Rank Brothers Ltd

Micro-Electrophoresis Apparatus Mk II

The Rank Brothers Micro-Electrophoresis Apparatus will determine the electrophoretic mobility of a wide range of suspended particles. It has a wide and established user base in all fields where flocculation, dispersion and surface adhesion are important parameters to control.

Micro-Electrophoresis Apparatus setup for use with Pyrex cell

Picture of Micro-Electrophoresis Apparatus setup for electrophoretic mobility measurements using Pyrex cylindrical thin walled cell, especially suitable for:

Physical and Biological Applications of Electrophoresis

The term electrophoresis refers to the motion of a charged particle when an electric field is applied. When the velocity of the particle is measured, by timing over a known distance, it is possible to calculate the electrical potential at the surface of shear between the particle and the surrounding medium and from this the electric charge contained within the surface of shear. When the particle is in a relative charge free medium, such as air or a low dielectric constant liquid, it becomes convenient to calculate the charge directly. Careful consideration must be given to whether the charge is an equilibrium property of the particle or whether it is an accidental property determined by the history of the particle and what it happens to have collided with. However in aqueous solution (or in liquids of all but the lowest dielectric constant) the surface potential and charge of a particle is a reproducible quantity that gives valuable information both on the way the particle can interact with other particles or surfaces and on the nature of the particle surface. In the latter respect it is noteworthy that only a few particles and therefore a minute surface area, are necessary for the measurement.

So far as inter-particle behaviour is concerned the electric charge is one of the most important factors leading to stability of a dispersion against flocculation, coagulation or adhesion to surfaces. In all technologies involving dispersions or suspensions, whether these are required to be flocculated or de-flocculated, a knowledge of the particle charge and/or potential is a necessary pre-requisite to prediction of the behaviour of the system, either alone or in the presence of additives.

Increasing use is being made of measurements of the electrophoretic mobility of the various particles present in blood to help predict and prevent clotting of the blood and its adhesion to the walls of both natural and artificial blood vessels.

Quite apart from using electrophoretic mobilities to explain or predict the behaviour of particles or surface coatings, such measurements can be used as an aid to identifying the chemical groupings present at the particle surface. For example, the variation of particle surface charge with variations of pH of aqueous solutions gives important information on the dissociation of surface acidic and basic groups and can be used to identify them. Alternatively, in complex biological systems, the mobilities of the various particles present (which to some extent can be obtained without separation) can be used to identify these particles and may be characteristic of pathological conditions. In this connection it should be remembered that electrophoretic mobilities are most susceptible to change in conditions and therefore most characteristic of the particles, when the mobilities are small. Conditions such as pH can often be adjusted to achieve this.

Capabilities of the Rank Brothers Mk II Electrophoresis Apparatus

This Electrophoresis Apparatus can be used whenever the particles can be made visible relative to the suspending medium. Such visibility depends (apart from the intensity of the illumination and efficiency of the viewing optics) on the size of the particles and on the ratio of the particle refractive index to that of the surrounding medium. Using the quartz-iodine illumination unit of the standard instrument, aqueous dispersion of polystyrene particles (which have a rather unfavourable refractive ratio, about 1.1), shown to be visible down to a diameter of about 0.2µm. Particles with a more favourable refractive index ratio, e.g. carbon particles, can be seen down to much smaller sizes but it is difficult to give any precise limit in cases where monodisperse suspensions cannot be separated.

Lower Limit of Particle Size

One effective means of lowering the limit of particle visibility is use of a laser illuminator. Even a 3mW He:Ne continuous laser can concentrate more illumination into the observed volume than the 100 watt conventional illuminator and polystyrene particles of diameter only 0.09µm become visible. It must be remembered however that the necessary illumination power goes up very sharply as the size of the particle decreases below the figures quoted. Rank Brothers are pleased to perform free trials of particle visibility on samples sent to us by prospective purchasers of the apparatus.

The cylindrical cell, with extremely thin walls and ultra microscope illumination, is especially suitable when very small particles are involved.

Upper Limit of Particle Size

There is obviously no upper limit of particle size so far as visibility is concerned, the effective limit being set by the rate of gravitational fall or rise in the dispersion medium concerned. The flat cell is especially useful here because sedimenting particles fall neither out of view nor out of the stationary level. Moreover provided the rectangular cross section of the flat cell has its major dimension vertical, the sediment collects on an electro-osmotically unimportant surface so that measurements at the stationary level remain valid. The vertical gravitational component of the particles' motion can quite properly be ignored while the horizontal electrophoretic component is measured. Since the field of view is about 500µm across it follows that if times of vertical transit in excess of 20 seconds are accepted, the upper useful limit of particle diameter in aqueous solution at 25°C with particle specific gravity 2.0, is about 20µm. Particles with density nearer to that of water can be used up to much larger sizes.

Micro-Electrophoresis Apparatus setup for use with flat cell

Picture of Micro-Electrophoresis Apparatus setup for use with flat cell, especially suitable for:

Instrument Details

The Standard Mk II Micro-Electrophoresis apparatus comes with the following:


Technical Data

Power Requirements:
110V, 220V or 240V 50/60Hz approx. 400VA (Voltage factory set).
80cm (w) x 30cm (d) x 54cm (h) approx.
40kg approx.

Operating Manual

The manuals on this website are provided as PDF files, please see the Downloads page for links to reader software.

Micro-Electrophoresis Apparatus Mk II Manual (563KB)

Ordering Information

Order Code Description
ELE001A Electrophoresis Apparatus Mark II 240V
ELE001B Electrophoresis Apparatus Mark II 220V
ELE001C Electrophoresis Apparatus Mark II 110V
ELE001D Electrophoresis Apparatus Mark II 100V
ELE001D Electrophoresis Apparatus Mark II 100V
ELE002A Electrophoresis App. MKII rectangular cell only 110V
ELE002Y Electrophoresis App. MKII rectangular cell only 240V
ELE002Z Electrophoresis App. MKII rectangular cell only 220V
ELE003A Rotating Prism System
ELE004A C/Circuit TV Camera & Mount for MKII
ELE005A TV - 9" Monochrome Monitor for MKII
ELE006A 3mW Laser and Mounts for MKII
ELE007A Side illuminated graticule and eyepiece
ELE100A Standard cylindrical cell for MKII
ELE101A Standard 10 x 1 rectangular cell for MKII
ELE102A 10mm x 2mm rectangular cell for MKII
ELE125A Pair of platinum electrodes
ELE126A Pair of palladium electrodes
ELE133A Stage Micrometer - Mount only
ELE134A 1mm x 10 Stage micrometer and mount
ELE161A Front window for perspex water bath
ELE162A Rear Window for perspex water bath
ELE163A Rectangular cell holder
ELE164A Cylindrical cell holder complete
ELE301A Quartz Iodine bulb for MKII lamp

Rank Brothers Ltd reserves the right to change specifications in the light of continuing development.

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