DOI: 10.1002/elan.201600120 Recognition and Quantification of Some Monoamines Neurotransmitters Mohamed A. F. Elmosallamy [a, b] and Amr L. Saber* [b, c] 1 Introduction Neurotransmitters are biochemical substances that are produced and secreted by a neuron and then diffused across a synapse to cause excitation or inhibition of other neurons. Dopamine, serotonin, and epinephrine are ex- amples of neurotransmitters. Dopamine (DA), 4-(2-ami- noethyl) benzene-1,2-diol (Fig. 1) is an organic compound of the catechol amine that plays important roles in the human brain and body. The brain comprises several dis- tinct dopamine systems, one of which plays an important role in reward-motivated behavior. Most types of reward increase the level of dopamine in the brain. Other brain dopamine systems control the release of various hor- mones and involve motor control. Several diseases of the nervous system are due to the dysfunctions of the dopa- mine system. Lack of dopamine levels in the body can cause Parkinson,s disease, highly altered levels of dopa- mine activity cause schizophrenia [1]. On the other hand, there are several methods reported in the literature for the quantification of DA comprising voltammetry [2–6], UHPLC [7–10], HPLC [11–13], GC [14], capillary elec- trophoresis [15–17], fluorimetry [18–22], electrochemilu- minescence [23, 24], all of these methods are of highly costly, time consuming and involve derivatization steps. Biosensors [25] and potentiometric sensors [26–29] have also been reported. Serotonin, 3-(2-aminoethyl) indol-5-ol, or 5-hydroxy- tryptamine (5-HT) (Fig. 1) is a monoamine neurotrans- mitter. It is primarily found in the gastrointestinal tract, blood platelets and the central nervous system of animal including humans. 5-HT is popularly thought to be a con- tributor to feelings of well-being and happiness [30]. The most widely used methods for the quantification of sero- tonin are UHPLC [7, 8], HPLC [31–33], GC [14], capilla- ry electrophoresis [15], voltammetry [6, 34–35]and fluo- rimetry [36]. So far, there is no potentiometric sensor for quantification of serotonin in the literature. Epinephrine known also as adrenaline, (R)-4-(1-hy- droxy-2-(methylamino) ethyl) benzene-1,2-diol (Fig. 1) is a hormone and a neurotransmitter [37], epinephrine and norepinephrine are separate but related hormones secret- ed by the medulla of the adrenal glands. The word adren- aline is used in common parlance to denote increased ac- tivation of the sympathetic system associated with the energy and excitement of the fight-or-fight response [38]. The reported methods for the determination of adrena- line are voltammetry [5,39], UPLC [7,8,10], HPLC [13, 12], capillary electrophoresis [15, 17] and fluorimetry [22]. Also there is no potentiometric sensor for the deter- [a] M. A. F. Elmosallamy Department of Chemistry, College of Science and Humanities P.O. Box 83, Prince Sattam Bin Abdulaziz University Alkharj 11942, Kingdom of Saudi Arabia [b] M. A. F. Elmosallamy, A. L. Saber Chemistry Department, Faculty of Science, Zagazig University, Zagazig, Egypt Tel.: + 966546546884; Fax: + 20552375354 *e-mail: alshefny@yahoo.com [c] A. L. Saber Department of Chemistry, Faculty of Applied Science Umm Al Qura University, Makkah, Kingdom of Saudi Arabia Abstract : Three neurotransmitter sensors for dopamine, serotonin, and epinephrine have been developed. Poten- tiometric sensors for serotonin and epinephrine are novel and first to be introduced. The neurotransmitter potentio- metric sensors are based on using dibenzo-30-crown-10 (DB30C10), dibenzo-24-crown-8 (DB24C8), and dibenzo- 18-crown-6 (DB18C6) as ionophores and neutral carriers incorporating in poly(vinyl chloride) matrix membrane plasticized with o-nitrophenyl octyl ether. Sensors based on dibenzo-30-crown-10 show good responses for the dopamine, serotonin, and epinephrine (Type I–III, respec- tively) with a cationic slope of 57.9 mV decade 1 and de- tection limit of 4.0  10 5 mol L 1 dopamine, cationic slope of 55.9 mV decade 1 and detection limit of 4.0  10 5 mol L 1 serotonin, and cationic slope of 54.4 mV de- cade 1 and detection limit of 2.0  10 5 mol L 1 epinephr- ine. The sensors based on DB24C8 and DB18C6 (Types IV–IX) show poor responses in terms of calibration range and slope. The effect of the interferents on the response of the sensors reveals a high selectivity for the neuro- transmitters over many inorganic cations, ascorbic and uric acids. The useful pH range for the three sensors is 3– 7, the response time is fast (11 s), and the life span is long (2.5 months). Sensors (Types I and III) are successfully used for the quantification of dopamine and adrenaline in pharmaceutical preparations. Keywords: Neurotransmitters · Crown ethers · Potentiometric sensors · Pharmaceutical preparations www.electroanalysis.wiley-vch.de  2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2016, 28, 1 – 7 &1& These are not the final page numbers! ÞÞ Full Paper