Living in Interesting Times, Part 2

Chromatography–Mass Spectrometry at Hong Kong Baptist University

The major research of this group focuses on method development and applications of chromatography coupled with mass spectrometry for trace analysis in complex systems, such as the environment, traditional Chinese medicines (TCM), food and biological matrices. The group is equipped with a wide range of state-of-the-art instrumentation, including GC, GC–MS (quadrupole, ion-trap and magnetic sector), HPLC, LC–MS (ion-trap and quadrupole-time of flight) and MALDI-TOFMS. Current research programmes include: HRGC–HRMS for the trace analysis of dioxins and dioxin-like PCBs; PBDEs in environmental and biota samples related to e-waste recycling; drug metabolism and pharmacokinetics of active components from TCM; metabolomics; and proteomics.

Chromatography plays an important role in successful analytical method development for trace analysis in complex matrices. To provide a specific example, they have focused on LC–MS method development for fast, specific and sensitive analysis of endogenous nucleotides and the phosphorylated metabolites of anti-HIV drugs, such as the nucleoside reverse transcriptase inhibitors (NRTIs). Nucleoside drugs that can block the production of new mitochondria have been developed against human HIV. Consequently, the determination of generated nucleotides in cells and tissues at trace levels has become more and more important for understanding the mechanism of action of these analogues in drug discovery and development. Reversed-phase HPLC–MS is an attractive approach to accurately qualify and quantify phosphorylated metabolites because of its separation efficiency and detection sensitivity.

However, most nucleotides are not effectively retained on reversed-phase columns using conventional mobile phases because of their extremely high polarity. The difficulty of separating analytes from the interference background has caused problems for sensitive detection and identification. Development of a suitable method to improve the retention times of nucleotides is therefore critical for the trace analysis of nucleotides in biological samples. Although several chromatographic conditions have been reported for the retention and separation of nucleotides, they were mostly "unfriendly" to ESI-MS. For the application of ion-paring LC–MS, the group found that dimethylhexylamine (DMHA) caused minimal interference with the ESI-MS analysis and allowed the simultaneous detection of nucleoside drugs and their corresponding nucleotides under the positive ion mode. Efforts have been made to apply the minimal levels of ion-paring agent; for example, by using smaller diameter columns to minimize ion suppression and ESI-MS source contamination from the ion-paring agent. The developed methods have been successfully applied to support several research programmes, including the trace analysis of phosphorylated metabolites in human liver cells treated with Ziagen (abacavir — a carbocyclic nucleoside analogue with activity against HIV).

To avoid using ion-pairing agents to improve ESI-MS sensitivity, the group is now exploring new approaches with various chromatographic conditions, particularly the selection of modified reversed-phase LC columns. Recent results have shown that porous graphitic carbon (PGC) columns might be promising. It has been found PGC columns can provide much better retention and selectivity for polar compounds compared with traditional and modified reversed-phase columns — allowing the direct sensitive detection of nucleotides with negative ion ESI-MS. Another advantage of PGC columns is their tolerance to a wide pH range, especially at pH > 8, under which the detection sensitivity of nucleotides might be greatly improved with the negative ion mode of ESI-MS. The LC–MS method with PGC columns has been developed and successfully applied for supporting biochemical research projects.

For more information, contact Professor Zongwei Cai on e-mail: zwcai@hkbu.edu.hk, or visit www.hkbu.edu.hk/~dioxin/ and www.hkbu.edu.hk/~caigroup/

Chromatography at the Department of Chemistry, Peking University

The Chromatography and Capillary Electrophoresis Group has focused on the fundamentals and applications of chromatographic techniques since the 1970s. It has also been known as the PKU-Agilent Analysis Laboratory since 1997 as part of the collaboration programme between Peking University and Agilent Technologies. At present, it comprises two staff and ten PhD students. Our research interests include:

• New separation media based on nanomaterials, especially for chiral separations.

• Doping control analysis, focusing on the detection of recombinant and human urinary erythropoietin (rHuEPO and uEPO) by CE and CE–MS. We have also developed CE–MS methods for the analysis of narcotics, such as heroin and related compounds.

• Analysis of herbal medicines by LC, CE, LC–MS and CE–MS. Many methods have been developed for the determination of components in traditional Chinese medicines, especially for toxic compounds, such as aristolochic acids.

• Development of a new microdevice used for online desalting digestion of biological samples for direct identification and quantification of crude protein extracts by LC–MS.

• Clinical analysis of phospholipid molecular species by LC–MS and CE–MS.

For more information, contact Professor Huwei Liu on e-mail: hwiu@pku.edu.cn or visit www.chem.pku.edu.cn/paal

Selected Publications since 2006:

1. X. Yang et al., "A comparative study of micellar and microemulsion electrokinetic chromatography for the separation of benzoylurea insecticides and their analogues", Electrophoresis, 28, 1744–1751 (2007).

2. X. Fu et al., "Carboxylmethyl chitosan-coated capillary and its application in capillary electrophoresis", Electrophoresis, 28, 1958–1963 (2007).

3. F. Gao, T. Wang and H. Liu, "Analysis of phospholipids by nonaqueous capillary electrophoresis with on-line electrospray ionization mass spectrometry", Electrophoresis, 28, 1418–1425 (2007).

4. W. Li et al., "Study on Separation of Aristolochic Acid I and II by Micellar Electrokinetic Capillary Chromatography and Competition Mechanism between SDS and β-Cyclodextrin", Electrophoresis, 27, 837–841 (2006).

5. C. Li et al., "Determination of tobacco-specific N-nitrosamines in rabbit serum by capillary zone electrophoresis and capillary electrophoresis-electrospray ionization-mass spectrometry with solid-phase extraction", Electrophoresis, 27, 2152–2163 (2006).

6. F. Gao et al., "Analysis of phospholipid species in the peritoneal surface layer of rats by high-performance liquid chromatography coupled with electrospray ionization ion-trap tandem mass spectrometry", BBA/Molecular and Cell Biology of Lipids, 1761, 667–676 (2006).

7. F. Gao et al., "Separation of phospholipids by capillary zone electrophoresis with indirect ultraviolet detection", J. Chromatogr. A, 1130, 259–264 (2006).

8. S. Gong et al., "Separation of hydrophobic solutes by organic-solvent-based micellar electrokinetic chromatography using cation surfactants", J. Chromatogr. A, 1121, 274–279 (2006).

9. D. Wen et al., "Determination of Evodiamine and Rutecarpine in Human Serum by Liquid Chromatography – Tandem Mass Spectrometry", Anal. Bioanal Chem., 385(6), 1075–1081 (2006).

10. Z. Zhang et al., "Application of nanomaterials in liquid chromatography: The opportunity for separation with high efficiency and selectivity", J. Sep. Sci., 29(12), 1872–1878 (2006).

11. X. Fu et al., "Fragmentation study of hexanitrdostilbene by ion trap multiple mass spectrometry and analysis by liquid chromatography-mass spectrometry", Rapid Commun. Mass Spectrom., 20, 2906–2914 (2006).

12. C. Li et al., "Study of the metabolism on tobacco-specific N-nitrosamines in the rabbit by solid-phase extraction and liquid chromatography–tandem mass pectrometry", Anal. Bioanal. Chem., 386, 1985–1993 (2006).

Separation Science at National Chi Nan University in Taiwan

The research interest of this group is focused on the development of a magnetic separation technique using thin channels (< 0.4 mm) and functional magnetic particles for biochemical applications. They have developed magnetic split-flow thin (SPLITT) fractionation for preparative applications and magnetapheresis for analytical applications on particles and cells. A magnetic field was applied perpendicular to the channel flow in both techniques. The throughputs of preparative separation were approximately 1.8 g/h. Particle susceptibility was determined in analytical applications.

Functional magnetic particles from a few nm to μm were prepared and conjugated with antibodies for various biochemical applications. Magnetic particles labelled with antibody were pumped through the channel to deposit a matrix for selective capture of antigens. The run time was less than 10 min. This method extends the applications of magnetic separation to nonmagnetic samples. New methods of blood typing and affinity reactions were demonstrated using this method, providing a simple, fast and selective analysis for particles, blood cells and immunoassay related applications. Various biochemical applications using functional magnetic nanoparticles are under development.

For more information, contact Professor C. Bor Fuh on e-mail: cbfuh@ncnu.edu.tw

Selected Publications

1. C.B. Fuh, "Split-flow Thin Fractionation: Versatile Techniques for Separation of Macromolecules, Colloids, and Particles", Anal. Chem., 72, 266A–271A (2000).

2. C.B. Fuh, Y.S. Su and H.Y. Tsai, "Magnetic Susceptibility Determination of Various Ion-labeled Red Blood Cells Using Analytical Magnetapheresis" J. Chrom. A, 1027, 289–296 (2004).

3. H.Y. Tsai et al., "New Method of Blood Typing Using Analytical Magnetapheresis", J. Chrom. A, 1120, 35–37 (2006).

Green Analytical Chemistry at National Tsing Hua University

The GMLab (Green Chemistry and Mass Spectrometry Laboratory) specializes in developing analytical chemistry methods for problem-oriented investigations and researching green chemistry. Examples of our work include:

1. HRGC–HRMS methods for surveying dioxins and polychlorinated biphenyls (PCBs) in Taiwanese ambient air and dietary products — the results of which are critical to regulatory control and prevention strategies.

2. GC–MS methods for analysing polybrominated diphenyl ethers (PBDEs) in indoor environments — the determintion of contaminant 'hot spots' at specific sites where people (and, in particular, children) gather warrants further investigations.

3. The integrated use of electronic nose, thermal desorption GC–MS–MS and ion chromatography to determine ambient odorous compounds in manufacturing plants and airborne molecular contaminants (AMCs) in cleanrooms. Our laboratory's analytical capability to identify the odour origins and to monitor follow-up engineering improvements has successfully helped resolve odorous complaints.

4. Synergistic developments in the use of GC–MS and LC–MS–MS methods have been examined for food adulteration studies. To enhance legal evidence, we have developed a HRGC–IRMS (isotope ratio mass spectrometry) method for both environmental and forensic identifcation of food origin, and transnational tracing of drugs of abuse.

5. We recently developed a one-pot chemical co-precipitation method to prepare functional suparamagnetic Fe₂O₃ nanoparticles for adsorbent use. The nanoadsorbent-based method coupled with secondary ion mass spectrometry (SIMS) has played an important role in our risk assessment of nanomaterials. In this aspect, we have established collaborative research activities in green and sustainable chemistry with the Australian Research Council Special Research Centre for Green Chemistry (Monash University), and in nanotoxicology with the domestic National Health Research Institute. Preliminary findings are both promising and encouraging.

For more information, contact Professor Y.C. Ling on e-mail: ycling@mx.nthu.edu.tw

Separation Sciences at Tsinghua University

The Analysis Center is a teaching and research institute for analytical chemistry at Tsinghua University, both in terms of fundamentals and applications. It also offers a public service for sample analysis. They have four main research areas for separation sciences at the centre:

First, they aim to develop analytical methods for the life sciences and new drug development based on separation technology. Their key research achievement has been in the theory and technology development of capillary electrophoresis (CE), including the theory and application of capillary electrochromatography, microchip electrophoresis, chiral separations, CE–MS and its application to biomolecular analysis, and immunoassay CE.

Second, the study of ion chromatography is another important research topic at Tsinghua, particularly retention mechanisms, stationary phases and simultaneous analysis of anions and cations.

Third, to address the problem of environmental pollution in China, they have developed some useful sample pretreatment methods for the trace analysis of persistent toxic substances (PTS). Molecularly imprinted polymers, cloud-point extraction, continuous-flow microextraction, solid-phase extraction with C30-bonded silica, flocculation-ultrasonic assisted extraction and nonequilibrium hollow-fibre liquid-phase microextraction have all been applied. GC–MS, LC–MS and capillary electrophoresis are used as analytical tools.

Fourth, they have focused on microfluidic chip design and the development of detection methods. Chemiluminescence, laser-induced fluorescence, end-channel amperometric detection, atomic fluorescence spectrometry and mass spectrometry have been coupled with our designed microfluidic devices and applied to the analysis of metal ions and organic compounds, for the monitoring and kinetics study of single particles on a simple microfluidic chip.

As an important research group in China, they receive grants from the National Nature Science Foundation of China, National Key Technology R&D Program and National High Technology Research and Development Program of China. They have collaborative programmes with many groups and companies both nationally and internationally. More than 40 members including foreign students, PhD and postdoctoral students in the group are studying to develop new and useful analytical methods for the life sciences and environmental protection.

For more information, contact Professor Jin-Ming Lin on e-mail: jmlin@mail.tsinghua.edu.cn

Selected Publications

1. Ke Li et al., "Solid-phase extraction with C30-bonded silica for analysis of polycyclic aromatic hydrocarbons in airborne particulate matters by gas chromatography-mass spectrometry", J. Chromatogr. A, 1154, 74–80 (2007).

2. Yufang Zheng et al., "Chip-based CE coupled to a quadrupole TOF mass spectrometer for the analysis of a glycopeptide", Electrophoresis, 28(9), 1305–1311 (2007).

3. Ru-Song Zhao et al., "Nonequilibrium hollow-fiber liquid-phase microextraction with in situ derivatization for the measurement of triclosan in aqueous samples by gas chromatography-mass spectrometry", Anal. Bioanal. Chem., 387, 2911–2915 (2007).

4. Bao-Lin Chu et al., "Studies on degradation of imazalil enantiomers in soil using capillary electrophoresis", J. Sep. Sci., 30, 923–929 (2007).

5. Rusong Zhao et al., "Sensitive measurement of ultratrace phenols in natural water by purge-and-trap with in situ acetylation coupled with gas chromatography-mass spectrometry", Anal. Bioanal. Chem., 387, 687–694 (2007).

6. Jiangjiang Liu, Haifang Li and Jin-Ming Lin, "Measurements of surface tension of organic solvents using a simple microfabricated chip", Anal. Chem., 79 (1), 371–377 (2007).

7. Chao Tian et al., "Monitoring and kinetics study of single particle on a simple microfluidic chip", Anal. Chem., 78, 6270–6274 (2006).