Determination of Sudan IV in hot chilli powder with luminol/dissolved oxygen chemiluminescence system.

A green, simple and sensitive flow injection chemiluminescence (CL) procedure is proposed for the determination of Sudan dyes. The method is based on the finding that Sudan I, II, III and IV markedly enhance the CL intensity of the luminol/dissolved oxygen reaction. The increment in CL intensity was proportional to the concentration of Sudan I, II, III and IV, giving calibration graphs linear over the ranges 0.007-1, 0.5-30, 1-10 and 0.7-300 ng mL(-1) respectively (R(2) >or= 0.9981), with limits of detection of 0.002, 0.2, 0.3 and 0.2 ng mL(-1) respectively. At a flow rate of 2 mL min(-1), complete determination of Sudan dyes, including sampling and washing, could be accomplished in 40 s, with relative standard deviations of less than 5% (n = 7). The proposed method was successfully applied to the determination of Sudan IV in contaminated hot chilli powder, with recoveries ranging from 89.3 to 108.4%. The possible mechanism of enhancement of the luminol/dissolved oxygen CL reaction by Sudan IV can be attributed to the acceleration of electron transfer. Compared with other procedures, the proposed CL method offers the highest sensitivity and the least reagent consumption for the determination of Sudan IV.