Analysis of nephroloxic and carcinogenic aristolochic acids in Aristolochia plants by capillary electrophoresis with electrochemical detection at a carbon fiber microdisk electrode

Aristolochic acids (AAs) are the main bioactive ingredients in the most of Aristolochia plants, which are used to make dietary supplements, slimming pills and Traditional Chinese Medicines (TCMs). Excessive ingestion of AAs can lead to serious nephropathy. Therefore, quantitative analysis and quality control for the plants containing AAs is of great importance. In this paper, capillary electrophoresis (CE) with electrochemical detection (ED) at a 33 mu m carbon fiber microdisk electrode (CFE) has been applied to detect AA-I and AA-II in Aristolochia plants. Under the optimum conditions: detection potential at 1.20 V, 2.0 x 10(-2) mol L-1 phosphate buffer solution (PBS) (pH 10.0), injection time 25 s at a height of 17 cm and separation voltage at 12.5 kV, the AA-I and AA-II were baseline separated within 5 min. Low detection limits for AA-I and AA-II were 4.0 x 10(-8) mol L-1 and 1.0 x 10(-7) mol L-1, respectively. Wide linear ranges were from 4.0 x 10(-8) mol L-1 to 1.9 x 10(-5) mol L-1 and 1.0 X 10(-7) mol L-1 to 5.0 x 10(-5) mol L-1 for AA-I and AA-II, respectively. The proposed method has been successfully applied to analyze AAs contents in plant extracts. The results indicated that the contents of AAs in each part of Aristolochia debilis Sieb. Et Zucc.

Determination of ranitidine in urine by capillary electrophoresis-electrochemiluminescent detection

The fast analysis of ranitidine is of clinical importance in understanding its efficiency and a patient's treatment history. In this paper, a novel determination method for ranitidine based on capillary electrophoresis-electrochemiluminescence detection is described. The conditions affecting separation and detection were investigated in detail. End-column detection of ranitidine in 5 mM Ru(bpy)(3)(2+) solution at applied voltage of 1.20 V was performed. Favorable ECL intensity with higher column efficiency was achieved by electrokinetic injection for 10 s at 10 kV. The R.S.D. values of ECL intensity and migration time were 6.38 and 1.84% for 10(-4) M and 6.01 and 0.60% for 10(-5) M, respectively. A detection limit of 7 x 10(-8) M (S/N = 3) was achieved. The proposed method was applied satisfactorily to the determination of ranitidine in urine in 6 min.

Chinese herb medicines analyses by capillary electrophoresis with amperometric detection

Capillary electrophoresis (CE) with amperometric detection (AD) has been widely used in various fields of analytical science, especially in the pharmaceutical industry recently due to its high separation efficiency and low detection limit. The determination of active ingredients in Chinese herb medicines by CE-AD is of great importance in developing the researches on pharmacology of herbs, quantitative analysis and quality control. Analyses of the effective components in Chinese herb medicines and compound Chinese herb medicine by CE-AD are reviewed in this paper. In contrast with other analysis methods, the advantage of CE-AD is discussed. The development in analyses of traditional Chinese medicine (TCM) by CE-AD in future is mentioned.

Simultaneous determination of tramadol and lidocaine in urine by end-column capillary electrophoresis with electrochemiluminescence detection

Tramadol and lidocaine, used as analgesic and local anesthetic in surgery, are partly excreted by kidney. For the first time, we developed a simple and sensitive method, based on capillary electrophoresis with electrochemiluminescence (ECL) detection by end column mode without joint to monitor tramadol and lidocaine in urine. To eliminate the influence of ionic strength of urine sample, analytes were extracted by ether. Tripropylamine (TPA) was used as internal standard. ne recoveries of tramadol and lidocaine were between 94% and 97% at different levels. The method exhibited the linear range for the tramadol and lidocaine from 1.0 X 10(-7) to 1.0 X 10(-4) mol/L with correlation efficient of 0.998. The relative standard deviation (RSD) was 2.9% and 2.7% (n = 8) for tramadol and lidocaine, respectively. The limit of detection (LOD) was 6.0 x 10(-8) mol/L and 4.5 x 10(-8), mol/L (S/N = 3) for tramadol and lidocaine, respectively. The application for detecting tramadol and lidocaine in urine of patients showed that the method was valuable in clinical and biochemical laboratories for detecting tramadol, lidocaine and other tertiary amine pharmaceuticals for various purpose, such as metabolism investigation.

Miniaturized tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescence detection cell for capillary electrophoresis and flow injection analysis

The design and performance of a miniaturized chip-type tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)(3)(2+)] electrochemiluminescence (ECL) detection cell suitable for both capillary electrophoresis (CE) and flow injection (FI) analysis are described. The cell was fabricated from two pieces of glass (20 x 15 x 1.7 mm), and the 0.5-mm-diameter platinum disk was used as working electrode held at +1.15 V (vs silver wire quasi-reference), the stainless steel guide tubing as counter electrode, and the silver wire as quasi-reference electrode. The performance traits of the cell in both CE and FI modes were evaluated using tripropylamine, proline, and oxalate and compared favorably to those reported for CE and FI detection cells. The advantages of versatility, sensitivity, and accuracy make the device attractive for the routine analysis of amine-containing species or oxalate by CE and FI with Ru(bPY)(3)(2divided by) ECL detection.

Fabrication of integrated microelectrodes for electrochemical detection on electrophoresis microchip by electroless deposition and micromolding in capillary technique

A new method for the fabrication of an integrated microelectrode for electrochemical detection (ECD) on an electrophoresis microchip is described. The pattern of the microelectrode was directly made on the surface of a microscope slide through an electroless deposition procedure. The surface of the slide was first selectively coated with a thin layer of sodium silicate through a micromolding in capillary technique provided by a poly(dimethylsiloxane) (PDMS) microchannel; this left a rough patterned area for the anchoring of catalytic particles. A metal layer was deposited on the pattern guided by these catalytic particles and was used as the working electrode. Factors influencing the fabrication procedure were discussed. The whole chip was built by reversibly sealing the slide to another PDMS layer with electrophoresis microchannels at room temperature. This approach eliminates the need of clean room facilities and expensive apparatus such as for vacuum deposition or sputtering and makes it possible to produce patterned electrodes suitable for ECD on microchip under ordinary chemistry laboratory conditions. Also once the micropattern is ready, it allows the researchers to rebuild the electrode in a short period of time when an electrode failure occurs. Copper and gold microelectrodes were fabricated by this technique. Glucose, dopamine, and catechol as model analytes were tested.

Microchip capillary electrophoresis with an integrated indium tin oxide electrode-based electrochemiluminescence detector

This paper describes an indium tin oxide (ITO) electrode-based Ru(bPY)(3)(2+) electrochemiluminecence (ECL) detector for a microchip capillary electrophoresis (CE). The microchip CE-ECL system described in this article consists of a poly(dimethylsiloxane) (PDMS) layer containing separation and injection channels and an electrode plate with an ITO electrode fabricated by a photolithographic method. The PDMS layer was reversibly bound to the ITO electrode plate, which greatly simplified the alignment of the separation channel with the working electrode and enhanced the photon-capturing efficiency. In our study, the high separation electric field had no significant influence on the ECL detector, and decouplers for isolating the separation electric field were not needed in the microchip CE-ECL system. The ITO electrodes employed in the experiments displayed good durability and stability in the analytical procedures. Proline was selected to perform the microchip device with a limit of detection of 1.2 muM (S/N = 3) and a linear range from 5 to 600 muM.

Discrete wavelets transform for signal denoising in capillary electrophoresis with electrochemiluminescence detection

Discrete wavelets transform (DWT). was applied to noise on removal capillary electrophoresis-electrochemiluminescence (CE-ECL) electropherograms. Several typical wavelet transforms, including Haar, Daublets, Coiflets, and Symmlets, were evaluated. Four types of determining threshold methods, fixed form threshold, rigorous Stein's unbiased estimate of risk (rigorous SURE), heuristic SURE and minimax, combined with hard and soft thresholding methods were compared. The denoising study on synthetic signals showed that wave Symmlet 4 with a level decomposition of 5 and the thresholding method of heuristic SURE-hard provide the optimum denoising strategy. Using this strategy, the noise on CE-ECL electropherograms could be removed adequately. Compared with the Savitzky-Golay and Fourier transform denoising methods, DWT is an efficient method for noise removal with a better preservation of the shape of peaks.

Direct tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescence detection of polyamines separated by capillary electrophoresis

Capillary electrophoresis (CE) with tris(2,2'-bipyridyl) ruthenium (II) (Ru(bpy)(3)(2+)) electrochemiluminescence (ECL) detection technique was developed for the analysis of four polyamines (putrescine (Put), cadaverine (Cad), spermidine (Spd), and spermine (Spm)) analysis. The four polyamines contain different amine groups, which have different ECL activity. There are several parameters which influence the resolution and ECL peak intensities, including the buffer pH and concentrations, separation voltage, sample injection, electrode materials, and Ru(bpy)(3)(2+) concentrations. Polyamines are separated by capillary zone electrophoresis in an uncoated fused-silica capillary (50 cm x 25 mum (ID) filled with acidic phosphate buffer (200 mmol/L phosphate, pH 2.0) - 1 mol/L phosphoric acid (9:1 v/v) and a separation voltage of 5 kV (25 muA), with end-column Ru(bpy)(3)(2+) ECL detection. A 5 mmol/L Ru(bpy)(3)(2+) solution plus 200 mmol/L phosphate buffer (pH 11.0) is added into the reagent reservoir. The calibration curve is linear over a concentration range of two or three orders of magnitude for the polyamines. The analysis time is less than 25 min. Detection limits for Put and Cad are 1.9 x 10(-7) mol/L and 7.6 x 10(-9) mol/L for Spd and Spm, respectively.

Evaluation of a sol-gel derived carbon composite electrode as an amperometric detector for capillary electrophoresis

In this paper, we report the construction and application of a sol-gel derived carbon composite electrode (CCE) as an amperometric detector for capillary electrophoresis. The electrochemical properties were characterized and compared with those of conventional carbon fiber and carbon paste electrode (CPE). Experimental results show that peak-to-peak noise of CCE was about 20% of CPE and electrode capacitance was comparatively low. When applied to the detection of dopamine and epinephrine, the optimal detection potential for CCE was 0.1 V lower than CPE under the same separation conditions; CCE with diameter of 75 and 100 mum could achieve a low detection limit of 3.10(-8) and 6.10(-8) M for the detection of epinephrine, which approaching that of the 33-mum diameter carbon fiber electrode. Also, the linearity for epinephrine at CCE was more than two orders of magnitude, which was slightly wider than that of carbon fiber electrode. Applications to real sample analysis were tested by the determination of betahistine dihydrochloride in tablets and human urine. Using CCE with diameter less than or equal to100 mum as an amperometric detector after capillary electrophoresis separation, a low detection limit and a wide linear range combined with excellent reproducibility were obtained. This CCE possesses of many advantages, namely, convenience, ease of fabrication, low cost and high stability.

Determination of biogenic amines by capillary electrophoresis with pulsed amperometric detection

The biogenic amines, putrescine, cadaverine, spermidine and spermine were separated and quantified by capillary electrophoresis with pulsed amperometric detection. Detection potential of the pulsed amperometric detection was optimized as 0.6 V Optimal separation of the biogenic amines was achieved using a separation buffer of 30 mM citrate at pH 3.5, while keeping the buffer in the detection cell as 20 mM NaOH. Using these conditions, the four biogenic amines were baseline separated. Extrapolated limits of detection for putrescine, cadaverime, spermidine and spermine were 400, 200, 100 and 400 nM for the standard mixture (polyamines dissolved in running buffer), respectively. These are lower than ultraviolet detection and comparable or even lower than laser-induced fluorescence detection results as reported in the literature. The number of theoretical plates was maintained at the 105 level, which is absolutely higher than any reported method. When applying capillary electrophoresis-pulsed amperometric detection to milk analysis, only spermidine was found in amounts varying between 0.1 and 0.5 mg/kg.

Determination of diphenhydramine by capillary electrophoresis with tris(2,2 '-bipyridyl)ruthenium(II) electrochemiluminescence detection

Tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence detection in a capillary electrophoresis separation system was used for the determination of diphenhydramine. In this study, platinum disk electrode (300 mum in diameter) was used as a working electrode and the influence of applied potential and buffer conditions were investigated. Under optimal conditions: 1.2 V applied potential, pH 8.50, 15 kV separation voltage and 10 mmol l(-1) running buffer, the calibration curve of diphenhydramine was linear over the range of 4 x 10(-8) to 1 x 10(-5) Mol l(-1). This technique gave satisfactory precision, and relative standard deviations of migration times and chemiluminescence peak intensities were less than 1 and 6%, respectively. The technique was applied to animal studies for determination of diphenhydramine extracted from rabbit plasma and urine samples, and the extraction efficiency were between 92 and 98.5%.

New technique for capillary electrophoresis directly coupled with end-column electrochemiluminescence detection

capillary electrophoresis (CE) is characterized. A 300 mum diameter Pt working electrode was used to directly couple with a 75 mum inner diameter separation capillary without an electric field decoupler. The hydrodynamic cyclic voltammogram (CV) of Ru(bpy)(3)(2+) showed that electrophoretic current did not affect the ECL reaction. The presence of high-voltage (HV) field only resulted in the shift of the ECL detection potential. The distance of capillary to electrode was an important parameter for optimizing detection performance as it determined the characteristics of mass transport toward the electrode and the actual concentration of Ru(bpy)(3)(2+) in the detection region. The optimum distance of capillary to electrode was decided by the inner diameter of the capillary, too. For a 75 mum capillary, the working electrode should be placed away from the capillary outlet at a distance within the range of 20-260 mum. The effects of pH value of ECL solution and molecular structure of analytes on peak height and theoretical plate numbers were discussed. Using the 75 mum capillary, under the optimum conditions, the method provided a linear range for tripropylamine (TPA) between 1 x 10(-10) and 1 X 10(-5) mol/L with correlation coefficient of 0.998. The detection limit (signal-to-noise ratio S/N = 3) was 5.0 x 10(-11) mol/L. The relative standard deviation in peak height for eight consecutive injections was 5.6%. By this new technique lidocaine spiked in a urine sample was determined. The method exhibited the linear range for lidocaine from 5.0 x 10(-8) to 1.0 X 10(-5) mol/L with correlation efficient of 0.998. The limit of detection (S/N = 3) was 2.0 x 10(-1) mol/L.

Capillary electrophoresis with solid-state electrochemiluminescence detector

We report capillary electrophoresis coupling to a solid-state electrochemiluminescence (ECL) detector for the first time. The solid-state ECL detector was fabricated by immobilizing the ECL reagent tris(2,2'-bipyridyf)ruthenium (TBR) in poly-(p-styrenesulfonate)-silica-poly(vinyl alcohol) grafting 4-vinylpyridine copolymer films. The excellent stability of the solid-state ECL detector in the phosphate solution satisfied application in CE. The CE with solid-state ECL detector system was characterized using tripropylamine (TPA) and proline. The influences of detection potential, the concentration of TBR in the film, and pH value of ECL buffer were investigated. The linear range for TPA and proline was 0.005-10 muM and 5-10 mM with correlation coefficients of 0.997 and 0.998, respectively. The detection limit (signal-to-noise ratio S/N = 3) was estimated to be 0.002 and 2.0 muM for TPA and proline, respectively. The relative standard deviations for 1.0 pm TPA and 1.0 mm proline were 8.7% and 7.5% with theoretical plate numbers of 70 000 and 16 000, respectively. Compared with the CE-ECL of TBR in aqueous solution, the CE coupling with solid-state ECL detector system gave the same sensitivity of analysis.

Capillary electrophoresis with electrochemiluminescence detection of procyclidine in human urine pretreated by ion-exchange cartridge

This paper describe a Ru(bpy)(3)(2+) based electrochemiluminescence (ECL) method to detect procyclidine in human urine following separation by capillary electrophoresis (CE). An ECL detection cell was designed for post-column addition of Ru(bpy)(3)(2+). Parameters affecting separation and detection were optimized, leading to a detection limit of 1 x 10(-9) mol/l in an on-capillary stacking mode. For application in urine, a cartridge packed with slightly acidic cation-exchange resin was used to eliminate the matrix effects of urine and improve the detection sensitivity. Extraction recovery was nearly 90%.