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    Development of Gum-Arabic-based polyurethane membrane-modified electrodes as voltammetric sensor for the detection of phenylalanine
    (Springer, 2021) Alisik, Funda; Burc, Muammer; Titretir Duran, Serap; Gungor, Oznur; Cengiz, Mahmut Alper; Koytepe, Suleyman
    In this study, L-phenylalanine (L-Phe) sensors were prepared from Gum-Arabic-based polyurethanes, by the modification of Pt electrode. Firstly, Gum-Arabic-based polyurethanes were synthesized by solution polymerization technique and characterized with Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis, scanning electron microscopy and atomic force microscopy techniques. Then, L-Phe selective electrodes were prepared by coating the platinum electrode with different thickness Gum-Arabic-based polyurethane. L-Phe responses of the modified electrodes were investigated by differential pulse voltammetry technique. Sensor parameters such as scanning speed, film thickness, electrolyte type and pH were examined in detailed. Prepared electrodes were showed R-2 = 0.9972 for the concentration range of 200-1000 mu M L-Phe. The limit of detection and the limit of quantification of the prepared L-Phe selective modified electrode were calculated as 48.01 mu M and as 144.02 mu M, respectively. After ten consecutive measurements with the prepared L-Phe selective electrode, 98.8% stable result was obtained between the first and tenth reading and the RSD% value was found to be 1.21% for ten replicates. Consequently, prepared Gum-Arabic-modified sensors can be used successfully for the detection of the L-Phe with large concentration areas, high sensitivity and repeatability. [GRAPHICS] .
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    Preparation of Molecularly Imprinted Electrochemical L-Phenylalanine Sensor with p-Toluene Sulfonic Acid Modified Pt Electrode
    (Electrochemical Soc Inc, 2020) Alisik, Funda; Burc, Muammer; Koytepe, Suleyman; Duran, Serap Titretir
    L-Phenylalanine (L-Phe) sensors were prepared with two steps by modifying the Pt electrode using the molecular imprinting technique. In first step, polymeric films based on p-toluene sulfonic acid (PTSA) were electropolymerized on the Pt electrode in the presence of L-Phe as template molecule. In the second step, L-Phe, the template molecule, was desorbed from the film structure coated on the electrode surface using acid. The surface properties and morphologies of the prepared modified electrodes were checked by SEM analysis technique. These modified electrodes were used for determination of L-Phe by differential pulse voltammetry (DPV). Electrodes obtained by molecular imprinting method showed R-2 = 0.9997 in the concentration range of 2-2000 mu M L-Phe. The limit of detection (LOD) of L-Phe selective electrodes was found as 0.59 mu M and the limit of quantification (LOQ) was 1.77 mu M. The first three repetition result with the same modified electrode was observed as 96.83% and the RSD value was 14.96% for ten replicates. For twenty modified electrodes, reproducibility was obtained as 97.67% stable between first electrode and twentieth electrode, and the RSD value was observed to be 2.33%. According to these results, prepared molecular imprinted electrodes have high repeatability, stability and selectivity for the determination of L-Phe.