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Chrysin and baicalein are the major flavonoids found in oroxylum indicum, an essential herb in traditional Chinese medicine (TCM). Owing to their similar characteristics and physiochemical property, it is a great challenge to detect both of them simultaneously. In this work, tantalum oxide (Ta 2 O 5 ) particles and chitosan modified carbon paste electrode (Ta 2 O 5 -CTS-CPE) was prepared and characterized by scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectrum(EIS). Under the optimum conditions, the prepared Ta 2 O 5 -CTS-CPE exhibited excellent electrocatalytic activity toward the oxidation of chrysin and baicalein, and it could serve as the sensor for highly sensitive and simultaneous determination both of them. The linear range is 0.08–4.0 μM for both of them, and the detection limits were determined to be 0.03 and 0.05 μM (S/N=3) for chrysin and baicalein, respectively. Furthermore, the proposed electrochemical sensor displayed high sensitivity, excellent stability and got satisfactory results in oroxylum indicum samples analysis. [ABSTRACT FROM AUTHOR]

A 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. 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 and discussed, and this could be a reference for the pharmacological action of palmatine in clinical study. 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 in human urine samples, medicinal tablets and the Chinese herb Fibraurea recisa Pierre with satisfactory results. [ABSTRACT FROM AUTHOR]

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]

A new type of voltammetric sensor, Langmuir-Blodgett (LB) film of multi-walled carbon nanotubes (MWCNTs) perpendicularly modified glassy carbon electrode (GCE), was prepared and applied in determination of methylparaben. Based on the excellent electrochemical property of vertical MWCNTs on the GCE (MWCNTs-LB/GCE), a sensitive voltammetric method for determination of methylparaben was erected with liner range from 1 × 10 −6 mol L −1 to 8 × 10 −5 mol L −1 and detection limit of 4 × 10 −7 mol L −1 . The electrochemical characters of MWCNTs-LB/GCE were investigated in detail and the reaction mechanism of methylparaben was discussed. Meanwhile, cosmetic samples were analyzed using proposed method and the results obtained were well satisfactory. [ABSTRACT FROM AUTHOR]

The nanocomposite of ruthenium oxide (RuO 2 ) loaded on Poly-(dimethyldiallylammonium chloride) (PDDA) functionalized reduced graphene oxide (RuO 2 -PDDA-rGO) was synthesized based on a one-step method. Based on the RuO 2 -PDDA-rGO modified glassy carbon electrode (GCE), a new electrochemical sensor (RuO 2 -PDDA-rGO/GCE) was fabricated and used in detection of baicalein for the first time. Compared with other reported electrochemical sensors for the detection of baicalein, the prepared RuO 2 -PDDA-rGO/GCE had a wider linear range (2–400 nM) and lower detection limit (0.6 nM, S/N = 3). The other advantages were the excellent repeatability of proposed method and good stability of prepared sensor. [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]

Arctigenin was determinated by an electrochemical method for the first time based on a novel voltammetric sensor, which was prepared by simple dipping-drying of SWCNTs on glassy carbon electrode (GCE) initially and then electrochemical deposition of Iodide. The resulting Iodide/SWCNTs/GCE displayed a significant voltammetric response to arctigenin due to the electrocatalytic ability of Iodide for arctigenin and a large specific surface area, excellent electric conductivity of SWCNTs. Meanwhile, the redox mechanism of arctigenin on Iodide/SWCNTs/GCE was also studied. The wide linear range of 3 × 10 − 8 mol L − 1 to 5 × 10 − 6 mol L − 1 and low detection limit of 1 × 10 − 8 mol L − 1 for the determination of arctigenin were achieved together with high sensitivity, selectivity, good stability. To examine the practical analytical utility of the proposed electrode, the real sample Fructus Arctii was examined and the result was found satisfactory. [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]

A 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 method could also be used to detect daphnetin in the medicinal capsules and Chinese medicinal herb Zushima with satisfactory results. [ABSTRACT FROM AUTHOR]

A new voltammetric sensor for simultaneous detection of bisphenol A and bisphenol S with high sensitivity has been constructed based on a three-component composite modified glassy carbon electrode. The three-component composite used herein is composed of AuAgPt ternary alloy nanocrystals (AuAgPt), porous β-cyclodextrin polymer (PCD) and oxide graphene (GO), abbreviated as AuAgPt-PCD-GO. The obtained composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM). The proposed modified electrode showed excellent electrochemical response to bisphenol A and bisphenol S simultaneously. Under optimal experiment conditions, the response linear ranges for bisphenol A and bisphenol S are from 6 nM to 4000 nM and 8 nM–8000 nM with detection limits of 2 nM and 2.67 nM (S/N = 3), respectively. Furthermore, this electroanalytical sensor could also be successfully applied to real sample analysis with satisfactory results. Image 1 • The three-component composite material AuAgPt-PCD-GO was designed to construct a novel electrochemical sensor for simultaneous BPA and BPS assay. • The possible electrochemical oxidation mechanism of BPA and BPS on the modified electrode was deduced. • The proposed sensor can be used for real sample assay with satisfactory results. [ABSTRACT FROM AUTHOR]