Biomedical subjects

Hanfa Zou

Publications and source records attributed to Hanfa Zou.

At least 55 records · Page 3Linked to original sources

PubMed2005

Capillary electrochromatography with a neutral monolithic column for classification of analytes and determination of basic drugs in human serum.

Capillary electrochromatography (CEC) using a neutral hydrophobic polymer-based monolithic column has been developed for classification of analytes based on their acidity and charges of group. The monolithic columns were prepared by in situ copolymerization of lauryl methacrylate and ethylene dimethacrylate without any charged monomers in the reaction mixture. The ionic analytes will only be driven by their electrophoretic mobilities and were separated on the basis of their differences in electrophoretic mobility and in hydrophobic interaction with the stationary phase. Only negatively or positively charged analyte (acid or basic) migrated toward detection window in a single run by applying negative or positive voltage. The CEC system was also applied for the analysis of basic drugs in human serum by internal standard method using acidic running buffer. The sample of human serum spiked with basic drugs was directly injected after a simple sample pretreatment. The calibration curves with regression coefficients (0.9995-0.9997) in the range of 0.318-80 microg/mL were obtained with the limits of detection being below 0.15 microg/mL. The intra- and inter-day precisions, determined as relative standard deviations, were less than 4.21%.

Atenolol↗

PubMed2005

Preparation of monolithic silica column with strong cation-exchange stationary phase for capillary electrochromatography.

A monolithic silica based strong cation-exchange stationary phase was successfully prepared for capillary electrochromatography. The monolithic silica matrix from a sol-gel process was chemically modified by treatment with 3-mercaptopropyltrimethoxysilane followed by a chemical oxidation procedure to produce the desired function. The strong cation-exchange stationary phase was characterized by its substantial and stable electroosmotic flow (EOF), and it was observed that the EOF value of the prepared column remained almost unchanged at different buffer pH values and slowly decreased with increasing phosphate concentration in the mobile phase. The monolithic silica column with strong cation-exchange stationary phase has been successfully employed in the electrochromatographic separation of beta-blockers and alkaloids extracted from traditional Chinese medicines (TCMs). The column efficiencies for the tested beta-blockers varied from 210,000 to 340,000 plates/m. A peak compression effect was observed for atenolol with the mobile phase having a low phosphate concentration.

Journal Article↗

PubMed2005

Chiral separation of 1,1'-bi-2-naphthol and its analogue on molecular imprinting monolithic columns by HPLC.

Two molecular imprinting polymer (MIP) monolithic columns with (S)-(-)-1,1'-bi-2-naphthol and (R)-(+)-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol as the templating molecules, respectively, have been prepared by in situ polymerization using 4-vinylpyridine and ethylene dimethacrylate as functional monomer and cross-linker, respectively. The columns with good flow-through properties were obtained by changing the molar ratio of the functional monomer and the template molecule. The effects of mobile-phase composition on separation of enantiomers were systematically investigated. The results indicate that hydrophobic interaction in aqueous solution and hydrogen-bonding interaction in ACN between the enantiomers and polymers could play important roles in the retention and resolution. The effects of chromatographic conditions, such as flow rate, column temperature, sample loading, on the enantioseparation were also studied. Further, these two MIP columns show a cross-reactivity.

Chromatography, High Pressure Liquid↗

PubMed2005

Carbon nanotubes as adsorbent of solid-phase extraction and matrix for laser desorption/ionization mass spectrometry.

A method with carbon nanotubes functioning both as the adsorbent of solid-phase extraction (SPE) and the matrix for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) to analyze small molecules in solution has been developed. In this method, 10 microL suspensions of carbon nanotubes in 50% (vol/vol) methanol were added to the sample solution to extract analytes onto surface of carbon nanotubes because of their dramatic hydrophobicity. Carbon nanotubes in solution are deposited onto the bottom of tube with centrifugation. After removing the supernatant fluid, carbon nanotubes are suspended again with dispersant and pipetted directly onto the sample target of the MALDI-MS to perform a mass spectrometric analysis. It was demonstrated by analysis of a variety of small molecules that the resolution of peaks and the efficiency of desorption/ionization on the carbon nanotubes are better than those on the activated carbon. It is found that with the addition of glycerol and sucrose to the dispersant, the intensity, the ratio of signal to noise (S/N), and the resolution of peaks for analytes by mass spectrometry increased greatly. Compared with the previously reported method by depositing sample solution onto thin layer of carbon nanotubes, it is observed that the detection limit for analytes can be enhanced about 10 to 100 times due to solid-phase extraction of analytes in solution by carbon nanotubes. An acceptable result of simultaneously quantitative analysis of three analytes in solution has been achieved. The application in determining drugs spiked into urine has also been realized.

Adsorption↗

PubMed2005

Combining restriction digestion and touchdown PCR permits detection of trace isoforms of histamine H3 receptor.

The conserved sequences of the mouse histamine H3 receptor at the potential alternative splice junctions suggest that the splice isoforms found in guinea pig, rat, human, and hamster may also be present in the mouse. However, the trace amount isoforms are hard to be detected by the regular PCR approach. In this paper, we report a method in which the unspliced long isoform is cut by restriction endonuclease so that the short isoforms can be amplified to detectable levels to confirm the existence of the splice isoforms of H3 receptor mRNA in the mouse. This method is applicable to the detection of trace amounts of splice isoforms that coexist with the long, more abundant isoforms.

Animals↗

PubMed2005

[Applications of two-dimensional liquid chromatography coupled to mass spectrometry for the separation and identification of compounds in ginkgo biloba extracts].

A comprehensive two-dimensional liquid chromatographic separation system based on the combination of an immobilized liposome chromatographic (ILC) column and an ODS column was developed for the separation of components in Ginkgo biloba, a traditional Chinese medicine. Two columns were coupled by a two-position, eight-port valve equipped with two storage loops, and the system was controlled by a computer. The effluent was detected both by a diode array detector and by an atmospheric pressure chemical ionization (APCI) mass spectrometer. Under the optimization separation conditions with the separation system, more than 41 components in the methanol extract of Ginkgo biloba were resolved. According to their UV and mass spectra, 13 of them were preliminarily identified as ginkgolide B, ginkgolide C, bilobalide, rutin, quercetin, quercetin-3-O-beta-D-glucosyl (1-2)-alpha-L-rhamnoside, quercetin-3-O-beta-D-glucoside, isorhamnetin, kaempferol-3-O-beta-D-glucosyl (1-2)-alpha-L-rhamnoside, isohamnetin-3-O-beta-D-rutinoside, kaempferol-3-O-beta-D-glucoside, kaempferol, kaempferol-3-O-beta-D-rutinoside.

Chromatography, High Pressure Liquid↗

PubMed2005

[Screening of antineoplastic components in Radix et Rhizoma Rhei using chromatographic fingerprints].

A new strategy for screening of antineoplastic components in the traditional Chinese medicine of Radix et Rhizoma Rhei has been developed using chromatographic fingerprints before and after metabolism by high performance liquid chromatography-mass spectrometry. The metabolizing method was established based on the in vitro metabolism by Sprague-Dawley (SD) rat liver homogenate. By means of the metabolism methods in vitro, the antineoplastic activity of the extracts, metabolites and components of Radix et Rhizoma Rhei were determined by microculture tetrazolium (MTT) assays in vitro. It was observed that the inhibition rate of the crude extract for HeLa cell was increased from 26.7% to 36.2% after 60 min of metabolism. The changes of activities resulted from the changes of components' structures and the bioactive components were discovered simultaneously in view of metabolism by inhibiting rate assay for the components in Radix et Rhizoma Rhei. It is concluded that the antineoplastic activity of the crude extract from Radix et Rhizoma Rhei was increased after in vitro metabolism because the antineoplastic activity of aloe-emodin, the metabolite of chrysophanol, is higher than its parent compounds.

Animals↗

PubMed2004

Strategy for analysis and screening of bioactive compounds in traditional Chinese medicines.

Traditional Chinese medicines (TCMs), due to their long time clinic test and reliable therapeutic efficacy, are attracting increased global attention served as excellent pools of bioactive compounds for the discovery of new drugs. However, hundreds or even thousands of components are usually contained in traditional Chinese medicines and only a few compounds are responsible for the pharmaceutical and/or toxic effects. The large numbers of other components in traditional Chinese medicines make the screening and analysis of the bioactive components extremely difficult. By the way, the combination effect of bioactive components on the pharmacological activity makes it very difficult to clear the therapeutic mechanism of TCMs. Therefore, some strategies have to design for screening of bioactive compounds in traditional Chinese medicines, which further leads to disclose the therapeutic mechanism of TCMs in molecular level. The review will summarize the present state of the art of screening strategy for active compounds in traditional Chinese medicines, and the chromatography methods for screening and analysis of bioactive compounds in traditional Chinese medicines will be emphasized.

Animals↗

PubMed2004

Monolithic column with zwitterionic stationary phase for capillary electrochromatography.

A capillary electrochromatography (CEC) monolithic column with zwitterionic stationary phases was prepared by in situ polymerization of butyl methacrylate, ethylene dimethacrylate, methacrylic acid, and 2-(dimethyl amino) ethyl methacrylate in the presence of porogens. The stationary phases have zwitterionic functional groups, that is, both tertiary amine and acrylic acid groups, so the ionization of those groups on the zwitterionic stationary phase was affected by the pH values of the mobile phase, and further affects the strength and direction of the electroosmotic flow (EOF). Separations of alkylbenzenes and polycyclic aromatic hydrocarbons based on the hydrophobic mechanism were obtained. Separation of various types of polar compounds, including phenols, anilines, and peptides, on the prepared column were performed under CEC mode with anodic and cathodic EOF, and different separation selectivities of those polar analytes were observed on the monolithic capillary column by using mobile phases with different pH values.

Journal Article↗

PubMed2004

Monolithic columns with mixed modes of reversed-phase and anion-exchange stationary phase for capillary electrochromatography.

A capillary electrochromatography (CEC) monolithic column with mixed modes of reversed-phase and anion-exchange stationary phases was prepared by in situ polymerization of 2-(methacryloxy)ethyltrimethylammonium methyl sulfate (MEAMS) and ethylene dimethacrylate (EDMA) in a binary porogenic solvent consisting 1-propanol and 1,4-butanediol. The ammonium groups on the surface of the stationary phase generate an electroosmotic flow (EOF) from cathode to anode, and serve as a strong anion-exchange stationary phase at the same time. The EOF of the stationary phase can be determined by the amount of MEAMS monomer in reaction mixtures during the polymerization. The monolithic stationary phases exhibited reversed-phase chromatographic behavior toward neutral solutes. For charged solutes, hydrophobic as well as electrostatic interaction/repulsion with the monoliths was observed. Separations of aromatic compounds and basic compounds on the prepared column were performed under the mode of CEC. Peak tailing of basic compounds was avoided and the efficient separation of aromatic acids was achieved using neutral mobile phase due to the same direction of EOF and electrophorestic mobility of negatively charged solutes.

Anion Exchange Resins↗

PubMed2004

Separation and identification of compounds in Rhizoma chuanxiong by comprehensive two-dimensional liquid chromatography coupled to mass spectrometry.

A comprehensive two-dimensional liquid chromatographic separation system based on the combination of a CN column and an ODS column is developed for the separation of components in a traditional Chinese medicine (TCM) Rhizoma chuanxiong. Two columns are coupled by a two-position, eight-port valve equipped with two storage loops and controlled by a computer. The effluent is detected by both the diode array detector and atmospheric pressure chemical ionization (APCI) mass spectrometer. More than 52 components in the methanol extract of R. chuanxiong were resolved and 11 of them were preliminary identified according to their UV and mass spectra.

Chromatography, Liquid↗

PubMed2004

Short columns with molecularly imprinted monolithic stationary phases for rapid separation of diastereomers and enantiomers.

Three molecularly imprinted monolithic columns with different length but almost identical column volume had been prepared. It was observed that the separation factors of diastereomers and enantiomers were almost unaffected by column length. However, the short column with dimension of 38 mm x 8 mm i.d. showed much lower resistance to flow rate so that it could be operated at much higher flow rates. By combining stepwise gradient elution with elevated flow rate, the diastereomers of cinchonine and cinchonidine and the enantiomers of Cbz-DL-Trp and Fmoc-DL-Trp were successfully separated within 3 min on the short column with dimension of 38 mm x 8 mm i.d. Based on the above results, a cinchonine imprinted monolithic disk with dimension of 10mm x 16 mm i.d. was further developed. The SEM image and the pore size distribution profile showed that large flow-through pores are present on the prepared monolith, which allowed mobile phase to flow through the disk with very low resistance. Chromatographic performances on the monolithic disk were almost unchanged compared with the long columns. A rapid separation of cinchonine and cinchonidine was achieved in 2.5 min at the flow rate of 9.0 ml/min. Furthermore, it was observed that there was almost no effect of the flow rate on the dynamic binding capacity at high flow rates. In addition, the effect of the loading concentration of analytes on the dynamic binding capacity, namely adsorption isotherm, was also investigated. A non-linear adsorption isotherm of cinchonine was observed on the molecularly imprinted monolith with cinchonine as template, which might be a main reason to result in the peak tailing of template molecule.

Chromatography, High Pressure Liquid↗

PubMed2004

Synthesis of chiral stationary phases with radical polymerization reaction of cellulose phenylcarbamate derivatives and vinylized silica gel.

Cellulose phenylcarbamate derivatives having methacrylate groups were synthesized with regioselective and non-regioselective procedures. These derivatives were chemically immobilized onto a vinylized silica gel, respectively, via a radical co-polymerization reaction. The immobilization was efficiently attained using a small amount of AIBN. The chiral recognition abilities of the prepared chiral stationary phases (CSPs) were evaluated by HPLC resolution of test enantiomers. It was observed that most of the enantiomers were completely resolved with markedly high column efficiency of 30,000-40,000 plates per metre for the eluted peaks. The effect of the amount of methacrylolyl chloride used for preparation on resolution was investigated. A direct comparison of the chiral recognition ability was made on the regioselectively and non-regioselectively prepared CSPs. In addition, the chemically bonded-type of CSPs were found to be relatively stable with addition of solvents such as tetrahydrofuran (THF) and chloroform into the mobile phase, which can lead to the dissolution of cellulose derivatives on the coated CSPs. Thus the choice of solvents used as the mobile phase is greatly extended and better resolution of several test enantiomers was observed on the prepared CSPs with THF and chloroform as a composition in the mobile phase. The batch-to-batch and run-to-run reproducibility was also discussed on the newly prepared CSPs.

Carbamates↗

PubMed2004

Determination of basic pharmaceuticals in human serum by hydrophilic interaction capillary electrochromatography.

Hydrophilic interaction capillary electrochromatography (HI-CEC) for the determination of basic pharmaceuticals spiked in human serum is described. The organic modifier content, ionic strength, and pH value of the mobile phase as well as the applied voltage are optimized for separation and elution of these drug analytes. Excellent separation was achieved for drugs using a mobile phase composition of 80% v/v acetonitrile in 100 mM triethylamine phosphate (TEAP) buffer at pH 2.8 with column efficiencies for analytes more than 200,000 plates/m. The samples of human serum spiked with basic drugs were directly injected after a simple acetonitrile treatment. The linear range and reproducibility of these basic drugs using an external and internal standard method were compared. As a result, the reproducibility could be greatly improved by using the internal standard method. Good calibration curves with regression coefficients more than 0.998 in the range of 5-160 microg/mL were observed with the internal standard method. The limits of quantitation, based on standards with acceptable relative standard deviations (RSDs), were below 5 microg/mL. The intra- and inter-day precisions, determined as RSDs, were less than 4.57%.

Acetonitriles↗

PubMed2004

Preparation of a positively charged cellulose derivative chiral stationary phase with copolymerization reaction for capillary electrochromatographic separation of enantiomers.

A positively charged chiral stationary phase (CSP) was prepared by chemically immobilizing cellulose 3,5-dimethylphenylcarbamate onto methacryloyldiethylenetriaminopropylated silica (MCDEAPS) via a radical copolymerization reaction. The prepared CSP was evaluated for enantiomer separation in nonaqueous capillary electrochromatography (CEC). Electroosmotic flow (EOF) generated on the prepared CSP could be significantly improved with introduction of positive charges into the CSP, and separation of enantiomers in CEC has been achieved with mobile phases of ethanol and hexane-ethanol, respectively. In addition, we investigated the solvent versatility of the immobilized CSP on enantioseparations in CEC and capillary liquid chromatography (CLC) due to the elimination of dissolution of chiral selector in a number of solvents. Chiral resolution of some enantiomers was improved by adopting tetrahydrofuran (THF) and chloroform as mobile-phase modifiers, respectively.

Cellulose↗

PubMed2004

Enzymatic reaction of the immobilized enzyme on porous silicon studied by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry.

Desorption/ionization on silicon mass spectrometry (DIOS-MS) is a matrix-free technique that allows for the direct desorption/ionization of low-molecular-weight compounds with little or no fragmentation of analytes. This technique has a relatively high tolerance for contaminants commonly found in biological samples. DIOS-MS has been applied to determine the activity of immobilized enzymes on the porous silicon surface. Enzyme activities were also monitored with the addition of a competitive inhibitor in the substrate solution. It is demonstrated that this method can be applied to the screening of enzyme inhibitors. Furthermore, a method for peptide mapping analysis by in situ digestion of proteins on the porous silicon surface modified by trypsin, combined with matrix-assisted laser desorption/ionization-time of flight-MS has been developed.

Animals↗

PubMed2004

Polar stationary phases for capillary electrochromatography.

This review article summarizes the variety of polar stationary phases that have been employed for capillary electrochromatographic separations. Compared with reversed-phase stationary phases, the polar alternatives provide a completely different retention selectivity towards polar and charged analytes. Different types of polar stationary phases are reviewed, including the possible retention mechanisms. Electrochromatographic separations of polar solutes, peptides, and basic pharmaceuticals on polar stationary phases are presented.

Chromatography, Liquid↗

PubMed2004

Enantiomer separation of dimethyl dicarboxy alpha-biphenyl (DDB) and its analogues on a covalently bonded cellulose tris-(3,5-dimethylphenylcarbamate) CSP.

Dimethyl dicarboxy alpha-biphenyl (DDB) and its analogues represent atropisomers which have been resolved on the covalently bonded cellulose tris-(3,5-dimethylphenylcarbamate) (CDMPC) CSP. Different kinds of alcohols, tetrahydrofuran (THF), and chloroform were employed as mobile phase modifiers (MPMs), and their influence on the retention and separation of the enantiomers was investigated. Ternary mobile phases (hexane/2-propanol/THF, hexane/2-propanol/chloroform) were employed to investigate the separation of the five enantiomers. The advantages of the broader choice of solvents offered by the covalently bonded CDMPC CSP were discussed. The effect of structural variation of the enantiomers on their retention and separation was investigated.

Buffers↗