Wei Li

Peking University, Peping, Beijing, China

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Publications (15)38.22 Total impact

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    ABSTRACT: Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed in 25 background and 80 agriculture soil samples collected from 21 sites in Beijing, China. The levels of PCDD/Fs in the north agriculture soils were low (0.15–0.58 ng I-TEQ/kg), which were compatible with those of the background soils (0.091–0.35 ng I-TEQ/kg). However, in the south agriculture soils, there was an abrupt jump in their concentration (0.27–3.3 ng I-TEQ/kg), several times higher. Comparison of PCDD/Fs congener compositions between possible sources and samples indicated that agriculture soils in Beijing had not been contaminated by the three main PCDD/Fs contamination sources in China, such as ferrous and non-ferrous metal, waste incineration and power generation, but had been slightly contaminated by the impurities of some organochlorine pesticides, such as sodium pentachlorophenate, also slightly contaminated by the biomass open burning, vehicle exhaust, atmospheric deposition, sediment and sewage sludge. These results have also been supported by the principal components analysis. Environ Toxicol Chem © 2014 SETAC
    No preview · Article · Sep 2014 · Environmental Toxicology and Chemistry
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    ABSTRACT: Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analysed in 95 mountainous and park soil samples collected from 19 sites in Beijing, China. The levels of PCDD/Fs in the mountainous soils were low (0.086–0.59; mean 0.29; median 0.23 ng I-TEQ/kg). The levels in the park soils far from the city centre were a little higher (0.39–0.88, mean0.68; median 0.75 ng I-TEQ/kg). However, in the park soils near to the city centre, there were an abrupt jump in their concentration (1.7–3.2; mean 2.3, median 1.7 ng I-TEQ/kg), about ten times higher than those in the mountainous sites. Comparison of PCDD/Fs homologues and congener compositions between possible sources and samples indicated that the mountainous and park soils in Beijing had been slightly contaminated mainly by sodium pentachlorophenate, sewage sludge, atmospheric deposition and vehicle exhaust. These results have also been supported by the principal component analysis.
    No preview · Article · May 2014 · International Journal of Environmental Analytical Chemistry
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    ABSTRACT: A method was developed for analysis of PCDD/Fs in fly ash and soil samples by using the combination of pressurized liquid extraction (PLE) and off-line HPLC fractionation with a porous graphite carbon (PGC) column, followed by analysis using HRGC/HRMS. The samples were automatically extracted by PLE. A multi-layer silica column was used for the preliminary cleanup. Then off-line fractionation was applied for the separation of PCDD/Fs and the collected PCDD/Fs fraction was analyzed by HRGC/HRMS. The use of solvent back-flushing at 70°C successfully solved the carry-over problem of PGC column. The procedure of single extraction and cleanup provided advantages of high automation and significant reduction of solvent and time compared to conventional methods. The method was validated by certified materials of fly ash and industrial sandy soil, and applied for the analysis of fly ash samples collected from three two-ton medical waste incinerators in Beijing and one farm soil sample collected in the vicinity of the incinerators.
    No preview · Article · Jan 2012 · International Journal of Environmental Analytical Chemistry
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    Han Liu · Wei Li · DaMing Du
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    ABSTRACT: The electronic effect of diphenylamine-linked bis(oxazoline) ligands was tuned through introduction of electron-withdrawing bromo and nitro substituents onto the 4 and 4′ position. The variation of the NH bond acidity was determined by the different chemical shifts of NH. The catalytic activity and enantioselectivity of the modified ligands were tested in the asymmetric Friedel-Crafts alkylation of indole with β-nitrostyrene. The effect of ligand skeleton rigidity was also investigated through the synthesis of iminodibenzyl-linked bis(oxazoline) ligands and evaluation of their catalytic activity in Friedel-Crafts alkylation.
    Full-text · Article · Sep 2009 · Science in China Series B Chemistry
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    ABSTRACT: A CE-MS method for rapid determination of aristolochic acid-I and aristolochic acid-II (AA-II) in traditional Chinese medicines and biological samples was described in the present paper. AA-I and AA-II can be baseline separated within 6 min by CE-MS with carboxymethyl-chitosan-coated capillary. CZE conditions including pH, concentration of buffer, applied voltage, and capillary temperature were systematically investigated, and the composition and flow rate of sheath liquid were also optimized for CE-MS. Furthermore, the CE-UV method without any additives in BGE solution was established and compared with the CE-MS method. The results showed that the two methods could achieve satisfactory separation efficiency, repeatability, and linearity, while the LOD was 0.6 microg/mL for CE-UV and 0.05 microg/mL for CE-MS. Compared with the CE-UV method, the sensitivity of CE-MS was significantly improved, in addition to the structure information provided by MS detection at the same time. As an application example, a spiked sample in human serum was analyzed by the CE-MS method, indicating that the new CE-MS method can be applied to analyze AAs in biological samples.
    No preview · Article · May 2009 · Electrophoresis
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    ABSTRACT: The concentration of long-chain fatty acids (LCFAs) in human serum is closely related to human health. It is therefore important to develop a fast, low-cost, efficient method for their determination. In this study, by using fast temperature programming and micro-bore short capillary columns, a fast gas chromatography method was developed for the direct analysis of non-derivatized LCFAs including n-dodecanoic acid to n-hexacosanic acid (C12:0-C26:0, even numbers only), linoleic acid (C18:2), oleic acid (C18:1), and erucic acid (C22:1) within 4.0 min. Method optimization including extraction and separation conditions is considered, and the analysis of real serum samples is presented. The results show that ten LCFAs were well separated with sufficient resolution, and the detection limit was in the range of 2.8-9.6 microg/mL. The reproducibility (RSD) for both intra-day and inter-day determination was always less than 15%, and the recoveries for these LCFAs were from 63.1 to 97.0%.
    No preview · Article · Jul 2007 · Journal of Separation Science
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    ABSTRACT: A hyphenated method of nonaqueous capillary electrophoresis coupled to electrospray ionization mass spectrometry (NACE-ESI-MS) is described for the simultaneous analysis of phospholipids. The best results were obtained with a mixed solution of methanol/ACN (40:60 v/v) containing 20 mM ammonium acetate and 0.5% acetic acid, under the applied voltage of 30 kV and capillary temperature of 25 degrees C. ESI-MS measurements were performed in the negative mode with methanol/ACN (40:60 v/v) containing 50 mM ammonium acetate as sheath liquid at a flow rate of 2 microL/min. Different phospholipid classes have been successfully separated within 16 min, and the molecular species of every single class have been identified by using MS(2) or MS(3), which generates characteristic fragments through CID. The developed method has been applied to analyze the phospholipids extracted from rat peritoneal surface and the molecular species of phospholipid classes are presented.
    No preview · Article · May 2007 · Electrophoresis
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    ABSTRACT: Chitosan and its derivatives have been widely used in many fields for their various function, there were some difference in bioactivities and applications between them. In this paper, a direct capillary zone electrophoresis (CZE) method without any pre-treatment was developed for separation of chitosan and its derivative, a water soluble chitosan called carboxymethyl chitosan (CM-chitosan), which was proved to be rapid and effective with satisfactory resolution. Optimization of conditions including pH, concentration of the buffer, and length of column were investigated, showing that when employing 50 mM sodium phosphate at pH 2.0 and untreated fused silica capillary, high-molecular weight chitosan and CM-chitosan were baseline separated with ultraviolet (UV) detector with satisfactory repeatability and excellent linear responses. Therefore, this method could be applied to separate and identify chitosan and CM-chitosan in biological samples and commercial products.
    Full-text · Article · Apr 2007 · Carbohydrate Polymers
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    ABSTRACT: 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.
    Full-text · Article · Nov 2006 · Journal of Chromatography A
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    ABSTRACT: 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.
    No preview · Article · Aug 2006 · Journal of Chromatography A
  • Wei Li · Zheng Chen · Yiping Liao · Huwei Liu
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    ABSTRACT: 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.
    No preview · Article · Feb 2006 · Electrophoresis
  • Wei Li · Zheng Chen · Yiping Liao · Huwei Liu
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    ABSTRACT: 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.
    No preview · Article · Oct 2005 · Analytical Sciences
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    ABSTRACT: Chinese herbs nephropathy (CHN) is a kind of severe kidney disease caused by excessively taking aristolochic acid (AA). Hence, it is essential for health security and quality control of related herbal medicines to develop an efficient method for separation and determination of these two important components in Traditional Chinese Medicines. In this study, a rapid capillary zone electrophoresis (CZE) method using 120 mM sodium borate buffer containing 10 mM beta-cyclodextrin (beta-CD) as modifier was firstly developed for the analysis of AA-I and AA-II within 4min in some medicinal plant samples. The separation conditions including pH of running buffer, CD content in the buffer system, applied voltage and capillary temperature were systematically optimized, and two kinds of aristolochic acids in 37 herbal samples of Aristolochia plants were successfully determined with high separation efficiency, satisfactory sensitivity, repeatability and recovery. The result indicated high variability in the contents of aristolochic acids due to different species and regions. The comparison of CZE method with high performance liquid chromatography (HPLC) was also discussed.
    No preview · Article · Oct 2004 · Journal of Chromatography A

  • No preview · Article · Aug 2004 · Se pu = Chinese journal of chromatography / Zhongguo hua xue hui
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    ABSTRACT: Aristolochic acids (AA) are toxic components of Aristolochia plants which result in diseases of the kidney such as urothelial cancer. It is, therefore, essential to monitor the amount of aristolochic acid in herbal medicines. In this study a reversed-phase high-performance liquid-chromatographic (HPLC) method has been developed for rapid determination of aristolochic acids I and II. Baseline separation was achieved within five minutes by use of an ODS C18 column with methanol–water, 60:40, as mobile phase. Two kinds of aristolochic acid were successfully determined in 31 herbal samples of Aristolochia fangchi Wu and Caulis Aristolochiae Manshuriensis. The results indicated that in most samples the aristolochic acid I content is much higher than that of aristolochic acid II. The two kinds of aristolochic acid were not detected in Aristolochia fangchi from the Guangdong region, so Aristolochia fangchi from this region is recommended for use in herbal remedies.
    No preview · Article · Jan 2004 · Chromatographia

Publication Stats

186 Citations
38.22 Total Impact Points

Institutions

  • 2004-2014
    • Peking University
      • • Environmental Science
      • • College of Environmental Science and Engineering
      • • Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education
      • • College of Chemistry and Molecular Engineering
      • • Institute of Analytical Chemistry
      Peping, Beijing, China