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Hanghui Liu

Bio: Hanghui Liu is an academic researcher from Texas Tech University. The author has contributed to research in topics: Drop (liquid) & Mass spectrometry. The author has an hindex of 18, co-authored 35 publications receiving 1885 citations. Previous affiliations of Hanghui Liu include Central South University & Northeastern University.

Papers
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Journal ArticleDOI
TL;DR: This unique microextraction system is simple and flexible, permits automated backwashing, consumes only microquantities of organic solvents, and is capable of being coupled with other analytical systems.
Abstract: An organic microdrop (∼1.3 μL) is suspended inside a flowing aqueous drop from which the analyte is extracted. The drop-in-drop system is achieved by a multitube assembly. The aqueous phase is continuously delivered to the outer drop and is aspirated away from the bottom meniscus of the drop. After the sampling/extraction period, a wash solution replaces the sample/reagent in the aqueous layer, resulting in a clear outer aqueous drop housing a colored organic drop containing the extracted material. This also results in an automatic backwash. The color intensity of the organic drop, related to the analyte concentration, is monitored by a light-emitting diode based absorbance detector. After the analytical cycle, the organic drop is removed and replaced by a new one. The performance of the system is illustrated with the determination of sodium dodecyl sulfate (a methylene blue active substance) extracted as an ion pair into chloroform. This unique microextraction system is simple and flexible, permits autom...

697 citations

Journal ArticleDOI
TL;DR: Two fundamental approaches for the coupling of microfabricated devices to electrospray mass spectrometry (ESI-MS) have been developed and evaluated and one is simple to fabricate and may thus be developed either as a part of a reusable system or as a disposable cartridge.
Abstract: Two fundamental approaches for the coupling of microfabricated devices to electrospray mass spectrometry (ESI-MS) have been developed and evaluated. The microdevices, designed for electrophoretic separation, were constructed from glass by standard photolithographic/wet chemical etching techniques. Both approaches integrated sample inlet ports, preconcentration sample loops, the separation channel, and a port for ESI coupling. In one design, a modular, reusable microdevice was coupled to an external subatmospheric electrospray interface using a liquid junction and a fused silica transfer capillary. The transfer capillary allowed the use of an independent electrospray interface as well as fiber optic UV detection. In the second design, a miniaturized pneumatic nebulizer was fabricated as an integral part of the chip, resulting in a very simple device. The on-chip pneumatic nebulizer provided control of the flow of the electrosprayed liquid and minimized the dead volume associated with droplet formation at t...

290 citations

Journal ArticleDOI
TL;DR: The basic principles of multichannel devices with an array of electrospray tips for high-throughput infusion electrosPRay ionization mass spectrometry (ESI-MS) have been developed and used for the MS determination of inhibition constants of several inhibitors of HIV-1 protease.
Abstract: The basic principles of multichannel devices with an array of electrospray tips for high-throughput infusion electrospray ionization mass spectrometry (ESI-MS) have been developed. The prototype plastic devices were fabricated by casting from a solvent-resistant resin. The sample wells on the device were arranged in the format of the standard 96-microtiter well plate, with each sample well connected to an independent electrospray exit port via a microchannel with imbedded electrode. A second plastic plate with distribution microchannels was employed as a cover plate and pressure distributor. Nitrogen gas was used to pressurize individual wells for transport of sample into the electrospray exit port. The design of independent microchannels and electrospray exit ports allowed very high throughput and duty cycle, as well as elimination of any potential sample carryover. The device was placed on a computer-controlled translation stage for precise positioning of the electrospray exit ports in front of the mass...

137 citations

Journal ArticleDOI
TL;DR: The use of a drop minimizes sample/reagent consumption and, like the dropping mercury electrode of Heyrovsky, allows a fresh reaction surface for every sample as mentioned in this paper.
Abstract: A liquid drop has some unique features, namely, reproducibility, renewability and the lack of containment walls. The value of these features are highlighted through a series of novel liquid drop-based systems: truly renewable gas sampling interfaces, windowless optical cells and reaction vessels for flow-injection turbidimetry and solvent extraction systems with nested drop arrangements. The use of a drop minimizes sample/ reagent consumption and, like the dropping mercury electrode of Heyrovsky, allows a fresh reaction surface for every sample. Drops are of particular value in solving problems in biphasic systems.

120 citations

Journal ArticleDOI
01 Jan 1993-Talanta
TL;DR: High performance, fully referenced, computer interfaced detectors are described that are pulsed at high speeds to attain measurement standard deviations in the range of 2-3 x 10(-6) absorbance.

104 citations


Cited by
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Journal ArticleDOI
TL;DR: The ability of DLLME technique in the extraction of other organic compounds such as organochlorine pesticides, organophosphorus pesticides and substituted benzene compounds were studied.

2,959 citations

Journal ArticleDOI
15 Jun 2000-Nature
TL;DR: Proteomics can be divided into three main areas: protein micro-characterization for large-scale identification of proteins and their post-translational modifications; ‘differential display’ proteomics for comparison of protein levels with potential application in a wide range of diseases; and studies of protein–protein interactions using techniques such as mass spectrometry or the yeast two-hybrid system.
Abstract: Proteomics, the large-scale analysis of proteins, will contribute greatly to our understanding of gene function in the post-genomic era. Proteomics can be divided into three main areas: (1) protein micro-characterization for large-scale identification of proteins and their post-translational modifications; (2) 'differential display' proteomics for comparison of protein levels with potential application in a wide range of diseases; and (3) studies of protein-protein interactions using techniques such as mass spectrometry or the yeast two-hybrid system. Because it is often difficult to predict the function of a protein based on homology to other proteins or even their three-dimensional structure, determination of components of a protein complex or of a cellular structure is central in functional analysis. This aspect of proteomic studies is perhaps the area of greatest promise. After the revolution in molecular biology exemplified by the ease of cloning by DNA methods, proteomics will add to our understanding of the biochemistry of proteins, processes and pathways for years to come.

2,345 citations

Journal ArticleDOI
TL;DR: Duong Tuan Quang was born in 1970 in Thanhhoa, Vietnam, and graduated from Hue University in 1992, where he obtained his M.S. degree in Chemistry and went to Korea University as a research professor in 2010, where his main task involved the development of chromogenic and fluorogenic molecular sensors to detect specific cations and anions.
Abstract: Heavy metal ions are of great concern, not only among the scientific community, especially chemists, biologists, and environmentalists, but increasingly among the general population, who are aware of the some of the disadvantages associated with them. In spite of the fact that some heavy metal ions play important roles in living systems, they are very toxic and hence capable of causing serious environmental and health problems.1-6 Some heavy metal ions, such as Fe(III), Zn(II), Cu(II), Co(II), Mn(II), and Mo(VI), are essential for the maintenance of human metabolism. However, high concentrations of these ions can lead to many adverse health effects.1,2,7-20 It is also a fact that others such as Hg(II), Cd(II), Pb(II), and As(III) are among the most toxic ions known that lack any vital or beneficial effects. Accumulation of these over time in the bodies of humans and animals can lead to serious debilitating illnesses.2,21-30 Therefore, the development of increasingly selective and sensitive methods for the determination of heavy metal ions is currently receiving considerable attention.7,23,31-36 Several methods, including atomic absorption spectroscopy, inductively coupled plasma atomic emission spectrometry, electrochemical sensoring, and the use of piezoelectric quartz crystals make it possible to detect low limits.37-40 However, these methods require expensive equipment and involve time-consuming and laborious procedures that can be carried out only by trained professionals. Alternatively, analytical techniques based on fluorescence detection are very popular because fluorescence measurements are usually very sensitive (parts per billion/trillion), easy to perform, and inexpensive.23,37,41-45 Furthermore, the photophysical properties of a fluorophore can be easily tuned using a range of routes: charge transfer, electron transfer, energy transfer, the influence of the heavy metal ions, and the destabilization of nonemissive n-π* excited states.5 Consequently, a large number of papers involving fluorescent chemosensors (see definition in section 2) have been published. In general to date, fluorescent chemosensors for anions and cations have proven popular, but those for many heavy metal ions such as Hg(II), Pb(II), Cu(II), Fe(III), and Ag(I) present challenges because these ions often act as fluorescence quenchers. Cu(II) is a typical ion that causes the chemosensor to decrease fluorescent emissions due to quenching of the fluorescence by mechanisms inherent to the paramagnetic species.46-48 Such decreased emissions are impractical for analytical purposes because of their low signal outputs upon complexation. In addition, temporal separation of spectrally similar complexes by time-resolved fluorimetry is subsequently prevented.49 Compared to the relatively well-developed fluorescent chemosensors, fluorescent chemodosimeters (see definition in section 2) have recently emerged as a research area of * Corresponding author. E-mail: jongskim@korea.ac.kr. † Hue University. ‡ Korea University. Duong Tuan Quang was born in 1970 in Thanhhoa, Vietnam, and graduated from Hue University in 1992, where he obtained his M.S. degree two years later and began his career as a lecturer in Chemistry soon afterwards. He received his Ph.D. degree in 2003 from Institute of Chemistry, Vietnamese Academy of Science and Technology. In 2006, he worked as a postdoctoral fellow in Professor Jong Seung Kim’s laboratory, Dankook University, Seoul, Korea. He was promoted as an associate professor in 2009 and went to Korea University as a research professor in 2010. His main task involved the development of chromogenic and fluorogenic molecular sensors to detect specific cations and anions. Chem. Rev. 2010, 110, 6280–6301 6280

1,207 citations

Journal ArticleDOI
TL;DR: This review focuses on the extra steps in sample preparation for application of DLLME in different matrixes such as food, biological fluids and solid samples and its applications in conjunction with different extraction techniques such as solid-phase extraction, solidification of floating organic drop and supercritical fluid extraction are summarized.

851 citations

Journal ArticleDOI
TL;DR: In this paper, the origins and the fundamentals of green analytical chemistry (GAC) are discussed, and the strategies and the tools available to make sample-pretreatment and analytical methods greener.
Abstract: We discuss the origins and the fundamentals of Green Analytical Chemistry (GAC), based on the literature published about clean, environmentally-friendly or GAC methods. We pay special attention to the strategies and the tools available to make sample-pretreatment and analytical methods greener. We consider that the main principles are to replace toxic reagents, to miniaturize and to automate methods, making it possible to reduce dramatically the amounts of reagents consumed and wastes generated, so reducing or avoiding side effects of analytical methods. We also consider on-line decontamination or passivation of wastes to be of special interest in making analytical chemistry sustainable.

806 citations