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Electrochemical Reference Electrodes

CARE AND MAINTENANCE INSTRUCTIONS

 Koslow offers several models of reference electrodes. Each reference electrode is individually inspected and tested for adherence to an acceptable range relative to a standard calomel electrode. Most electrodes are configured to work with many of the standard flow cells. Some feature glass-body construction with a porous KT frit at the solution interface. Others are constructed of plastic where glass can’t be tolerated.  The purpose of the reference electrode is to provide a stable, reproducible voltage to which the working (detector) electrode potential may be referenced.  A reference electrode may be considered a small battery whose voltage (potential) is determined by the chemistry taking place between a solid conductor (usually a metal salt) and the electrolytic solution around it. Ideally, if a small current is passed through the electrode, the potential change is negligible, and in any case, returns to the initial value when the current ceases. In addition, the potential value should not vary with time and should be reproducible from electrode to electrode.


SAFE HANDLING OF INSTRUMENTS

  • Like the handling of any chemical, good industrial hygiene practices are imperative
  • Instruments may be hazardous. Caution should be exercised in the instrument use
  • Wear a shop coat or protective clothing. Some solutions can stain or damage clothing
  • Use eye protection or splash resistant goggles
  • Use gloves to prevent unnecessary exposure to skin
  • Work in a well ventilated area
  • Wipe spills quickly. Wash hands after use
  • Only use instruments for industrial or laboratory testing purposes
  • Dispose of instrument contents according to local regulations

·         For complete information, consult the S.D.S. sheet

Version 10.5

Full Name of Reference Electrode

Formula

Chemical Used

Description/Notes

Koslow Series

No.

Compare to:

Mercury/ Mercury Oxide

Hg/HgO

Our standard conc. is 20% KOH

Custom is avail

Mercury (II) oxide, also called mercuric oxide or simply mercury oxide, has a formula of HgO. Safe for use in alkali or fluoride media. All plastic construction.

5088

Lab Battery Probe

Mercury/Mercurous Sulfate

Hg/Hg2SO4

Sat. Potassium Sulfate Solution

The Hg/HgSO4 Reference Electrode is recommended when chloride ion is not desired in the electrolyte.  Has a filling solution of potassium sulfate.

5100P

+410 vs.

SCE

Mercury/Mercurous Sulfate

Hg/HgKO4

Sulfuric Acid

 Mercury-Mercurous sulfate reference electrodes, has been widely used in the past, in order to measure half-cell potentials in lead-acid batteries.

5100A

Lab Probe

Mercury/ Mercury Chloride Or Saturated Calomel

Hg2Cl2

Mercury(I) chloride Sat. KCL Solution

The universal standard reference.  The Saturated Calomel Electrode (SCE) is a reference electrode based on the reaction between elemental mercury and mercury (I) chloride.

1001

-410 vs.

Hg/Hg2SO4

Silver/ Silver Chloride

Ag/AgCl

Silver (I) Chloride Sat. KCL/ AgCI

The silver chloride electrode is the most commonly used reference electrode for testing cathodic protection corrosion control systems in sea water environments. 

1004

-47 vs.

SCE

Silver/ Silver Sulfate

 Ag/Ag2SO4

 Sulfuric acid disilver(I) salt         Saturated potassium sulfate and silver

 A reproducible and stable electrode potential, situated 38.4 mV positive with respect to that of the Hg/Hg2SO4 couple. The preparation and application of a simple silver/silver sulfate reference electrode for an aqueous solution, which can be used as an alternative in chloride-free systems.  

 1003

+38 vs.

Hg/Hg2SO4 

ROTATION

We recommend that three reference electrodes be rotated in your analytical reference electrode system. Place the first electrode into the storage container. In another two weeks, replace the reference electrode with the third reference electrode provided in the kit. By rotating the three reference electrodes provided with your detector on a continuous basis, you can maximize their lifetimes. Depending on the mobile phase conditions and detector use, the reference electrodes can last for a very long time. When you replace reference electrodes, replace all three of them at the same time.


TESTING

Read the potential difference with a voltmeterIf you are concerned about the viability of a particular reference electrode, you can test it using a simple voltmeter, additional reference electrodes of the same type (or a calomel reference electrode), and a small beaker of the same as the filling solution.

 Ideally the difference between two electrodes of the same type would be zero. However, in actual practice there is commonly up to a 5 mV variation. If the two electrodes are of the same type (e.g., Ag/AgCl vs. Ag/AgCl, or calomel vs. calomel) the meter should read 0 ± 20 mV. If your reading for any pair of electrodes is significantly different, you should have another electrode of the same type handy to help distinguish which of the two is bad. When comparing an Ag/AgCl reference electrode to a calomel electrode, make the calomel the black (negative) input on the voltmeter


STORAGE

Electrodes are easily ruined by drying. Keep the tips moist at all times and store in the same as the filling solution when not in use. A reference electrode storage vial is available from Koslow. Be sure that you check the electrodes periodically and replace the solution in the storage vessel with fresh solution to keep the tips wet. Do not entirely immerse. Keep the lead wires and jack pins dry, or they will corrode and contaminate the reference electrode. Reference electrodes will naturally change with use due to the transport of ions and solvent across the junction. The rate of change is a function of the difference in composition between the sample solutions. Storing the reference electrode in solution between experiments will extend its lifetime. In spite of all attempts to extend their lifetimes, reference electrodes are still expendable items, so be certain to have spares on hand as needed.

REPLACING THE FRIT TIP AND REFILLING

  1. The probe tip should be replaced if it is chipped, or if the probe gives unstable readings.
  2. Wear protective eyewear, gloves, and clothing. Electrode refill solution is needed.
  3. Open the filling hole by carefully sliding away the flexible cover.
  4. Using a utility knife or razor, cut off the transparent Teflon sleeve from the probe tip.  This will allow the tip to be discarded.
  5. Gently flick the liquid out through the bottom.
  6. With the probe upside down (lead wire on the bottom) insert a fresh Teflon sleeve over the constricted, narrow part of the body.
  7. Insert a fresh tip. The tip should seat roundly on the edge.  Tip should be clear, white or slightly yellow.  If tip appears amber, brown or black, it is not effective for use. 
  8. Gently heat the plastic tubing with a heat gun to shrink fit it onto the glass. Do not over-heat and melt the plastic! Cool and check that the plastic tubing cannot be rotated or moved.  If tip does move, heat it again until it firmly grasps the glass and the porous disc.
  9. Trim off the excess Teflon with the razor blade. Be sure the glass is cool to the touch before filling solution contacts the glass.
  10. Insert a syringe, or pipette, if supplied, and fill to just below the level of the filling hole.
  11. Shake to dislodge any air bubbles which may be trapped in the small diameter, constricted part (neck) of the electrode body.
  12. A new electrode should be given a few minutes to stabilize.  Check its potential against a second electrode.  They should be within a few Millivolts of each other.  If filling reference electrode with a different concentration of solution, waiting 24 hours might be necessary for a stable reading.
  13. Store electrodes in a cool dark place when not in use.  Fill hole should be covered. Replace protective tip cover.  Air tight packaging is recommended to keep tip from excessive drying. Refill solutions and electrode storage bottles are available from www.Koslow.com.

Koslow Scientific Company

 

172 Walkers Lane

Englewood, NJ 07631 USA

 

 011 (201) 541-9100

 

sales@koslow.com

 

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