Determination of Rutin in Black Tea by Adsorption Voltammetry (AdV) in the Presence of Morin and Quercetin

This paper presents a sensitive method to rutin determination on a screen-printed multi-walled carbon nanotube electrode modified with poly(3,4-ethylenedioxythiophene) and ionic liquid (SMWCNT-PEDOT-IL). Several studies show that rutin may be absorbed onto the surface of electrodes modified with PEDOT. On the other hand, the presence of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄) on the surface of the modified electrode increased the oxidation current by nearly 30 % and facilitates the oxidation of rutin to values less positive potential compared with the modified electrode only with PEDOT. Cyclic voltammetry was used to quantify and characterize the modified electrode. pH and electrochemical parameters, potential adsorption, time adsorption, and scan rate were optimized based on the oxidation of rutin to obtain the following values: pH 6.0; Eads, −0.10 V; tads, 80 s; and scan rate 50 mV s⁻¹. The detection limit (3σ) was 7.7 × 10⁻⁸ mol L⁻¹ and the RSD was 1.5 %. The new method was used to quantify rutin in black tea samples in the presence of others flavones with consistent results.