Mechanism and Analytical Applicability of Luminol-Specific Extrinsic Lyoluminescence of UV-Irradiated Potassium Peroxodisulfate

Luminol shows strong chemiluminescence with an emission maximum at ∼430 nm in the presence of sulfate radicals. Sulfate radicals were produced by the dissolution of UV-irradiated potassium peroxodisulfate powder in aqueous luminol solutions. The UV irradiation at 6.7 eV produces a solid solution of sulfate radical in potassium peroxodisulfate by rupturing −O−O− bonds, as in solution, but now the solid solution is stable in a time scale of years in dryness. In the present system, luminol chemiluminescence is produced via several parallel pathways having a common triggering step, one-electron oxidation of luminol monoanion by sulfate or hydroxyl radical. Present chemiluminescence allows sensitive luminol detection from picomolar to micromolar level with a linear response over 5 orders of magnitude, after which luminescence is too strong for single-photon counting. The high sensitivity of luminol detection allows us to propose extrinsic lyoluminescence of potassium peroxodisulfate as a new and simple method for detection step of bioaffinity assays using luminol or isoluminol derivatives as label compounds.