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This work establishes a highly sensitive and simple stripping voltammetric method for the direct determination of trace iodide. In the presence of abounding bromide and appropriate amount of cetylpyridine bromide (CPB), the iodine was accumulated on the glassy carbon electrode surface as ion association complex (CPBI 2 Br). After accumulation for a period of time, a linear sweep potential with negative scanning was applied and the I 2 in CPBI 2 Br was reduced again into the solution. Under the optimization conditions, the stripping signals (peak current) were linear relationship with iodide concentration in range of 3.81×10 −3 µg/mL to 0.114 μg/mL and 0.127 μg/mL to 2.54 μg/mL, with a detection limit of 1.02 ng/mL ( S / N =3) for a accumulation time of 180 s. Determination of trace iodine in pharmaceutical sample, kelp and table salt were performed with high accuracy and satisfactory recovery results. [ABSTRACT FROM AUTHOR]

Abstract: A new and sensitive sensor for morphine, based on electrochemically reduced MWNTs-doped graphene oxide (ER-MWNTs-doped-GO) composite film modified glassy carbon electrode, was reported. Electrochemical impedance spectroscopy and scanning electron microscopy were employed to study the characteristic of the ER-MWNTs-doped-GO film. The electrochemical behaviour of morphine on this sensor was investigated in pH 4.5 phosphate buffer solution by cyclic voltammetry and linear sweep voltammetry. Significant advantages were achieved by combining the excellent conductivity of MWNTs and ER-GO with the film forming properties of GO. And some merits for response towards morphine from this sensor were showed such as wide linear range, fine selectivity and sensitivity, low detect limit and easy surface renewing. The application of the proposed method in analysis of real sample was also evaluated with good performance. [Copyright &y& Elsevier]

A composite LangmuirBlodgett film prepared from DNA and polyaniline was deposited on the surface of a glassy carbon electrode (GCE) to give a new voltammetric sensor for the β2-agonist salbutamol (SAL). Cyclic voltammetry and electrochemical impedance spectroscopy were employed to study the characteristic of the modified electrode. The electrochemistry of SAL at the modified electrode was investigated at pH 6.8 by cyclic voltammetry and differential pulse anodic voltammetry. The oxidation of SAL at this electrode is an adsorption-controlled irreversible process. A sensitive electroanalytical method for determination of SAL was worked out that displays high precision and good reproducibility. The method was applied to quantify SAL in tablets with satisfactory results. [ABSTRACT FROM AUTHOR]

Abstract: Gold nanoparticles/polyaniline nanocomposite thin film was deposited onto the surface of glassy carbon electrode(GCE) by Langmuir–Blodgett(LB) technology to fabricate a new voltammetric sensor (GNPs/PAn-LB GCE) for epinephrine(EP) and uric acid(UA) detection. Cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy were employed to study the characteristic of the GNPs/PAn-LB film. Electrochemical behaviors of EP and UA at the modified electrode were investigated in pH 6.6 phosphate buffer solutions. A sensitive electroanalytical method for simultaneous determination of EP and UA was proposed with high precision and good reproducibility. [Copyright &y& Elsevier]

In the present work, a new voltammetric sensor, Langmuir-Blodgett (LB) film of tetraoxocalix[2]arene[2]triazine (TOCT) modified glassy carbon electrode (LB-GCE), for trace analysis of copper ion in water samples, was prepared. The morphology of LB-GCE was characterized by cyclic voltammetric method, electrochemical impedance spectroscopy, and atomic force microscope. The recognizing mechanism of LB-GCE for copper ion in aqueous solution was discussed. Under the optimum experimental conditions, using square wave stripping voltammetry and accumulation time of 300 s, the peak currents were linear relationship with Cu concentrations in the range of 2 × 10 to 1 × 10 mol L, with detection limit of 1 × 10 mol L. By this method, real samples (lake water, drinking water, and city wastewater) were analyzed with satisfactory results. In addition, the fabricated electrode exhibited a distinct advantage of simple preparation, non-toxicity, good reproducibility, and stability. [ABSTRACT FROM AUTHOR]

We have prepared a new voltammetric sensor for guanine and adenine. It is based on a glassy carbon electrode modified with a Langmuir-Blodgett film made from tetraoxocalix[2]arene[2]triazine. The direct electro-oxidation of adenine and guanine was investigated and the results indicat that in contrast to a bare glassy carbon electrode both guanine and adenine cause an increase in the oxidation peak currents along with a negative shift of the oxidation potentials. The electrode enables the simultaneous determination of guanine and adenine using square wave voltammetry. Analysis of acid denatured calf thymus DNA was carried out and the value of (G + C)/(A + T) was correctly found to be 0.75. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A novel electrochemically activated nanocomposite, CoS 2 Nanoparticles and MoS 2 Nanosheets decorated poly(diallyldimethylammonium chloride)-functionalized graphene (CoS 2 -MoS 2 -PDDA-GR), was successfully synthesized through a simple and low-cost method. X-ray diffraction (XRD), Transmission electron microscopy (TEM), Electrochemical impedance spectroscopy (EIS) and Cyclic voltammetry (CV) techniques were used to characterize the nanocomposites. Based on the CoS 2 -MoS 2 -PDDA-GR nanocomposite modified glassy carbon electrode, the electrochemical properties of eriocitrin were investigated in detail and a sensitive determinative method was established synchronously. Compared with others, this sensor exhibited larger effective surface area, more reactive site and excellent voltammetric response for eriocitrin. Under optimum conditions by DPV, the oxidation peak currents responded to eriocitrin linearly over a concentration range from 2.0 × 10 −9 to 1.0 × 10 −6 mol L −1 with a detection limit of 6.7 × 10 −10 mol L −1 (S/N = 3). In addition, this fabricated sensor was successfully applied to detect eriocitrin in real samples with satisfactory results. [ABSTRACT FROM AUTHOR]

A novel voltammetric sensor was constructed by simple dripping single-walled carbon nanotubes (SWCNTs) on to the glass carbon electrode (GCE) firstly and electro-polymerizing l -Citrulline film subsequently. The resulting poly( l -Citrulline)/SWCNTs/GCE showed a significant voltammetric response to picroside II due to the synergistic effect of SWCNTs and poly( l -Citrulline) film. The first electroanalytical method of picroside II was proposed with detection linear range from 8.0×10 −8 to 5.0×10 −6 mol L −1 and a detection limit of 3×10 −8 mol L −1 .The high sensitivity, selectivity and long-term stability made the sensor suitable for the determination of picroside II. Moreover, based on the systematically investigation and some kinetics parameters calculated in the experimentation, the reaction mechanism of picroside II at the poly( l -Citrulline)/SWCNTs modified GCE was obtained reliably. Lastly, the proposed sensor was used for the determination of picroside II in real sample with satisfactory results. This work promoted the potential applications of amino acid materials and SWCNTs in electro-chemical sensors. [ABSTRACT FROM AUTHOR]

In this paper, a simple, low cost, highly sensitive voltammetric method for determination of tetrahydropalmatine was described, which was based on a new electrochemical sensor, poly (L-glutamic acid) functionalized electrochemical reduction graphene oxide modified glassy carbon electrode. The electrochemical behavior of tetrahydropalmatine was investigated in detail and some dynamic parameters of electrode process were calculated for the first time. Due to large surface area and good conductivity of proposed sensor, a wider linear range (3.0×10 −7 –2.0×10 −5 mol L −1 ) and lower detection limit (1.0×10 −7 mol L −1 ) were achieved for determination of tetrahydropalmatine. Meanwhile, the proposed method was used in determination of tetrahydropalmatine in Rhizoma Corydalis with well results. [ABSTRACT FROM AUTHOR]

A simple electrochemical method for the highly sensitive determination of hyperin was established based on poly(diallyldimethylammonium chloride)-functionalized graphene modified electrode (PDDA-Gr/GCE). The nanocomposite was characterized by X-ray diffraction (XRD), ultraviolet/visible spectra (UV–vis), Fourier Transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The electrochemical characteristics of hyperin were studied in detail via cyclic voltammetry (CV), chronocoulometry (CC). Dynamics parameters of electrode process were also calculated to discuss the reaction mechanism. Under the optimized conditions, a lower detection limit of 5 × 10 − 9 mol L − 1 (S/N = 3) and a wide linear detection range from 7 × 10 − 9 to 7 × 10 − 7 mol L − 1 were achieved by the differential pulse voltammetry (DPV). Additionally, this simple, sensitive sensor was proved to be suitable for the determination of hyperin in Chinese herb Hypericum Perforatum with satisfactory results. [ABSTRACT FROM AUTHOR]

With the aid of polyaniline (PANI), multi-wall carbon nanotubes (MWCNTs) were vertically arrayed on electrode surface by Langmuir–Blodgett technology, which was a novel preparation strategy of vertically aligned MWCNTs modified electrode. The proposed method was applied to design a sensitive voltammetric sensor for the determination of daidzein. Compared to the randomly dispersed MWCNTs modified electrode, a lower detection limit (8 × 10 −8 mol L −1 ) and wider linear range (1.0 × 10 −7 –9.0 × 10 −6 mol L −1 ) were achieved by the proposed sensor. The results indicated that the aligned morphology of MWCNTs could effectively facilitate the transportation of electrons and electrolyte ions. [ABSTRACT FROM AUTHOR]

A highly sensitive voltammetric sensor, based on reduced graphene oxide on SWCNTs modified glassy carbon electrode (GCE), was constructed and used for sensitive detection of hesperetin. The electrochemical behavior of hesperetin at this sensor was investigated systematically and a novel voltammetric method for determination of hesperetin was proposed. The redox characters of hesperetin was discussed in detail and a reasonable reaction mechanism was proposed also. As the analytical method, the response currents were linear relationship with the hesperetin concentrations in the range of 5.0×10 −8 to 3.0×10 −6 mol L− 1 , with a detection limit of 2.0×10 −8 mol L −1 ( S / N =3). The method was also applied successfully to detect hesperetin in biological samples and Chinese herbal medicine Flos buddlejae with satisfactory results. [ABSTRACT FROM AUTHOR]