Definition
An electrophoresis instrument is an analytical instrument designed based on the principle of electrophoresis, which is used to separate and detect charged particles (such as biological macromolecules such as proteins and nucleic acids or colloidal particles) under the action of an electric field. It provides a stable DC or pulsed electric field that drives the sample to migrate through the support medium (e.g., gel, capillaries), enabling separation and analysis based on charge, size, and shape. Electrophoresis instruments are fundamental tools in the fields of biochemistry, molecular biology, clinical diagnostics, and materials science.
Principle
The core principle of the electrophoresis is the directional migration of charged particles in an electric field. When the sample is placed in an electric field, the positively charged particles move towards the cathode and the negatively charged particles move towards the anode, and the migration rate depends on the charge density, size, shape, and medium properties of the particles. The migration behavior can be described using the following formula:
v = μE
where v is the migration rate, μ is the electrophoretic mobility, and E is the electric field strength. The mobility μ is directly proportional to the net charge q of the particle and inversely proportional to the coefficient of friction f, i.e., μ = q/f. The coefficient of friction is affected by factors such as particle size and medium viscosity, so electrophoresis can achieve effective separation of mixed components.
Measurement method
Electrophoretic measurements typically include the following steps: first prepare a support medium (such as agarose gel or polyacrylamide gel) and load the sample into the dosing well; The medium is then placed in the electrophoresis tank and the buffer is connected to form a closed circuit; apply a set voltage and current to migrate the sample; After migration, the separated bands were detected by staining, fluorescence labeling, or UV absorption. Quantitative analysis can be achieved by comparing the migration distance of the standard or measuring the band strength using an imaging system.
Influencing factors
The separation effect of electrophoresis is affected by a variety of factors. Electric field parameters such as voltage, current, and operating time directly affect the migration rate and resolution. Excessive voltage can lead to heat generation and banding spread. The pH, ionic strength, and composition of the buffer affect the particle charge state and electroosmotic flow. The pore size, uniformity, and concentration of the supporting media determine the molecular weight range of the separation. The charge, size, and concentration of the sample itself can also affect band clarity. In addition, the ambient temperature needs to be stable to avoid media deformation or buffer evaporation.
Application
Electrophoresis instruments are widely used in many fields. In life sciences, it is used for DNA fragment analysis, RNA detection, protein molecular weight determination, and purity assessment. In clinical medicine, it is used in the diagnosis of diseases such as hemoglobin mutation detection and serum protein analysis. The food safety field is used to detect genetically modified ingredients or allergens. It can be used in environmental monitoring to analyze microbial communities. In addition, electrophoresis instruments can be used to evaluate the surface charge and dispersion of particles in nanomaterial characterization.
Selection
When choosing an electrophoresis instrument, it is necessary to consider the experimental needs comprehensively. According to the separation object, agarose gel electrophoresis is mostly used for nucleic acid analysis, and polyacrylamide gel electrophoresis or bidirectional electrophoresis system is required for fine protein separation. For high-throughput detection, capillary electrophoresis can be considered to increase automation. It is necessary to pay attention to whether the voltage and current output range of the instrument meet the separation conditions and whether the temperature control system is effective. In terms of safety, it should have overload protection and leakage protection. Compatibility requires support for multiple gel formats and detection methods. The operation interface should be clear and easy to use, making it easy to set parameters and read data.