Thermo Scientific 9101BN User manual

Thermo Fisher Scientific
Environmental Instruments
Water Analysis Instruments
166 Cummings Center
Beverly, MA 01915 USA
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Toll Free: 800-225-1480
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www.thermo.com/water
User Guide
Refillable Ag/AgCl
pH Electrodes

1Refillable Ag/AgCl pH Electrode User Guide
Introduction
This user guide contains information on the preparation,
operation and maintenance of the Thermo Scientific Orion
refillable Ag/AgCl (silver/silver chloride) pH electrodes.
All refillable Ag/AgCl pH electrodes have a pH range of 0 to 14
and silver/silver chloride reference system. Refillable Ag/AgCl
electrodes have a pH precision of 0.02 or 0.01. The electrodes
have a temperature range of 0 to 90 °C or 0 to 100 °C.
Refillable Ag/AgCl Electrodes
Refillable Ag/AgCl pH electrodes include a wide selection of
electrode shapes and sizes for measuring a variety of samples.
These reliable electrodes are built for everyday use.
Sure-Flow®Refillable Ag/AgCl Electrodes
Sure-Flow electrodes incorporate a free-flowing junction that is
easy to clean and never clogs. These electrodes are ideal for
dirty or viscous samples that clog traditional electrodes.
PerpHecT®Refillable Ag/AgCl Electrodes
PerpHecT electrodes are designed to be used with PerpHecT
meters to provide both pH and temperature measurements.
The PerpHecT meters use patented LogR technology that
allows temperature to be measured using the resistance of the
PerpHecT electrode.

2Refillable Ag/AgCl pH Electrode User Guide
Cat. No. Description
9101BN /
9101SC
Ag/AgCl pH half-cell electrode with glass
body and BNC connector / screw cap
connector
9102BNWP /
9102SC
Refillable Ag/AgCl combination pH electrode
with glass body and waterproof BNC
connector / screw cap connector
9103BNWP /
9103SC
Refillable Ag/AgCl combination pH electrode
with glass body, semi-micro tip, and
waterproof BNC connector / screw cap
connector
9104BNWP /
9104SC
Refillable Ag/AgCl combination pH electrode
with glass body, rugged bulb, and waterproof
BNC connector / screw cap connector
9156BNWP /
915500 /
9156SC
Refillable Ag/AgCl combination pH electrode
with epoxy body and waterproof BNC
connector / U.S. standard connector / screw
cap connector
9157BNMD Refillable Ag/AgCl pH/ATC Triode with epoxy
body and waterproof BNC and 8 pin MiniDIN
connectors
9157BN Refillable Ag/AgCl pH/ATC Triode with epoxy
body and BNC and 8 pin DIN connectors
9161BN /
9161SC
Ag/AgCl pH half-cell electrode with glass
body, low resistance bulb, and BNC
connector / screw cap connector
9162BNWP /
9162SC
Refillable Ag/AgCl combination pH electrode
with glass body, low resistance bulb, and
waterproof BNC connector / screw cap
connector
9163SC Refillable Ag/AgCl combination pH electrode
with glass body, spear tip and screw cap
connector
9164SC Refillable Ag/AgCl combination pH electrode
with glass body, 14/15 standard taper and
screw cap connector
9165BNWP Sure-Flow refillable Ag/AgCl combination pH
electrode with epoxy body and waterproof
BNC connector
9166SC Refillable Ag/AgCl combination pH electrode
with glass body, sleeve junction and screw
cap connector

3Refillable Ag/AgCl pH Electrode User Guide
Cat. No. Description
9167SC Refillable Ag/AgCl combination pH electrode
with glass body, semi-micro and flat surface
tip, and screw cap connector
9172BNWP Sure-Flow refillable Ag/AgCl combination pH
electrode with glass body and waterproof BNC
connector
9202BN PerpHecT refillable Ag/AgCl combination pH
electrode with glass body and BNC connector
9203BN PerpHecT refillable Ag/AgCl combination pH
electrode with glass body, semi-micro tip and
BNC connector
9256BN PerpHecT refillable Ag/AgCl combination pH
electrode with epoxy body and BNC connector
9272BN PerpHecT Sure-Flow refillable Ag/AgCl
combination pH electrode with glass body and
BNC connector
• All electrodes with a waterproof BNC, BNC and U.S.
standard connector have one meter cable lengths.
• All electrodes with a screw cap connector require a
separate cable.
• Electrodes with a waterproof BNC connector can be used
on any pH meter with a BNC connection.
• The 9101BN / 9101SC and 9161BN / 9161SC pH half-cell
electrodes can be used with the 900100 single junction
reference electrode or 900200 double junction reference
electrode.

4Refillable Ag/AgCl pH Electrode User Guide
Required Equipment
1. Thermo Scientific Orion pH 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.
Refillable Ag/AgCl pH electrodes can be used on any
pH 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 Ag/AgCl Triodes have temperature connectors that
are compatible with specific meters, refer to the list below.
2. Thermo Scientific Orion refillable Ag/AgCl pH electrode.
• The 9157BNMD pH/ATC Triode has a temperature
connector that is compatible with the Star Series
pH meters.
• The 9157BN pH/ATC Triode has a temperature connector
that is compatible with the A+ Series meters.
3. Ag/AgCl electrode filling solution, Cat. No. 900011.
4. pH electrode storage solution, Cat. No. 910001.
5. pH buffers, at least two pH buffers are recommended for
precise measurements. One buffer should be near pH 7
and buffers should be one to three pH units apart.
6. Beakers, plastic or glass.
7. 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.
8. Distilled or deionized water.

5Refillable Ag/AgCl pH 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. A
minimum of 20% water must be present in the sample for the
best measurement results. Visit www.thermo.com/water to
download Dr. Martin S. Frant’s article “How to Measure pH in
Mixed and Nonaqueous Solutions” and for additional information
on non-aqueous pH measurements.
The refillable Ag/AgCl 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 sensing bulb, so extra care
should be taken to keep the electrode clean while measuring
samples that contain proteins.

6Refillable Ag/AgCl pH Electrode User Guide
Electrode Preparation
Electrode Preparation for Non-Sure-Flow®Models
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. Place the electrode in an electrode holder and suspend
the electrode in air for 5 minutes to thoroughly wet the
reference junction.
5. Shake the electrode downward (similar to a clinical
thermometer) to remove air bubbles.
6. Soak electrode in pH electrode storage solution, Cat. No.
910001, for 30 to 60 minutes.
7. Connect the electrode to the meter.
filling hole
Ag/AgCl
internal
reference
filling
solution
chamber
ceramic
reference
junction
pH
sensing
bulb
fill hole
AgAgCl
internal
reference
reference
filling solution
chamber
Sure-Flow
junction
pH
sensing bulb
Refillable Ag/AgCl Combination pH Electrode

7Refillable Ag/AgCl pH Electrode User Guide
Electrode Preparation for Sure-Flow®Models
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. 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. Soak electrode in pH electrode storage solution, Cat. No.
910001, for 30 to 60 minutes.
7. Connect the electrode to the meter.
filling hole
Ag/AgCl
internal
reference
filling
solution
chamber
ceramic
reference
junction
pH
sensing
bulb
fill hole
AgAgCl
internal
reference
reference
filling solution
chamber
Sure-Flow
junction
pH
sensing bulb
Sure-Flow Refillable Ag/AgCl Combination pH Electrode

8Refillable Ag/AgCl pH Electrode User Guide
Measuring Hints
• Always use fresh buffers for calibration. Choose buffers
that are one to three pH units apart.
• Check the electrode slope daily by performing a two buffer
calibration. The slope should be 92 to 102%.
• Remove the filling hole cover during measurements to
ensure a uniform flow of filling solution.
• Between measurements, rinse electrodes with distilled
water and then with the next solution to be measured.
• Stir all buffers and samples at a uniform rate.
• Place a piece of insulating material, such as Styrofoam or
cardboard, between the magnetic stirrer and beaker to
prevent measurement errors from the transfer of heat to
the sample.
• To reduce the chance of error due to polarization, avoid
rubbing or wiping the electrode bulb. Use a lint-free tissue
and gently blot the electrode bulb.
• If the electrode is used in dirty or viscous samples or the
electrode response becomes sluggish, empty the electrode
completely and hold the junction under running water.
Empty any water from the electrode and refill it with fresh
electrode filling solution.
• If a Sure-Flow electrode is used in dirty or viscous samples
or the electrode response becomes sluggish, empty the
electrode completely and hold the junction open under
running water. Empty any water from the electrode and
refill it with fresh electrode filling solution. Press 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.
• Flat surface electrodes may be used on any moist surface
or in liquids.

9Refillable Ag/AgCl pH Electrode User Guide
Filling hole should
be uncovered
Fresh pH buffer
Stir all samples
and buffers
Filling solution level
must be higher than
sample level
Reference junction
must be immersed
Place insulation
between stirrer
and beaker
Measuring Hints
Using a Flat Surface Electrode

10 Refillable Ag/AgCl pH Electrode User Guide
Electrode Calibration
General Calibration Procedure
For detailed instructions on pH calibration, manual pH calibration
and temperature compensation, consult your meter user guide.
When using PerpHecT electrodes with a PerpHecT pH meter,
refer to the PerpHecT meter user guide for instructions on
temperature calibration and LogR temperature compensated
pH measurements.
One Buffer Calibration
1. Choose a buffer near expected sample pH.
2. The buffer should be at same temperature as the sample.
If the buffer and samples are at varying temperatures,
temperature compensation is recommended.
3. Prepare the meter according to the meter user guide.
4. Rinse the electrode first with distilled water and then with
the buffer being used for calibration.
5. Place the electrode into the buffer. When the reading is
stable, set the meter to the pH value of the buffer at the
measured temperature. Refer to the meter user guide for a
detailed procedure. Table 1 provides pH values at
various temperatures.
6. Proceed to the pH Measurement section.
Table 1
pH Values of Buffers at VariousTemperatures
Nominal
Buffer Value
at 25°C
Temperature
0 ° 5 ° 10 ° 20 ° 30 °
1.68 1.67 1.67 1.67 1.67 1.68
3.78 3.86 3.84 3.82 3.79 3.77
4.01 4.00 4.00 4.00 4.00 4.02
6.86 6.98 6.95 6.92 6.87 6.85
7.00 7.11 7.08 7.06 7.01 6.98
7.41 7.53 7.50 7.47 7.43 7.40
9.18 9.46 9.40 9.33 9.23 9.14
10.01 10.32 10.25 10.18 10.06 9.97

11Refillable Ag/AgCl pH Electrode User Guide
Two Buffer Calibration
This procedure is recommended for precise measurements.
1. Select two buffers that bracket the expected sample pH.
The first buffer should be near the electrode isopotential
point (pH 7) and the second should be near the expected
sample pH (pH 4 or pH 10).
2. The buffers should be at same temperature as the sample.
If the buffers and samples are at varying temperatures,
temperature compensation is recommended.
3. Rinse the electrode first with distilled water and then with
the first buffer.
4. Place the electrode into the first buffer. When the reading
is stable, set the meter to the pH value of the buffer at the
measured temperature. Refer to the meter user guide for
a detailed procedure. Table 1 provides pH values at
various temperatures.
5. Rinse the electrode first with distilled water and then with
the second buffer.
6. Place the electrode into the second buffer. When the
reading is stable, set the meter to the pH value of the
buffer at the measured temperature. Refer to the meter
user guide for a detailed procedure. Table 1 provides pH
values at various temperatures.
7. Proceed to the pH Measurement section.
Temperature
40 ° 50 ° 60 ° 70 ° 80 ° 90 °
1.69 1.71 1.72 1.74 1.77 1.79
3.75 3.75
4.04 4.06 4.09 4.13 4.16 4.21
6.84 6.83 6.84 6.85 6.86 6.88
6.97 6.97 6.97 6.99 7.03 7.08
7.38 7.37
9.07 9.01 8.96 8.92 8.89 8.85
9.89 9.83

12 Refillable Ag/AgCl pH Electrode User Guide
pH Measurement
1. Calibrate the electrode as described in the Electrode
Calibration section.
2. Rinse the electrode with distilled water and then with
the sample.
3. Place the electrode into the sample.
4. When the reading is stable, record the pH and temperature
of the sample.
Electrode Storage
To ensure a quick response and free-flowing junction, the
sensing element and reference junction must not dry out.
Short-term Storage (up to one week)
Soak the electrode in pH electrode storage solution,
Cat. No. 910001. To prevent crystallization of the fill solution,
cover the fill hole whenever the electrode is being stored and
open the fill hole when calibrating and measuring.
Long-term Storage (more than one week)
Fill the reference chamber and securely cover the filling hole.
Cover the sensing element and reference junction with the
protective cap/sleeve containing a few drops of storage
solution. Before returning the electrode to use, prepare it as
a new electrode.
Electrode Maintenance
1. Inspect the electrode for scratches, cracks, salt crystal
buildup, or membrane/junction deposits.
2. Rinse off any salt buildup with distilled water. Remove any
membrane/junction deposits as directed in the General
Cleaning section.
3. Drain the reference chamber, flush it with fresh filling
solution and refill the chamber with fresh filling solution.

13Refillable Ag/AgCl pH Electrode User Guide
Electrode Cleaning Procedures
General Cleaning
1. Soak the electrode in 0.1 M HCl or HNO3for half an hour.
The electrode can also be soaked for 15 minutes in a 1:10
dilution of household laundry bleach or a 0.1 to 0.5% liquid
detergent solution mixed with hot water. The solution
should be stirred at a moderate to fast rate.
2. Drain the reference chamber and refill it with fresh filling
solution.
3. Soak the electrode in pH electrode storage solution for at
least one hour.
Cleaning Solutions
Cat. No. 900021– pH cleaning solution A for removing protein
contaminants.
Cat. No. 900022– pH cleaning solution B for removing bacterial
contaminants.
Cat. No. 900023– pH cleaning solution C for general cleaning.
Cat. No. 900024– pH cleaning solution D for removing oil and
grease contaminants.
Cat. No. 900020– pH cleaning solution kit, includes cleaning
solutions A, B, C and D.

14 Refillable Ag/AgCl pH Electrode User Guide
Electrode Characteristics
Temperature Effects
The most common cause of error in pH measurements is
temperature. There are at least five ways that temperature
variations can affect pH: electrode slope, buffers, samples,
reference element drift and temperature sensor errors.
Electrode Slope Changes
The electrode slope will change with variations in temperature.
Slope changes may be compensated manually, automatically
with an automatic temperature compensation (ATC) probe
or with LogR technology when using a PerpHecT meter and
electrode. Thermo Scientific Orion pH meters calculate the
slope based on the measured temperature and automatically
adjust the pH value based on the temperature.
Buffer and Sample pH Changes
Buffer and sample pH values change with temperature because
of their temperature dependent chemical equilibria. The pH
electrode should be calibrated with buffers that have known
pH values at different temperatures. Buffer values at different
temperatures are given in Table 1. Thermo Scientific Orion
pH meters automatically calibrate with the correct pH buffer
values based on the measured temperature. All pH meters are
unable to correct pH values back to a reference temperature
because every sample has a unique pH value vs. temperature
relationship. Therefore, calibration and measurements should
be performed at the same temperature and pH values should be
reported with temperature.
Reference Element Drift
Drift can occur when the internal reference elements inside the
pH and reference portions of the electrode are reaching thermal
equilibrium after a temperature change. Long-term drift or slow
response can last until the sample and electrode are at the
same temperature.

15Refillable Ag/AgCl pH Electrode User Guide
Temperature Sensor Errors
When a pH and temperature probe are placed into a sample
that varies significantly in temperature, the readings can
drift for two reasons. First, the temperature response of the
electrode and temperature probe may not be similar, which
prolongs equilibration and drift. Second, a sample may not
have a uniform temperature. Therefore, the pH electrode and
temperature probe are responding to different environments.
Using LogR technology, PerpHecT meters sense the
temperature directly from the PerpHecT pH electrodes. The pH
and temperature response is identical and both measurements
occur at the sensing bulb. Drift is minimized and errors due to
environmental differences are eliminated.
Sure-Flow®Electrode Leak Rate
The junction of the Sure-Flow electrodes has been designed
to leak at a rate of approximately 1 mL per 24 hours. To keep
the junction from clogging, the leak rate is slightly higher than
conventional electrodes. During the average pH measurement
time the loss of filling solution is minimal and the filling solution
does not contaminate the sample.

16 Refillable Ag/AgCl pH Electrode User Guide
PerpHecT®Electrode Operation with
PerpHecT®pH Meters
When PerpHecT electrodes are used with a PerpHecT pH meter,
enhanced temperature compensation is achieved without the
need of a separate ATC probe. Using LogR technology, the
temperature of the solution is measured through the resistance
of the pH electrode. PerpHecT pH electrodes are manufactured
to meet the PerpHecT meter specifications, so optimum
performance and accuracy are achieved in LogR mode.
Each PerpHecT pH electrode must be calibrated for temperature
before a pH measurement is performed using LogR technology.
Refer to the PerpHecT meter user guide for details. For
maximum precision, a three point temperature calibration
is recommended. Do not perform a one point temperature
calibration if measured solutions will be below 20 °C. The
following tables illustrate the expected pH compensation error
for one, two and three point temperature calibrations. The
accuracy values are valid only when the temperature calibration
is performed within the stated temperature range. The higher
temperature range data will apply to measurements made
above that temperature range, provided that calibration points
are within 20 °C of each other. When highly accurate pH results
are desired, a separate ATC probe is recommended.
One Point Temperature Calibration
Electrode
Average
temp. error
20-30 °C
Average
temp. error
30-50 °C
Average
pH error
20-30 °C
Average
pH error
30-50 °C
9202BN 0.26 0.17 0.003 0.002
9203BN 0.12 0.21 0.001 0.003
9256BN 0.22 0.12 0.003 0.001
9272BN 0.08 0.11 0.001 0.001
Two Point Temperature Calibration
Electrode
Average
temp. error
0-25 °C
Average
temp. error
20-40 °C
Average
pH error
0-25 °C
Average
pH error
20-40 °C
9202BN 0.21 0.06 0.003 0.001
9203BN 0.20 0.10 0.002 0.001
9256BN 0.27 0.07 0.003 0.001
9272BN 0.22 0.06 0.003 0.001
Three Point Temperature Calibration
Electrode
Average
temp. error
0-25 °C
Average
temp. error
20-40 °C
Average. pH
error
0-25 °C
Average. pH
error
20-40 °C
9202BN 0.02 0.04 0.000 0.000
9203BN 0.03 0.06 0.000 0.001
9256BN 0.07 0.07 0.001 0.001
9272BN 0.02 0.00 0.000 0.000

17Refillable Ag/AgCl pH Electrode User Guide
Interferences
Sodium ions are the principal interference of the pH electrode
and cause increasing error at higher pH (lower hydrogen
ion activities) and at higher temperatures. Because the pH
membrane is composed of special low sodium error glass, error
due to sodium is negligible when measuring at pH values less
than 12. When measuring at pH values greater than 12, add the
correction value from the nomograph below to the observed
pH reading.
10
11
12
13
80
70
60
50
40
30
°C 20 0.1 M
25 0.5 M
1 M
2 M
5 M
5 M
0.5 M
0.1 M
1 M
2 M
20°C
25
30
40
50
60
70
80
0.70
0.60
0.50
0.40
0.30
0.25
0.20
0.15
0.10
0.08
0.06
0.05
0.04
0.03
0.02
0.01
0.005
pH correction
to be added
Sample
pH reading
sample
sodium
concentration
Typical Sodium Error
Example:
pH reading 12.10
Sodium concentration 0.5 M
Temperature 50 °C
Correction 0.01
Corrected pH reading 12.11

18 Refillable Ag/AgCl pH Electrode User Guide
Troubleshooting
Follow a systematic procedure to isolate the problem. The pH
measuring system can be divided into four components for ease
in troubleshooting: pH meter, electrode, sample/application
and technique.
pH Meter
The meter is the easiest component to eliminate as a possible
cause of error. Thermo Scientific Orion pH meters include
an instrument checkout procedure and shorting cap for
convenience in troubleshooting. Consult the pH meter user
guide for directions.
Electrode
To test electrode operation:
1. Connect the electrode to a working meter that has a mV
measuring mode.
2. Set the meter to the mV measuring mode.
3. Rinse the electrode with distilled water and then insert the
electrode into fresh pH 7 buffer.
4. When the reading is stable, record the mV value of the
pH 7 buffer. The mV value should be -30 to +30 mV.
5. Rinse the electrode with distilled water and then insert the
electrode into fresh pH 4 buffer.
6. When the reading is stable, record the mV value of the
pH 4 buffer. The mV value should be +150 to +210 mV.
7. Calculate the absolute mV difference between the two
buffers. The mV difference should be 160 to 180 mV. The
actual mV values will change as the electrode ages, but the
mV difference between the two buffers should always be
160 to 180 mV.
If the electrode fails this procedure, clean the electrode
thoroughly as directed in the Electrode Maintenance section.
If the electrode response is slow or drifting, drain and refill the
electrode with fresh filling solution, Cat. No. 900011. Replace
the electrode if cleaning and maintenance fail to rejuvenate it.