A paper-based analytical device with in-situ Carrez pretreatment for the determination of total polyphenolic content and antioxidant capacity.

A µPAD to determine the total polyphenol content (TPC) by Folin-Ciocalteau (FC) method, and antioxidant capacity by ABTS method, coupling an in-situ pretreatment zone with Carrez reagents is proposed. Conditions of FC, KSO, ABTS reagents concentrations, pH, and incubation were established using 2 factorial designs. The proposed µPAD showed linearities upper than 0.99 in ranges 0.150-2.000 mg L and 0.100-1.000 mg L for FC and ABTS methods, respectively, detection limits were lower than 0.135 mg L, precision lower than 13.47 %, and recoveries between 82.27 % and 114.60 %. Ten different food samples were analyzed to demonstrate the applicability of the µPAD, and the results were compared with those obtained by the batch methods, showing no significant differences (p > 0.05). The µPAD in-situ sample treatment allowed removing interferences before the TPC and ABTS detection avoiding overestimation of the results.