Chemiluminescence study of carbonate and peroxynitrous acid and its application to the direct determination of nitrite based on solid surface enhancement

Peroxynitrous acid (ONOOH) was produced by the on-line mixing of acidified hydrogen peroxide with nitrite in a flow system. A strong chemiluminescent (CL) emission was observed when ONOOH reacted with carbonate without any special CL reagents. When cotton was present in the CL cell, the CL emission was enhanced significantly. The method was developed to determine nitrite, which showed a key improvement that any CL reagents and sensitizers were not used, resulting in better selectivity. The applicability of the present CL system was demonstrated for the sensitive and selective determination of nitrite in natural water samples without any special pretreatment. Good agreements were obtained for the determination of nitrite in tap and well waters between the present approach and a standard spectrophotometric method. The average precision was 4.6% (n=7) and detection limit (S/N=3) was 1.0×10⁻⁷ M. Based on the CL spectrum, UV spectra, and dissolved oxygen measurement, a possible CL mechanism was proposed. ONOOH was an unstable compound in acidic solution and could be quenched into peroxynitrite (ONOO⁻) in basic solution. ONOO⁻ reacted with CO₂ to produce ONOOCO₂⁻, which can rapidly decompose into NO₂ and CO₃⁻ radicals. In the presence of H⁺, CO₃⁻ radicals can protonate to bicarbonate radical (HCO₃). The recombination of HCO₃ radicals and decomposition can lead to light emission.