Study on the fluorescence enhancement in Lanthanum(III)-carminic acid-cetyltrimethylammonium bromide system and its analytical application.

A fluorescent enhancement system carminic acid (CA)-La3+-CTAB is found and based on this finding a new fluorimetric method for the determination of CA is developed. Under optimized conditions, the enhanced intensities of fluorescence are quantitatively in proportion to the concentrations of CA in the range of 0.01231-12.31 μg mL(-1). The detection limit is 10.92 ng mL(-1). Compared with other methods that have been reported to determine CA, this method has high sensitivity, stability and wide linear range. In addition, the luminescence mechanism indicates that the complex of La3+-CA (1:2) forms and solubilizes in CTAB micelle.