Simultaneous colorimetric measurements of antioxidant capacity by flow injection analysis with paired emitter detector diode

2019 Analytical Sciences  
26 An effective flow injection analysis (FIA) system employing paired emitter detector diode (PEDD) 27 for simultaneous dual antioxidant assays is proposed. The total antioxidant capacity (TAC) was measured 28 using the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay in parallel with the ferric 29 reducing antioxidant power (FRAP) assay. Ascorbic acid was used as the reference antioxidant and the 30 TAC value reported as ascorbic acid equivalent (AAE). A ten-port valve
more » ... en-port valve furnished with two injection loops 31 allowed the sample from one loop to react with the ABTS reagent and detected by one PEDD. At the same 32 time the sample from the second loop reacted with the FRAP reagent and is detected at the second PEDD. 33 Pair of red light emitting diodes (634 nm) was employed for both PEDDs. The linearity range was 10 to 50 34 µM ascorbic acid, with limit of detection of 3.18 µM and 4.37 µM, and precision of 2.41 and 2.15 %RSD 35 (for 30 µM ascorbic acid, n = 10) for the ABTS and FRAP assay, respectively. Sample throughput of 90 36 samples/h was achieved. The method was applied to the measurement of TAC of commercial fruit juice, 37 instant tea products and vitamin C tablets. The observed AAE values were in good agreement with those 38 obtained using batch methods with a spectrophotometer. 39 40
doi:10.2116/analsci.18p512 fatcat:spsvlcfznbgu7dv2nepspmll7e