Catalytic effect of rhodium(III) on the chemiluminescence of luminol in reverse micelles and its analytical application

Abstract

Even in the absence of potassium periodate, rhodium(III) caused an increase in the chemiluminescence (CL) of luminol both in conventional aqueous basic buffer solution and in a reverse micellar medium of cetyltrimethylammonium chloride in chloroform—cyclohexane (6:5, v/v)—water (buffered with sodium carbonate). The CL emission intensity was observed to decrease significantly when oxygen was excluded from the reaction. The rhodium(III)-catalyzed CL emission from luminol oxidation by oxygen in a reverse micellar medium can be used for analytical purposes. Under the optimized experimental conditions, the present emission was applied to determine rhodium(III) in chloroform using a flow-injection system. A detection limit of 50 ng ml −1 Rh(III) and a linear calibration graph was obtained with a dynamic range from 0.40 μg ml −1 to 10 μg ml −1.