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Biomedical subjects

Huwei Liu

Publications and source records attributed to Huwei Liu.

At least 19 recordsLinked to original sources
PubMed2006

Study of the metabolism on tobacco-specific N-nitrosamines in the rabbit by solid-phase extraction and liquid chromatography-tandem mass spectrometry.

Metabolism of four tobacco-specific N-nitrosamines (TSNAs), N'-nitrosonornicotine (NNN), N'-nitrosoanatabine (NAT), N'-nitrosoanabasine (NAB), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) has been studied by solid-phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS-MS). 4-(Methylnitrosamino)-4-(3-pyridyl)-1-butanol (iso-NNAL) was used as internal standard. SPE and LC-MS-MS was found to be a rapid, simple, sensitive, and selective method for analysis of TSNAs in rabbit serum. The relative standard deviation (R.S.D., n = 6) for analysis of 5 ng mL(-1) and 0.5 ng mL(-1) standards and of serum sample spiked with 5 ng mL(-1) standards of five TSNAs was 2.1-11% and recovery of 5 ng mL(-1) standards from serum was 100.2-112.9%. A good linear relationship was obtained between peak area ratio and concentration in the range of 0.2-100 ng mL(-1) for NNAL and 0.5-100 ng mL(-1) for other four TSNAs, with correlation coefficients (R2) >0.99 (both linear and log-log regression). Detection limits for standards in solvent were between 0.04 and 0.10 ng mL(-1). Doses of TSNAs administered to rabbits via the auricular vein were 4.67 microg kg(-1) and 11.67 microg kg(-1), in accordance with the different levels in cigarettes. Metabolic curves were obtained for the four TSNAs and for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolite of NNK; on the basis of these curves we modeled metabolic kinetic equations for these TSNAs by nonlinear curve fitting.

Animals↗
PubMed2006

Separation of hydrophobic solutes by organic-solvent-based micellar electrokinetic chromatography using cation surfactants.

In this study, the separation of 13 homologous stick-like hydrophobic solutes, i.e., biphenyl nitrile derivatives, by organic-solvent-based micellar electrokinetic chromatography (MEKC) was investigated in terms of separation medium composition, species and concentration of surfactant, other additives, separation voltage and temperature. The results showed that the 13 strong hydrophobic compounds were baseline separated in 25 min with a repeatability of less than 1.3% (RSD) for migration time. The separation medium was a mixture of methanol, 2-propanol and water (58.5:10:31.5), containing 150 mM cetyltrimethylammonium bromide (CTAB) and 20 mM sodium borate. Variety of solvent composition, temperature and applied voltage all showed remarkable effect on the separation. The organic-solvent-based MEKC method proved to be superior to the aqueous MEKC and microemulsion electrokinetic chromatography (MEEKC) methods for the separation of strongly hydrophobic compounds.

Cations↗
PubMed2006

Determination of evodiamine and rutecarpine in human serum by liquid chromatography-tandem mass spectrometry.

Evodiamine and rutecarpine are two kinds of indole alkaloids contained in the fruit of Evodiae fructus, which have been shown to exhibit various bioactivities in humans. A liquid chromatography-tandem mass spectrometric method (LC-MS/MS) was developed for the determination of evodiamine and rutecarpine in human serum. The serum was extracted by solid-phase extraction (SPE) and analyzed using a C18 column and a mobile phase consisting of methanol-water (85:15) solution containing 5 mmol/L ammonium formate at a flow rate of 0.5 mL/min. The mass spectrometer was operated in positive mode, employing the extracted ion chromatogram (EIC) for detection and quantitation of evodiamine (m/z 288) and rutecarpine (m/z 304). Good linear relationships between the peak area and the concentration were obtained in the ranges of 5.2-1040 ng/mL and 10.2-1020 ng/mL, with correlation coefficients (r) of 0.999 and 0.998, for evodiamine and rutecarpine, respectively. The repeatabilities (RSD, n=6) of quantitation for evodiamine and rutecarpine were 2.18-4.00% and 2.99-5.67%, respectively, and the recovery ranged from 90.5% to 98.1%. A comparative study of the different ionization and quantitation modes, including ESI-MS, ESI-MS/MS, APCI-MS and APCI-MS/MS, was also accomplished. The MS/MS fragmentation mechanism of the base peak ([M+H](+), m/z 304) of evodiamine was investigated in order to identify the analytes in more complicated body fluid samples.

Chromatography, Liquid↗
PubMed2006

Analysis of phospholipid species in rat peritoneal surface layer by liquid chromatography/electrospray ionization ion-trap mass spectrometry.

The main phospholipids in rat peritoneal surface layer were analyzed by normal-phase high-performance liquid chromatography (HPLC) coupled with electrospray ionization (ESI) ion-trap mass spectrometry (MS). By using a silica gel column and a gradient of hexane/isopropanol/water as mobile phase containing 5 mmol/L ammonium formate as modifiers, a baseline separation of glycerophosphoehtanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylcholine (PC), sphingomyelin (SM) and lyso-phosphatidylcholine (LPC) was obtained and more than 90 phospholipid constituents in rat peritoneal surface were identified and determined by on-line ion-trap MS detection. The major ethanolamine glycerophospholipids in rat peritoneal surfaces were plasmalogens that were highly enriched in polyunsaturated fatty acids at the sn-2 position. In addition, the fragmentation patterns for each phospholipid class by the ion-trap MS were discussed.

Animals↗
PubMed2006

Separation of phospholipids by capillary zone electrophoresis with indirect ultraviolet detection.

A simple method for separation of different anionic and zwitterionic phospholipid classes by capillary zone electrophoresis (CZE), using indirect UV detection with adenosine monophosphate (AMP) as background electrolyte and the UV-absorbing additive, was successfully developed in this study. The separation conditions including apparent pH (pH*) of running buffer, concentration of AMP, organic solvent, applied voltage and capillary temperature were systematically optimized. The application of this method to human blood sample was also briefly examined.

Adenosine Monophosphate↗
PubMed2006

Study on separation of aristolochic acid I and II by micellar electrokinetic capillary chromatography and competition mechanism between SDS and beta-cyclodextrin.

In this study, a rapid MEKC method using 40 mM sodium borate buffer containing 50 mM SDS as surfactant was developed for the analysis of aristolochic acid (AA) in Aristolochia plants. Baseline separation of AA-I and AA-II was achieved within 3 min with high separation efficiency, satisfactory sensitivity, repeatability, and recovery. Resolution between AA-I and AA-II is above 5 and great performance with higher than 200,000 theoretical plate numbers was obtained. The detection limits (based on 3 S/N) were both 1.0 microg/mL. Two kinds of AA in 35 herbal samples of Aristolochia plants were successfully determined. The competition mechanism between beta-CD and SDS was also investigated by changing the content ratio of beta-CD and SDS.

Antiviral Agents↗
PubMed2006

Analysis of amphetamine, methamphetamine and methylenedioxy-methamphetamine by micellar capillary electrophoresis using cation-selective exhaustive injection.

Cation-selective exhaustive injection (CSEI) is used as an on-line concentration method for the high-sensitivity analysis of illicit amphetamines using CE. Optimum conditions for the determination of amphetamine, methamphetamine and methylenedioxy-methamphetamine were investigated. Sodium dodecyl sulfate (25 mM) in 100 mM phosphate buffer (pH 2.9) with 20% methanol as organic additive was used as the background electrolyte for CE separation. The LOD, based on an S/N of 3:1, was about 0.01 microg/mL using normal capillary micellar electrokinetic chromatography, while by using CSEI in combination with micellar sweeping the sensitivity increased up to 1000-fold with the LOD lower than 50 pg/mL. The reproducibility of CSEI combined with micellar sweeping for analyzing amphetamines was satisfactory (relative standard deviation around 10% by using area ratios against an internal standard). This method is highly sensitive and can be used to analyze trace amount amphetamines in human hair.

Amphetamine↗
PubMed2006

Determination of tobacco-specific N-nitrosamines in rabbit serum by capillary zone electrophoresis and capillary electrophoresis-electrospray ionization-mass spectrometry with solid-phase extraction.

In this paper, we propose a new strategy for separation and determination of tobacco-specific N-nitrosamines (TSNAs), a group of strong carcinogens found only in tobacco products, by using CZE and CE-MS associated with SPE. Six TSNAs: N'-nitrosonornicotine, N'-nitrosoanatabine, N'-nitrosoanabasine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, and 4-(methylnitrosamino)-4-(3-pyridyl)-1-butanol were simultaneously separated by either of two CZE methods, one of which worked with ammonium formate buffer (pH 2.5) and another with citrate buffer (pH 2.4), as well as a CE-MS method. The CZE conditions including pH and concentration of running buffer, capillary length, applied voltage, and capillary temperature were systematically optimized. For CE-MS method, an optimized sheath liquid consisted of methanol-water was used at a flow rate of 10 muL/min. With SPE procedure, our proposed CE-MS method was successfully applied to determine TSNAs after 15 min metabolism in rabbits. A comparison study between CZE and CE-MS methods for quantitative purposes was carried out, showing that both methods provided similar separation efficiency, selectivity, repeatability, linearity, and recovery. However, CE-MS method was better suited for the analysis of TSNAs in complicated biological samples for its sensitivity and extra information on molecular structure. Having good accordance with our previous work by using LC-MS, the new CE-MS method is expected to be an alternative to the LC-MS method and applied to study the metabolism of TSNAs.

Animals↗
PubMed2006

Applications of nanomaterials in liquid chromatography: opportunities for separation with high efficiency and selectivity.

During recent decades, great efforts have been made to improve the chemical stability, selectivity, and separation efficiency of stationary phases in liquid chromatography. Significant progress has been achieved, especially after the introduction of nanomaterials into separation science. This review covers the applications of nanomaterials playing various roles in liquid chromatography. Future possibilities for developing nanomaterial-based stationary phases are also discussed.

Chromatography, Liquid↗
PubMed2006

Fragmentation study of hexanitrostilbene by ion trap multiple mass spectrometry and analysis by liquid chromatography/mass spectrometry.

The fragmentation pathways of three explosive compounds with similar structures, hexanitrostilbene (HNS), cyclotrimethylene trinitramine (RDX), and 2,4,6-trinitrotoluene (TNT), have been investigated by multiple mass spectrometry (MSn, n = 1, 2, 3) with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) sources. The electron capture mechanism for these compounds in negative ion APCI and ESI mode differs from the usual negative ion mechanism, deprotonation or addition of other species. This was shown for HNS and TNT, which both gave a [M]- anion but not a [M-H]- ion in APCI, and the [M]- anion of HNS was observed in ESI. The quantitative analysis of HNS was performed by liquid chromatography (LC)/ESI-MS, and the results obtained by the internal standard (ISTD) method were compared with those from the external standard (ESTD) method, demonstrating that both quantitation approaches are useful, with good sensitivity, reproducibility and linearity, and ESTD is preferable in routine applications.

Chromatography, High Pressure Liquid↗
PubMed2005

Ionic liquid-based aqueous two-phase system, a sample pretreatment procedure prior to high-performance liquid chromatography of opium alkaloids.

An ionic liquid, 1-butyl-3-methylimidazolium chloride ([C4 mim]Cl)/salt aqueous two-phase systems (ATPS) was presented as a simple, rapid and effective sample pretreatment technique coupled with high-performance liquid chromatography (HPLC) for analysis of the major opium alkaloids in Pericarpium papaveris. To find optimal conditions, the partition behaviors of codeine and papaverine in ionic liquid/salt aqueous two-phase systems were investigated. Various factors were considered systematically, and the results indicated that both the pH value and the salting-out ability of salt had great influence on phase separation. The recoveries of codeine and papaverine were 90.0-100.2% and 99.3-102.0%, respectively, from aqueous samples of P. papaveris by the proposed method.

Chemical Fractionation↗
PubMed2005

A universal HPLC method for the determination of phenolic acids in compound herbal medicines.

A universal method to separate and quantify 13 phenolic acids (gallic acid, chlorogenic acid, gentsic acid, vanillic acid, caffeic acid, syringic acid, sinapic acid, p-coumaric acid, ferulic acid, anisic acid, rosmarinic acid, salicylic acid, and cinnamic acid) in some compound herbal medicines was established by liquid chromatographic (HPLC). On an Agela XBP-C18 (5 microm, 4.6 mm x 150 mm) column, a multistep binary gradient elution program and a simplified sample pretreatment approach were used in the experiment. For all of the phenolic acids, detection limits ranged around 0.01 mg/L. Linear ranges of higher than 2 orders of magnitude were obtained with a correlation coefficient of 0.9991 to 1. Repeatability was 0.39-2.24% (relative standard deviation, RSD) for intraday, 1.17-3.96% (RSD) for interday, and 0.14-5.33% (RSD) for drug sample analysis. Recovery, tested by a standard addition method, ranged from 83.3% to 104.9% for various trace phenolic acids.

Acids, Carbocyclic↗
PubMed2005

Extraction of testosterone and epitestosterone in human urine using aqueous two-phase systems of ionic liquid and salt.

Based on aqueous two-phase systems (ATPS) consisting of 1-butyl-3-methylimidazolium chloride, a hydrophilic ionic liquid (IL), and K2HPO4, a new and simple extraction technique, coupled with a reversed-phase high performance liquid chromatography (RP-HPLC), was developed for the simultaneous concentration and analysis of testosterone (T) and epitestosterone (ET) in human urine. Under the optimal conditions, the extraction efficiencies for both analytes were 80-90% in a one-step extraction. The method required only 3.0 mL of urine and a single hydrolysis/deproteinization/extraction step followed by direct injection of the IL-rich upper phase into HPLC system for analysis. The method has been satisfactorily applied to the analysis of T and ET in human urine with detection limits of 1 ng/mL and linear ranges of 10-500 ng/mL for both compounds. Compared with conventional liquid-liquid extraction or solid phase extraction, this new method is much "greener" due to no use of volatile organic solvent and low consumption of IL. The proposed extraction technique opens up new possibilities in the separation of other drugs.

Chemical Fractionation↗
PubMed2005

Ionene-dynamically coated capillary for analysis of urinary and recombinant human erythropoietin by capillary electrophoresis and online electrospray ionization mass spectrometry.

In this article, a series of ionene polymers were synthesized and used to coat fused-silica capillaries for the separation of recombinant and urinary human erythropoietin (rhEPO and uEPO) standards by CE. The influence of the charge density of coatings on the separation of rhEPO and uEPO glycoforms was investigated. Then, we further studied the method for fast separation and detection of rhEPO and uEPO standards by CE-ESI-MS. The influence of several CE and MS operating parameters, such as the concentration of CE running buffer, applied external pressure, and the composition and flow rate of sheath liquid on CE-ESI-MS was studied. The results demonstrated that when the capillary was permanently coated with 6,6-ionene and the pH value of acetic acid-ammonium acetate running buffer was 4.80 and 5.50, respectively, a significantly reproducible separation was achieved for rhEPO and uEPO glycoforms. In the online CE-ESI-MS experiments, we not only achieved the online MS signal of uEPO, but also obtained baseline separation of three major rhEPO glycoforms successfully and reproducibly on the 6,6-ionene-coated capillaries. Furthermore, the standard mixture of rhEPO and uEPO was separated, and two incompletely resolved peaks that were identified to be rhEPO and uEPO by the unique MS "fingerprint" were obtained. Additionally, the molecular weight of rhEPO and uEPO were verified and compared to the results by MALDI-TOF-MS. It can be concluded that, in contrast to other indirect methods, the online CE-ESI-MS technique with the combination of the advantages of both CE and MS shows great potential for the separation and detection of rhEPO doping directly in competitive sports.

Electrophoresis, Capillary↗
PubMed2005

Separation methods for toxic components in Traditional Chinese Medicines.

Traditional Chinese medicines (TCMs) with many unique functions for treating diseases have attracted the interest of people worldwide. They have been popularly utilized for therapy and health promotion in most Asian countries and even in many European and North American countries. However, it should be clearly noted that TCMs are mixtures with complicated composition usually containing hundreds, even thousands of chemically different constituents, and it is the multiple constituents that work synthetically to determine the ultimate effect of a formula of TCM. Meanwhile, some components with toxicity in some TCMs, having various negative effects on different parts of body, may do serious harm to people's health; such harm in particular requires our attention. In this article, applications of different chromatographic and electrophoretic techniques in the analysis of toxic components in TCMs in recent decades have been comprehensively reviewed and some hyphenated procedures (combinations of two kinds of measurement) applied in this field are also summarized.

Alkaloids↗
PubMed2005

[Analysis of recombinant erythropoietin and its tryptic digest by capillary electrophoresis and capillary electrophoresis-electrospray ionization-mass spectrometry using capillary coated with 6,6-ionene].

The microheterogeneity of recombinant human erythropoietin (rhEPO) was analyzed by capillary electrophoresis (CE) using a capillary coated with 6,6-ionene. The applicability of a volatile electrolyte for fast analysis of tryptic fragments of rhEPO with online CE-electrospray ionization-mass spectrometry (ESI-MS) was investigated, resulting in a reproducible separation of eleven rhEPO tryptic fragments within 22 min under the following conditions: running buffer 300 mmol/L acetic acid-ammonium acetate (HAc-NH4Ac), pH 4.80, separation voltage -15 kV and capillary temperature 25 degrees C. The proposed method is rapid and effective, and can be used for the structural analysis of related proteins.

Electrophoresis, Capillary↗