Biomedical subjects

Jiye Jin

Publications and source records attributed to Jiye Jin.

9 recordsLinked to original sources

PubMed2005

Application of wavelet transform in pulsed ultrasonic modulation voltammetry.

In this study, wavelet transform was employed to achieve the different current components in pulsed ultrasonic modulation voltammetry. It was found that the pulsed sonovoltammograms could be decomposed into wavelet approximations and wavelet details by projecting wavelet transform on the signals in question. Since wavelet approximations with a certain scale parameter may retain the waveform of the original signal, the current components resulted from ultrasound "on" and "off" in pulsed sonovoltammograms could be separated at a certain scale parameter in multiplying wavelet approximation. With this method, the current components corresponding to pulse-on and pulse-off can be recorded separately without the external data acquisition system used in general modulation voltammetric measurements. The current difference between the two states was found to be proportional to the concentration of the electro-active species. The analytical usefulness of this approach was exploited for determination of ferrocyanide ion at sub-micromolar concentrations.

Journal Article↗

PubMed2005

Photometric detection of cyclodextrins in liquid chromatography by using iodine generated electrochemically in-situ.

A method has been developed for photometric detection of cyclodextrins (CD) in liquid chromatography using iodine (I2) generated electrochemically in-situ. Iodide ion in the mobile phase was electrochemically oxidized to I2 which was subsequently reacted with I-, in an electrochemical flow cell, forming I3-. The absorbance of I3- was found to be greatly enhanced when CD were present in the mobile phase. The absorbance enhancement was caused by the change in the mole fraction of I3-, because of the inclusion reaction of I3- with CD. On the basis of this phenomenon, CD were detected by means of a photodiode-array UV-visible detector positioned downstream of the electrochemical flow cell. The signals were found to be linearly dependent on CD concentration. Because the formation constants of I3- with CD decrease in the order alpha-CD>beta-CD>gamma-CD, alpha-CD was most detectable by the method. Detection limits were 1.0 micromol L(-1) for alpha-CD, 65 micromol L(-1) for monoG1-beta-CD, 100 micromol L(-1) for beta-CD, and 200 micromol L(-1) for gamma-CD.

Chromatography, High Pressure Liquid↗

PubMed2004

Signals ratio method combined with wavelet transform: application to resolution of overlapped electrochemical signals.

A signals ratio method combined with wavelet transform was proposed for the resolution of a weak voltammetric signal overlapped by other components. The signals ratio method usually suffers from interference from noise and baseline contained in the original signals because these factors cause distortion of the signals ratio. The multiresolution capability of the wavelet transform method was exploited here to simultaneously remove or reduce the noise and background. As a result, a deformation-free signals ratio with good signal-to-noise ratio (SNR) was obtained even for very noisy signals. The properties of the proposed method were compared to other resolution methods. It was demonstrated that the combined signals ratio wavelet transform method was particularly applicable to resolve a minor component in the presence of large amount of other components, suggesting that it can provide improved detection limits and quantified results for minor components. The method was employed for the voltammetric determination of residual chlorine in the presence of N,N-diethyl-p-phenylenediamine (DPD).

Chlorine↗

PubMed2004

A miniaturized FIA system for the determination of residual chlorine in environmental water samples.

The present study was aimed at developing a portable miniaturized FIA system with a two-electrode based amperometric detector for on-site monitoring of residual chlorine in environmental samples. The electrode potential control and current data collection were conducted with a home-designed potentiostat with a size of 150 x 100 x 40 mm and the weight of 350 g. It was confirmed that the amperometric response increased in proportion to the chlorine concentration up to 5 microg/ml, and the detection limit for chlorine was 0.05 microg/ml. Besides a drastic reduction in the size of the analytical system, such miniaturization achieved the advantages of increased speed, minimal mobile-phase consumption, and high sensitivity. The proposed method was successfully applied to the determination of residual chlorine in samples of pool water and tap water. The results were well agreed with those obtained by the N,N-diethyl-p-phenylenediamine (DPD) photometric method.

Journal Article↗

PubMed2003

Genetic algorithms based on wavelet transform for resolving simulated overlapped spectra.

Wavelet transform-based genetic algorithms are proposed for resolving simulated overlapped spectra. Wavelet transform as a derivative method is used for de-noising, for deducting background absorption as well as for peak finding in order to get an estimation of parameters of unresolved spectra. Then genetic algorithms, using the estimations of parameters as input values, are employed to resolve unresolved bands. As a consequence, a good optimized solution was achieved since the reliable estimation of initial values can greatly facilitate the convergence of genetic algorithms and the calculation time is shortened accordingly.

Journal Article↗

PubMed2003

Liquid chromatography with amperometric detection using functionalized multi-wall carbon nanotube modified electrode for the determination of monoamine neurotransmitters and their metabolites.

The fabrication and application of a novel electrochemical detection (ED) method with the functionalized multi-wall carbon nanotubes (MWNTs) chemically modified electrode (CME) for liquid chromatography (LC) were described. The electrochemical behaviors of dopamine (DA) and other monoamine neurotransmitters at the CME were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results indicated that the CME exhibited efficient electrocatalytic effects on the current responses of monoamine neurotransmitters and their metabolites with high sensitivity, high stability and long-life activity. In LC-ED, DA, norepinephrine (NE), 3-methoxy-4-hydroxyphenylglycol (MHPG), 3,4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) had good and stable current responses at the CME. The linear ranges of seven analytes were over four orders of magnitude and the detection limits were 2.5 x 10(-10) mol/l for DA, 2.5 x 10(-10) mol/l for NE, 5.0 x 10(-10) mol/l for MHPG, 3.0 x 10(-10) mol/l for DOPAC, 3.5 x 10(-10) mol/l for 5-HT, 6.0 x 10(-10) mol/l for 5-HIAA, 1.25 x 10(-9) mol/l for HVA. The application of this method coupled with microdialysis sampling for the determination of monoamine neurotransmitters and their metabolites in Parkinsonian patients' cerebrospinal fluid was satisfactory.

Biogenic Monoamines↗

PubMed2003

Simultaneous determination of the monoamine neurotransmitters and glucose in rat brain by microdialysis sampling coupled with liquid chromatography-dual electrochemical detector.

A new type of chemically modified electrode based ring-disk electrode as the dual electrochemical detector (DECD) for high-performance liquid chromatography (HPLC) to simultaneously determine the monoamine neurotransmitters and glucose is described. The ring electrode was modified with an ion-exchange polymer-overoxidized polypyrrole (OPPy) and the disk electrode was modified with nano Au colloid and glucose oxidase (GOD). The electrochemical behaviors of dopamine (DA) and ascorbic acid (AA) at the OPPy chemically modified electrode (CME) were investigated by differential pulse voltammetry (DPV). It was found that the CME could permeate dopamine cations and repelled the ascorbate anions, which could be used to determine the monoamine neurotransmitters and avoid the interference of AA. The electrochemical behavior of glucose at the Nafion/GOD-Au colloid/GC CME was investigated by amperometry and flow injection analysis (FIA). It was found that the sensitivity of the CME increased apparently in determination of glucose. In order to obtain better separation and current responses of the analytes in HPLC-DECD, several operational parameters have been investigated. Under the optimum conditions, the method showed good stability and reproducibility. The application of this method coupled with microdialysis sampling for in vivo simultaneous determination of monoamine neurotransmitters and glucose in rat brain was satisfactory.

Animals↗

PubMed2002

Amperometric determination of glutathione and cysteine on a Pd-IrO(2) modified electrode with high performance liquid chromatography in rat brain microdialysate.

A Pd/IrO(2) co-electrodeposited glassy carbon electrode was prepared and the electrochemical behavior of glutathione (GSH) at this chemically modified electrode (CME) has been studied by cyclic voltammetry (CV). The results indicated that the modified electrode efficiently exhibited electrocatalytic oxidation for GSH with relatively high sensitivity, stability, and long-life. Coupled with high-performance liquid chromatography (HPLC), the Pd/IrO(2) modified electrode was utilized for the electrochemical detection (ECD) of the thiocompounds, glutathione and cysteine (Cys). The peak currents were linear with the substance concentrations in the range of 1.0 x 10(-5) mol L(-1) to 8.0 x 10(-4) mol L(-1) for GSH and 4.0 x 10(-6) mol L(-1) to 2.0 x 10(-4) mol L(-1) for Cys. The detection limits were 2.0 x 10(-6) mol L(-1) for GSH and 5.0 x 10(-7) mol L(-1) for Cys with S/N of 3. The method has been successfully applied to assess the contents of GSH and Cys in rat brain microdialysates.

Animals↗

PubMed2002

Use of disposable GRC electrodes for the detection of phenol and chlorophenols in liquid chromatography.

In this study, a wall-jet flow cell with a GRC (graphite reinforced by carbon) electrode was designed for the amperometric detection of phenol and chlorophenols in liquid chromatography. The voltammetric responses of these analytes at the GRC electrodes are very similar to those at conventional glassy carbon electrodes. As the GRC electrodes were made of the same materials as commercially available mechanical pencil leads, they exhibit the advantages of low cost, simple surface renewability, lower residual current, and good electrode-to-electrode reproducibility, and thus can be used as disposable-type electrodes. Chromatographic separations of phenol, o-chlorophenol (o-CP), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) were achieved with an ODS column using a mobile phase containing a mixture of CH3CN and H20 (40:60) containing 25 mM L-(+)tartaric acid (pH = 4.5). Amperometric detections were based on the electrochemical oxidation of these compounds around +0.9 V vs. Ag/AgCl. Under the optimized conditions, linear calibrations were obtained in a range up to 100 microM for phenol, o-CP, 2,4-DCP, 2,4,6-TCP, and 200 microM for PCP, with the correlation coefficients r2 of 0.9992, 0.9997, 0.9986, 0.9992, and 0.9968, respectively. The chromatographic detection limits for the tested analytes were obtained at pmol levels.

Journal Article↗