Nanostructures on gold electrodes for the development of an L-tyrosine electrochemical sensor based on host-guest supramolecular interactions

Supramolecular host-guest interactions between beta-cyclodextrins and L-tyrosine have been employed to develop a selective electroanalytical method for the determination of this amino acid. For this purpose, self-assembled monolayers of thiolated beta-cyclodextrins on a gold electrode have been built up. The benefits derived from the immobilization of these macromolecular receptors on the electrode surface are shown by the resolution of a mixture of electroactive amino acid analysed with the proposed modified electrode. In addition to this, all parameters affecting the gold electrode modification and the L-tyrosine determination through differential pulse voltammetry have been optimized. During the electrode modification step, pentanethiol was employed to fill up the exposed surface between beta-cyclodextrin molecules. The current is proportional to the concentration of L-tyrosine from 3.6 x 10(-5) M to 2.4 x 10(-4) M. The detection limit and the sensitivity were found to be 1.2 x 10(-5) M and 16.9 x 10(-4) AxM(-1) respectively, with Er values smaller than 13.0% and a RSD (%) (n = 5) values equal or lower than 5.4 achieving good accuracy and precision. Moreover, the developed methodology was successfully applied to L-tyrosine determination in pharmaceutical formulation samples with a RSD(n = 5) of 6.3% in average and an Er(n = 5) minor than 7.0%. (C) 2010 Elsevier B.V. All rights reserved.