Specificity of Lucigenin Solubility, and Solvent and Base Effects on Lucigenin Chemiluminescence

The solubility of lucigenin was measured in alcohols and aqueous alcohol mixtures. The solubility of lucigenin in normal alcohols exponentially decreased with increasing molecular weight of primary normal alcohols, whereas in alcohol–water mixtures it showed a maximum at specific alcohol concentrations. Solvent and bases effects on chemiluminescence (CL) of lucigenin have been investigated for methanol, ethanol, 1-propanol, 1-butanol, and aqueous mixtures of methanol and ethanol, and for various amine and alkaline metal bases, respectively. The CL intensities of lucigenin decreased in two-step processes: the main one with a short apparent lifetime of 0.3 ± 0.1 s and another one due to subreactions with a relatively long lifetime dependent on base concentration. At lower concentration of bases, the apparent CL lifetime increased in the order LiOH < NaOH < KOH. Both solvent and base effects on the solubility and CL of lucigenin are discussed from a standpoint of the amphipathic nature of lucigenin and solvents.