Fabrication Of Graphene And Amino Acid Modified Electrode And Applications In Pharmaceutical Analysis

Dating from the mid-70 s of the 20 th century, the chemically modified electrodes(CME) have received widespread attention, and have gradually become a research hotspot in eletroanalytical chemistry. As a novel two-dimensional single-atom-thick carbon material, graphene is widely used in electrochemical analysis due to its unique physicochemical properties, such as large specific surface area,fast electron transfer rate, high mechanical strength and so on. In addition, the poly amion acids modified electrodeswere also extensively applied at the determination of pharmaceuticaldrugs owing to theirexcellent electrocatalytic properties and biocompatibility. Meanwhile, amino acid functionalized graphene modified electrode could be easily constructed by direct electrochemical reduction of amino acid-functionalized graphene oxide(GO). We are dedicated to develop new electrochemical sensors based on the merit of graphene and amino acids, and exploit their applications in pharmaceutical analysis. The main points of this thesis are described as follows:1.Electrochemical behavior of daphnetin and its sensitive determination based on electrochemically reduced graphene oxide modified electrodeA sensitive electrochemical method for determination of daphnetin at reduced graphene oxide(RGO) modified glassy carbon electrode(GCE) was developed. The graphene nanosheets were simply directly deposited onto a GCE surface through cyclic voltammetric reduction of graphene oxide colloidal solution. The redox character of daphnetin at ERGO/GCE was studied systematically and some dynamic parameters were calculated for the first time. The electroanalytical method for determination of daphnetin was established by differential pulse voltammograms(DPV). Under optimum conditions, the response peak currents were linear related with daphnetin concentrations in the range of 5.0×10-8 to 2.0×10-6 mol L-1 with a detection limit of 3.0×10-8 mol L-1. Therefore, the high sensitivity for daphnetin sensing at the proposed electrode was achieved, which was attributed to the introduced graphene films modified on GCE. Additionally, the proposed methodcould also be used to detect daphnetin in the medicinal capsules and Chinese medicinal herb Zushima with satisfactory results.2. Electrochemical behavior of tectoridin and its sensitive determination based on L-arginine modified electrodeA simple, inexpensive and highly sensitive voltammetric method for the determination of tectoridin was developed using a poly(L-Arginine) modified electrode. The redox character of tectoridin at proposed electrode was studied systematically and some dynamic parameters were calculated for the first time. A reasonable reaction mechanism of tectoridin on the poly(L-Arginine)/GCE was also dicussed and proposed, which could be a reference for the pharmacological action of tectoridin in clinical study. And the electroanalytical method for determination of tectoridin was established by DPV. Under optimum conditions, the response peak currents were linear relationship with tectoridin concentrations in the range of5.0×10-8 to 2.0×10-6 mol L-1 with a detection limit of 4.0×10-8 mol L-1. Therefore, the high sensitivity for tectoridin sensing at the proposed electrode was achieved, and the proposed method could also be used to detect tectoridin in the Chinese medicinal herb Blackberrylily with satisfactory results.3.Electrochemical behavior of palmatine and its sensitive determination based on an electrochemically reduced L-methionine functionalized graphene oxide modified electrodeA new and sensitive voltammetric sensor for palmatine, based on an electrochemically reduced L-methionine functionalized graphene oxide modified glassy carbon electrode(L-Met-ERGO/GCE)is reported.L-methionine functionalized graphene oxide was characterized with scanning electron microscopy(SEM),ultraviolet-visible spectrum(UV-vis) and infrared spectrum(IR). The electrochemical characteristics of palmatine at the proposed sensor were studied systematically and some dynamic parameters were calculated for the first time. A reasonable reaction mechanism for palmatine on the L-Met-ERGO/GCE electrode was proposed. Under optimized conditions, the peak current had a linear relationship with palmatine concentration in the range of 1×10-7 to 5×10-5 mol L-1 with a detection limit of 6 ×10-8 mol L-1. Additionally, the proposed method was also used to detect palmatine inhuman urine samples, medicinal tablets and the Chinese herb Fibraurea recisa Pierre with satisfactory results.