GE GM-1 User Manual

instructions

Gradient Mixer GM-1

1. Introduction

The Gradient Mixer GM-1 (120 V, Code No. 19-0495-01,
230 V Code No. 19-0485-01) consists of two identical
reservoirs mounted on a base plate; connection between the
reservoirs is made via a valve. Mounted above the mixing
reservoir is a motor unit which drives a stirrer blade. The
outlet from the mixing reservoir to the column is fitted with
a flow control valve, FCV-1. The Gradient Mixer is
conveniently supported on a laboratory stand. Capillary
tubing, 2 m, is also supplied.

2. Safety

Warning!

When using hazardous chemicals, all suitable protective
measures such as protective glasses, must be taken.

3. Unpacking

Unpack the equipment carefully and check the contents of
the carton against the packing list.

4. Description

THE BASE PLATE (11)* is a precision machined
polypropylene block on which the reservoir cylinders (7) are
mounted.

Sealing between the base plate and the cylinders is provided
by O-rings (8).

THE RESERVOIR CYLINDERS (7) are straight
polymethylpentene tubes threaded at one end and with air
inlets at the other end. Each cylinder has a capacity of 300 ml
and is graduated to 250 ml at 25 ml intervals to give a rapid
check of the volume of liquid remaining in the reservoirs.
The mixing reservoir carries the motor unit (1, 2) and the
other reservoir is fitted with a snap-on lid (3).

THE MOTOR UNIT (1, 2) consists of a fully encapsulated
low speed 250 or 300 rpm synchronous motor mounted in
polypropylene housing. A phasing condensor ensures that
the direction of stirring is always the same and that the

stirrer blade (6) lifts the liquid entering the mixing reservoir.
The motor unit is supplied for operation from 100–120 or
220–240 V AC, 50 or 60 Hz.

THE STIRRER BLADE (6) is secured to the motor axle by a
nylon screw (5). It is unnecessary to remove the screw to
release the stirrer blade.

THE CONTROL VALVE (12) regulates the flow of liquid
between the two reservoirs. It is fully open when screwed out
one complete revolution from the closed position.

THE FLOW CONTROL VALVE (18) is a needle valve
designed for shut-off as well as flow control. The valve
nipple accepts capillary tubing 1.6–1.9 mm o.d. Eluent flow
is regulated with the large knob (A). The line on this knob
and the markings on the valve housing can be used as a flow
rate guide. The valve can thus be opened to a previously
determined position to obtain a given flow rate. To obtain
reproducible flow rates the valve should always be returned
to the shut position before setting.

THE STAND MOUNT (21) may be used to support the
Gradient Mixer on a laboratory stand. When not required,
it may be removed from the base plate (11) by unscrewing
the retaining knob (20).

5. Installation

Connection of tubing to the flow control valve

1. Cut the tubing cleanly at a 45° angle.

2. Remove the screw cap and slip it over the tubing.

3. Remove the rubber cone with the help of the metal
stopper.

4. Push the tubing through the rubber cone until it projects
about 1 cm.

5. Seat the tubing in the nipple. Slide the cone along the
tubing, into the nipple.

6. Finger tighten the screw cap.

* Numbers refer to the enclosed Spare Parts drawing.

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Dismantling the Gradient Mixer

The reservoir cylinders (7), control valve (12) and flow
control valve (18) may be removed from the base plate by
unscrewing them. To remove the stirrer blade (6) from the
motor unit (1, 2), unscrew the nylon screw (5) a few turns.
It is not necessary to remove the screw completely. The lid of
the motor unit should not be removed.

the stirrer blade but not the motor unit, may be autoclaved
at 121 °C for 20 min.

Caution!

Do not autoclave the motor unit or drain the motor in
strong detergents.

8. Technical specification

6. Operation

Operating the Gradient Mixer

1. Close the control valve (12) and flow control valve (18)
and pour the required amount of starting solution into
the mixing reservoir. The graduations may be used as an
approximate guide to the volume of liquid in the
reservoirs.

2. Mount the motor unit (1, 2), with the stirrer blade (6),
on the mixing reservoir.

3. Open the control valve (12) slightly so that the channel
between the reservoirs fills with solution and a small
amount of liquid emerges into the other reservoir. Close
the control valve.

4. Pour the gradient-forming solution into the empty
reservoir until the liquid levels in the two reservoirs are
nearly the same. The level in the mixing reservoir should
be slightly higher than the level in the other reservoir to
avoid a step at the beginning of the elution.

5. Open the control valve (12) fully, one complete
revolution, start the motor and begin the elution by
opening the flow control valve (18). If a pump is used to
control the eluent flow, the flow control valve (18)
should be fully open, one complete revolution .

The Gradient Mixer will give linear ionic strength gradients
and reproducible, but non-linear, pH gradients. The exact
shape of the pH gradient obtained will depend on the buffer
salts used and the ionic strengths and pH’s of the buffer
solutions. The use of gradient elution in ion exchange
chromatography is described in the booklet “Ion Exchange
Chromatography – principles and methods.”

Mixing chamber 300 ml
volume

Environment +4–40 °C

20–95% relative humidity

Material of Polymethylpentene,
wetter parts Polypropylene, glass fibre reinforced

polypropylene and fluororubber.

Chemical resistans The wetted parts are resistant to

aqueous and organic solvents
commonly used in ion change
chromatography and solutions
containing inorganic and organic
acids, alkalis and alcohols.

Power requirements 100–120 VAC or 220–240 VAC,

50–60 Hz

Power consumption 7 VA

Safety standards This products meets the requirements

of the Low Voltage Directive (LVD)
73/23/EEC through the harmonized
standards EN61010-1 and EN60742.

Note: The declaration of conformity is valid for the

instrument when it is:

• used in laboratory locations,

• used in the same state as it was delivered from

GE Healthcare Bio-Sciences AB

except for alterations described in the
user manual,

• used as a “stand alone” unit or connected to other CE

labelled GE Healthcare Bio-Sciences AB instruments or other

products as recommended.

7. Maintenance

Warning!

When using hazardous chemicals, all suitable protective
measures such as protective glasses, must be taken.

Cleaning

Ordinary laboratory detergents may be used to clean the
gradient mixer. Enzyme detergents are recommended for
removing protein aceous contaminants. The mixer, including

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