DCcan
Well-Known Member
Just some basics put together for keeping everyone green.
Note that Ph meters and EC meters should be stored in different liquids, and why.
Keep Your pH Electrode Hydrated:
If your electrode is dry, rehydrate the sensing tip by soaking the bulb and junction in an electrode storage solution for at least one hour, ideally overnight. Storing your electrode in storage solution also improves its life span and performance.
Storing your pH electrode in storage solution rather than water is important for reducing microbial growth, preventing the reference electrolyte from leaching out, and keeping the junction clear. If you're out of storage solution, pH 4 or 7 buffers can be used in a pinch.
A pH electrode is active and stable only after wetting! For this purpose, an electrode that has been stored dry must be immersed for at least ten hours in the reference electrolyte solution (1-4 M KCl solution, check your manual...)
Cleaning & reconditioning pH electrodes:
The pH electrode wears away by being used. If the electrode tends to respond slower and calibration becomes difficult, even after cleaning, it should be replaced by a new one.
Chemicals needed: Water , Detergents, HCl (Hydrochloric Acid), and NaOH (Sodium Hydroxide).
Method 1
Soak the electrode in a 0.4 molar concentration of HCl (hydrochloric acid) for 10 minutes, then rinse the electrode with deionized or distilled water. This should remove any organic protein from the glass electrode and the surface of the reference electrode.
Method 2
Soak the electrode in a 3.8 or 4.0 molar KCl (potassium chloride) solution heated to 50°C for 1 hour. Allow the KCl solution to cool down to room temperature, then rinse the electrode with deionized or distilled water. This will open and clean the reference electrode of all contaminants.
Method 3
Soak the electrode in a 4.01 pH buffer solution , heated to 50°C for 1 hour. Allow the buffer to cool down to room temperature, then rinse the electrode with deionized or distilled water. This will open and clean the reference electrode.
Method 4
After each use, rinse the electrode in 0.5 N or 1% HCl. If you have a build-up of oil or protein contaminants, try soaking the electrode in warm detergent and water solution. Degreasing dishwashing detergents or stain removing pre wash pretreatment are ideal for this: any brand will do. An overnight soak may be needed if build-up is heavy. Then rinse the pH sensor in deionized or distilled water and soak for 10 minutes in 1% HCl. Rinse the pH sensor in deionized or distilled water and check in buffers. If the pH sensor calibrates to buffers it can be used in tests. When the pH electrode cannot be calibrated even after attempts to clean it, it must be replaced.
Method 5
For protein removal, soak the pH electrode in contact lens enzymatic cleaner solution overnight. The enzymes will remove proteins from glass and plastic.
Storage
Note: never store your PH electrode in distilled water!
Proper electrode storage extends performance and life.
Maintenance,Cleaning & Reconditioning of Conductivity electrodes (EC meter):
Conditioning
The electrodes of conductivity cells are coated with a layer of platinum black. The platinum black creates a higher effective surface area for the electrodes and eliminates polarization error. If the platinum black is dry, dirty, or peeled off, it will adversely affect the conductivity measurement.
Calibration and Measurement
Cleaning
A clean conductivity cell is necessary in performing an accurate conductivity measurement. The choice of cleaning solution should effectively remove all contaminants based on sample tested without damaging the conductivity cell.
Clean the part of conductivity cell in contact with sample using the appropriate solution and then rinse it thoroughly with clean water. Abrasive objects should never be used in cleaning. A piece of cotton soaked in a cleaning solution can be used with caution.
Procedure 1 to 4: Clean the cell by dipping or filling it with the cleaning solution and agitating for two or three minutes.
When a stronger cleaning solution is required, try concentrated 4M HCl . Rinse the cell several times with distilled or deionised water and remeasure the cell constant before use.
Storage
Conductivity cells should be clean before they are stored for any length of time.
Some platinum conductivity cells are coated with platinum black before calibration. This coating is extremely important to cell operation, especially in solutions of high conductivity. Electrodes are platinised to avoid errors due to polarisation. Cells should be inspected periodically. If the black coating appears to be wearing or flaking off the electrode or if the cell constant has changed by 50%, the cell should be cleaned and the electrodes replatinised or replaced.
Note that Ph meters and EC meters should be stored in different liquids, and why.
Keep Your pH Electrode Hydrated:
If your electrode is dry, rehydrate the sensing tip by soaking the bulb and junction in an electrode storage solution for at least one hour, ideally overnight. Storing your electrode in storage solution also improves its life span and performance.
Storing your pH electrode in storage solution rather than water is important for reducing microbial growth, preventing the reference electrolyte from leaching out, and keeping the junction clear. If you're out of storage solution, pH 4 or 7 buffers can be used in a pinch.
A pH electrode is active and stable only after wetting! For this purpose, an electrode that has been stored dry must be immersed for at least ten hours in the reference electrolyte solution (1-4 M KCl solution, check your manual...)
Cleaning & reconditioning pH electrodes:
The pH electrode wears away by being used. If the electrode tends to respond slower and calibration becomes difficult, even after cleaning, it should be replaced by a new one.
Chemicals needed: Water , Detergents, HCl (Hydrochloric Acid), and NaOH (Sodium Hydroxide).
Method 1
Soak the electrode in a 0.4 molar concentration of HCl (hydrochloric acid) for 10 minutes, then rinse the electrode with deionized or distilled water. This should remove any organic protein from the glass electrode and the surface of the reference electrode.
Method 2
Soak the electrode in a 3.8 or 4.0 molar KCl (potassium chloride) solution heated to 50°C for 1 hour. Allow the KCl solution to cool down to room temperature, then rinse the electrode with deionized or distilled water. This will open and clean the reference electrode of all contaminants.
Method 3
Soak the electrode in a 4.01 pH buffer solution , heated to 50°C for 1 hour. Allow the buffer to cool down to room temperature, then rinse the electrode with deionized or distilled water. This will open and clean the reference electrode.
Method 4
After each use, rinse the electrode in 0.5 N or 1% HCl. If you have a build-up of oil or protein contaminants, try soaking the electrode in warm detergent and water solution. Degreasing dishwashing detergents or stain removing pre wash pretreatment are ideal for this: any brand will do. An overnight soak may be needed if build-up is heavy. Then rinse the pH sensor in deionized or distilled water and soak for 10 minutes in 1% HCl. Rinse the pH sensor in deionized or distilled water and check in buffers. If the pH sensor calibrates to buffers it can be used in tests. When the pH electrode cannot be calibrated even after attempts to clean it, it must be replaced.
Method 5
For protein removal, soak the pH electrode in contact lens enzymatic cleaner solution overnight. The enzymes will remove proteins from glass and plastic.
Storage
Note: never store your PH electrode in distilled water!
Proper electrode storage extends performance and life.
- Fill an electrode bottle almost completely with the reference electrolyte solution (mostly 3…4 M KCl), place it on the electrode and make sure it is properly closed to prevent leakage during the storage.
- Bluelab uses 4M KCI, Apera uses 3M KCI, others use 1M KCI solution, proper chemical makes it read faster and more accurately and extends service life.
- It is also possible to use a 1:1 mixture of pH 4 buffer and 3..4 M KCl solutions. Mostly is it the best to use a non-colored buffer solution as otherwise the porous reference diaphragm might become colored also.
Maintenance,Cleaning & Reconditioning of Conductivity electrodes (EC meter):
Conditioning
The electrodes of conductivity cells are coated with a layer of platinum black. The platinum black creates a higher effective surface area for the electrodes and eliminates polarization error. If the platinum black is dry, dirty, or peeled off, it will adversely affect the conductivity measurement.
- Prior to use, soak the conductivity cell in clean water (e.g., tap, distilled, or deionized water) for at least 1 hour, if the platinum black is dry. Make sure that the water level is right on the mark indicated in the cell body or it fully covers the electrodes.
- Note that a plastic conductivity cell is soaked in pure water when shipped to prevent the platinum black from drying.
Calibration and Measurement
- Before and after measurement of each solution (standard or sample), rinse the conductivity cell with clean water and/or with a portion of the next solution to be measured. If water is used in rinsing, wipe the conductivity cell with a tissue to remove excess water. Rinsing between measurements prevents cross contamination.
- When immersing the conductivity cell in a solution, make sure that the solution level is right on the mark indicated in the conductivity cell body. If there is no marking indicated in the body, make sure that the metal electrodes are completely immersed in a solution.
- Calibrate at least once a day using a fresh standard solution that has a conductivity value as close as possible to the expected sample value. After calibration with a standard solution, the meter will display a calibrated cell constant. The calibrated cell constant should be within ±10% of the nominal cell constant. The conductivity standard solution should give a reading of expected value ± 5%
- To detect temperature and compensate its effect on conductivity, use a conductivity cell with built-in temperature sensor. If the conductivity cell has no built-in temperature sensor, check the solution temperature using a calibrated thermometer and compensate.
- Stir conductivity standards and sample at same rate. Stirring provides representative conductivity value of a solution. If stirring is not possible due to limited sample volume or other reasons, it may be abandoned in both calibration and measurement.
- Dislodge any bubbles formed inside the conductivity cell.
Cleaning
A clean conductivity cell is necessary in performing an accurate conductivity measurement. The choice of cleaning solution should effectively remove all contaminants based on sample tested without damaging the conductivity cell.
Clean the part of conductivity cell in contact with sample using the appropriate solution and then rinse it thoroughly with clean water. Abrasive objects should never be used in cleaning. A piece of cotton soaked in a cleaning solution can be used with caution.
- General samples – Simply wash the conductivity cell with clean water. If there are sample residues clinging to the conductivity cell, immerse the conductivity cell in diluted detergent solution for 5 to 10 minutes while moderately stirring the solution.
- Oily samples – Immerse the conductivity cell in warm, diluted detergent solution for 5 to 10 minutes while moderately stirring the solution. Alternatively, wash or wipe the conductivity cell with acetone or ethanol.
- Note: Never soak the plastic-body conductivity cell in organic solvents such as alcohol, acetone etc. because these solutions may damage it. Also, this action will void the warranty.
- Lime or hydroxide-containing samples – Soak the conductivity cell in 1M HCl for 30 minutes. Alternatively, soak the conductivity cell in detergent solution containing 5% household bleach for 30 minutes.
Procedure 1 to 4: Clean the cell by dipping or filling it with the cleaning solution and agitating for two or three minutes.
When a stronger cleaning solution is required, try concentrated 4M HCl . Rinse the cell several times with distilled or deionised water and remeasure the cell constant before use.
Storage
Conductivity cells should be clean before they are stored for any length of time.
- Short-term: Between measurements and overnight, store the conductivity cell in clean water. Before inserting the conductivity cell into the protective cap, place sufficient amount of clean water to cover the metal electrodes. Those conductivity cells without protective cap can be soaked in a beaker containing clean water.
- Long-term: Store the conductivity cell dry. Make sure to perform conditioning before use (See Conditioning).
- Avoid storing the conductivity cell in places with direct sunlight or high temperature and humidity.
Some platinum conductivity cells are coated with platinum black before calibration. This coating is extremely important to cell operation, especially in solutions of high conductivity. Electrodes are platinised to avoid errors due to polarisation. Cells should be inspected periodically. If the black coating appears to be wearing or flaking off the electrode or if the cell constant has changed by 50%, the cell should be cleaned and the electrodes replatinised or replaced.
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