FI-CL Determination of Quercetin in Flos Sophorae Immaturus

The chemiluminescence of oxidation of luminol by hydrogen peroxide in an alkaline medium was found to be inhibited strongly by quercetin, and the magnitude of decrease of CL intensity was found to keep linear relationship with the concentration of quercetin in a definite range. Based on this fact and combining the use of flow-injection technique, a method of FI-CL determination of quercetin in flos sophorae immaturus was proposed. The optimum concentration of reagents used in the reaction system were as follows: ① cH2O2=0.2 mol·L-1; ② cluminol=8.5×10-4mol·L-1; and ③ cNaOH=0.01 mol·L-1. Range of linearity of quercetin was found between 2.65×10-6~5.31×10-4mol·L-1, with value of detection limit (3s/k) of 9.26×10-7mol·L-1. Value of RSD (n=11) found with 4×10-4mol·L-1 of quercetin was 3.0%. The sample of flos sophorae immaturus was pretreated by first extraction of rutin from the sample in an alkaline solution of pH 8-9, and then the rutin was hydrolyzed in a slightly acidic solution of pH 5 to give crude quercetin, which, after purification by re-crystallization, was dissolved in C2H5OH-H2O(40+60) solution and used for FI-CL analysis.