Thermo Products REDOX-ORP 9678BNWP User Manual

User Guide

Redox/ORP
Electrodes

Introduction

This user guide contains information on the preparation,
operation and maintenance of the Thermo Scientific Orion ORP
electrodes. These ORP electrodes combine a platinum redox
sensing electrode and a silver/silver chloride reference electrode
in one body.

The redox/ORP electrodes can be used to make direct
measurements of redox potentials or perform potentiometric
titrations. The ORP Triode electrodes have a built-in thermistor
for measuring temperature.

Epoxy Sure-Flow Combination Redox/ORP Electrodes,
Cat. No. 9678BNWP and 967800

The Sure-Flow junction prevents the electrode from clogging in
dirty, viscous or wastewater samples. The epoxy body is break­resistant for rugged environments.

Glass Combination Redox/ORP Electrodes,
Cat. No. 9778BNWP and 9778SC

The glass body enables the electrode to be used in solutions
that contain organic solvents. Use the electrode in water,
wastewater, metal plating and organic solvent samples.

Epoxy Refillable ORP/ATC Triode,
Cat. No. 9180BNMD and 9180BN

The electrode includes a built-in temperature probe for
measuring ORP and temperature with one electrode. The
refillable design allows the electrode filling solution to be
changed in case of contamination or clogging.

Epoxy Low Maintenance ORP/ATC Triode,
Cat. No. 9179BNMD and 9179BN

The electrodes include a built-in temperature probe for
measuring ORP and temperature with one electrode. The
electrodes contain a gel reference solution, so no filling solution
is required.

Note: Redox/ORP electrodes are not designed for constant
current or amperometric titrations, such as Karl Fischer
moisture analysis.

1Redox/ORP Electrode User Guide

Required Equipment

1. Thermo Scientific Orion pH/mV meter, such as the 3-Star
pH meter, 4-Star pH/ISE meter, 4-Star pH/DO meter, 4-Star
pH/conductivity meter or 5-Star pH/ISE/DO/conductivity
meter.

ORP electrodes can be used on any pH/mV meter with a

BNC or U.S. standard connection. The electrodes can also
be used on meters with a variety of inputs when an adapter
cable is used. Visit www.thermo.com/water for details.

Refillable ORP Triodes have temperature connectors that

are compatible with specific meters, refer to the list below.

2. Thermo Scientific Orion ORP electrode.

• The 9180BNMD and 9179BNMD ORP/ATC Triode

electrodes have a temperature connector that is
compatible with the Star Series meters.

• The 9180BN and 9179BN ORP/ATC Triode electrode

have a temperature connector that is compatible with
the A+ Series meters.

3. ORP electrode filling solution. Use Cat. No. 900011
filling solution for samples that have a total ionic strength
greater than 0.2 M. Use Cat. No. 900001 filling solution for
samples that have a total ionic strength less than 0.2 M.

ORP electrode filling solution is not required if using a

9179BNMD or 9179BN low maintenance ORP/ATC Triode

4. ORP standard, Cat. No. 967901 or 967961.

ORP standard is highly recommended to ensure accurate

ORP measurements.

5. Beakers, plastic or glass.

6. Magnetic stirrer or Orion stirrer probe, Cat. No. 096019.
The stirrer probe can be used with 3-Star, 4-Star and 5-Star
benchtop meters.

7. Distilled or deionized water.

2 Redox/ORP Electrode User Guide

Sample Requirements

Electrodes with an epoxy body should only be used in aqueous
solutions.

Electrodes with a glass body may be used in non-aqueous
solutions and solutions that contain organic solvents.

The ORP electrodes contain a silver/silver chloride (Ag/AgCl)
reference that may become clogged in solutions that contain
silver complexing or binding agents such as TRIS, proteins and
sulfides. Frequent cleaning may be required when measuring
solutions that contain these agents. Proteins cause the
additional problem of coating the electrode, so extra care should
be taken to keep the electrode clean while measuring samples
that contain proteins.

3Redox/ORP Electrode User Guide

Electrode Preparation

Electrode Preparation for Refillable Electrodes

1. Remove the protective shipping cap from the sensing
element and save the cap for storage.

2. Clean any salt deposits from the exterior of the electrode by
rinsing with distilled water.

3. Uncover the filling hole by removing the tape and then add
electrode filling solution, Cat. No. 900011, to the electrode.
To maintain an adequate flow rate, the level of filling
solution must always be above the reference junction and
at least one inch above the sample level. The filling hole
should be open whenever the electrode is in use.

4. For Sure-Flow electrode only, wet the junction by pressing
down on the electrode cap to let a few drops of the filling
solution flow out of the electrode and then replenish any
lost solution.

5. Shake the electrode downward (similar to a clinical
thermometer) to remove air bubbles.

6. Connect the electrode to the meter.

Note: The fill hole must be open when the electrode is in use.

Electrode Preparation for Gel-Filled Electrodes

1. Remove the protective shipping cap from the sensing
element and save the cap for storage.

2. Clean any salt deposits from the exterior of the electrode by
rinsing with distilled water.

3. Shake the electrode downward (similar to a clinical
thermometer) to remove air bubbles.

4. Connect the electrode to the meter.

4 Redox/ORP Electrode User Guide

filling hole

Ag/AgCl

internal

reference

filling
solution
chamber

ceramic
reference
junction

sensing
element

Figure 1– Refillable ORP Electrode

filling hole

Ag/AgCl

internal

reference

filling
solution
chamber

ceramic
reference
junction

sensing
element

fill hole

AgAgCl

internal

reference

reference
filling solution
chamber

Sure-Flow
junction

sensing
element

Figure 2– Sure-Flow Refillable ORP Electrode

5Redox/ORP Electrode User Guide