Potassium hydroxide (KOH) is a strong alkaline compound widely used in biochemical and molecular biology laboratories. Owing to its high solubility and strong reactivity, it is commonly employed for applications such as cell lysis, nucleic acid extraction, and pH neutralization. Compared with sodium hydroxide (NaOH), KOH provides efficient dissolution and strong basic conditions that are particularly useful in laboratory protocols requiring rapid chemical reactions and reliable alkalinity control.
Chemical Properties
Potassium hydroxide (KOH; molar mass 56.11 g/mol) typically appears as white hygroscopic pellets or flakes with a density of approximately 2.044 g/cm³ and a melting point of about 360°C. It dissolves readily in water through a strongly exothermic process (ΔH ≈ −57 kJ/mol), producing highly alkaline solutions that can reach concentrations of up to 50% w/v with a pH above 14. KOH solutions demonstrate high chemical reactivity and can hydrolyze esters, amides, and certain silicates. Due to its hygroscopic nature and strong alkalinity, KOH is also capable of etching glass surfaces and must therefore be handled with appropriate laboratory precautions.
Biochemical Applications
In molecular biology, potassium hydroxide is frequently used in alkaline lysis protocols for plasmid DNA extraction. Concentrations typically ranging from 1–5 M KOH enable selective denaturation of chromosomal DNA, while detergents such as SDS facilitate the precipitation of proteins and lipids, allowing efficient recovery of plasmid DNA. In protein research workflows, lower concentrations (0.1–0.5 M) may be applied to solubilize inclusion bodies or assist in the regeneration and cleaning of polyacrylamide gels used in SDS-PAGE analyses.
Laboratory and Analytical Uses
Potassium hydroxide is also used in cell disruption and biochemical preparation techniques. For example, mild alkaline solutions containing approximately 10–50 mM KOH combined with EDTA can facilitate gentle membrane disruption during bacterial spheroplast preparation. Additionally, KOH is widely applied in analytical chemistry for neutralization titrations and standardization procedures, where it serves as a strong base for quantifying acidic solutions and preparing buffer systems for biochemical assays.
