Recognition and Quantification of Some Monoamines Neurotransmitters

Three neurotransmitter sensors for dopamine, serotonin, and epinephrine have been developed. Potentiometric sensors for serotonin and epinephrine are novel and first to be introduced. The neurotransmitter potentiometric 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, respectively) with a cationic slope of 57.9 mV decade−1 and detection 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 decade−1 and detection limit of 2.0×10−5 mol L−1 epinephrine. 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 neurotransmitters 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.