Amersham Pharmacia Biotech AKTA design pH/C-900 User manual

User Manual
18-1120-06
Monitor pH/C-900
18-1120-06_AC.qxd 1999-04-14 14:16 Sida 1 (1,1)

Trademarks
ÄKTA and UNICORN are trademarks of Amersham
Pharmacia Biotech Limited or its subsidiaries.
Amersham is a trademark of Nycomed Amersham plc.
Pharmacia and Drop Design are trademarks of
Pharmacia & Upjohn Inc.
Terms and Conditions of Sale
All goods and services are sold subject to the terms
and conditions of sale of the company within the
Amersham Pharmacia Biotech group which supplies
them. A copy of these terms and conditions of sale is
available on request.
Addresses
Amersham Pharmacia Biotech AB
SE-751 84 Uppsala
Sweden
Amersham Pharmacia Biotech UK Limited
Amersham Place
Little Chalfont
Bucks, HP7 9NA
England
Amersham Pharmacia Biotech Inc
800 Centennial Avenue
PO Box 1327
Piscataway, NJ 08855
USA
Amersham Pharmacia Biotech Europe GmbH
Postfach 5480
D-79021 Freiburg
Germany
©Amersham Pharmacia Biotech AB 1999
– All rights reserved
Important user information
Meaning: Consult the instruction manual to avoid
personal injury or damage to the product or other
equipment.
WARNING!
The Warning sign is used to call attention to the
necessity to follow an instruction in detail to avoid
personal injury. Be sure not to proceed until the
instructions are clearly understood and all stated
conditions are met.
CAUTION!
The Caution sign is used to call attention to
instructions or conditions that shall be followed to
avoid damage to the product or other equipment. Be
sure not to proceed until the instructions are clearly
understood and all stated conditions are met.
Note
The Note sign is used to indicate information
important for trouble-free or optimal use of the
product.
Should you have any comments on this instruction, we
will be pleased to receive them at:
Amersham Pharmacia Biotech AB
SE–751 84 Uppsala
Sweden
!
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Contents
1 Introduction
1.1 General ..................................................................................................................1
1.2 Safety.....................................................................................................................1
2 Installation
2.1 Unpacking..............................................................................................................2
2.2 General precautions ...............................................................................................2
2.3 Installing the conductivity cell ...............................................................................2
2.4 Installing the pH electrode.....................................................................................3
2.5 Connecting electrical signal cables .........................................................................4
2.6 Connecting to communication link........................................................................4
2.7 Connecting to supply voltage.................................................................................5
2.8 Preparing the instrument for use............................................................................5
3 Operation
3.1 On/off....................................................................................................................6
3.2 Menu selection and settings ...................................................................................6
3.3 Main menu overview .............................................................................................7
3.4 Reading pH and conductivity values......................................................................8
3.5 Setting conductivity scale.......................................................................................8
3.6 Calibrating pH.......................................................................................................9
3.7 Calibrating conductivity ......................................................................................11
3.8 Using an external chart recorder..........................................................................11
3.9 Storage and shut-down ........................................................................................12
3.10 Restart after power failure...................................................................................12
4 Maintenance
4.1 Periodic maintenance ...........................................................................................13
4.2 Cleaning-in-place .................................................................................................13
4.3 Cleaning and checking the pH electrode..............................................................13
4.4 Changing pH electrode ........................................................................................14
4.5 Cleaning the conductivity flow cell......................................................................14
4.6 Changing conductivity flow cells .........................................................................14
4.7 Instrument housing ..............................................................................................14
5 Trouble shooting
5.1 General ................................................................................................................15
5.2 Faults and actions................................................................................................15
5.3 Error messages.....................................................................................................18
Monitor pH/C-900
User Manual 18-1120-06 Edition AC i
Contents
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Reference information
A Description ..........................................................................................................19
A.1 Instrument.................................................................................................19
A.2 pH electrode..............................................................................................20
A.3 Conductivity cell .......................................................................................20
B Menus..................................................................................................................21
B.1 Check menu ..............................................................................................21
B.1.1 Check Monitor Cell and Electrode ...........................................21
B.1.2 Check Service Mode .................................................................21
B.2 Setup menu ...............................................................................................21
B.2.1 Setting up conductivity temperature compensation...................21
B.2.2 Calibrating the conductivity cell ...............................................22
B.2.3 Entering the conductivity cell constant .....................................23
B.2.4 Setting up pH temperature compensation.................................24
B.2.5 Setting up the pH display..........................................................24
B.2.6 Calibrating the temperature sensor...........................................24
B.2.7 Setting up the temperature display............................................25
B.2.8 Selecting language.....................................................................25
B.2.9 Setup unit number ....................................................................25
B.2.10 Setup display angle ...................................................................25
B.3 Setting and using the alarm timer..............................................................26
B.4 Service displays .........................................................................................26
B.5 Menu overview .........................................................................................27
C Technical specifications .......................................................................................28
D Accessories and spare parts..................................................................................31
Short instructions on back page
About this manual
This manual comprises two parts; a practical part (sections 1 – 5)
and a reference part (sections A – D).
Sections 1 – 5 contain the necessary information for operating the
instrument.
Monitor pH/C-900
User Manual 18-1120-06 Edition AC
ii
Contents
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1 Introduction
1.1 General
Monitor pH/C-900 is a high precision on-line monitor for
measurement of pH and conductivity in liquid chromatography.
The pH/C-900 features:
• Fast response
• High accuracy and reproducibility
• Flow cells with low dead volume
• Accurate and reliable monitoring through self-test and
self–calibration
• Flow cells can be connected close together, minimizing band
broadening and time delay between detectors.
1.2 Safety
• The instrument is designed for indoor use only.
• Do not use in a dusty atmosphere or close to spraying water.
• Operate in accordance with local safety instructions.
pH/C-900
Monitor pH/C-900
User Manual 18-1120-06 Edition AC 1
WARNING! The instrument must not be opened by the user. It
contains high voltage circuits which can be capable of delivering a
lethal electric shock.
WARNING! Always disconnect the power supply before
attempting to replace any item on the instrument during
maintenance.
WARNING! The instrument must be connected to a grounded
mains socket.
Introduction 1
WARNING! When using hazardous chemicals, all suitable
protective measures, such as protective glasses, must be taken.
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2 Installation
2.1 Unpacking
Unpack the instrument and check the items against the supplied
packing list. Inspect the items for obvious damage which may have
occurred during transportation.
It is recommended that all packing materials should be retained if
onward transport of the instrument is expected.
2.2 General precautions
The instrument should be located in a place of low temperature
variations, away from heat sources, draughts and direct sunlight.
The instrument may be operated at normal ambient temperatures in
the range +4 to 40 °C.
The instrument should be installed on a stable laboratory bench or
in ÄKTA™ explorer or ÄKTA™ purifier. To ensure correct
ventilation a free space of 0.1 m is required behind and in front of
the instrument. Do not use any soft material under the instrument,
to ensure that the ventilation inlet in the front is not blocked.
2.3 Installing the conductivity cell
1 Place the conductivity cell in a suitable
place, for example on the shelf of the
Monitor UV-900 using the clip provided
with the UV monitor. The cell can be
placed up to 1.5 m from the monitor
housing.
2 Connect the conductivity cell to the socket
Conductivity Flow Cell on the rear panel of
the instrument.
3 Connect the tubing with the “Fingertight” connectors. The flow
cell itself does not have a recommended flow direction. In
conjunction with the pH electrode, place the conductivity flow
cell and select its flow direction so that the screw head end of the
flow cell faces the pH flow cell (in ÄKTApurifier systems, the pH
electrode is optional).
CAUTION! The following information should be read carefully
to ensure that the instrument is installed correctly.
Monitor pH/C-900
User Manual 18-1120-06 Edition AC
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2 Installation
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2.4 Installing the pH electrode (optional in ÄKTApurifier systems)
Mounting the flow cell holder
1 Hook the flow cell holder on the right hand
side of the housing. Secure it with the slide
clamp.
If the flow cell holder is not used, the flow
cell must still be installed at an angle of 30°
from the vertical with the outlet placed
higher than the inlet to prevent air bubbles
being trapped in the cell.
The flow direction is marked on the flow cell.
2 Connect the tubing with the “Fingertight” connectors.
Inserting the pH electrode
Note: Handle the pH electrode with care.
1 Unpack the pH electrode. Ensure that it is not broken or dry.
2 Prior to first using the electrode, remove the electrode end cover
and immerse the glass bulb in buffer for 30 minutes.
3 Remove the dummy electrode from the
flow cell and store it in the flow cell
holder.
4 Carefully insert the electrode in the
flow cell. Tighten the nut by hand to
secure the electrode.
Note: If the electrode is not fully
inserted, the system will leak and a
dead volume will occur in the holder.
5 Connect the pH electrode cable to the
rear of the instrument to the socket pH
Probe.
CAUTION! The tip of the pH electrode consists of a thin glass
membrane. Protect it from breakage, contamination and drying
out or the electrode will be destroyed. Always store the electrode
with the end cover filled with a 1:1 mixture of pH 4 buffer and
1 M KNO3. Do NOT store in water only.
Monitor pH/C-900
User Manual 18-1120-06 Edition AC 3
Installation 2
End
cover
To instrument
rear
”pH Probe”
Electrode
Flow direction
Dummy
Flow cell
holder Flow cell
Nut
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2.5 Connecting electrical signal cables
The sockets for electrical signals are located on the rear panel.
Connecting to chart recorder (if used)
The external chart recorder outputs for pH and conductivity from
the monitor are 0 – 1 V. There is also a 4 – 20 mA signal available
at the same output connectors.
1 Connect the chart recorder to the DIN-socket pH or Cond using
the cable supplied:
a. For 0 - 1 V use wire 1 (+) and 2 (–). Use a recorder with
floating inputs (i.e. none of the inputs connected to ground).
b. For 4 - 20 mA use wire 5 (+) and wire 6 (–).
Note: The signal cable is delivered with protective covers on each
wire. Do not remove the protective covers from unused
connections as a short circuit may disturb the measurements.
2 Set the recorder to 0–1 V or 4 - 20 mA input, full scale.
2.6 Connecting to communication link
The monitor can be used in ÄKTAexplorer and ÄKTApurifier, and
can be controlled from a PC running UNICORN™ version 2.20 or
higher, using UniNet cables.
Connect two UniNet cables to the UniNet 1 connectors. The
instrument can be connected in series anywhere between the PC and
a termination plug. The UniNet 1 link connects, in series, the PC
with Pump P-900, Monitor pH/C-900, Monitor UV-900 and the
Frac-900. The termination plug is connected to the last instrument in
the chain.
Analogue out 0-1V
UniNet 1 Mains On/off
pH Cond
Conductivity
Flow Cell
pH
Probe
pH
Ground
Monitor pH/C-900
User Manual 18-1120-06 Edition AC
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2 Installation
CAUTION! The mains power to ÄKTApurifier must be switched
OFF before connecting the instrument to the UniNet 1 link.
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2.7 Connecting to supply voltage
1 Make sure the on/off switch is in the OFF-position (O).
2 Connect the supplied mains cable between the instrument and a
grounded mains socket. Any voltage 100–240 V AC, 50–60 Hz
can be used.
The instrument contains no user replaceable fuse.
2.8 Preparing the instrument for use
Before the instrument is ready to use:
• Set the conductivity cell constant, see section B.2.3.
• Calibrate the temperature sensor, see section B.2.6.
• Calibrate the pH electrode (optional in ÄKTApurifier), see
section 3.6.
Note: The conductivity cell constant is shown on the packaging.
Retain the packaging in case the conductivity cell constant needs to
be re-entered.
Note: The measured temperature is the temperature in the
conductivity flow cell, which can differ from the ambient
temperature, in ÄKTAexplorer systems.
Note: When running chromatography using organic solvents, it is
recommended that the pH electrode is removed and the dummy
electrode inserted in its place, as organic solvents will cause pH
electrode degeneration.
Before performing these procedures you are recommended to read
sections 3.1–3.3.
Monitor pH/C-900
User Manual 18-1120-06 Edition AC 5
Installation 2
WARNING! The instrument must be connected to a grounded
mains socket.
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Monitor pH/C-900
User Manual 18-1120-06 Edition AC
6
3 Operation
3 Operation
3.1 On/off
Switch on the instrument at the mains switch on the rear panel.
At switch on, the instrument performs a selftest and then starts
calibration. After approx. 30 seconds the display shows
Cond Temp pH and the instrument is ready to use. All parameters
are factory set to default values.
If the conductivity cell is not connected the Temp and Cond fields are
blank. The pH field is blank if Show pH is set to off.
The monitor can be used immediately but the full specifications are
not obtained until after a 1 hour warm–up.
3.2 Menu selection and settings
Moving between menus
A specific menu is selected by turning the front selection dial
clockwise or counterclockwise. When the required menu is visible
the menu or selection is accepted by pressing the OK-button.
Menu selection OK-button ESC-button
Select sub-menu Return one menu level
If a menu has sub levels, the sub menu is displayed by pressing the
OK-button. Pressing the ESC-button moves back one menu level.
Calibrating
Please wait...
Selftest
Please wait...
Cond Temp pH
25.4% 22.9°C 11.50
Main menu 1
Main menu 2
Main menu 3
Main menu 4
Main menu 5
Main menus Sub menus Sub menus
Sub menu 2.3.1
Sub menu 2.3.2
Sub menu 2.1
Sub menu 2.2
Sub menu 2.3
Sub menu 2 .1.1
ESC
OK
ESC
OK
ESC
OK
Monitor pH/C900
V1.00
Calibration OK
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Return to main menu
Pressing ESC repeatedly, always returns to the main menu 1 which is
the main operating menu.
Select value
A cursor below a text or numerical value shows what is affected by
the dial. To increase the value turn the dial clockwise. To decrease
the value turn the dial counterclockwise. The value can be reset by
turning the dial several clicks counterclockwise.
When setting numerical values the cursor moves up to the next digit
if the dial is turned quickly in one direction (22.0), to simplify
entering large values. The cursor moves back one place to the right
every two seconds if the dial is not turned. The text or numerical
value displayed is accepted by pressing the OK-button. To cancel,
press the ESC-button.
3.3 Main menu overview
Monitor pH/C-900
User Manual 18-1120-06 Edition AC 7
Set Cond Scale 100%
(50.00mS/cm)
Calibrate pH
(7.00–10.00)
Set pH Analogue Out
Check
Alarm/Timer 00:30:52
Setup
Cond Temp pH
25.4% 22.9°C 11.50
4.000 mS/cm 22.9°C
––– 25.4%
Main operating menu. The menu is accessed from all positions by
pressing the ESC-button repeatedly.
Alternative display of conductivity with horizontal bar graph.
Setting conductivity full scale.
Calibration of pH monitor.
Setting the recorder output for the pH measurement.
Check internal operating values. See Reference information section
B.1.
Setup conductivity, pH, temp., language, etc. See Reference
information section B.2.
Set different timer options. See Reference information section B.3.
Main menu 1
Main menu 2
ESC ESC ESC ESC
Setup Cond ref temp
(20.0°C) 22.0
Parameter
Current value New value to be set
Set Cond Scale 0%
(1.000mS/cm) Setting conductivity zero point.
Operation 3
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Monitor pH/C-900
User Manual 18-1120-06 Edition AC
8
3 Operation
3.4 Reading pH and conductivity values
The main operating menu shows the conductivity as a percentage of
full scale together with the current temperature in the flow cell, and
the pH value. If the pH value is not stable or is changing, an asterisk
is displayed after the value, e.g. 4.02*. The menu is reached from
any other menu by pressing the ESC-button repeatedly.
If temperature compensation is switched-on, the display will show
CondTc instead of Cond, see menu Setup conductivity temperature
compensation in section B.2.1 of Reference information.
By turning the dial one click clockwise, an alternative display of the
conductivity is shown. This display shows the actual conductivity
value in mS/cm together with the percentage value and as a
horizontal bar graph with 10% resolution. If temperature
compensation is switched on, Tc is shown in the display.
The display of pH and temperature can be disabled, see menu Setup
pH display in section B.2.5 and Setup temperature display in section
B.2.7 of Reference information.
3.5 Setting conductivity scale
The monitor measures conductivity over the complete working
range. No range settings are required. However, to obtain a usable
output signal for a recorder, or to view the conductivity as a
percentage of buffer B, it is possible to set a 0 to 100% range. This
can be done with reference to the buffers used or by selecting any
fixed range between 0 µS/cm and 999.9 mS/cm.
To set the scale with reference to the buffers do as follows:
1 Start the flow with the high conductivity buffer. Select main
menu Set Cond Scale 100%, press OK.
2 When the conductivity level has stabilized, set the value which
should correspond to 100% by pressing OK. If required, the value
can be changed with the setting dial.
3 Change to the low conductivity buffer. Select main menu Set
Cond Scale 0%, press OK.
4 When the conductivity level has stabilized, set the value which
should correspond to 0% by pressing OK. If required, the value
can be changed with the setting dial.
The scale can be set without pumping buffer through the cell. Follow
the same procedure, and simply set the the conductivity values
directly at points 2 and 4, ignoring the measured conductivity values
displayed. The difference between the value for 100% and 0% value
(span) must be at least 1 mS/cm. The settings remain until they are
changed. Values above 150% are shown as 150%, values below 0%
as 0%.
Cond Temp pH
25.4% 22.9°C 11.50
Tc 4.000mS/cm 22.9°C
––– 25.4%
Set Cond Scale 100%
(50.00mS/cm)
Set Cond Scale 0%
(1.000mS/cm)
or
Bar graph
CondTc Temp pH
25.4% 22.9°C 11.50
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3.6 Calibrating pH (optional in ÄKTApurifier systems)
A good laboratory routine is to calibrate the instrument once a day,
when the electrode is replaced and if the ambient temperature is
changed. The pH monitor is calibrated using standard buffer
solutions in a two point calibration. The two buffer solutions can
have any pH value as long as the difference between them is at least
1 pH unit. Calibration can also be performed from UNICORN. In
UNICORN select System Control:System:Calibrate. Select the pH
monitor. The calibration procedure can be done with the pH
electrode either fitted in or removed from the flow cell.
Calibrating with the electrode outside the flow cell
When calibrating the electrode out of the flow cell and changing
from one buffer to another, rinse the electrode tip with distilled
water and dab it carefully with a soft tissue to absorb the remaining
water. Do NOT wipe the electrode as this may charge it and give
unstable readings.
The steps below describe the procedure used with the electrode
removed from the flow cell.
Note: The Monitor must be unlocked if connected to a UNICORN
control system.
1 Remove the pH electrode from the flow cell and immerse the
electrode in the 1:st standard buffer solution (normally pH 7.0).
2 Select main menu Calibrate pH. The display shows the current
low and high calibrated pH value. Press OK.
3 Select sub menu Calib pH Buffer 1, press OK. When the pH value
has stabilized, the Please wait message will disappear.
4 Adjust the pH value in the display using the dial, so that it
corresponds to the known pH value of the 1:st buffer solution,
press OK. The sub menu Calib pH Buffer 2 is shown.
5 Rinse the electrode tip with distilled water and then immerse the
electrode in the 2:nd standard buffer solution (e.g. 4.0 or 9.0),
press OK.
6 When the pH value has stabilized, the Please wait message will
disappear.
7 Adjust the pH value in the display using the dial, so that it
corresponds to the known pH value of the 2:nd buffer solution,
press OK.
Monitor pH/C-900
User Manual 18-1120-06 Edition AC 9
Operation 3
Calib pH Buffer 1
Calib pH Buffer 2
Calibrate pH
(7.00 – 10.00)
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Monitor pH/C-900
User Manual 18-1120-06 Edition AC
10
3 Operation
8 The sub menu Calibrated
Electrode Slope shows the
slope of the calibration curve
where 100% corresponds to
59.16 mV per pH step at
25°C. The asymmetry
potential at pH 7 is shown
as a mV value. Press ESC to
return to the main menu.
9 Before use, rinse the
electrode using distilled
water.
A new electrode has a slope of, typically, 95 - 102% and an
asymmetry potential within ±30 mV. As the electrode ages the slope
decreases and the asymmetry potential increases.
As a rule, when an electrode has an asymmetry potential outside of
±60 mV and a slope lower than 80%, and no improvement can be
achieved by cleaning, it should be replaced.
An electrode is still usable at lower slopes and higher asymmetry
potentials but the response will be slower and the accuracy
diminished.
Calibrating with the electrode in the flow cell
When calibrating with the electrode fitted in the flow cell in
ÄKTApurifier, follow the above procedure. Before adjusting the pH
monitor, ensure that the pH has stabilized. Leave the pump running
while calibrating. Switch to the other standard buffer solution and
repeat the procedure. For a description of calibration from
UNICORN with the electrode fitted in the flow cell, see section 6.6
in UNICORN User Manual.
Voltage (mV)
pH
0 mV
+500 mV
–500 mV
7
Asymmetry
potential
at pH 7
Calibration curve
The calibration curve
shows the relationship
between pH and the
output signal from the
monitor in mV.
Calibrated Electrode
Slope 97.5% 8 mV
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3.7 Calibrating conductivity
The cell constant for the particular flow cell is written on the flow
cell packaging. Refer to section B.2.3 in Reference information for
how to enter the cell constant.
Adjustment of the cell constant is only necessary when the monitor
is to be used to determine specific conductivity with high accuracy.
The procedure is described in Reference information section B.2.2.
Calibration can also be performed from UNICORN.
3.8 Using an external chart recorder
The external chart recorder outputs for pH and conductivity from
the monitor are 0 – 1 V. There is also a 4 – 20 mA signal available
at the same output connectors.
For the conductivity signal, 0% represents 0 V and 100% represents
1 V as set under main menus Set Cond scale 0% and Set Cond scale
100%.
For the pH signal, the full scale and zero level has to be set
according to below.
1 Select main menu Set pH Analogue Out, press OK.
2 Select sub menu Set pH Full Scale. Set the range value, press OK.
The range is the full scale pH range for the chart recorder (1 V).
3 Select sub menu Set pH Zero Level, press OK.
4 Set the value, press OK. The zero level is the pH value
corresponding to 0 V to the chart recorder. The difference
between zero level and full scale must be at least 1 pH unit.
Monitor pH/C-900
User Manual 18-1120-06 Edition AC 11
Operation 3
Set pH Zero Level
(pH 2.00) 4.00
Set pH Full Scale
(pH12.00) 11.00
Set pH Analogue Out
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3.9 Storage and shut-down
Storage of conductivity flow cell
Overnight: The conductivity cell can be left filled with a buffer.
Weekend or Long time storage: Flush the conductivity cell with
water and fill with 20% ethanol.
Storage of pH electrode.
The pH electrode should always be stored
in a 1:1 mixture of pH 4 buffer and 1
M KNO3when not in use. When the pH
electrode is removed from the flow cell,
the dummy electrode (supplied) can be
inserted in the flow path.
Electrode regeneration: If the electrode
has dried out, immerse the lower end of
the electrode in buffer with a 1:1 mixture
of pH 4 buffer and 1 M KNO3overnight.
3.10 Restart after power failure
If the power supply to the instrument is interrupted, the instrument
automatically restarts itself and displays the main operating window.
All set values are retained in the instrument.
CAUTION! Never leave the pH electrode in the flow cell for any
period of time when the system is not used, since this may cause
the glass membrane of the electrode to dry out. Dismount the pH
electrode from the flow cell and fit the end cover filled with a 1:1
mixture of pH 4 buffer and 1 M KNO3.
Do NOT store in water only.
Monitor pH/C-900
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3 Operation
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4 Maintenance
4.1 Periodic maintenance
Interval Action (see procedures below)
Every 6 month Change pH electrode
or more often if required
When required Clean the conductivity cell
Clean the pH electrode
4.2 Cleaning the flow cell
Remove the pH electrode and install the dummy electrode in the pH
flow cell.
Pump a cleaning or sanitizing agent through the flow cells. The
standard recommendation is to pump 1 M NaOH for 30 minutes
and then wash out with buffer.
4.3 Cleaning the pH electrode
Note: The pH electrode has a limited life length and should be
replaced every six months or when the response time is slow.
Use one of the following procedures to clean the electrode to
improve the response:
•Salt deposits: Dissolve the deposit by immersing the electrode first
in 0.1 M HCl, then in 0.1 M NaOH, and again in 0.1 M HCl.
Each immersion is for a 5 minute period. Rinse electrode tip in
distilled water between each solution.
•Oil or Grease Films: Wash electrode tip in a liquid detergent and
water. If film is known to be soluble in a particular organic
solvent, wash with this solvent. Rinse electrode tip in distilled
water.
•Protein deposits: Dissolve the deposit by immersing the electrode
in a 1% pepsin solution, in 0.1 M HCl, for five minutes,
followed by thorough rinsing with distilled water.
Monitor pH/C-900
User Manual 18-1120-06 Edition AC 13
Maintenance 4
WARNING! Disconnect the power supply before attempting to
replace any item on the instrument during maintenance.
CAUTION! Only spare parts approved or supplied by Amersham
Pharmacia Biotech may be used for maintaining and servicing the
instrument.
WARNING! NaOH is injurious to health. Avoid spillage.
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If these procedures fail to rejuvenate the electrode, the problem is
most likely a clogged liquid junction.
1 Heat a 1 M KNO3solution to 60 - 80°C.
2 Place the electrode tip in the heated KNO3solution.
3 Allow the electrode to cool while immersed in the KNO3solution
before re-testing.
If these steps fail to improve the electrode response, replace the
electrode.
4.4 Changing pH electrode
See section 2.4 Installing the pH electrode.
4.5 Cleaning the conductivity flow cell
If the conductivity measurements are not comparable to previous
results, the electrodes in the flow cell may be contaminated and
require cleaning. To clean the flow cell:
1 Pump 15 ml of 1 M NaOH at 1 ml/min through the flow cell
either by using a pump or a syringe.
2 Leave it for 15 minutes.
3 Rinse thoroughly with 50 ml de-ionised water.
Note: If the flow cell is totally blocked, the blockage can be broken
using a thin needle or a piece of string with a diameter less than
0.8 mm.
4.6 Changing conductivity flow cells
The flow cells can be changed when required. Make sure the
instrument is switched off, before disconnecting/connecting the cells
to the rear of the instrument housing.
1 If the cell is replaced with a new flow cell, the monitor must be
calibrated with the new cell constant value which is written on
the flow cell package. See sub menu Setup conductivity in section
B.2.3 in Reference information. If the cell constant is not known,
it can be determined (see section B.2.2 in Reference information).
4.7 Instrument housing
Wipe the instrument housing regularly with a damp cloth. Let the
instrument dry completely before use.
Monitor pH/C-900
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4 Maintenance
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5 Trouble shooting
5.1 General
When contacting Amersham Pharmacia Biotech for support, state
the program version of the instrument, which is shown for 2 seconds
during switch-on.
5.2 Faults and actions
If the suggested actions do not correct the fault, call Amersham
Pharmacia Biotech.
pH measurement (optional in ÄKTApurifier systems)
Fault Action
No response to pH changes 1 Check that the electrode cable is connected properly to
the rear of the instrument.
2 The electrode glass membrane may be cracked. Replace
the electrode.
Small response to pH changes 1 Clean the pH electrode according to section
4.3 and
recalibrate.
2 If the problem remains, replace the pH electrode.
1 Check the pH electrode tip. If it is contaminated
clean the electrode following the instructions in section
4.3 Cleaning the pH electrode .
2 If the membrane has dried out, the electrode may be
restored by soaking it in buffer overnight.
3 Clogged liquid junction. Refer to section
4.3 Cleaning the pH
electrode
.
Incorrect/ unstable pH reading 1 Check that the electrode cable is connected properly to
the rear of the instrument.
2 Check that the pump and valves operates correctly.
3 Check that the electrode is correctly inserted in the flow cell
and, if necessary, hand-tighten the nut.
4 If air in the flow cell is suspected, tap the flow cell carefully
or tilt it to remove the air. Alternatively flush the flow cell with
buffer at 8 ml/min for 1/2 min.
5 Check that the pH electrode is not broken.
6 Check that the pH electrode is calibrated.
Monitor pH/C-900
User Manual 18-1120-06 Edition AC 15
Trouble shooting 5
Monitor pH/C900
V1.00
Slow pH response
or
Calibration impossible
WARNING! The instrument must not be opened by the user. It
contains high voltage circuits which can be capable of delivering a
lethal electric shock.
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Fault Action
7 Check the slope (see section 3.6 Calibrating pH ).
If it is outside the range 80–105% or the asymmetry potential
deviates more than 60 mV from 0 mV, clean the pH
electrode. Recalibrate and if the problem persists, replace
the pH electrode.
8 Clean the pH electrode if required, see section 4.3 Cleaning
the pH electrode.
9 Compare the response of the pH electrode with that of
another pH electrode. If the response differ greatly, the
electrode may require cleaning or replacement.
10 There may be interference from other equipment. Connect
the pH flow cell and the rear panel of the monitor using a
standard laboratory 4 mm “banana plug” cable.
11 Check that the pH electrode has been calibrated at the
correct temperature.
12 In organic solvents such as ethanol, methanol and
acetonitrile, stable pH measurements are not possible since
dehydration of the membrane will occur. It is recommended
that the pH electrode is not used in applications using
organic solvents. Mount the dummy electrode instead.
13 Clogged liquid junction. Refer to section
4.3 Cleaning the pH
electrode
.
pH values vary with varied 1 Replace the pH electrode.
back-pressure
Conductivity measurement
Fault Action
Incorrect or unstable reading 1 Check that the conductivity flow cell cable is connected
properly to the rear of the instrument.
2 Check that the pump and valves operate correctly.
3 If temperature compensation is being used, check that the
temperature sensor is calibrated, and that the correct
temperature compensation factor is in use.
4 Check that the column is equilibrated. If necessary clean the
column.
5 Check the operation of the mixer.
Baseline drift or noisy signal 1 There may be air in the flow cell. Use a flow restrictor after
the flow cell.
2 Check for leaking tubing connections.
3 Check the column is equilibrated. If necessary clean the
column.
4 Check the operation of the mixer and the pump.
5 Clean the flow cell according to procedure in section
4.5 Cleaning the conductivity flow cell .
Monitor pH/C-900
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5 Trouble shooting
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