title: Nanomolar simultaneous determination of tryptophan and melatonin by a new ionic liquid carbon paste electrode modified with SnO2-Co3O4@rGO nanocomposite.
abstract: This work describes the development of a new sensor for simultaneous determination of tryptophan and melatonin. The proposed sensor was an ionic liquid carbon paste electrode modified with reduced graphene oxides decorated with SnO2-Co3O4nanoparticles. The voltammetric oxidation of the analytes by the proposed sensor confirmed that the electrooxidation process undergoes a two-electron/one-proton reaction for melatonin and a two-electron/two-proton reaction for tryptophan in diffusion-controlled processes. Moreover, based on the excellent electrochemical properties of the modified electrode, a sensitive voltammetric method was used for individual and simultaneous determination of melatonin and tryptophan in the aqueous solutions. Under the optimized experimental conditions, a linear response obtained in the range of 0.02 to 6.00μmolL-1with detection limits of 4.1 and 3.2nmolL-1for melatonin and tryptophan, respectively. The prepared sensor possessed accurate and rapid response toward melatonin and tryptophan with a good sensitivity, selectivity, stability, and repeatability. Finally, the applicability of the proposed sensor was verified by evaluation of melatonin and tryptophan in various real samples including human serum and tablet samples.
authors.affiliation: Department of Chemistry, Payame Noor University, Qazvin, Iran.
authors.forename: Homa
authors.initials: H
authors.lastname: Zeinali
authors.affiliation: Chemical Injuries Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran. Electronic address: h.bagheri82@gmail.com.
authors.forename: Hasan
authors.initials: H
authors.lastname: Bagheri
authors.affiliation: Department of Chemistry, Payame Noor University, Qazvin, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Monsef-Khoshhesab
authors.affiliation: Department of Internal Medicine, Zabol University of Medical Sciences, Zabol, Iran.
authors.forename: Hosein
authors.initials: H
authors.lastname: Khoshsafar
authors.affiliation: Laboratory for Sensors, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges Köhler Allee 103, 79110 Freiburg, Germany.
authors.forename: Ali
authors.initials: A
authors.lastname: Hajian
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D004566:Electrodes; D006108:Graphite / Q000737:chemistry*; D006801:Humans; D052578:Ionic Liquids / Q000737:chemistry*; D008550:Melatonin / Q000032:analysis* / Q000097:blood; D053761:Nanocomposites / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D017971:Tin Compounds / Q000737:chemistry*; D014364:Tryptophan / Q000032:analysis* / Q000097:blood
chemical_list: D052578:Ionic Liquids; D010087:Oxides; D017971:Tin Compounds; D003035:Cobalt; D006108:Graphite; D014364:Tryptophan; D008550:Melatonin; C045358:stannic oxide; C060728:cobalt oxide
keywords: Electrochemical sensors; Melatonin; Modified electrode; Simultaneous determination; SnO(2)-Co(3)O(4)@rGO nanocomposite; Tryptophan