLED OR DEIONIZED WATER.

Maintenance and Cleaning:

• Rinse the electrode with clean water after use before putting it away and store it wet (see above).
• Periodically clean the electrode thoroughly, by leaving it soaking for 10 to 15 minutes in a cleaning solution (for General Purpose use HI 7061M, for oily samples HI 7077M, for Inorganic samples HI 7074M and for protein etc. use HI 7073M cleaning solution).
• Inspect the electrode for any scratches or cracks on the bulb or stem. If any are present, replace the electrode.

Trouble Shooting:

• pH Meter: Follow attentively the meter's operating and calibration procedures from the manual.
• Electrode: Evaluate your electrode performance based on the following possibilities:

1. Noise: (Readings fluctuate) could be due to Clogged/Dirty Junction: Refer to Maintenance above; or Air Bubble insulating the junction: Shake the electrode down as with a clinical thermometer.
2. Dry Membrane/Junction: Soak in a Storage Solution (HI 70300M) or pH 7 (HI 7007M) or 4 (HI 7004M) buffer for at least an hour.
3. Drifting: Soak the electrode tip in warm (about 120 °F) pH 4 Solution (HI 7004M) for about an hour then rinse the tip with distilled or deionized water.
4. Low Slope: Refer to Maintenance above.
5. No Slope: (pH meter reads the same value all the time) Check for cracks in glass, stem or bulb. Replace electrode.
6. Slow Response/Excessive Drift: Soak the tip in a Cleaning Solution (for General Purpose use HI 7061M, for oily samples HI 7077M, for Inorganic samples HI 7074M and for protein etc. use HI 7073M cleaning solution) for 30 minutes, rinse thoroughly with distilled or deionized water and then soak the electrode in a Storage Solution (HI 70300M) for an hour and recalibrate the meter.

Using pH Electrodes

Installing the Electrode

1. All Hanna electrodes are shipped with a cap that protects the bulb and junction from damage. The cap must be REMOVED and set aside.
2. Remove any salt (Potassium Chloride) deposit that may have formed on the surface of the electrode during storage or shipping by thorough rinsing with tap water. The presence of salt deposits is normal and generally indicates that the reference junction is open and free-flowing.
3. Lower the rubber sleeve or unscrew the plug to expose the reference fill hole. This allows the reference chamber to "breath" and quickens the electrode's response time. This does not apply to gel and solid-filled electrodes.
4. All refillable Hanna electrodes are shipped with the reference chamber filled. Once the level of the reference solution is 1/2" (1cm) below the fill hole, add more reference electrolyte with a syringe by unscrewing the plug or lowering the sleeve. Use 3.5 M KCl/AgCl Reference Electrolyte (HI 7071) for single junction electrodes and 3.5 M KCl (HI 7082) for double junction electrodes. Hold the electrode horizontally to obtain a level above the fill hole. Replace the plug or slide the cover back when finished.
5. The electrode's glass bulb should always be kept wet. If dry, the tip should be soaked in Electrode Storage Solution (HI 70300) or in its absence, in pH 4 buffer or tap water for 2 hours to hydrate the pH glass membrane before use or calibration.
6. Connect the electrode to the meter.

Calibration of the pH meter with a pH Electrode

Good calibration will ensure reliable, repeatable pH/ORP measurements. The sensitive parts of the electrode are the bulb (pH), or metal (ORP), and the reference junction. These are located at the bottom (1" [2 1/2cm]) of the electrode and must be kept wet at all times. Both the bulb and reference have to be in contact with the solution to read the pH or ORP.

1. Rinse the electrode tip with tap water.
2. ADJUSTING THE OFFSET
   IMMERSE the electrodes tip into a sample (1"/1/2cm deep) of buffer solution. This is usually pH 7.01 or pH 6.86 (HI 7007 or HI 7006). Turn the meter ON and allow the reading to stabilize. HI 8014, HI 8519, HI 9110, HI 9210:
   Adjust the manual temperature setting of meter to that of the buffer and then turn the OFFSET trimmer or knob until the reading reaches the proper pH value at that temperature. (See the temperature/pH chart on the solution label).
   HI 8314, HI 8915, PICCOLO, PICCOLO2, PICCOLO+:
   For meters with automatic temperature compensation and manual calibration, turn the trimmer or knob until the meter reads pH 7.01 and has stabilized. Be sure that the temperature probe is also immersed in the sample (HI 8314 & HI 8915).
   HI 8424, HI 8520, HI 8521, HI 8417, HI 9017, HI 9023, HI 9214, HI 9218, HI 9219, HI 9224, HI 92240, HI 931400, HI 9318, HI 9321 with AUTOMATIC BUFFER RECOGNITION:
   Enter the calibration mode by pressing the CAL button. The pH icon will continue to flash while the electrode is stabilizing. Once the pH icon stops flashing press the CFM/CON (confirmation) button.
   HI 9024, HI 9025 with AUTOMATIC CALIBRATION:
   Enter the Calibration mode by pressing the CAL Button. Follow the prompts that appear on the display for confirmation.
3. Rinse the tip thoroughly with tap water to prevent cross contamination of the buffer solutions.
4. ADJUSTING THE SLOPE
   Select a buffer with a value close to the range that you will be measuring. For example, if your sample is from pH 2 to pH 7, select the pH 4.01 (HI 7004) as your SLOPE calibration buffer. Other choices are pH 9.18 or pH 10.01 (HI 7009, HI 7010).
   HI 8014, HI 8519, HI 9110, HI 9210:
   IMMERSE the tip in the buffer sample. Once the display has stabilized, turn the SLOPE trimmer or knob to the proper pH value at that temperature. Follow the same temperature compensation procedure as OFFSET calibration.
   HI 8314, HI 8915, PICCOLO, PICCOLO2, PICCOLO+:
   IMMERSE the electrode tip in the buffer sample and adjust SLOPE trimmer or knob until display shows the buffer value.
   HI 8424, HI 8520, HI 8521, HI 8417, HI 9017, HI 9023, HI 9214, HI 9218, HI 9219, HI 9224, HI 92240, HI 931400, HI 9318, HI 9321 with AUTOMATIC BUFFER RECOGNITION:
   IMMERSE the electrode tip into the buffer sample and wait for the pH icon to stop flashing then press CFM/CON button.
   HI 9024, HI 9025 with AUTOMATIC CALIBRATION:
   After immersing the electrode into the buffer sample, press the CFM button when prompted to do so.
5. RINSE the electrode thoroughly with tap water.
6. Periodically re-check the calibration to ensure maximum performance.

ORP Electrode Instruction Guide

Preparation and Measurement:

• Remove the protective cap. DO NOT BE ALARMED IF ANY SALT DEPOSITS ARE PRESENT. This is normal with electrodes and they will disappear when rinsed with water.
• Shake the electrode down as with a glass thermometer to eliminate any air bubbles inside the electrode.
• For a faster response time, pretreat the ORP electrode prior to use by soaking it in the pretreatment solution for 15 minutes. As a general rule, if the mV reading corresponding to the pH measurement is higher than the value in the table below, an oxidizing treatment (HI 7092M) is necessary, otherwise use a reducing treatment (HI 7091M):
  

  pH Value	mV Value	pH Value	mV Value	pH Value	mV Value	pH Value	mV Value	pH Value	mV Value
  0	990	3	800	6	640	9	460	12	280
  1	920	4	740	7	580	10	400	13	220
  2	860	5	680	8	520	11	340	14	160

  Use an iron sulfate solution such as quinhydrone (HI 7091M) for a reducing treatment, otherwise use an oxidant such as sodium hypochlorite neutralized at pH 7 with 1 M hydrochloric acid (HI 7092M) or bleach. If pretreatment is not performed, the electrode will take a significantly longer time to respond.
• To measure the ORP, immerse the tip in the sample, stir gently and wait for the reading to stabilize.

Storage:

• To minimize clogging and ensure a quick response time, the tip and the junction should be kept moist. Replace protective cap with a few drops of a Storage Solution HI 70300M), or in its absence, pH 4 buffer (HI 7004M).
• NEVER STORE THE ELECTRODE IN DISTILLED OR DEIONIZED WATER.

Maintenance and Cleaning:

• Rinse the electrode with clean water after use before putting it away and store it wet (see above).
• Periodically clean the electrode thoroughly, by leaving it soaking for 10 to 15 minutes in a cleaning solution (HI 7061M).
• Inspect the electrode for any scratches or cracks on the bulb or stem. If any are present, replace the electrode.
• The surface of the platinum electrode must be clean and smooth. To clean the ORP electrode, rinse it briefly in turpentine, then wash it with abundant water and polish it with a light abrasive lint-free (emery) material, if necessary. The surface of the platinum electrode must not be scratched in the process and all traces of these cleaning substances must be rinsed off.

Trouble Shooting:

• Noise/Slow Response/Excessive Drift: Could be due to Clogged/Dirty Junction: Refer to Maintenance above; or Air Bubble insulating the junction: Shake the electrode down as with a glass thermometer.
• Drifting: Use a an emery (lint free) cloth and rub the platinum tip of the ORP electrode thoroughly to remove any grease or deposits and then follow the cleaning procedure above.
• No Slope: (Meter always reads the same value) Check for cracks in glass, stem or bulb and replace electrode.