The Individual and Simultaneous Voltammetric Determination of significant biomolecules in pathological and biomedical chemistry ,L-DOPA, L-tyrosine and Uric acid, by Cysteic acid Modified Glassy Carbon electrode

In this study a compact and uniform polymeric structure of cysteic acid layer film is immobilized on glassy carbon electrode by electrochemical oxidation of L-cysteine. Then, the nanocomposite modified electrode characterize using field emission scanning electron microscopy (FESEM). Differential pulse voltammetry (DPV) responses was used to estimate the Levodopa (L-DOPA), L-tyrosine (Tyr), uric acid (UA) linear calibration range and the limit of detection individually and simultaneously. Levodopa (L-DOPA), is a biochemical substance, it can prepared via biosynthesis from tyrosine a non-essential amino acid [1]. Tyrosine (Tyr), a non-essential amino acid synthesized from another amino acid that called phenylalanine. Tyrosine also exists in dairy products, eggs, beans and meats. It often added to food products and to pharmaceutical formulations [2]. Uric acid (UA), is an antioxidant that is present in biological fluids like urine and blood serum [3]. Linear relationship is observed in the individually determination in concentration range of 0.35μM to 45µM and 0.6µM to 49 µM for L-DOPA and UA. Calibration plot of Tyr consists of two linear ranges from 1.7 to 6μM and from 6 to 50μM. The limit of detection for L-DOPA, Tyr, and UA is calculated to be 0.11, 0.55 and 0.2μM, respectively. It was found that, at cysteic acid/GCE three well separated peaks (0.08, 0.53 and 0.2 mV) were observed corresponding to the oxidation of L-DOPA, Tyr, and UA respectively. So the potential differences were large enough for simultaneously determine of these analytes together. Thus electro-catalytic activity of Cysteic acid/GCE is exploited for the simultaneous determination of L-DOPA, Tyr, and UA by keeping the concentrations of the two analytes constant and varying the concentration of the third analyt. The LODs were evaluated as 0.2, 1.1 and 0.36μM for L-DOPA, Tyr, and UA respectively. In light of efficient and comparable results and efficient electro-catalytic activity the electrochemical sensor can be utilized successfully for the simultaneous determination of the L-DOPA, Tyr, and UA species in real samples.