Voltage Information and Courses from MediaLab, Inc.

The net charge of a molecule is the most important factor affecting the mobility of that molecule. The greater the net charge, the greater the mobility or the more quickly the molecule migrates. The net charge of a particular compound depends upon the buffer and the resultant pH set by that buffer. The size and shape of a molecule also influence the rate of migration in that the larger the size, the slower the molecule will move in electrophoresis.The viscosity and the pore size in the support media or gels used for electrophoresis influence the rate of migration. Increased viscosity slows the migration and increasing pore size speeds up the migration.Increased heat increases the rate of migration. Increasing the strength of the electrical field by increasing voltage and increasing the temperature used for the electrophoresis both increase the mobility and rate of migration. When increasing these factors that affect mobility, caution is necessary. Each will lead to an increase in temperature that can possibly denature the sample and alter the characteristics of the support medium. The ionic strength of the buffer and its effect on mobility are more complicated. The ionic strength of the buffer affects the thickness of the ionic cloud, the rate of migration, and the sharpness of the separated solutes. In electrophoresis, a cloud of ions forms over the medium and is composed of buffer ions, sample ions and other nonbuffer ions. Increasing the buffer ionic strength increases the buffer ions in the cloud and slows the movement of solutes and creates sharper bands. However, this also increases heat production.

In addition to the specimen sample, support medium and buffer for electrophoresis, a power supply, positive and negative electrodes, chamber, and identification or detection method are needed.The power supply is a source of constant voltage or current that provides energy to the electrodes. This drives the movement of the ions in the medium and results in the movement and separation of the molecules or solutes in the specimen. Control of current or voltage comes with the power source in order to make adjustments.The chamber is divided into two sections or has two reservoirs for the buffer and one electrode is placed in each. The support medium is laid over the chamber in such a way that it connects the two reservoirs. A lid or cover is placed over the chamber during electrophoresis.

Capillary electrophoresis (CE) combines electrophoresis and high performance liquid chromatography. CE takes place in a very thin fused silica capillary tube with polyacrylamide or agarose gel. Polyacrylamide is the most common gel used. The ends of the capillary tube are placed in two buffer reservoirs with the anode in one, and the cathode in the other. A high voltage power supply and cooling system are included.One major difference in CE is the detection of separated solutes as migration and separation occur, instead of detection after separation. An optical detector attached to the capillary detects solutes after separation but while still in the capillary; the detector is linked to data collection and storage.

Manufacturers are required to label appliances and instruments with electrical ratings including voltage, frequency, current, and/or wattage of the device and precautionary statements if applicable. Operating and safety instructions are provided with electrical equipment. It is prudent for personnel to familiarize themselves with this information before using the equipment. Personnel should be aware of the hazards associated with the use of defective electrical equipment. Defective equipment should be tagged and repaired or discarded. Keep liquids, chemicals, and heat sources away from electrical outlets and cords.