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Simultaneous analysis of ascorbic acid (AA), uric acid (UA), and dopamine (DA) is desirable as they are important biomarkers that coexist in biological fluids. Electrochemical detection of these molecules can be challenging as their oxidation peaks are poorly resolved at most unmodified electrodes. Modifications are typically necessary for analysis which increase cost and complicate fabrication. Herein, inexpensive and moldable polystyrene thermoplastic electrodes (PS TPEs), that can be used for simultaneous analysis of AA, DA, and UA, without surface modification, were presented. Electrode composition was optimized for conductivity, capacitance, and electrochemistry. Detection limits were 4, 0.9, and 4 μm for AA, DA and UA respectively. PS TPEs were also challenged in urine; excellent recoveries (90–110 %) were seen for AA and UA. DA showed lower recoveries (82 % for 10 μm and 47 % for 5 μm), but in the future, higher recoveries can be achieved through design considerations and further material optimization. [ABSTRACT FROM AUTHOR]

Dopamine (DA) is an important neurotransmitter, which is created and released from the central nervous system. It plays a crucial role in human activities, like cognition, emotions, and response to anything. Maladjustment of DA in human blood serum results in different neural diseases, like Parkinson's and Schizophrenia. Consequently, researchers have started working on DA detection in blood serum, which is undoubtedly a hot research area. Electrochemical sensing techniques are more promising to detect DA in real samples. However, utilizing conventional electrodes for selective determination of DA encounters numerous problems due to the coexistence of other materials, such as uric acid and ascorbic acid, which have an oxidation potential close to DA. To overcome such problems, researchers have put their focus on the modification of bare electrodes. The aim of this review is to present recent advances in modifications of most used bare electrodes with carbonaceous materials, especially graphene, its derivatives, and carbon nanotubes, for electrochemical detection of DA. A brief discussion about the mechanistic phenomena at the electrode interface has also been included in this review. [ABSTRACT FROM AUTHOR]