How do Horizontal Electrophoresis work?
In a horizontal system the agarose gel is cast in a tray, placed in a tank and submerged a few millimetres below running buffer, usually TAE or TBE. When voltage is applied between the platinum or stainless-steel electrodes, negatively charged nucleic acids migrate toward the anode through the pores of the agarose. Shorter fragments move faster, so the bands sort by length, and a size ladder allows estimation of fragment size. The buffer carries current and conducts away Joule heat, which is why voltage per centimetre of electrode spacing is limited, typically to 5–10 V/cm. Bands are visualised with intercalating dyes such as ethidium bromide or safer alternatives under UV or blue light. Key components are the tank, gel tray, combs that form wells, electrode leads and a safety lid.
Which Horizontal Electrophoresis variants are available?
- Mini Horizontal Gel Electrophoresis System — A compact horizontal tank for gels around 7 x 10 cm that uses little buffer and finishes runs in 20–40 minutes.
- Midi Horizontal Gel Electrophoresis System — A mid-size horizontal tank for gels of roughly 15 x 15 cm that holds 20–40 samples and gives sharper resolution than mini formats.
- Wide-Format Horizontal Gel Electrophoresis System — A large horizontal tank with a wide gel bed, typically 20 x 25 cm, built for multi-channel pipette loading and up to 96 or more samples per gel.
- Dual-Tray Multi-Gel Horizontal Electrophoresis System — A horizontal tank that runs two or more gel trays in the same buffer chamber, either side by side or stacked, doubling throughput without a second tank or power supply.
- Pulsed-Field Gel Electrophoresis System — A horizontal system that switches the electric field direction periodically to separate very large DNA molecules from about 10 kb up to several megabases.
How do I choose the right variant?
Choose the gel size first, because it fixes run time, sample number and resolution. Mini tanks give fast checks of a few samples, midi and standard formats balance throughput and resolution, and wide-format tanks accommodate multi-channel pipetting for 96-well workflows. Check the maximum voltage and buffer volume, as a larger tank needs a bigger power supply and more buffer. Consider whether dual trays or removable casting systems help speed. Pulsed-field systems are only needed for fragments above roughly 50 kb, such as genomic DNA typing. Also confirm comb thickness and tooth options, electrode material, lid interlock design and chemical resistance of the polycarbonate or acrylic body, and whether replacement trays and combs are easy to source.
Where are Horizontal Electrophoresis used?
Horizontal Electrophoresis are specified in PCR product verification, restriction digest analysis, RNA integrity checking, plasmid and DNA purification QC and genomic DNA typing by pulsed-field gels.
Which standards and certifications apply?
Work with Horizontal Electrophoresis is commonly governed by IEC 61010-1, IEC 61326-1, ISO 17025 and Ph. Eur. 2.2.31. Instrument certifications such as CE marking are confirmed per configuration and never assumed.
What are the key considerations before purchase?
Place the tank on a level, vibration-free bench away from sinks and keep the power supply outside the splash zone. Replace running buffer regularly, because ion depletion and pH drift degrade resolution after repeated runs. Clean tanks with mild detergent and rinse with deionised water; avoid solvents that craze acrylic. Inspect electrodes for corrosion and check that lid interlocks and lead insulation remain intact. Handle ethidium bromide and UV sources under local chemical and optical safety rules, or switch to safer stains. Electrical safety should follow IEC 61010-1. Record voltage, time, gel percentage and buffer batch for traceability, and use ladders appropriate to the fragment range.
