Flow injection analysis of total curcuminoids in turmeric and total antioxidant capacity using 2,2'-diphenyl-1 -picrylhydrazyl assay

Abstract A simple flow injection analysis procedure is proposed for the determination of curcuminoids content in turmeric extracts. The method is based on the formation of a coloured complex between 4-aminoantipyrine and curcuminoids, in the presence of an oxidising reagent such as potassium hexacyanoferrate (III) in alkaline media. Conditions selected as a result of these trials were implemented in a flow injection analytical system in which the influence of injection volume, flow rate, reagent concentration and mixing coil length, was evaluated. Under the optimum conditions the total amount of curcuminoids could be determined within a concentration range of 5–50 μg mL −1 which can be expressed by the regression equation y  = 0.003 x  − 0.0053 ( r 2  = 0.9997). The limits of detection and quantitation were found to be 0.6 μg mL −1 and 1.8 μg mL −1 , respectively. The reproducibility of analytical readings was indicative of standard deviations