Electrochemical sensors based on l-tryptophan molecularly imprinted polypyrrole and polyaniline

• Electrochemical sensor based on the molecularly imprinted polymer (MIP) for the detection of l -Tryptophan. • Pyrrole and aniline were used for electrochemical deposition of MIP Ppy and MIP PANI layers on the graphite electrode. • MIP Ppy and MIP PANI layers were electrochemically deposited on the electrode by potential cycling. • MIP-modified electrodes were evaluated by differential pulse voltammetry (DPV) and cyclic voltammetry. • MIP Ppy layer has greatest affinity towards l -Tryptophan molecules in comparison with other evaluated layers. The aim of this work was to compare two different conducting polymers (polypyrrole and polyaniline) in the design of the molecularly imprinted polymer (MIP). An l -tryptophan was selected as a template molecule in such MIP-based layers deposited on the graphite electrodes. Further, the MIPs with l -tryptophan imprints were applied in the design of electrochemical sensors for the detection of l -tryptophan. All polymer layers were electrochemically deposited on the electrode surface by the application of potential cycling. The characteristics of all modified electrodes were evaluated by differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The results demonstrate that the molecularly imprinted polypyrrole MI Ppy layer has a greater affinity toward l -tryptophan molecules in comparison with other layers evaluated in this study. This observation proves that polypyrrole is more suitable for the design of the molecularly imprinted polymer-based sensors for the determination of l -tryptophan than polyaniline. The linear relationship between the current intensity of DPV signal obtained on the molecularly imprinted polypyrrole and the concentration of l -tryptophan was obtained from 50 µM to 100 µM with the limit of detection (LOD) of 16.6 µM and the limit of quantitation (LOQ) of 49.8 µM.