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Introduction: Hirsutine and hirsuteine are the main pharmacological activity ingredients of Uncaria rhynchophylla (UR), playing an important role in treating mental and cardiovascular diseases, such as Alzheimerʼs disease, hypertension, Parkinson's disease, potential anti‐cancer activities and so on. Objective: To develop a cyclodextrin‐modified micellar electrokinetic capillary chromatography (CD‐MEKC) method for the simultaneous separation and determination of hirsutine and hirsuteine from UR and its formulations. Methodology: The optimal method was developed by investigating influences of significant factors on the separation, and this method was successfully applied for the determination of hirsutine and hirsuteine in UR and its formulations. Results: The optimal background electrolyte (BGE) consisted of 40 mM sodium dihydrogen phosphate (pH 7.0), 150 mM 2,6‐dimethyl‐β‐cyclodextrin (DM‐β‐CD), 3 mM mono‐(6‐ethylenediamine‐6‐deoxy)‐β‐cyclodextrin (ED‐β‐CD), and 30 mM sodium cholate (SC). Under these conditions, hirsutine and hirsuteine were successfully separated within 13 min at the separation voltage of 15 kV, temperature of 25°C and the detection wavelength of 224 nm. For the analytes, linear calibration curves were performed within the range 5.0–160.0 μg/mL. The limit of detection (LOD, S/N = 3) and the limit of quantitation (LOQ, S/N = 10) were 0.41, 1.42 μg/mL for hirsutine and 0.60, 2.17 μg/mL for hirsuteine, respectively. The recoveries of three samples were from 97.9% to 102.3%. Conclusion: The method was successfully applied to the determination of hirsutine and hirsuteine in UR and its formulations. Meanwhile, it provides an effective reference of the quality control of UR and its formulations. A cyclodextrin‐modified micellar electrokinetic capillary chromatography (CD‐MEKC) method consisted of mono‐ (6‐ethylenediamine‐6‐deoxy)‐β‐cyclodextrin (ED‐β‐CD), 2,6‐dimethyl ‐β‐cyclodextrin (DM‐β‐CD) and sodium cholate (SC) was developed for the separation and determination of uncaria alkaloids (hirsutine and hirsuteine). The method was successfully applied to the determination of hirsutine and hirsuteine in uncaria rhynchophylla (UR) and its formulations. Meanwhile, it provides an effective reference of the quality control of the UR and its formulations. [ABSTRACT FROM AUTHOR]

An elegant atomic layer deposition (ALD) method has been employed for the controllable preparation of a uniform Fe2O3-coated graphene nanostructure (Fe2O3@graphene). The Fe2O3 coating thickness of the Fe2O3@graphene nanostructure can be tuned by varying the cycle number of Fe2O3 ALD. The produced Fe2O3@graphene composites are characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and cyclic voltammetry (CV). It is revealed that Fe2O3 is effectively deposited on the surface of graphene. Combined with the high affinity and specificity of an aptamer, a simple, rapid and sensitive electrochemical aptasensor was successfully fabricated for thrombin detection. The resulting electrochemical aptasensor displays a linear response to thrombin in the 1.0 × 10−11 to 4.0 × 10−9 M concentration range with the detection limit of 1.0 × 10−12 M (at an S/N of 3). The described controllable multifunctional graphene nanomaterials from ALD are expected to be applied in a biosensing platform which will exhibit wide applications in biological, medical, and environmental fields. [ABSTRACT FROM AUTHOR]

The formation of a novel complex with cyclodextrin was investigated for the separation of cinchona alkaloids including the diastereomeric pairs of quinine, quinidine, cinchonine, and cinchonidine. The optimized separation of mixed cinchona alkaloids was obtained using 18 mM tris(hydroxymethyl)aminomethane, 3 mM Cu(II), and 20 mM hydroxypropyl-β-cyclodextrin at pH 5.7 with an applied voltage of 20 kV. Under these conditions, the four cinchona alkaloids were completely separated with resolution values between 9.08 and 3.94. The linear dynamic ranges for the analytes were from 10 to 1000 µg/mL with separation in less than 30 minutes. This method was used for the analysis of cinchona bark, quinine injection, and tonic water. [ABSTRACT FROM PUBLISHER]

Abstract: Large‐volume sample stacking (LVSS) is commonly used as an effective online preconcentration method in capillary zone electrophoresis (CZE). In this paper, the method LVSS combined with CZE has been proposed to analyze camptothecin alkaloids. Optimum separation can be achieved in the following conditions: pH 9.0; 25m m borate buffer containing 20 m m sulfobutylether‐β‐cyclodextrin and 20 m m ionic liquid 1‐ethyl‐3‐methyllimidazole l‐lactate; applied voltage 20 kV; and capillary temperature 25 °C. The LVSS was optimized as hydrodynamic injection 4 s at 5.0 psi and the polarity switching time was 0.17 min. Under the above conditions, the analytes could be separated completely in <20 min and the detector response was increased compared with conventional hydrodynamic injection. The limits of detection were between 0.20 and 0.78 μg/L. A good linearity was obtained with correlation coefficients from 0.9991 to 0.9997. The recoveries ranged from 97.72 to 103.2% and the results demonstrated excellent accuracy. In terms of the migration time and peak area, the experiment was reproducible. The experimental results indicated that baseline separation can be obtained and this method is suitable for the quantitative determination of camptothecin alkaloids in real samples. [ABSTRACT FROM AUTHOR]

A non-aqueous capillary electrophoresis method has been developed for the separation and simultaneous determination of fraxin, esculin and esculetin in Cortex fraxini and its preparation for the first time. Optimum separation of the analytes was obtained on a 47 cm × 75 µm i.d. fused-silica capillary using a non-aqueous buffer system of 60 mm sodium cholate, 20 mm ammonium acetate, 20% acetonitrile and 3% acetic acid at 20 kV and 292 K, respectively. The relative standard deviations (RSDs) of the migration times and the peak heights of the three analytes were in the range of 0.23-0.28 and 2.12-2.60%, respectively. Detection limits of fraxin, esculin and esculetin were 0.1557, 0.4073 and 0.5382 µg[sol ]mL, respectively. In the tested concentration range, good linear relationships (correlation coefficients 0.9995 for fraxin, 0.9999 for esculin and 0.9992 for esculetin) between peak heights and concentrations of the analytes were observed. This method has been successfully applied to simultaneous determination of the three bioactive components with the recoveries from 90.2 to 109.2% in the five samples. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A simple and sensitive non-aqueous capillary electrophoresis method has been developed for simultaneous assay of three bioactive components (puerarin, daidzein and wogonin) in three traditional medicinal preparations for the first time. Optimum separation of the analytes was obtained on a 47 cm × 75 µm i.d. capillary using a non-aqueous buffer system of 20% acetonitrile, 25 m m ammonium acetate and apparent pH 9.00, with applied voltage and capillary temperature of 20 kV and 16°C, respectively. The relative standard deviations (RSDs) of the migration times and the peak areas of the three analytes were in the ranges 2.5-4.0% and 3.2-3.9%, respectively. Detection limits of puerarin, daidzein and wogonin were 0.090, 0.145 and 0.090 µg mL−1, respectively. In the tested concentration range, good linear relationships (correlation coefficients: 0.9998 for puerarin, 0.9998 for daidzein and 0.9978 for wogonin) between peak areas and concentrations of the analytes were observed. This method has been successfully applied to simultaneous determination of the three bioactive components with recoveries from 91.0 to 114.0%. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A novel, simple and efficient capillary electrophoresis method was developed to simultaneous determination of six furanocoumarins (psoralen, isopsoralen, imperatorin, isoimperatorin, phellopterin, and cnidilin). The separation buffer consisted of 30 mM boric acid, 12 mM sulfobutylether-β-cyclodextrin and 1.5 mM 2-hydroxypropyl-β-cyclodextrin (pH 7.8); the voltage was 20 kV, the temperature was 25 °C and the detection wavelength was at 246 nm with a diode array detector (DAD). Under the above conditions, the analytes could be separated with high resolution in less than 7 min. This method was used to simultaneously determine the content of psoralen, imperatorin, isoimperatorin and phellopterin in Angelica Dahurica Radix. And good linearities were obtained with correlation coefficients from 0.9992 to 0.9999. The limits of detection (LOD, S/N = 3) and the limits of quantitation (LOQ, S/N = 10) ranged from 0.6 to 3.0 μg/mL and from 2.1 to 9.9 μg/mL, respectively. The recoveries ranged between 98.8% and 101.8%. The results indicated the method can achieve baseline separation and quantitative analysis of furanocoumarins in Chinese herbal medicines and formulations. Effect of HP-β-CD Concentration. [Display omitted] • We evaluated various kinds of real samples. • We separated analytes with dual CDs system. • The methods can simultaneously separate six analytes in 7 min. [ABSTRACT FROM AUTHOR]

An elegant atomic layer deposition (ALD) method has been employed for the controllable preparation of a uniform Fe 2 O 3 -coated graphene nanostructure (Fe 2 O 3 @graphene). The Fe 2 O 3 coating thickness of the Fe 2 O 3 @graphene nanostructure can be tuned by varying the cycle number of Fe 2 O 3 ALD. The produced Fe 2 O 3 @graphene composites are characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and cyclic voltammetry (CV). It is revealed that Fe 2 O 3 is effectively deposited on the surface of graphene. Combined with the high affinity and specificity of an aptamer, a simple, rapid and sensitive electrochemical aptasensor was successfully fabricated for thrombin detection. The resulting electrochemical aptasensor displays a linear response to thrombin in the 1.0 × 10 -11 to 4.0 × 10 -9 M concentration range with the detection limit of 1.0 × 10 -12 M (at an S/N of 3). The described controllable multifunctional graphene nanomaterials from ALD are expected to be applied in a biosensing platform which will exhibit wide applications in biological, medical, and environmental fields.