Lithium hydroxide (LiOH) is an inorganic alkali hydroxide widely used in analytical chemistry, molecular biology, and materials science. Due to its high solubility in water and its relatively moderate alkalinity compared with other alkali hydroxides such as sodium hydroxide or potassium hydroxide, LiOH is frequently employed in controlled biochemical reactions and laboratory protocols requiring precise pH adjustment or selective hydrolysis.
Chemical Properties
Lithium hydroxide (LiOH; molecular weight 23.95 g/mol) forms a white, hygroscopic crystalline solid with a density of approximately 1.46 g/cm³ and a melting point of about 462 °C. It is highly soluble in water, with solubility values around 12.8 g/100 mL at 20 °C and increasing to approximately 17.5 g/100 mL at 100 °C. The small ionic radius of the lithium cation (Li⁺) promotes strong hydration interactions in aqueous solutions, generating moderately alkaline solutions with a pH of approximately 12 for a 1 M solution. Lithium hydroxide reacts with atmospheric carbon dioxide to form lithium carbonate (Li₂CO₃) and can slowly react with glass surfaces through silicate formation.
Applications in Molecular Biology
In molecular biology workflows, lithium hydroxide is used in RNA extraction protocols to neutralize acidic phases generated by acid guanidinium–phenol reagents such as TRIzol™. At concentrations typically ranging from 0.1 to 0.5 M, LiOH facilitates the precipitation of DNA and proteins while maintaining RNA in solution prior to isopropanol purification. This property can provide improved selectivity compared with stronger bases such as sodium hydroxide.
Analytical and Biochemical Applications
Lithium hydroxide is also employed in enzymology and analytical chemistry. Low-millimolar LiOH buffers (typically 10–50 mM) are used in studies involving lithium-sensitive enzymes, including investigations of phosphatase activity and glycogen phosphorylase regulation. In nucleic acid analysis, saturated LiOH solutions can hydrolyze RNA into nucleotide monomers, enabling spectrophotometric quantification at 260 nm. Additionally, LiOH is used in electrochemical and battery research for the dissolution of lithium dendrites during post-mortem analysis of lithium-based energy storage systems.
