Development of voltammetric phenylalanine sensor

Phenylalanine is found in the structure of proteins necessary for the body and is an essential amino acid [1]. Phenylalanine is the metabolic precursor of the non-essential tyrosine amino acid and its derivatives [2]. The phenylalanine hydroxylase enzyme (PAH) synthesized in the liver turns phenylalanine into tyrosine. Phenylketonuria (PKU) occurs with PAH deficiency. If the disease is not diagnosed and treated early, phenylketonuria leads to neurological dysfunction, autism, eczema and severe behavior disorder. Early detection can prevent many effects of the disease [3]. In this thesis study electrochemical sensors for the determination of L-Phe were prepared by two different methods. As the first, molecularly imprinted phenylalanine electrodes were prepared by electrochemical method. In this method, the electrochemical sensor was prepared by electropolymerization on the platinum electrode surface in the presence of the template molecule (L-Phe) and functional monomer (para-toluenesulfonic acid). In the second method, phenylalanine sensors were prepared by chemical modification. In this method, phenylalanine selective electrodes were prepared using GUM based polyurethane coatings. Firstly, gum-based polyurethanes were synthesized by solution polymerization technique and characterization of the polymer was carried out by FTIR, SEM, DSC, TGA and DTA. Polymer film coated electrodes were prepared by dropping the solutions of GUM polymers onto the platinum electrode. To determine the phenylalanine sensitive sensor property of the modified electrodes; parameters such as scanning speed, electrolyte type, pH and film thickness were investigated using alternating voltammetry (CV), differential pulse voltammetry (DPV) and whether or not linear response was obtained by analyte concentration. As a result, voltammetric phenylalanine sensors were obtained for the determination of the phenylalanine with sensitivity of 0.997 and 0.9972.