Ascorbic acid as an alternative coreactant for luminol reaction and sensitive chemiluminescence determination of ascorbic acid in soft drinks

Ascorbic acid can serve as an efficient coreactant for luminol chemiluminescence (CL) reaction. An observable CL emission is produced when mixing ascorbic acid with luminol in an alkaline condition. The CL signal is further dramatically enhanced by cobalt(II) ions. This CL system was exploited as a new method for direct determination of ascorbic acid with a flow injection mode. A good linear response is acquired between the CL signal and ascorbic acid concentration in 5.0–1000.0 ng/mL range with a detection limit of 1.3 ng/mL. The relative standard deviations are 2.3% for intra–day (n = 11) and 3.7% for inter–day (n = 3) by parallel determination of 0.5 μg/mL ascorbic acid solution. The method has good selectivity for ascorbic acid since no obvious responses are observed for a variety of inorganic ions and biological substances. The practicability of the method has been demonstrated by the analysis of ascorbic acid in some soft drinks.