UV-irradiated potassium peroxodiphosphate and nitrate as excitation sources for luminol chemiluminescence

Abstract

Luminol-specific extrinsic lyoluminescence of UV-irradiated potassium peroxodiphosphate and potassium nitrate has been studied. UV irradiation of solid peroxodiphosphate can induce rupture of the peroxide bond and produce a stable solid solution of phosphate radicals in potassium peroxodiphosphate. The dissolution of the irradiated salt can liberate phosphate radicals which initiate a luminol chemiluminescence-generating pathway in alkaline solution. UV irradiation of solid potassium nitrate induces partial photoisomerisation to potassium peroxonitrite, which has been previously reported to generate hydroxyl radicals during dissolution in aqueous solution. Support for hydroxyl radical generation was obtained and the hydroxyl radical was observed to be a key intermediate for strong chemiluminescence of luminol during dissolution of irradiated KNO₃ in luminol sample solutions. Both lyoluminescence systems allow the detection of luminol down to sub-nM levels with linear calibration curves spanning five orders of magnitude of luminol concentration, suggesting that they can be used as tools in bioaffinity assays utilising luminol and isoluminol derivatives as labels.