Development and optimization of an analytical method for the determination of Sudan dyes in hot chilli pepper by high-performance liquid chromatography with on-line electrogenerated BrO−-luminol chemiluminescence detection

The determination of four Sudan dyes by means of high-performance liquid chromatography (HPLC) with chemiluminescence (CL) detection was proposed. The method was based on the enhancement effect of Sudan dyes on the chemiluminescence reaction between luminol and BrO−, which was on-line electrogenerated by constant current electrolysis. The separation was carried out on Nucleosil RP-C18 column (250 mm × 4.6 mm i.d., 5 μm, pore size, 100 Å) at 35 °C. The mobile phase consisted of a V (methanol): V (0.2% aqueous formic acid) = 90:10 solution. At a flow-rate of 1.0 ml min−1, the total run time was 25 min. The effects of several parameters on the HPLC resolution and CL emission were studied systematically. For the four Sudan dyes, the limits of detection (LOD) at a signal-to-noise of 3 ranged from 4 to 8 μg kg−1 and the limits of quantification (LOQ) at a signal-to-noise of 10 ranged from 13 to 27 μg kg−1. The relative standard deviations (RSD) of intra-and inter-day precision were below 4.4%. The average recoveries for all four Sudan dyes (spiked at the levels of 1.0 and 1.5 mg kg−1) in chilli tomato sauce and hot chilli pepper ranged from 94% to 105%, and the relative standard deviations of the quantitative results were from 2.5 to 4.2%. The proposed method had been successfully applied to the determination of four Sudan dyes in hot chilli products.