A Simple Synchronous Fluorescence Approach for Rapid and Sensitive Determination of Rhodamine B in Chilli Products

Rhodamine B (RhB), reported as potentially carcinogenic and mutagenic, is strictly forbidden for use in foods. In this research, a first-derivative constant wavelength synchronous fluorescence approach has been proposed for sensitive and rapid determination of RhB in chilli products including chilli oil, chilli powder and chilli sauce. The constant wavelength interval was set at 25 nm for the wavelength difference according to the emission peak and excitation peak of RhB. Experimental conditions such as solvent selection, volume of extraction solvent and time of extraction process were studied and optimized. Under the optimized conditions, limits of detection (LODs) for RhB were 0.52 ng/g in chilli oil, 1.3 ng/g in chilli powder and 0.24 ng/g in chilli sauce. The relative standard deviations (RSDs) were between 4.91 and 8.10 % (n = 5), and recoveries at three levels ranged from 76.5 to 108 % for different spiked chilli samples. The results obtained by our method were in consistence with those obtained by high-performance liquid chromatography coupled with fluorescence (HPLC-FL) measurement. The established method is a sensitive, economical and rapid approach for the determination of RhB in chilli products.