Biomedical subjects

Xingguo Chen

Publications and source records attributed to Xingguo Chen.

At least 73 records · Page 4Linked to original sources

PubMed2004

Micellar electrokinetic chromatography with laser-induced fluorescence detection for sensitive determination of ephedrine and pseudoephedrine.

A selective and sensitive micellar electrokinetic chromatography method with laser-induced fluorescence detection was developed for the quantification of ephedrine (E) and pseudoephedrine (PE) derivatized with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole. After conducting a series of optimizations, a running buffer of 10 mM sodium borate + 16 mM SDS was used for separation of the derivatives. A linear relationship for E and PE was obtained in the range of 0.044-6.6 microg mL(-1) (correlation coefficient: 0.9943 for E, 0.9946 for PE), and the detection limits for E and PE were 0.70 and 0.30 ng mL(-1), respectively. The sensitivity of E and PE was improved by several multiples of ten over those of CZE-LIF method. The method was applied to the analysis of the two alkaloids in ephedra herbal medicine and preparations with recoveries in the range of 98.3-107.1%.

Adrenergic Agents↗

PubMed2004

Investigation of the factors that induce analyte peak splitting in capillary electrophoresis.

Peak splitting has a detrimental effect on analyses by capillary electrophoresis. Many papers have reported it and several mechanisms have been proposed to explain the phenomenon. We investigated the electrophoretic behavior of an amphoteric analyte, levodopa, in phosphate buffer and observed a peak splitting phenomenon at moderate sample concentrations and under general analytical conditions, even without organic solvent. The dependence of effective mobility on pH was taken into account and pKa values of 2.30, 8.11, and 9.92 were obtained for levodopa. Then, we constructed pH-dependent distribution diagrams of levodopa and phosphate species present in aqueous solution and proposed that the most relevant factors contributing to peak splitting are the presence of ionizable groups in the analyte molecule and the occurrence of ionization, yielding charged species which interacted with buffer electrolyte species in a definite pH range to form complexes. This result is different from those presented in the literature and broadens our understanding of amphoteric analyte peak splitting.

Borates↗

PubMed2004

Analysis of unknown organic pollutants in sewage by solid-phase extraction combined with gas chromatography-mass spectrometry.

A rapid, simple, and reliable method of solid-phase extraction (SPE) combined with gas chromatography (GC)-mass spectrometry (MS) is developed for the analysis of a wide range of polarity of unknown organic pollutants in sewage. Wastewater samples are extracted by passing them through disposable C(18) cartridges, and the extracts are then analyzed by GC-MS. Different SPE parameters for ten organic compounds in the list of priority pollutants suggested by the China Environmental Protection Agency (EPA) are studied, and their breakthrough volumes are determined. Extraction recoveries for the tested compounds are greater than 60%, except the recovery of 1,2-dichloroethane is 48%. The relative standard deviations are less than 7.8% (n = 3). The developed approach is successfully applied for the identification of organic components in a sewage sample. Over 220 organic pollutants are identified, with 5 of these present in the list of priority pollutants suggested by the U.S. EPA and 4 from the list by the China EPA.

Environmental Pollutants↗

PubMed2003

On-line concentration by field-enhanced sample injection with reverse migrating micelles in micellar electrokinetic capillary chromatography for the analysis of flavonoids in Epimedium brevicornum Maxim.

A simple and sensitive micellar electrokinetic capillary chromatography (MEKC) method was developed for the separation and determination of six flavonoids in Epimedium brevicornum Maxim. Field-enhanced sample injection with reverse migrating micelles (FESI-RMM) was used for on-line concentration of the flavonoids. An electrolyte containing 20 mM H3PO4, 100 mM SDS, 20% acetonitrile and 2% 2-propanol (pH 2.0) was chosen as the electrophoretic buffer. By optimizing the stacking conditions, about 40-360-fold improvement in the detection sensitivity was obtained for the flavonoids.

Buffers↗

PubMed2003

Determination of p-tyrosol and salidroside in three samples of Rhodiola crenulata and one of Rhodiola kirilowii by capillary zone electrophoresis.

A capillary zone electrophoresis (CZE) method has been developed for simultaneous assay of two bioactive components (p-tyrosol and salidroside) in Rhodiola crenulata and Rhodiola kirilowii for the first time. Those analytes were successfully separated within 15 min using 50 mmol L(-1) (pH 9.62) borate containing 30% methanol as running buffer. Regression equations revealed linear relationships (correlation coefficients 0.9998-0.9999) between peak area and concentration of the two analytes. The relative standard deviations ( RSD) of the migration times and the peak areas of two constituents ranged from 0.51 to 0.57% and from 0.65 to 1.17%, respectively, intra-day, and from 4.91 to 6.93% and from 3.51 to 5.33%, respectively, inter-day. The recoveries of two constituents ranged from 96.24 to 103.15%.

Calibration↗

PubMed2003

Interaction of magnolol with bovine serum albumin: a fluorescence-quenching study.

The interaction of magnolol with bovine serum albumin(BSA) was studied using fluorescence spectroscopy under physiological conditions. The binding constants, K, and the ratio of quantum yields of protein fluorescence for complex and free protein, f, at 298 K, 304 K, and 310 K were obtained; the values were 6.799x10(5) L mol(-1), 5.541x10(5) L mol(-1), and 4.344x10(5) L mol(-1) and 0.17, 0.30, and 0.34, respectively. The standard enthalpy change (delta H degrees ) and the standard entropy change (delta S degrees ) were calculated to be -28.53 kJ mol(-1) and 15.88 J mol(-1) K(-1), which indicated that hydrophobic forces played major role in the interaction of magnolol and BSA. The binding average distance between magnolol and BSA (4.32 nm) was obtained on the basis of the theory of Förster energy transfer.

Animals↗

PubMed2003

Capillary electrophoresis with field-enhanced stacking for rapid and sensitive determination of strychnine and brucine.

A new capillary electrophoresis procedure with field-enhanced stacking concentration for the analysis of strychnine and brucine is established. After optimization of the separation and concentration conditions, the two alkaloids can be separated within 5 min and quantified with high sensitivity (The detection limits were 1.0 ng mL(-1) for strychnine and 1.4 ng mL(-1) for brucine). The method was useful for qualitative and quantitative analysis of strychnine and brucine in Strychnos nux-vomica L with recovery of 105.1% for strychnine and 98.4% for brucine.

Drugs, Chinese Herbal↗

PubMed2003

Study of the reaction of proteins with 3-hydroxy-4-(2-hydroxy-4-sulfo-1-naphthalenyl)azo (Cal-Red) by Rayleigh light scattering technique.

This is the first report on the determination of proteins with 3-hydroxy-4-(2-hydroxy-4-sulfo-1-naphthalenyl)azo (Cal-Red) by Rayleigh light scattering (RLS). At pH 4.07, the weak RLS of Cal-Red can be enhanced greatly by the addition of proteins. On this basis, the reaction of Cal-Red and proteins was studied. A new quantitative determination method for proteins has been developed. This method is very sensitive (0.45-36.9 microgml(-1) for bovine serum albumen (BSA)), rapid (<2min), simple (one step), and tolerant of most interfering substances. The maximum binding number of Cal-Red to BSA was 143 and the binding constant was 4.1x10(6)mol(-1)L. Four samples of total protein in human serum were determined and the maximum relative error is no more than 3%.

Amino Acids↗

PubMed2003

Determination of paeonol in rat plasma by high-performance liquid chromatography and its application to pharmacokinetic studies following oral administration of Moutan cortex decoction.

Quantification of paeonol, the principal bioactive component of Moutan cortex, in rat plasma following oral administration of Moutan cortex decoction was achieved by using a simple and sensitive high-performance liquid chromatographic method. The calibration curves for paeonol were linear in both the low (25-200 ng/mL) and the high concentration range (200-4000 ng/mL) with r(2) values of 0.9928 and 0.9993, respectively. The coefficients of variation of intra- and inter-day assays were 14.36, 6.52, 1.76, 1.25, 5.36, 3.30 and 1.42% and 12.70, 1.19, 2.98, 1.91, 1.75, 1.78 and 0.96% at concentrations of 25, 50, 100, 200, 500, 1000 and 2000 ng/mL, respectively. The recoveries of paeonol from rat plasma were found to be 101.9, 104.5, 105.4 and 101.2% for concentrations of 50, 500, 1000 and 2000 ng/mL, respectively. The paeonol plasma concentrations were fitted to two-compartment model with fi rst order absorption. The mean terminal half-lives (t(1/2)) of paeonol was 80.9 min.

Acetophenones↗

PubMed2003

Study on the relationship between intake of trace elements and breast cancer mortality with chemometric methods.

Several chemometric methods were employed to survey the interaction among the trace elements and the relationship between the intake of these elements and the breast cancer mortality. It is indicated that there are strong interactions among the trace elements so as to form a dynamic balance; the intake of Cr is the most important factor that could cause the increase of breast cancer mortality; no definite relation can be observed between the intake of Cu and that of Zn. However, either the ratio of the intake of Cu and that of Zn or the intake of Cd could show a certain state of dynamic balance among some of the trace elements. Comparison of the analytical methods reveals that it is important to select a suitable method so as to obtain the most appropriate explanation.

Breast Neoplasms↗

PubMed2003

Sensitive determination of ephedrine and pseudoephedrine by capillary electrophoresis with laser-induced fluorescence detection.

A CE-LIF method was developed for the separation and sensitive detection of ephedrine and pseudoephedrine after derivatization by 4-chloro-7-nitrobenzo-2-oxa-1,3-diazol (NBD-C1). The derivatization and separation conditions were investigated in detail and the optimum conditions were obtained. Under the optimum experiment conditions, good linearity relationships (correlation coefficients: 0.9942 for ephedrine and 0.9970 for pseudoephedrine) between the peak heights and concentrations of the analytes were obtained (0.7-140 microM). The detection limits were 0.16 microM for ephedrine and 0.17 microM for pseudoephedrine, which indicated that the sensitivities were at least ten times improved over those reported in the literature obtained by UV detection. The method was applied to the analysis of ephedrine and pseudoephedrine in ephedra herb plants and preparations with good results.

Electrophoresis, Capillary↗

PubMed2003

Separation and determination of ephedrine and pseudoephedrine by combination of flow injection with capillary electrophoresis.

A simple, rapid, and accurate method for the separation and determination of ephedrine and pseudoephedrine using direct UV absorbance detection has been developed by the combination of flow injection with capillary electrophoresis for the first time. The buffer solution used is a 40 mM borate solution with the pH adjusted to 9.5 using a 2 M NaOH solution. The linear calibration range is 50 to 1000 microg/mL (r = 0.9996) for both analytes, and the recoveries are 91.2-108.2% for ephedrine and 92.6-107.3% for pseudoephedrine, respectively. The relative standard deviation of the peak area is 1.6% for ephedrine and 1.3% for pseudoephedrine (n = 6) at a concentration of 500 microg/mL, respectively. A series of samples is injected repeatedly without current interruption and subsequent rinsing, and the contents of these two alkaloids in three marketed drugs and the medical plant, Ephedra sinica, are determined with satisfactory results by this method.

Calibration↗

PubMed2002

Application of artificial neural networks in multivariable optimization of an on-line microwave FIA system for catalytic kinetic determination of iridium(III).

A new rapid, selective and sensitive on-line microwave flow injection-kinetic method was developed for spectrophotometric determination of micro amounts of Ir(III), based on its catalytic effect on the m-acetylchlorophosphonazo (CPA-mA) and KIO(4) reaction in NaOH media. An on-line microwave oven was employed to accelerate the reaction. The reaction was followed spectrophotometrically by measuring the decrease of the absorbance of CPA-mA at 580 nm. The effect of five variables for the determination of Ir(III) was optimized by means of a multilayer artificial neural network using extended delta-bar-delta (EDBD) algorithms. Under the optimum experimental conditions, Ir(III) could be determined in the range 0.060-0.60 micro gZZZ;mL(-1) with detection limit of 0.02 micro gZZZ;mL(-1) and the sampling frequency of 34 h(-1). The proposed method was applied to the determination of micro amounts of Ir(III) in refined ore and secondary alloy with the recoveries from 91.4% to 109%.

Journal Article↗

PubMed2002

Separation of diastereoisomers of podophyllum lignans by micellar electrokinetic chromatography.

Seven pairs of diastereoisomers of podophyllum lignans at 2-position, including two pairs of spin-labeled compounds, were separated by micellar electrokinetic chromatography with 5 mM sodium tetraborate-20 mM NaH2PO4-120 mM sodium dodecylsulfate-30% (v/v) 2-propanol (pH 6.5-7) within 35 min. The migration behaviors of the compounds with different types and concentrations of organic modifiers were studied. The method can be used to identify the purification of the lignans, monitor the 2-H configuration transformation, and determine the 2-H configuration of the spin-labeled derivatives.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2002

Field-amplified sample stacking in capillary electrophoresis for on-column concentration of alkaloids in Sophora flavescens Ait.

A simple and rapid capillary zone electrophoresis method was developed for the separation of the main alkaloids from Sophora flavescens Ait. with the optimum buffer solution containing 110 mM NaH(2)PO(4) and 15% 2-propanol (pH 3.0). The field-amplified sample stacking (FASS) technique was applied to the on-line concentration of the alkaloids. The data presented in this work demonstrate that the use of a short water plug at the column inlet is essential for improving the reproducibility of FASS with electro-injection, and that the water plug injection time affected the sensitivity significantly. The sample concentration was further increased by about 2-3-fold by the introduction of a relatively longer water plug. With this stacking measure, the concentration sensitivity was about 3-4 orders of magnitude higher than in hydrodynamic injection.

Alkaloids↗

PubMed2002

Development of a quantitative structure-property relationship model for predicting the electrophoretic mobilities.

Electrophoretic mobility (mu0) is the most important parameter governing the separation of solutes in capillary zone electrophoresis. In this paper, a new model was constructed by means of a multilayer neural network using extended delta-bar-delta (EDBD) algorithm to estimate complex property of electrophoretic mobilities of aliphatic carboxylates and amines from simpler experimental properties. The molecular weight (W), molecular volume (V), the code (+1 or -1) of acid and base and pK value were used as input parameters to predict electrophoretic mobility. The networks' architecture and the learning times were optimized. The optimum artificial neural networks (ANNs) could give excellent prediction results.

Journal Article↗

PubMed2002

Identification and determination of ecdysones and flavonoids in Serratula strangulata by micellar electrokinetic capillary chromatography.

The simultaneous determination of 20-hydroxyecdysone ( 1), 25-deoxy-11,20-dihydroxyecdysone ( 2), kaempferol 4',7-dimethyl ether ( 3) and biochanin A ( 4) in the fruit, leaf and root of Serratula strangulata Iljin has been investigated by micellar electrokinetic capillary chromatography for the first time. With an electrolyte containing 15 mmol/L borate, 60 mmol/L SDS, 20 % (v/v) methanol, at pH 9.08 and 20 kV applied voltage, the four analytes were completely separated within 22.7 min. The effects of concentration of borate, electrolyte pH, the concentrations of SDS and organic modifier and the applied voltage on electrophoretic behavior and separation were studied. Regression equations revealed linear relationships (correlation coefficients: 0.9986 - 0.9997) between the peak areas of the analytes and the corresponding concentrations. The levels of analytes in the different parts of S. strangulata were easily determined with recoveries ranging from 95.3 % to 104.0 %.

Asteraceae↗

PubMed2000

[The Comparison between the Killing Effects of Two Anti-T Immunotoxins on Target Cells]

The key to killing target cells by immunotoxin depends on the specific recognition of antibody to target cell and the cytotoxic effect of toxin. The comparative study of the killing effects of two anti-T immunotoxins, CD5:Ricin and CD5:rRA, on target cells was performed. The elimination rate of immunotoxins was analysed by flow cytometry and MLR. The effect of immunotoxins on the proliferation of hematopoiesis was evaluted by CFU-GM. The results showed that (1) CD5(+) T cells were eliminated and CD25(+) CD3(+) activated T cells were concentration-dependently inhibited by the two immunotoxins in the range of 10(-9) - 10(-11) mol/L; (2) both immunotoxins significantly inhibited the mixed lymphocyte reaction, and the inhibiting effect of CD5:rRA to T cell proliferation was markedly lower than that of CD5:Ricin in the range of 10(-10) - 10(-11) mol/L; (3) the combination of CD5:rRA with 10 mmol/L NH(4)Cl increased the T cell elimination rate; and (4) the two immunotoxins and the combination of NH(4)Cl and CD5:rRA did not suppressed proliferation of granulocyte-macrophage progenitors in the range of concentrations with killing effect. It was concluded that T cell and activated T cell could be eliminated effectively by immunotoxins, the proliferation of granulocyte-macrophage progenitor was not inhibited significantly.

Journal Article↗