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

Supramolecular host–guest interactions between β-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 β-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 β-cyclodextrin molecules. The current is proportional to the concentration of l-tyrosine from 3.6 × 10−5 M to 2.4 × 10−4 M. The detection limit and the sensitivity were found to be 1.2 × 10−5 M and 16.9 × 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%.