Development of a voltammetric sensor for catechol in nanomolar levels using a modified electrode with Cu(phen)2(TCNQ)2 and PLL

A sensor based on glassy carbon (GC) electrode modified with bis(1,10-phenantroline)copper(II) bis(tetracyanoquinodimethanide) [Cu(phen)2(TCNQ)2] immobilized in a poly-l-lysine (PLL) film is proposed for catechol (CA) determination with differential pulse voltammetry (DPV) technique. The modified electrode showed excellent stability as well as the ability to detect catechol in nanomolar catechol levels. A linear response range from 10 nmol l−1 up to 20 μmol l−1 with a sensitivity of 2.29 μA l μmol−1 cm−2 and detection limit of 3.0 nmol l−1 were observed in the optimized conditions. The repeatability of the mesurements with the proposed sensor was 2% evaluated in term of relative standard deviation, with n = 10 for 10 μmol l−1 CA. Cyclic voltammetry and rotating disk electrode (RDE) experiments indicated that the catechol oxidation reaction involves two-electrons and a heterogenous rate constant (k) average value of about 1.30 × 103 M−1 s−1. The catechol diffusion coefficient (Do) value was estimated as being 7.6 × 10−6 cm2 s−1. The sensor was successfully applied for CA determination in powdered guarana samples.