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

BACKGROUND: 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. RESULTS: 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). CONCLUSION: 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.

A study of the chemiluminescence behavior of cephalosporins with luminol and its analytical application.

The chemiluminescence intensity of luminol-dissolved oxygen was decreased when cephalosporins were mixed with luminol. The decrease chemiluminescence intensity was linear with the logarithm of cephalosporins concentration over the range from nanogram to microgramme level, with the limits of detection at nanogram level. The sensitivities of determination for cephalosporins were in the order of cefoperazone > ceftriaxone > cefuroxime > cefaclor > cefalexin > cefradine. The proposed method was applied to monitor the excretion of cefradine in human urine after taken cefradine capsules. The possible chemiluminescence mechanism and relationship between the determination sensitivities and generations of cephalosporins were also discussed.

Study on the interaction mechanism of lysozyme and bromophenol blue by fluorescence spectroscopy.

The interaction of lysozyme with bromophenol blue (BPB) in acetate buffer (pH 6.0) was studied by fluorescence quenching method for the first time. It was found that BPB could conspicuously quench the fluorescence of lysozyme by the static quenching process, possibly due to the binding on the active site near Trp62. The binding parameters including the binding constant and the number of binding site were calculated. The thermodynamic parameters DeltaH degrees, DeltaS degrees and DeltaG degrees at different temperatures were obtained. The formation of lysozyme-BPB complex depended on the cooperation of the hydrophobic and electrostatic forces. And the binding average distance between lysozyme and BPB was determined. The effect of common metal ions on the binding constant of lysozyme-BPB was also examined.