GE EPS 601 User manual

Electrophoresis Power Supply
EPS 601
GE Healthcare
User Manual
Manuel d’Utilization
Bedienungsanleitung
Manual del usuario
Manuale dell’operatore

Fig. 1. The front panel of the EPS 601.
Figure 1. Le panneau avant de l’EPS 601.
Abb. 1. Die Fronttafel des EPS 601.
Figura 1. Panel frontal de la EPS 601.
Figura 1. Pannello anteriore dell’EPS 601.
Fig. 2. The rear panel of the EPS 601.
Figure 2. Le panneau arrière de l’EPS 601.
Abb. 2. Die Rückwand des EPS 601.
Figura 2. Panel posterior de la EPS 601.
Figura 2. Pannello posteriore dell’EPS 601.
Program
HV on
Electrophoresis Power Supply - EPS 601
STOP
run exit enter
more set
pause
continue
Voltage 100-120/220-240 V AC
Frequency 50/60 Hz
Power 140 W 2.5 A Max
100-120 220-240
MAINS
Disconnect before servicing
I
0
Program
HV on
Electrophoresis Power Supply - EPS 601
STOP
run exit enter
more set
pause
continue
Voltage 100-120/220-240 V AC
Frequency 50/60 Hz
Power 140 W 2.5 A Max
100-120 220-240
MAINS
Disconnect before servicing
I
0

ITALIANOESPAÑOLDEUTCHFRANÇAISENGLISH
Important user information
All users must read this entire manual to fully understand the
safe use of EPS 601.
WARNING!
The WARNING! sign highlights instructions that must
be followed to avoid personal injury. It is important
not to proceed until all stated conditions are met and
clearly understood.
CAUTION!
The CAUTION! sign highlights instructions that must be followed
to avoid damage to the product or other equipment. It is
important not to proceed until all stated conditions are met and
clearly understood.
Note
The Note sign is used to indicate information important for
trouble-free and optimal use of the product.
CE Certifying
This product meets the requirements of applicable CE-directives.
A copy of the corresponding Declaration of Conformity is
available on request.
The CE symbol and corresponding declaration of conformity, is
valid for the instrument when it is:
– used as a stand-alone unit, or
– connected to other CE-marked GE Healthcare instruments, or
– connected to other products recommended or described in
this manual, and
– used in the same state as it was delivered from GE Healthcare
except for alterations described in this manual.
WARNING!
This is a Class A product. In a domestic environment this product
may cause radio interference in which case the user may be
required to take adequate measures.
Recycling
This symbol indicates that the waste of electrical
and electronic equipment must not be disposed
as unsorted municipal waste and must be
collected separately. Please contact an authorized
representative of the manufacturer for information
concerning the decommissioning of your equipment.
Safety Standards
This product meets the requirement of the Low Voltage Directive
(LVD) 73/23/EEC through the following harmonized standards:
• EN 61010-1
• IEC 61010-1
• CAN/CSA-C22.2 No. 61010-1
• UL61010-1
EMC Standards
This device meets the requirements of the EMC Directive 89/336/
EEC through the following harmonized standards:
• EN 61326 (emission and immunity)
• EN 55011, GR 1, Class A (emission)
• This device complies with part 15 of the FCC rules (emission).
Operation is subject to the following two conditions:
1 This device may not cause harmful interference.
2 This device must accept any interference received,
including interference that may cause undesired
operation.

ENGLISHFRANÇAISDEUTCHESPAÑOLITALIANO

1. Introduction ..................................................................................................................................................................................................................................................... 7
2. Safety information ........................................................................................................................................................................................................................... 9
2.1 Safety precautions ................................................................................................................................................................................................................... 9
2.2 In-built safety features
................................................................................................................................................................................................ 10
3. Unpacking and installation ..................................................................................................................................................................................... 11
4. Technical description ............................................................................................................................................................................................................ 13
4.1 Front panel ........................................................................................................................................................................................................................................ 13
4.1.1 Display ................................................................................................................................................................................................................................ 13
4.1.2 Keyboard ........................................................................................................................................................................................................................ 13
4.1.3 Output sockets ..................................................................................................................................................................................................... 14
4.2 Rear panel ........................................................................................................................................................................................................................................... 14
5. Operation ......................................................................................................................................................................................................................................................... 15
5.1 Overview ................................................................................................................................................................................................................................................ 15
5.2 Programming ................................................................................................................................................................................................................................ 15
5.3 Running a program
............................................................................................................................................................................................................ 15
5.4 Optional programming
................................................................................................................................................................................................ 19
5.5 Choosing run parameters ...................................................................................................................................................................................... 20
5.6 Short instructions .................................................................................................................................................................................................................. 22
6. Maintenance ............................................................................................................................................................................................................................................. 23
7. Trouble shooting .............................................................................................................................................................................................................................. 25
8. Technical specifications .................................................................................................................................................................................................. 27
9. Ordering information ............................................................................................................................................................................................................ 29
Contents
ITALIANOESPAÑOLDEUTCHFRANÇAISENGLISH
Contents
5
Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD

ENGLISHFRANÇAISDEUTCHESPAÑOLITALIANO
Contents
6Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD

Introduction 1
1 Introduction
The GE Healthcare Electrophoresis Power Supply EPS 601 is a high quality, high precision
and safe power supply for electrophoresis applications that require a maximum of
600 volts and 400 mA.
EPS 601 is primarily designed for the following techniques:
1. SDS-PAGE (Polyacrylamide Gel Electrophoresis)
2. Native PAGE
3. Agarose electrophoresis
4. Electroblotting
5. DNA pulsed field electrophoresis
6. DNA fragment separation
7. DNA submarine electrophoresis
Electrophoresis separations can be controlled by voltage, current or power. The EPS 601
automatically switches over the controlling parameter according to programmed limits
and conductivity variations in the system.
Two electrophoresis units can be connected to the EPS 601 and run with the same
programmed method at one time. Three programs can be saved.
7
Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
ITALIANOESPAÑOLDEUTCHFRANÇAISENGLISH

ENGLISHFRANÇAISDEUTCHESPAÑOLITALIANO
8Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
1 Introduction

ITALIANOESPAÑOLDEUTCHFRANÇAISENGLISH
2 General Description
General Description 2
9
Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
2.1 Safety precautions
Extreme caution should be exercised in the operation of this instrument as it can
develop sufficient voltage and current to produce a lethal shock.
To avoid any risk of injury, the instrument should only be operated by properly trained
personnel and always in accordance with the instructions provided.
Read this entire manual before using this power supply.
1. This instrument is designed for indoor use only.
2. The instrument must always be used with the protective earth lead of the power
cord correctly grounded to earth at the mains outlet.
3. To permit sufficient cooling, ensure that the vents in the rear and sides of the
instrument are not covered.
4. Do not operate the instrument in extreme humidity (above 95%). Avoid
condensation by letting the unit equilibrate to ambient temperature when taking
the power supply from a colder to a warmer environment.
5. Keep the instrument as dry and clean as possible. Wipe regularly with a soft damp
cloth. Let the power supply dry completely before use. If wetted, unplug the power
supply until the instrument is dry.
6. Use only undamaged electrical wire and equipment specified for the voltages you
will use. High voltages wires must meet the requirements of the
IEC 1010-2-031:1993 electrical standard. Any electrophoresis equipment connected
to the power supply should meet the requirements of the IEC 1010-1:1993
electrical standard.
7. Note that the output is connected to the chassis/reference earth.

ENGLISHFRANÇAISDEUTCHESPAÑOLITALIANO
2 Geneal Description
10 Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
2.2 Built-in safety features
The EPS 601 has been tested and complies with the IEC 61010-1 (EN 61010-1) electrical
safety standard. The power supply also has several built-in safety functions. Error
messages are also shown on the display (see 7. Trouble shooting):
1. Functional earth leakage.
Should the power supply be connected to an electrophoresis unit that has a leakage
path to earth, the EPS 601 will detect this fault and the high voltage is turned off.
2. Start current check.
To ensure that an electrophoresis unit is connected correctly, the power supply
checks that the resistance is not higher than a specified limit at a low safety voltage
(<40V). If this resistance is too high, the voltage is turned off. Too high a resistance
can also be caused by using buffers with extremely low conductivity. The high
voltage is also turned off in this case and an error message is shown. This function
can be disabled to perform certain applications (see 5.4 Optional programming).
3. Sudden load change detection.
This function prevents accidents under running conditions due to a break in the
electrical circuit such as a bad connection to the electrophoresis unit. The high
voltage is turned off in such an event.
Error messages for sudden fails are also shown on the display.

ITALIANOESPAÑOLDEUTCHFRANÇAISENGLISH
Unpacking and installation 3
Unpacking
Check the contents against the packing list supplied. Inspect for any damage that may
have occurred during transit. Report any damage immediately to your local
GE Healthcare representative and to the transport company concerned.
Mains connection
Select the appropriate voltage range, 100–120 or 220–240 V. See Fig. 2 inside front cover.
WARNING! If the power supply is connected to 220–240 V with the range set to
100–120 V, the instrument can be severely damaged.
WARNING! Only use mains cables delivered or approved by GE Healthcare.
WARNING! Do not block the rear panel of the system. The mains power switch must
always be easy to access.
Select the appropriate mains cable and connect one end to the mains socket on the
EPS 601 power supply (see Fig. 2, inside front cover) and the other end to an AC
grounded outlet.
Connection of the electrophoresis unit(s)
Connect the leads from the electrophoresis unit (red to red, and black or blue to blue),
see Fig. 1 inside front cover. The red lead is the positive and black or blue is the negative.
WARNING! Use only undamaged electrical wire and equipment approved for the
voltage you will use. Two electrophoresis units can be run simultaneously with
the same program. Please remember to double the limiting current and power if
two electrophoresis units are run at the same time. The voltage will be the same
regardless of the number of units.
3 Unpacking and installation
11
Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD

ENGLISHFRANÇAISDEUTCHESPAÑOLITALIANO
3 Unpacking and installation
12 Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
Local regulation for Great Britain
WARNING IMPORTANT
This appliance must be earthed.
The wires in the mains lead are coloured in accordance with the following code:
Green and yellow Earth
Blue Neutral
Brown Live
If the plug provided is unsuitable for socket outlets, the plug must be cut off and
suitable plug fitted. The cut-off plug should be disposed of and must not be inserted
into any 13 amp socket as this can result in electric shock. The plug or adapter or
the distribution panel should be provided with 13 amps fuse. As the colours of the
wires in the mains lead of this appliance may not correspond with coloured markings
identifying the terminals in your plug, proceed as follows:
The green and yellow wire must be connected to the terminal in the plug which is
marked with the letter E or by the earth symbol, or coloured green, or green and
yellow.
The blue wire must be connected to the terminal which is marked with the letter N or
coloured black.
The brown wire must be connected to the terminal which is marked with the letter L
or coloured red.
NOTE: After replacing or changing a fuse, the fuse cover in the plug must be
replaced with a fuse cover which corresponds to the colour of the insert in
the base of the plug or the word that is embossed on the base of the
plug, and the appliance must not be used without a fuse cover. Only 13 Amps
fuse approved to B.S. 1362 A.S.T.A. should be used.
Switch on the power. Each time the instrument is turned on a self diagnostic test is
done. If an error is detected during the test a message will appear on the display and
an alarm will sound.

4 Technical description
4.1 Front panel
The front panel consists of an alphanumeric display, a keyboard with 9 membrane keys,
a light emitting diode (LED) that lights when voltage is applied (HV on) and connectors for
two electrophoresis units.
4.1.1 Display
A 32 digit alphanumeric display guides you through the programming, shows current
parameter values during the electrophoresis and final parameter values afterwards. It
also asks questions and shows error messages. The display has an upper and lower row.
Fig. 1 (inside front cover) shows the display in the start position when power is switched
on for the first time. The mode (in this case SET) is shown in the upper row on the left.
The program number is in the center of the upper row. The number shown is that of the
previously entered program. As no program has yet been entered, the first available
program number, P1, is shown. The blinking figure, in this case “1”, indicates that it can
be changed by using the /keys. The upper right shows the programmed breakpoint. In
this case it is off.
The lower left, middle and right positions show voltage, current and power respectively.
4.1.2 Keyboard
ENTER
Enters a value, locks the value if correct, and moves programming to the next field.
Valid values are voltage 6–600 V, current 1–400 mA, power 1–100 W, time 0:01–500 h,
volthours 1–500 000 Vh.
SET
Puts the instrument into SET, its programming and starting mode. In the RUN mode,
pressing SET also shows the programmed parameters for the actual run. In addition,
SET allows you to make changes in the program during a run after first pressing PAUSE
CONTINUE.
CHANGE UP/CHANGE DOWN
Changes the parameter, value or other choice in the field which is blinking. Numerical
values are changed in an accelerating manner when a key is held down. Clicking a key
changes the value in preset increments. Parameters or units (e.g. Vh) and yes/no choices
are changed with one key push. The keys can also be used to switch between time and
volthours in RUN, PAUSE and END. The values scroll i.e. they automatically change from
maximum to minimum value or vice versa.
RUN
Pressing RUN starts the run and puts the program into RUN mode. The program number,
current values for voltage, current and power are shown on the display. The elapsed
time or volthours are also displayed. Switch between time and volthours with /.
enter
set
/
run
ITALIANOESPAÑOLDEUTCHFRANÇAISENGLISH
Technical description 4
13
Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD

PAUSE CONTINUE
Puts the instrument in PAUSE mode and switches off the voltage. The display shows
the status of the run at the time the key was pressed. PAUSE CONTINUE only operates
in RUN mode. Time and integration values are retained. In the pause mode, SET can
be used to make changes in the program. Return to RUN mode by pressing PAUSE
CONTINUE or by pressing RUN.
STOP
Stops the run and puts the instrument in END mode. The voltage is switched off and the
end parameters are displayed. Switch between time and integrated voltage by pressing
/. A run cannot be continued after pressing STOP.
Continue by pressing RUN to run the same method again or pressing SET to choose
another program, program a new method or make changes in an existing method.
MORE
You can disable the start current check that otherwise detects if the resistance is too
high and switches off the power. See Section 5.4.
EXIT
Stops the execution of an operation, such as the entry of a value. Only values/units
that have already been confirmed by ENTER are retained. Returns the instrument to the
mode that was left or the start position in SET.
4.1.3 Output sockets
There are two sets of output sockets to allow two electrophoresis units to be connected
and run at the same time, see Fig. 1 inside front cover. The voltage output is 0–600 V. The
negative output socket gives between 0 and –300 V and the positive gives between 0
and +300 V.
4.2 Rear panel
The rear panel is shown in Fig. 2, see inside front cover. On the rear panel there is:
1. A mains switch. Press in Ito switch on the power to the power supply. Press 0to
switch off thepower.
2. A socket for the mains cable.
3. A switch for voltage range. The left position corresponds to 100–120 V and the right
to 220–240 V.
4. Vent openings.
pause
continue
STOP
more
exit
14 Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
4 Technical description
ENGLISHFRANÇAISDEUTCHESPAÑOLITALIANO

ITALIANOESPAÑOLDEUTCHFRANÇAISENGLISH
Operation 5
5 Operation
5.1 Overview
The operation of the EPS 601 is described in the following sequence.
1. Programming or editing a method.
2. Running a method.
When the method is running, it can be interrupted (put in PAUSE mode) to apply samples
and/or change the program. During a run it is also possible to look at the program
settings.
Programming and running are discussed in more detail in the following two sections.
Blinking characters are shown as bold characters.
5.2 Programming
Start position
When the power supply is switched on, the display shows the start position in SET mode.
The previous program set is shown and that program number is blinking, for example:
SET: P1 2:00 h
200 V 40mA 10 W
(If the power supply is switched on for the first time, the breakpoint parameter and the alarm
are off and the values for voltage, current, and power are 6 V, 400 mA and 100 W respectively).
Choosing a program
Up to 3 programs can be entered. Press ENTER to confirm the program shown on the
display or use /keys to choose another. Confirm with ENTER. The programming
procedure can be followed step by step in Fig. 3.
Setting voltage, current and power limits
The display will now flash for the set voltage limit. Using the /keys, select the
maximum voltage desired for the run. Confirm with ENTER. Repeat the same procedure
for limiting current and limiting power. Programmable values for voltage are 6–600 V,
current, 1–400 mA, power, 1–100 W, time, 0:01–500 h, volthours, 1–500 000 Vh.
Setting break-point
Choose between manual break or automatic break. For automatic break, choose
breakpoint units in either Volthours (Vh) or time (h). Select the correct unit or, for manual
break, choose “OFF” with /. Confirm with ENTER. If volthours or h (time) were chosen,
the display will flash for the break value. Set the value with /and confirm with ENTER.
Choosing alarm
When a breakpoint has been entered, the following question is shown: Alarm at End ? Y.
Select YES or NO with /and confirm with ENTER. If YES is selected, a small “A” appears
on theright of the program number, i.e. 2A.
15
Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD

ENGLISHFRANÇAISDEUTCHESPAÑOLITALIANO
5 Operation
16 Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
SET: P1OFF
200 V 40 mA 10 W
enter
Select by
Confirm by
SET: P2 OFF
6V 400 mA 100 W
enter
Select by
Confirm by
SET: P2 OFF
600 V 400 mA 100 W
enter
Select by
Confirm by
SET: P2 OFF
600 V 50 mA 100 W
enter
Select by
Confirm by
SET: P2 OFF
600 V 50 mA 30 W
enter
Select by
Confirm by
SET: P2 0:00 h
600 V 50 mA 30 W
enter
Select by
Confirm by
Alarm at End ? Y
enter
Select by
Confirm by
SET: P2A2:00 h
600 V 50 mA 30 W
SET: P2OFF
600 V 50 mA 30 W
1. Choose Program
number
2. Set Voltage limit
3. Set Current limit
4. Set Power limit
5. Choose Breakpoint
unit (h or Vh) or no
Breakpoint (OFF).
6. Set Breakpoint
7. Choose Alarm
YES or NO
8. Program ready
Breakpoint off
Fig. 3.Step-by-step summary of programming.

Back to start position
The program is now back to the start position in the SET mode with the program number
flashing. It is possible to go back to this position at any stage during programming in SET
mode by pressing EXIT or STOP. Note that the program is saved automatically when EXIT
is pressed.
Disabling the current check
See Section 5.4 if you want to use this feature.
5.3 Running a program
Connect the leads from the electrophoresis unit (red to red, and black or blue to blue).
Red is positive and black or blue negative. Up to two electrophoresis units can run at the
same voltage at one time. Please remember to double the maximum current and power
conditions if two units are to be run. Voltage will be the same regardless of how many
units are run. The current should also be doubled if two gels are run on the same unit.
Choosing a program
Press SET and select the program you wish to run by pressing /until the value after
the “P” is correct. Confirm with ENTER. (Omit this step if you have just programmed a
method as described in section 5.2.)
Running a program is described schematically in Fig. 4.
Running
Press RUN to start the electrophoresis. The display will show current values for voltage,
current, power and elapsed time or volthours. You can switch between showing the
elapsed time or volthours by /. The limiting parameter will attain the programmed
limit. The unit for that parameter is underlined. A light emitting diode shows when
voltage is applied (HV on). If no current is displayed, please check the electrical
connections to the electrophoresis equipment.
Pausing
You can interrupt the electrophoresis for sample loading and/or changing parameter
values by pressing PAUSE CONTINUE. Voltage and current will no longer be supplied,
the HV on LED goes off, and you may safely load your samples. The display shows
the status of the run when PAUSE CONTINUE was pressed. Switch between time and
integrated voltage by pressing /. When sample loading is complete, press PAUSE
CONTINUE again or RUN and the run will continue from where it was interrupted. When
in the PAUSE mode you can also press SET to make changes in the program. This mode
is called the P-SET mode. When the P-SET mode is entered you can make changes as
described under programming. The P-SET mode is the same as the SET mode apart
from restrictions in setting the breakpoint. Naturally, it is not possible to enter a time or
volthour that is already passed. PressEXIT or PAUSE CONTINUE to go back from P-SET to
PAUSE. Press RUN or PAUSE CONTINUE to proceed with the electrophoresis.
View programmed values
It is also possible to view the programmed values during a run by pressing SET. Note that
no values can be changed here. The display returns automatically to show RUN values
after 5s. Alternatively use EXIT or RUN.
ITALIANOESPAÑOLDEUTCHFRANÇAISENGLISH
Operation 5
17
Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD

Stopping the run and viewing end parameter values
When the programmed time or volthour is attained, the program will enter the End
mode. It is also possible to break the run manually by pressing STOP. In both cases, the
voltage, current and power will go to zero as indicated by the HV on LED switching off.
The end parameter values are displayed. Switch between elapsed time and integrated
voltage by /. An alarm will sound if selected in the program. You can stop the alarm
by pressing STOP.
A run cannot be continued after pressing STOP.
Disconnect the leads and proceed with post-electrophoretic techniques. Since diffusion
will begin as soon as the voltage is turned off, you should remove the gel and begin
staining, blotting or autoradiography immediately.
SET: P1OFF
200 V 40 mA 10 W
Select by
1. Choose Program number.
2. Start the run.
3. During a run you can view the
settings. It is also possible to interupt
the run and make changes in the
program.
4. Stop the run manually.
5. The run is stopped automatically.
SET: P2A2:00 h
600 V 50 mA 30 W
RUN: P2A0:01 h
300 V 50 mA 25 W
RUN: P2A1:45 h
600 V 50 mA 24 W
END: P2A2:00 h
600 V 35 mA 21 W
SET: P2A2:00 h
600 V 50 mA 30 W
PAUSE: P2A0:30 h
500 V 50 mA 100 W
P-SET: P2A2:00 h
600 V 50 mA 30 W
END: P2A1:45 h
600 V 40 mA 24 W
or wait 5 s
set pause
continue
pause
continue
run
or
set pause
continue or
STOP
RUN: P2A0:30 h
500 V 50 mA 25 W
Programming
run
Start by
exit
exit
18 Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
5 Operation
ENGLISHFRANÇAISDEUTCHESPAÑOLITALIANO
Fig. 4. Step-by-step summary of run and pause function.

5.4 Optional programming
You can disable the start current check that otherwise checks that the resistance is not
higher than a specified limit. This disabling function is set in the MORE mode instead of
the SET mode in order not to confuse users who do not need this feature, and for safety
reasons.
The MORE mode is described in Fig. 5. After pressing MORE, the program asks you for
the program number and if you want to keep the start current check. Choose program
number and change between ”YES” and ”NO” by /and confirm with ENTER. Choosing
”NO” for start current check means that the function is disabled and high voltage can be
applied despite a very high resistance. Leave the MORE mode byEXIT.
WARNING! By disabling the start current check, the power supply can deliver high
voltage even if it is not connected to electrophoresis equipment.
ITALIANOESPAÑOLDEUTCHFRANÇAISENGLISH
Operation 5
19
Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
SET: P2A2:00 h
600 V 50 mA 30 W
Select MORE by
MORE: P2
Select program
enter
Select by
Confirm by
1. Enter MORE
2. Select program
3. Choose current check no
4. Back to SET mode
Current check at
start? YES/no
enter
Select by
Confirm and
Exit by
SET: P2A2:00 h
600 V 50 mA 30 W
more
Fig. 5. Disabling the current check.

5.5 Choosing run parameters
EPS 601 is an automatic cross-over power supply that allows the user to set limits for
voltage, current and power. During electrophoresis, only one of the parameters is limiting
at a time. The limiting parameter determines, together with the conductivity in the
electrophoresis system, the values for the other two parameters. Voltage, current, power
and conductivity are related by the following equations:
U = I / L (1)
P = U × I (2)
Where U = Voltage, I = Current, P = Power and L = Conductivity
Equation (1) is more familiar if the conductivity is replaced by the reciprocal resistance (R):
U = R × I (Ohm’s law)
The electric field E, measured in V/cm, is the driving force behind electrophoresis.
E = U / d
where E = Electrical field strength, U = Voltage, d = distance
The electrical field strength is achieved by applying a voltage. The higher the voltage, the
faster the electrophoresis. Fast electrophoresis is beneficial since it counteracts diffusion.
The disadvantage of increasing the voltage too much is that most of the generated
electrical energy, the product of power and time, is transformed to heat. Therefore
cooling of electrophoresis equipment is recommended. Cooling will also reduce “smiling”
effects which are caused by mobility differentials across an electrophoresis gel resulting
from poor heat transfer. Since the cooling efficiency cannot be increased indefinitely, the
power should be limited when programming the power supply.
The parameter that should be chosen as the constant and thus control the
electrophoresis depends on the type of electrophoresis. In the case of homogeneous
buffers throughout the system (same electrode and gel buffer), the conductivity is
constant during the electrophoresis. If the conductivity is constant, the voltage will be
proportional to the current and the power to the square of the current, according to (1)
and (2). This means that the result of the electrophoresis will be the same, regardless
which parameter is chosen for constant. For historical and practical reasons, voltage
is most commonly used for regulation. Submarine gel electrophoresis of DNA/RNA
and pulsed field electrophoresis are usually run at constant voltage. SDS-PAGE using
continuous buffer systems is run at constant voltage or current.
20 Electrophoresis Power Supply EPS 601 User Manual 18-1130-19 Edition AD
5 Operation
ENGLISHFRANÇAISDEUTCHESPAÑOLITALIANO