Kunjing Li

Study on the electrochemical properties of maltol at a carbon paste electrode and its analytical application

A new voltammetric sensor for the detection of maltol was developed, based on the carbon paste electrode (CPE) which allows for lower background current and more reproducible responses. The resulting sensor exhibits excellent redox activity towards maltol. For contrast, the electrochemical properties of maltol were compared on three paste electrodes, based on graphite powder (GP), carbon nanotubes (CNT) and graphene (Gr). The best response of maltol was obtained at the CPE. Further experiments demonstrated that the oxidative peaks increased linearly with maltol concentration in the range of 1.0 × 10−7 to 4.0 × 10−5 mol L−1 with a detection limit of 4.0 × 10−8 mol L−1. The method was successfully applied to detect maltol in beers with satisfactory results. Furthermore, the dynamic parameters and mechanism of electrode reaction were investigated using various electrochemical techniques.

The electrochemical characterization of curcumin and its selective detection in Curcuma using a graphene-modified electrode

A sensitive voltammetric sensor, a graphene-modified glassy carbon electrode (GR/GCE), for the detection of trace amounts of curcumin is proposed. The GR/GCE was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical behavior of curcumin at the GR/GCE was investigated by CV and liner sweep voltammetry (LSV). The reaction mechanisms of curcumin on the GR/GCE were also investigated and discussed systematically. In addition, the currents measured by LSV presented a good linear relationship with curcumin concentrations in the range of 5.0 × 10−8 to 3.0 × 10−6 mol L−1, with a low detection limit of 3.0 × 10−8 mol L−1. The method was also applied successfully to detect curcumin in a Curcuma longa L. sample with high selectivity and accuracy, as well as good recovery.

Sensitive voltammetric sensor for bergenin based on poly(L-lysine)/graphene modified glassy carbon electrode

A sensitive and novel electrochemical sensor for detection of bergenin by linear sweep voltammetry (LSV) is presented. This sensor was fabricated by dripping well-dispersed graphene onto glassy carbon electrode (GCE) surface firstly, and then poly(L-lysine) films were subsequently electropolymerized on it to prepare poly(L-lysine)/graphene/GCE. The dynamic detection range of this sensor to bergenin was 4.0 × 10−8 to 5.0 × 10−6 mol L−1 and 6.0 × 10−6 to 1.7 × 10−5 mol L−1, with the detection limit of 1.0 × 10−8 mol L−1. A new voltammetric method for determination of bergenin was erected and shows high sensitivity and selectivity, wider linear relationship, very easy surface update and good stability. The proposed sensors were tested for bergenin detection in pharmaceutical tablets with high accuracy and satisfactory recovery results was obtained. In addition, the oxidation mechanism is proposed and discussed, which could be a reference for the pharmacological action of bergenin in clinical studies.

Study of the voltammetric behavior of jatrorrhizine and its sensitive determination at electrochemical pretreatment glassy carbon electrode

A simple, inexpensive and highly sensitive electrochemical method for the determination of jatrorrhizine was developed using an electrochemically pretreated glassy carbon electrode (EPGCE). The electrochemical behavior of jatrorrhizine was systematically investigated in detail and some kinetic parameters were calculated for the first time. A reasonable reaction mechanism of jatrorrhizine on the EPGCE was also discussed and proposed, which could be a reference for the pharmacological action of jatrorrhizine in clinical study. And the first electroanalytical method of jatrorrhizine was established with a wide linear range from 7.0×10(-8) to 2.0×10(-5)mol L(-1) and a low detection limit of 5.0×10(-8)mol L(-1). The proposed method was successfully applied in determination of jatrorrhizine in pharmaceutical sample, Tinospora capillipes Gagnep (a traditional Chinese medicine), with satisfactory results.

Sensitive determination of urapidil at an electrochemically pretreated glassy carbon electrode by linear sweep voltammetry

A very simple and sensitive voltammetric method for the determination of urapidil was proposed by electrochemical pretreatment using a glassy carbon electrode as the voltammetric sensor (EPGCE). The EPGCE was obtained by cycling the electrode between a potential of −1.5 and 2.5 V, for five cycles in 0.1 M pH 7.0 PBS. Compared with the bare GCE, the EPGCE had an excellent response towards the oxidation of urapidil. Under the optimal conditions, the selective detection of urapidil in a linear concentration range of 2.0 × 10−8 to 5.0 × 10−6 mol L−1 was obtained with a determination limit of 2.0 × 10−8 mol L−1. At the same time, the EPGCE was also applied to the detection of urapidil content in urapidil sustained-release tablets and urine samples with satisfactory results.

Sensitive determination of colchicine at carbon paste electrode doped with multiwall carbon nanotubes

A carbon paste electrode doped with multiwall carbon nanotubes was constructed for the determination of colchicine. Cyclic voltammetry, differential pulse voltammetry and chronocoulometry have been used to investigate the electrochemical response characteristics and the kinetics parameters of colchicine on the proposed voltammetric sensor. Results show that the doped multiwall carbon nanotubes can greatly promote the electrochemical response of colchicine. Under optimum conditions, the oxidation current of colchicine was proportional to the concentration of colchicine in a wide linear range from 1.0 × 10−8 mol L−1 to 2.5 × 10−5 mol L−1 with a low detection limit of 8.0 × 10−9 mol L−1 in 0.15 mol L−1 H2SO4 (pH 0.8). The newly recommended sensor shows several merits including extreme simplicity, wide linear range, low detection limit, good stability and excellent reproducibility. Furthermore, it was successfully employed for the determination of colchicine in pharmaceutical formulations with satisfactory results.

The detailed electrochemical character of brucine at a poly(aspartic acid)-modified electrode and its sensitive determination

A simple and reliable electrochemical sensor based on poly(DL-aspartic acid)-modified glassy carbon electrode was proposed for direct determination of brucine. The electrochemical character of brucine on this sensor was carefully and systematically studied by cyclic voltammetry. Some kinetic parameters were calculated and a reasonable reaction mechanism for brucine at the poly(DL-aspartic acid)/GCE was also proposed. Meanwhile, a new electroanalytical method for determination of brucine was proposed with a highly sensitive detection limit of 3 × 10−8 mol L−1 (S/N = 3) and a wide linear range of 5.0 × 10−8 to 9.0 × 10−5 mol L−1. More importantly, this sensor exhibited good stability and excellent reproducibility in the response for brucine.

Sensitive voltammetric determination of neohesperidin dihydrochalcone based on SWNTs modified glassy carbon electrode

A new voltammetric sensor, based on single-walled carbon nanotubes (SWNTs) modified glassy carbon electrode, was established and used for the determination of neohesperidin dihydrochalcone (NHDC). The electrochemical characterization of NHDC on this sensor was studied systematically by cyclic voltammetry, and the kinetics parameters were calculated for the first time. Compared with a bare GCE, the proposed sensor exhibited excellent redox activity towards NHDC, and a new voltammetric analytical method for NHDC was proposed with a wide linear range from 5 × 10−8 mol L−1 to 8 × 10−6 mol L−1 and a low detection limit of 2 × 10−8 mol L−1. In addition, a reasonable mechanism was also proposed and discussed. Finally, the developed method was successfully applied for the quantitative determination of NHDC in beverages with high accuracy and satisfactory recovery results.