Electrochemical Analysis of Hydroquinone using glassy carbon electrode coated with a clay film amended by L-cysteine

Abstract

In this study, an amino acid namely L-cystein was used to modify a smectite type clay. The modified
smectite was characterized by X-rays diffraction and thermal analysis. The results obtained showed
that L-cysteine was successfully absorbed on the smectite external layers. Due to its organophilic
character, the modified-clay was evaluated as electrode modifier for the accumulation of
hydroquinone. The modified electrode was obtained by drop coating of previously modified clay on
glassy carbon electrode. The cyclic voltammetry curves of hydroquinone exhibited one well-defined
anodic peak around 0.4 V and one reduction peak around 0.2V. The peak current obtained on glassy
carbon electrode coated by thin film of modified clay was two times higher than that obtained on bare
glassy carbon electrode and three times higher than that exhibited by the same substrate covered by a
film of the pristine clay. Many parameters that can affect the differential pulse voltammetric (DPV)
response of hydroquinone (pH of the detection medium, pre-concentration medium, accumulating
time, electrolysis potential) were systematically investigated to optimize the sensitivity of organoclaymodified electrode. After optimization, a linear curve was obtained in the concentration range of 2.10-6
mol L-1
to 10-5 mol L-1
leading to a detection limit of 8.10-7 mol L-1