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Swee Ngin Tan
Natural Sciences and Science Education Academic Group, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore, 637616, Singapore

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Journal article
Published: 01 January 2020 in Journal of Chromatography A
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From the analytical chemistry point-of-view, an ideal sample preparation method should be simple, rapid, automatic, selective, precise, exhaustive, reproducible and protect the analyte-of-interest from degradation. In this study, a novel sample preparation method, named pressurized matrix solid-phase dispersion (p-MSPD) extraction was developed for simultaneously extracting, separating, purifying, isolating, and analyzing endogenous components in a solid sample matrix. Etlingera elatior, a traditional medicinal plant known as the torch ginger, was applied as a sample matrix to evaluate the p-MSPD process. The entire extraction, separation, isolation, fractionation and detection were performed automatically with a commercial LC-MS system. The novel method was satisfactorily applied for the preparation of real samples without optimization, which had the ability to selectively isolate pure compounds from the solid sample matrix for further NMR analysis. Therefore, the method is recommended for quality control of traditional medicines, research efforts when sample amounts are limited, and laboratories that have ordinary LC-MS instrumentation.

ACS Style

Liya Ge; Jean Wan Hong Yong; Swee Ngin Tan; Shao-Ping Li. Simultaneous extraction, separation, isolation and identification of endogenous components from Etlingera elatior by pressurized matrix solid-phase dispersion using liquid chromatography–mass spectrometry. Journal of Chromatography A 2020, 1611, 460604 .

AMA Style

Liya Ge, Jean Wan Hong Yong, Swee Ngin Tan, Shao-Ping Li. Simultaneous extraction, separation, isolation and identification of endogenous components from Etlingera elatior by pressurized matrix solid-phase dispersion using liquid chromatography–mass spectrometry. Journal of Chromatography A. 2020; 1611 ():460604.

Chicago/Turabian Style

Liya Ge; Jean Wan Hong Yong; Swee Ngin Tan; Shao-Ping Li. 2020. "Simultaneous extraction, separation, isolation and identification of endogenous components from Etlingera elatior by pressurized matrix solid-phase dispersion using liquid chromatography–mass spectrometry." Journal of Chromatography A 1611, no. : 460604.

Original articles
Published: 06 December 2018 in International Journal of Phytoremediation
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Phytoremediation is an emerging technology that utilizes plants to remediate contaminated environments. In the present study, Axonopus compressus (Sw.) Beauv, a fast-growing and hardy groundcover with wide geographical distribution, was exposed to soil Mo treatments ranging from 100 to 1000 mg/kg under tropical greenhouse conditions for five weeks. Generally, Mo accumulation increased as concentration of Mo in the soil increased. The species was found to accumulate about 4000 mg/kg of Mo without exhibiting severe physiological stress at 600 mg/kg of soil Mo. Maximum accumulation of 6000 mg/kg Mo was observed at the 1000 mg/kg soil Mo treatment, though with severe necrosis and eventual plant mortality. The physiological observations, Mo accumulation behavior and bioconcentration factor of about 1 indicated that A. compressus could be a potential biomonitor of Mo.

ACS Style

Shi Wan Tiffany Tow; Zhi Xian Eng; Seok Peng Wong; Liya Ge; Swee Ngin Tan; Jean Wan Hong Yong. Axonopus compressus (Sw.) Beauv.: A potential biomonitor for molybdenum in soil pollution. International Journal of Phytoremediation 2018, 20, 1363 -1368.

AMA Style

Shi Wan Tiffany Tow, Zhi Xian Eng, Seok Peng Wong, Liya Ge, Swee Ngin Tan, Jean Wan Hong Yong. Axonopus compressus (Sw.) Beauv.: A potential biomonitor for molybdenum in soil pollution. International Journal of Phytoremediation. 2018; 20 (14):1363-1368.

Chicago/Turabian Style

Shi Wan Tiffany Tow; Zhi Xian Eng; Seok Peng Wong; Liya Ge; Swee Ngin Tan; Jean Wan Hong Yong. 2018. "Axonopus compressus (Sw.) Beauv.: A potential biomonitor for molybdenum in soil pollution." International Journal of Phytoremediation 20, no. 14: 1363-1368.

Journal article
Published: 01 January 2018 in International Journal of Waste Resources
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Vandkvalitets Institute (VKI) process is a treatment technology which employs the technique of extraction and chemical stabilization on waste, targeting an end pH of 7 to 10 using water, concentrated phosphoric acid (H3PO4) and carbon dioxide (CO2) as the main stabilizing materials. Different parameters for the ash stabilization were investigated. Based on the acid neutralizing capacity (ANC) and pH-dependent leaching results of Singapore’s air pollution control (APC) residues produced from a municipal solid waste (MSW) incineration plant, the main objective of this study was to examine the suitable end pH to be used to treat APC residues. After which, a two-step VKI treatment was carried out on APC residues, using CO2 and H3PO4 dosing as the two main stabilizing items. ANC results showed that there was a steep drop in pH from 10 to 7 at approximately 20.40 equivalent/kg of acid addition, while pH-dependent leaching results indicated that the most ideal pH range for the suppression of most heavy metal release was between 7 and 10. Subsequently, pH 7 was then selected as the end pH for the VKI treatment process. Under optimum conditions of 0.2 g and 0.5 g of H3PO4/100 g of APC residues (equivalent to 2 and 5 kg H3PO4/ton of residues) with a CO2 flow rate of 1500 cm3/min, the treated APC residues had an end pH of around 7 after 100 and 80 minutes of treatment, respectively. Toxicity characteristic leaching procedure (TCLP) was used to evaluate the leaching of heavy metals (Cd, Cr, Cu, Pb, Zn) before and after treatment. The results showed that the leaching of Pb was significantly reduced after treatment, and was able to meet Singapore’s acceptance criteria for landfill disposal. However, the leaching of Cd increased by two orders of magnitude after treatment, but was still below Singapore’s acceptance criteria for landfill disposal.

ACS Style

Kim Soon Heng; Xiaolong Sun; Alec Liu; Geetha Salgunan; Ganesh Kumar; Swee Ngin Tan. Physicochemical Characterization of Singapore’ Municipal Solid Waste Air Pollution Control Residues and its Stabilization by VKI Treatment. International Journal of Waste Resources 2018, 08, 1 -7.

AMA Style

Kim Soon Heng, Xiaolong Sun, Alec Liu, Geetha Salgunan, Ganesh Kumar, Swee Ngin Tan. Physicochemical Characterization of Singapore’ Municipal Solid Waste Air Pollution Control Residues and its Stabilization by VKI Treatment. International Journal of Waste Resources. 2018; 08 (03):1-7.

Chicago/Turabian Style

Kim Soon Heng; Xiaolong Sun; Alec Liu; Geetha Salgunan; Ganesh Kumar; Swee Ngin Tan. 2018. "Physicochemical Characterization of Singapore’ Municipal Solid Waste Air Pollution Control Residues and its Stabilization by VKI Treatment." International Journal of Waste Resources 08, no. 03: 1-7.

Journal article
Published: 10 June 2017 in International Journal of Environmental Research and Public Health
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In the present work, thermal treatment was used to stabilize municipal solid waste incineration (MSWI) fly ash, which was considered hazardous waste. Toxicity characteristic leaching procedure (TCLP) results indicated that, after the thermal process, the leaching concentrations of Pb, Cu, and Zn decreased from 8.08 to 0.16 mg/L, 0.12 to 0.017 mg/L and 0.39 to 0.1 mg/L, respectively, which well met the limits in GB5085.3-2007 and GB16689-2008. Thermal treatment showed a negative effect on the leachability of Cr with concentrations increasing from 0.1 to 1.28 mg/L; nevertheless, it was still under the limitations. XRD analysis suggested that, after thermal treatments, CaO was newly generated. CaO was a main contribution to higher Cr leaching concentrations owing to the formation of Cr (VI)—compounds such as CaCrO4. SEM/EDS tests revealed that particle adhesion, agglomeration, and grain growth happened during the thermal process and thus diminished the leachability of Pb, Cu, and Zn, but these processes had no significant influence on the leaching of Cr. A microbial assay demonstrated that all thermally treated samples yet possessed strong bactericidal activity according to optical density (OD) test results. Among all samples, the OD value of raw fly ash (RFA) was lowest followed by FA700-10, FA900-10, and FA1100-10 in an increasing order, which indicated that the sequence of the biotoxicity for these samples was RFA > FA700-10 > FA900-10 > FA1100-10. This preliminary study indicated that, apart from TCLP criteria, the biotoxicity assessment was indispensable for evaluating the effect of thermal treatment for MSWI fly ash.

ACS Style

Bing Gong; Yi Deng; Yuanyi Yang; Swee Ngin Tan; Qianni Liu; Weizhong Yang. Solidification and Biotoxicity Assessment of Thermally Treated Municipal Solid Waste Incineration (MSWI) Fly Ash. International Journal of Environmental Research and Public Health 2017, 14, 626 .

AMA Style

Bing Gong, Yi Deng, Yuanyi Yang, Swee Ngin Tan, Qianni Liu, Weizhong Yang. Solidification and Biotoxicity Assessment of Thermally Treated Municipal Solid Waste Incineration (MSWI) Fly Ash. International Journal of Environmental Research and Public Health. 2017; 14 (6):626.

Chicago/Turabian Style

Bing Gong; Yi Deng; Yuanyi Yang; Swee Ngin Tan; Qianni Liu; Weizhong Yang. 2017. "Solidification and Biotoxicity Assessment of Thermally Treated Municipal Solid Waste Incineration (MSWI) Fly Ash." International Journal of Environmental Research and Public Health 14, no. 6: 626.

Journal article
Published: 15 March 2017 in Separations
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Simultaneous quantitative analysis of 10 indole compounds, including indole-3-acetic acid (IAA, one of the most important naturally occurring auxins) and some of its metabolites, by high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) after solid-phase extraction (SPE) was reported for the first time. The analysis was carried out using a reverse phase HPLC gradient elution, with an aqueous mobile phase (containing 0.1% formic acid) modified by methanol. Furthermore, a novel SPE procedure was developed for the pre-concentration and purification of indole compounds using C18 SPE cartridges. The combination of SPE, HPLC, and LC-MS was applied to screen for the indole compounds present in sugar cane (Saccharum officinarum L.) juice, a refreshing beverage with various health benefits. Finally, four indole compounds were successfully detected and quantified in sugar cane juice by HPLC, which were further unequivocally confirmed by LC-MS/MS experiments operating in the multiple reaction monitoring (MRM) mode.

ACS Style

Jean Wan Hong Yong; Liya Ge; Wei San Wong; Zhen Ma; Swee Ngin Tan. Analyses of Indole Compounds in Sugar Cane (Saccharum officinarum L.) Juice by High Performance Liquid Chromatography and Liquid Chromatography-Mass Spectrometry after Solid-Phase Extraction. Separations 2017, 4, 7 .

AMA Style

Jean Wan Hong Yong, Liya Ge, Wei San Wong, Zhen Ma, Swee Ngin Tan. Analyses of Indole Compounds in Sugar Cane (Saccharum officinarum L.) Juice by High Performance Liquid Chromatography and Liquid Chromatography-Mass Spectrometry after Solid-Phase Extraction. Separations. 2017; 4 (1):7.

Chicago/Turabian Style

Jean Wan Hong Yong; Liya Ge; Wei San Wong; Zhen Ma; Swee Ngin Tan. 2017. "Analyses of Indole Compounds in Sugar Cane (Saccharum officinarum L.) Juice by High Performance Liquid Chromatography and Liquid Chromatography-Mass Spectrometry after Solid-Phase Extraction." Separations 4, no. 1: 7.

Journal article
Published: 13 March 2017 in Biosensors
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Metallothioneins (MTs) are a family of cysteine-rich proteins whose biological roles include the regulation of essential metal ions and protection against the harmful effects of toxic metals. Due to its high affinity for many toxic, soft metals, recombinant human MT isoform 1a was incorporated into an electrochemical-based biosensor for the detection of As3+ and Hg2+. A simple design was chosen to maximize its potential in environmental monitoring and MT was physically adsorbed onto paper discs placed on screen-printed carbon electrodes (SPCEs). This system was tested with concentrations of arsenic and mercury typical of contaminated water sources ranging from 5 to 1000 ppb. The analytical performance of the MT-adsorbed paper discs on SPCEs demonstrated a greater than three-fold signal enhancement and a lower detection limit compared to blank SPCEs, 13 ppb for As3+ and 45 ppb for Hg2+. While not being as low as some of the recommended drinking water limits, the sensitivity of the simple MT-biosensor would be potentially useful in monitoring of areas of concern with a known contamination problem. This paper describes the ability of the metal binding protein metallothionein to enhance the effectiveness of a simple, low-cost electrochemical sensor.

ACS Style

Gordon W. Irvine; Swee Ngin Tan; Martin J. Stillman. A Simple Metallothionein-Based Biosensor for Enhanced Detection of Arsenic and Mercury. Biosensors 2017, 7, 14 .

AMA Style

Gordon W. Irvine, Swee Ngin Tan, Martin J. Stillman. A Simple Metallothionein-Based Biosensor for Enhanced Detection of Arsenic and Mercury. Biosensors. 2017; 7 (4):14.

Chicago/Turabian Style

Gordon W. Irvine; Swee Ngin Tan; Martin J. Stillman. 2017. "A Simple Metallothionein-Based Biosensor for Enhanced Detection of Arsenic and Mercury." Biosensors 7, no. 4: 14.

Review
Published: 14 October 2016 in Journal of Separation Science
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Gibberellins, as a group of phytohormones, exhibit a wide variety of bio-functions within plant growth and development, which have been used to increase crop yields. Many analytical procedures, therefore, have been developed for the determination of the types and levels of endogenous and exogenous gibberellins. As plant tissues contain gibberellins in trace amounts (usually at the level of nanogram per gram fresh weight or even lower), the sample pre-treatment steps (extraction, pre-concentration, and purification) for gibberellins are reviewed in details. The primary focus of this comprehensive review is on the various analytical methods designed to meet the requirements for gibberellins analyses in complex matrices with particular emphasis on high-throughput analytical methods, such as gas chromatography, liquid chromatography, and capillary electrophoresis, mostly combined with mass spectrometry. The advantages and drawbacks of the each described analytical method are discussed. The overall aim of this review is to provide a comprehensive and critical view on the different analytical methods nowadays employed to analyze gibberellins in complex sample matrices and their foreseeable trends.

ACS Style

Chaozhi Pan; Swee Ngin Tan; Jean Wan Hong Yong; Liya Ge. Progress and development of analytical methods for gibberellins. Journal of Separation Science 2016, 40, 346 -360.

AMA Style

Chaozhi Pan, Swee Ngin Tan, Jean Wan Hong Yong, Liya Ge. Progress and development of analytical methods for gibberellins. Journal of Separation Science. 2016; 40 (1):346-360.

Chicago/Turabian Style

Chaozhi Pan; Swee Ngin Tan; Jean Wan Hong Yong; Liya Ge. 2016. "Progress and development of analytical methods for gibberellins." Journal of Separation Science 40, no. 1: 346-360.

Journal article
Published: 15 August 2015 in Talanta
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Polyhydroxyalkanoates (PHAs) are commercially-valuable biocompatible and biodegradable polymers with many potential medical, pharmaceutical and other industrial applications. The analysis of PHA monomeric composition is especially challenging due to the broad chemical diversity of PHA monomers and lack of analytical standards to represent the chemically-diverse PHA monomer constituents. In this study, a novel strategy based on on-line liquid chromatography–mass spectrometry (LC–MS) and off-line liquid chromatography–nuclear magnetic resonance (LC–NMR) was established to quantify seven PHA monomers with available standards and used to elucidate the structures of unknown PHA monomers. The strategy was successfully applied for the determination of monomeric composition in bacterial PHAs isolated from Pseudomonads cultivated on different carbon sources after hydrolysis. The results of this work demonstrated that the newly-developed strategy was efficient, repeatable, and could have good potential to be employed for detailed analysis of PHA monomeric composition.

ACS Style

Liya Ge; Giin-Yu Amy Tan; Lin Wang; Chia-Lung Chen; Ling Li; Swee Ngin Tan; Jing-Yuan Wang. Determination of monomeric composition in polyhydroxyalkanoates by liquid chromatography coupled with on-line mass spectrometry and off-line nuclear magnetic resonance. Talanta 2015, 146, 107 -113.

AMA Style

Liya Ge, Giin-Yu Amy Tan, Lin Wang, Chia-Lung Chen, Ling Li, Swee Ngin Tan, Jing-Yuan Wang. Determination of monomeric composition in polyhydroxyalkanoates by liquid chromatography coupled with on-line mass spectrometry and off-line nuclear magnetic resonance. Talanta. 2015; 146 ():107-113.

Chicago/Turabian Style

Liya Ge; Giin-Yu Amy Tan; Lin Wang; Chia-Lung Chen; Ling Li; Swee Ngin Tan; Jing-Yuan Wang. 2015. "Determination of monomeric composition in polyhydroxyalkanoates by liquid chromatography coupled with on-line mass spectrometry and off-line nuclear magnetic resonance." Talanta 146, no. : 107-113.

Journal article
Published: 01 July 2015 in Talanta
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Vermicompost (VC), a widely used premium organic fertilizer, is the by-product of symbiotic interactions between earthworms and microorganisms living within them. It has been postulated that phytohormones are plausible "magic compounds" in VC that are responsible for making them such good fertilizers. Thus, a novel approach involving ultrasound-assisted extraction (UAE) and solid-phase extraction (SPE) was developed as a fast and efficient sample preparation method to screen for different classes of phytohormones in VC by liquid chromatography-tandem mass spectrometric (LC-MS/MS) analysis. Nine phytohormones from three different classes, including trans-zeatin (tZ), kinetin (K), N(6)-[2-isopentyl]adenine (iP), N(6)-benzyladenine (BA), N(6)-isopentenyladenosine (iPR), indole-3-acetic acid (IAA), 4-[3-indolyl]butyric acid (IBA), 1-naphthaleneacetic acid (NAA) and (+)-abscisic acid (ABA), were simultaneously screened. The extraction parameters influencing UAE efficiency were optimized to provide comparable recovery to the conventional mix-stirring (MSt) method. The optimized UAE method was subsequently applied on the analysis of phytohormones in VC, i.e. phytohormone extract was further pre-concentrated and purified using C18 and MCX SPE cartridges prior to LC-MS/MS analysis. The following phytohormones, namely iP, iPR and IAA, were detected and quantified to be 0.49, 0.53, 79.78ngg(-1), respectively; tZ was found to be below the limit of quantitation. Recoveries of 10.2%, 9.1%, 18.9% and 0.3% for tZ, iP, iPR and IAA were obtained. This is one of the few reported works for the successful detection and quantitation of cytokinins and auxins in VC, that provided the key empirical evidence to explain the growth efficacy of applying VC in promoting plant growth. Additionally, this pioneering work could potentially be applicable for the analysis of other types of organic fertilizers such as composts and activated composted materials awaiting phytohormone analyzes for quality assessment and control.

ACS Style

Hong Zhang; Swee Ngin Tan; Chee How Teo; Yan Ru Yew; Liya Ge; Xin Chen; Jean Wan Hong Yong. Analysis of phytohormones in vermicompost using a novel combinative sample preparation strategy of ultrasound-assisted extraction and solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry. Talanta 2015, 139, 189 -197.

AMA Style

Hong Zhang, Swee Ngin Tan, Chee How Teo, Yan Ru Yew, Liya Ge, Xin Chen, Jean Wan Hong Yong. Analysis of phytohormones in vermicompost using a novel combinative sample preparation strategy of ultrasound-assisted extraction and solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry. Talanta. 2015; 139 ():189-197.

Chicago/Turabian Style

Hong Zhang; Swee Ngin Tan; Chee How Teo; Yan Ru Yew; Liya Ge; Xin Chen; Jean Wan Hong Yong. 2015. "Analysis of phytohormones in vermicompost using a novel combinative sample preparation strategy of ultrasound-assisted extraction and solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry." Talanta 139, no. : 189-197.

Journal article
Published: 01 January 2015 in Fuel
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ACS Style

Yan Fei Ng; Liya Ge; Wen Kiat Chan; Swee Ngin Tan; Jean Wan Hong Yong; Timothy Thatt Yang Tan. An environmentally friendly approach to treat oil spill: Investigating the biodegradation of petrodiesel in the presence of different biodiesels. Fuel 2015, 139, 523 -528.

AMA Style

Yan Fei Ng, Liya Ge, Wen Kiat Chan, Swee Ngin Tan, Jean Wan Hong Yong, Timothy Thatt Yang Tan. An environmentally friendly approach to treat oil spill: Investigating the biodegradation of petrodiesel in the presence of different biodiesels. Fuel. 2015; 139 ():523-528.

Chicago/Turabian Style

Yan Fei Ng; Liya Ge; Wen Kiat Chan; Swee Ngin Tan; Jean Wan Hong Yong; Timothy Thatt Yang Tan. 2015. "An environmentally friendly approach to treat oil spill: Investigating the biodegradation of petrodiesel in the presence of different biodiesels." Fuel 139, no. : 523-528.

Journal article
Published: 22 December 2014 in Chromatography
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Capillary electrophoresis (CE) coupled with mass spectrometry (MS) or tandem mass spectrometry (MS/MS) is reported as an alternative and potentially useful method for the simultaneous analysis of various classes of phytohormones with diversified structures, including indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), abscisic acid (ABA), gibberellic acid (GA), zeatin (Z), N6-benzyladenine (BA), α-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D). The key to the CE-MS/MS analysis was based on electroosmotic flow reversal using a cationic polymer-coated capillary. Under optimum conditions, a baseline separation of eight phytohormones was accomplished within 30 min using 60 mM ammonium formate/formic acid buffer of pH 3.8 with −20 kV as the separation voltage. The accessibility of MS/MS together with the characterization by migration properties obtained by CE allows for the development of CE-MS/MS as an emerging potential method for the analysis of different classes of phytohormones in a single run. The utility of the CE-MS/MS method was demonstrated by the comprehensive screening of phytohormones in coconut (Cocos nucifera L.) water after pre-concentration and purification through solid-phase extraction (SPE) cartridge. IAA, ABA, GA and Z were detected and quantified in the purified coconut water extract sample.

ACS Style

Swee Ngin Tan; Jean Wan Hong Yong; Liya Ge. Analyses of Phytohormones in Coconut (Cocos Nucifera L.) Water Using Capillary Electrophoresis-Tandem Mass Spectrometry. Chromatography 2014, 1, 211 -226.

AMA Style

Swee Ngin Tan, Jean Wan Hong Yong, Liya Ge. Analyses of Phytohormones in Coconut (Cocos Nucifera L.) Water Using Capillary Electrophoresis-Tandem Mass Spectrometry. Chromatography. 2014; 1 (4):211-226.

Chicago/Turabian Style

Swee Ngin Tan; Jean Wan Hong Yong; Liya Ge. 2014. "Analyses of Phytohormones in Coconut (Cocos Nucifera L.) Water Using Capillary Electrophoresis-Tandem Mass Spectrometry." Chromatography 1, no. 4: 211-226.

Chromatography
Published: 06 January 2012 in Analytical Letters
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In this article, a new and relatively simple liquid chromatography-mass spectrometry (LC-MS) method was developed for the simultaneous determination of five flavonoid compounds. Under optimized conditions, the LC-MS analysis can be achieved on a reverse-phase C18 column (50 × 2.1 mm, 1.8 µm), with a binary mobile phase consisting of 0.1% formic acid in water and methanol under gradient elution conditions. The relative standard deviations (RSDs) of the retention times and peak areas for all analytes were in the range of 0.1–0.5% and 3.2–5.2%, respectively. The LODs and LOQs were in the range of 2.1–7.0 ng mL−1 and 6.9–23 ng mL−1, respectively. Furthermore, the developed LC-MS method was successfully applied to analyze flavonoids in different parts of two medicinal Zingiberaceae plants (i.e., Costus speciosus and Etlingera elatior) from different sources. The proposed LC-MS method was simple, effective, and reliable, and thus it has potential to be used for the quality control of other medicinal herbs.

ACS Style

Yong Qin Chang; Swee Ngin Tan; Jean Wan Hong Yong; Liya Ge. Determination of Flavonoids inCostus speciosusandEtlingera elatiorby Liquid Chromatography-Mass Spectrometry. Analytical Letters 2012, 45, 345 -355.

AMA Style

Yong Qin Chang, Swee Ngin Tan, Jean Wan Hong Yong, Liya Ge. Determination of Flavonoids inCostus speciosusandEtlingera elatiorby Liquid Chromatography-Mass Spectrometry. Analytical Letters. 2012; 45 (4):345-355.

Chicago/Turabian Style

Yong Qin Chang; Swee Ngin Tan; Jean Wan Hong Yong; Liya Ge. 2012. "Determination of Flavonoids inCostus speciosusandEtlingera elatiorby Liquid Chromatography-Mass Spectrometry." Analytical Letters 45, no. 4: 345-355.

Journal article
Published: 01 July 2011 in Talanta
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As a first attempt, cloud point extraction (CPE) was developed to preconcentrate bisphenol A (BPA), α-naphthol and β-naphthol prior to performing capillary zone electrophoresis (CZE) analysis. The parameters influencing the CPE efficiency, such as Triton X-114 concentrations, pH value, extraction time and temperature were systematically evaluated. After diluting with acetonitrile, the surfactant-rich phase of CPE can be injected directly into the CE instrument. The CZE baseline separation was achieved with running buffer (pH 9.5) composed of 50mM sodium tetraborate in 30% (v/v) methanol, and an applied voltage of 25 kV. Under the optimized CPE and CZE conditions, an preconcentration factor of 50 times could be obtained and the limit of quantification for the three analytes were found to be 1.67 μg L(-1), 0.80 μg L(-1) and 0.67 μg L(-1) for BPA, α-naphthol and β-naphthol, respectively. The proposed methods have shown to be a green, rapid and effective approach for determination of three analytes present in river water samples.

ACS Style

Shuxian Zhong; Swee Ngin Tan; Liya Ge; Weiping Wang; Jianrong Chen. Determination of bisphenol A and naphthols in river water samples by capillary zone electrophoresis after cloud point extraction. Talanta 2011, 85, 488 -492.

AMA Style

Shuxian Zhong, Swee Ngin Tan, Liya Ge, Weiping Wang, Jianrong Chen. Determination of bisphenol A and naphthols in river water samples by capillary zone electrophoresis after cloud point extraction. Talanta. 2011; 85 (1):488-492.

Chicago/Turabian Style

Shuxian Zhong; Swee Ngin Tan; Liya Ge; Weiping Wang; Jianrong Chen. 2011. "Determination of bisphenol A and naphthols in river water samples by capillary zone electrophoresis after cloud point extraction." Talanta 85, no. 1: 488-492.

Evaluation study
Published: 20 January 2011 in Journal of Separation Science
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Micellar electrokinetic chromatography (MEKC), a mode of capillary electrophoresis (CE), is considered an efficient analytical technique allowing for the reduction of organic solvent consumption during the experimental procedure. However, during sample preparation of natural products, the usage of large amount of organic solvent is generally unavoidable. In this article, therefore, a fast, simple, efficient, highly automatic and organic solvent-free sample preparation method, namely surfactant-assisted pressurized liquid extraction (PLE), was developed for the extraction of flavonoids in Costus speciosus flowers before MEKC analysis. The various experimental parameters such as the type and concentration of surfactant, and extraction time were evaluated systematically. Under the optimized conditions, the extraction efficiencies of surfactant-assisted PLE methods were comparable with Soxhlet extraction using organic solvent. The combination of surfactant-assisted PLE and MEKC was shown to be a green, rapid and effective approach for extraction and analysis of flavonoids in C. speciosus flowers.

ACS Style

Yong Qin Chang; Swee Ngin Tan; Jean Yong; Liya Ge. Surfactant-assisted pressurized liquid extraction for determination of flavonoids from Costus speciosus by micellar electrokinetic chromatography. Journal of Separation Science 2011, 34, 462 -468.

AMA Style

Yong Qin Chang, Swee Ngin Tan, Jean Yong, Liya Ge. Surfactant-assisted pressurized liquid extraction for determination of flavonoids from Costus speciosus by micellar electrokinetic chromatography. Journal of Separation Science. 2011; 34 (4):462-468.

Chicago/Turabian Style

Yong Qin Chang; Swee Ngin Tan; Jean Yong; Liya Ge. 2011. "Surfactant-assisted pressurized liquid extraction for determination of flavonoids from Costus speciosus by micellar electrokinetic chromatography." Journal of Separation Science 34, no. 4: 462-468.

Journal article
Published: 15 January 2011 in Talanta
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Uncaria sinensis (Oliv.) Havil (Rubiaceae) has been used as an important Traditional Chinese Medicine (TCM) herb for the treatment of fevers and various nervous disorders. The major bioactive secondary metabolites from different classes of chemical compounds, i.e. organic acid, flavonoid and alkaloid, present in this TCM herb, namely catechin, caffeic acid, epicatechin and rhynchophylline, were extracted by microwave-assisted extraction (MAE) method with ultra-pure water as the extraction solvent. The optimal extraction conditions for this green solvent MAE method were found to be 100 °C for 20 min. The recoveries of the compounds were found to be comparable to that of heating under reflux using ultra-pure water for 60 min. The method precision (RSD, n = 6) was found to vary from 0.19% to 5.60% for the proposed method on different days for the secondary metabolites. Simultaneously, the key primary metabolites such as sucrose and phenylalanine for the biosynthesis of bioactive secondary metabolites were successfully characterized by GC–MS. Furthermore, an approach using the combination of primary and secondary metabolite profiling based on their chemical fingerprints with Principal Component Analysis (PCA) was successfully developed to evaluate the quality of U. sinensis obtained from different sources. This approach was shown to be feasible in discriminating U. sinensis from different origins and thus a potential application for the quality control of other medicinal herbs.

ACS Style

Swee Ngin Tan; Jean Wan Hong Yong; Chin Chye Teo; Liya Ge; Yee Wen Chan; Choy Sin Hew. Determination of metabolites in Uncaria sinensis by HPLC and GC–MS after green solvent microwave-assisted extraction. Talanta 2011, 83, 891 -898.

AMA Style

Swee Ngin Tan, Jean Wan Hong Yong, Chin Chye Teo, Liya Ge, Yee Wen Chan, Choy Sin Hew. Determination of metabolites in Uncaria sinensis by HPLC and GC–MS after green solvent microwave-assisted extraction. Talanta. 2011; 83 (3):891-898.

Chicago/Turabian Style

Swee Ngin Tan; Jean Wan Hong Yong; Chin Chye Teo; Liya Ge; Yee Wen Chan; Choy Sin Hew. 2011. "Determination of metabolites in Uncaria sinensis by HPLC and GC–MS after green solvent microwave-assisted extraction." Talanta 83, no. 3: 891-898.

Journal article
Published: 15 June 2010 in Talanta
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As the first attempt, ionic liquid solutions have been employed for direct extraction of proteins from yeast cells. Compared with effects of 21 different ionic liquid solutions on the extraction efficiency, 3-(dimethylamino)-1-propylaminium formate ([DMAPA]FA) was selected as the suitable ionic liquid solution. As this ionic liquid can be easily removed under vacuum, contamination by the chemical noise can be effectively reduced. Both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and 2-dimensional gel electrophoresis (2-DE) were employed to separate numerous proteins, and the results indicated that the chemical properties of target proteins remained unchanged during the extraction process. Furthermore, extracted proteins were applicable to the standard method for Western blotting which showed proteins maintain immunoreactivity and biological functions. These investigations indicated that the ionic liquid [DMAPA]FA is a promising reagent for protein extraction in yeast cells.

ACS Style

Liya Ge; Xiao-Tao Wang; Swee Ngin Tan; Heng Hang Tsai; Jean Wan Hong Yong; Lin Hua. A novel method of protein extraction from yeast using ionic liquid solution. Talanta 2010, 81, 1861 -1864.

AMA Style

Liya Ge, Xiao-Tao Wang, Swee Ngin Tan, Heng Hang Tsai, Jean Wan Hong Yong, Lin Hua. A novel method of protein extraction from yeast using ionic liquid solution. Talanta. 2010; 81 (4):1861-1864.

Chicago/Turabian Style

Liya Ge; Xiao-Tao Wang; Swee Ngin Tan; Heng Hang Tsai; Jean Wan Hong Yong; Lin Hua. 2010. "A novel method of protein extraction from yeast using ionic liquid solution." Talanta 81, no. 4: 1861-1864.

Review
Published: 09 December 2009 in Molecules
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Coconut water (coconut liquid endosperm), with its many applications, is one of the world’s most versatile natural product. This refreshing beverage is consumed worldwide as it is nutritious and beneficial for health. There is increasing scientific evidence that supports the role of coconut water in health and medicinal applications. Coconut water is traditionally used as a growth supplement in plant tissue culture/micropropagation. The wide applications of coconut water can be justified by its unique chemical composition of sugars, vitamins, minerals, amino acids and phytohormones. This review attempts to summarise and evaluate the chemical composition and biological properties of coconut water.

ACS Style

Jean Yong; Liya Ge; Yan Fei Ng; Swee Ngin Tan. The Chemical Composition and Biological Properties of Coconut (Cocos nucifera L.) Water. Molecules 2009, 14, 5144 -5164.

AMA Style

Jean Yong, Liya Ge, Yan Fei Ng, Swee Ngin Tan. The Chemical Composition and Biological Properties of Coconut (Cocos nucifera L.) Water. Molecules. 2009; 14 (12):5144-5164.

Chicago/Turabian Style

Jean Yong; Liya Ge; Yan Fei Ng; Swee Ngin Tan. 2009. "The Chemical Composition and Biological Properties of Coconut (Cocos nucifera L.) Water." Molecules 14, no. 12: 5144-5164.

Journal article
Published: 15 October 2009 in Journal of Pharmaceutical and Biomedical Analysis
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In present study, a capillary electrophoresis–mass spectrometry (CE–MS) method was developed for the simultaneous analysis of 12 nucleosides and nucleobases including cytosine, adenine, guanine, cytidine, cordycepin, adenosine, hypoxanthine, guanosine, inosine, 2′-deoxyuridine, uridine and thymidine in natural and cultured Cordyceps using 5-chlorocytosine arabinoside as an internal standard (IS). The CE separation conditions and MS parameters were optimized systematically for achieving good CE resolution and MS response of the investigated compounds. The optimum CE electrolyte was 100 mM formic acid containing 10% (v/v) methanol. The optimum MS parameters were as follows: 75% (v/v) methanol containing 0.3% formic acid with a flow rate of 3 μL/min was selected as the sheath liquid; the flow rate and temperature of drying gas were 6 L/min and 350 °C, respectively. The optimized CE–MS method was successfully applied for the simultaneous determination of 12 nucleosides and nucleobases in natural and cultured Cordyceps. On the basis of quantitative results, the total content of nucleosides is much higher in cultured Cordyceps (9138 ± 4823 μg/g for cultured C. sinensis; 3722 ± 1446 μg/g for C. militaris) than in natural ones (2167 ± 412 μg/g). However, the hypoxanthine (131 ± 47 μg/g) and inosine (335 ± 90 μg/g) are much higher in natural C. sinensis. Cordycepin, which is abundant in cultured C. militaris (2276.5 ± 842.6 μg/g), is only found in natural C. sinensis with very low content and cannot be detected in the cultured ones.

ACS Style

Feng-Qing Yang; Liya Ge; Jean Wan Hong Yong; Swee Ngin Tan; Shao-Ping Li. Determination of nucleosides and nucleobases in different species of Cordyceps by capillary electrophoresis–mass spectrometry. Journal of Pharmaceutical and Biomedical Analysis 2009, 50, 307 -314.

AMA Style

Feng-Qing Yang, Liya Ge, Jean Wan Hong Yong, Swee Ngin Tan, Shao-Ping Li. Determination of nucleosides and nucleobases in different species of Cordyceps by capillary electrophoresis–mass spectrometry. Journal of Pharmaceutical and Biomedical Analysis. 2009; 50 (3):307-314.

Chicago/Turabian Style

Feng-Qing Yang; Liya Ge; Jean Wan Hong Yong; Swee Ngin Tan; Shao-Ping Li. 2009. "Determination of nucleosides and nucleobases in different species of Cordyceps by capillary electrophoresis–mass spectrometry." Journal of Pharmaceutical and Biomedical Analysis 50, no. 3: 307-314.

Journal article
Published: 31 March 2009 in TrAC Trends in Analytical Chemistry
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The development of sensitive analytical methods for the determination of cytokinin levels in plant tissues is essential for elucidating the roles of cytokinins in life science. In the past decade, more advanced analytical systems have been applied for the rapid analyses of endogenous cytokinins. This review primarily focuses on emerging analytical methods designed to meet the requirements for cytokinin analyses in complex matrices with special emphasis on high-performance liquid chromatography, gas chromatography and capillary electrophoresis coupled with different detectors. We highlight the advantages and the limitations of the techniques. As sample preparation is a key factor in determining the success of cytokinin analyses, we devote a section to discussing sample-extraction and clean-up techniques prior to analysis.

ACS Style

Petr Tarkowski; Liya Ge; Jean Wan Hong Yong; Swee Ngin Tan. Analytical methods for cytokinins. TrAC Trends in Analytical Chemistry 2009, 28, 323 -335.

AMA Style

Petr Tarkowski, Liya Ge, Jean Wan Hong Yong, Swee Ngin Tan. Analytical methods for cytokinins. TrAC Trends in Analytical Chemistry. 2009; 28 (3):323-335.

Chicago/Turabian Style

Petr Tarkowski; Liya Ge; Jean Wan Hong Yong; Swee Ngin Tan. 2009. "Analytical methods for cytokinins." TrAC Trends in Analytical Chemistry 28, no. 3: 323-335.

Validation study
Published: 01 May 2008 in ELECTROPHORESIS
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In this paper, we present the results of simultaneous screening of eight gibberellins (GAs) in coconut (Cocos nucifera L.) water by MEKC directly coupled to ESI-MS detection. During the development of MEKC-MS, partial filling (PF) was used to prevent the micelles from reaching the mass spectrometer as this is detrimental to the MS signal, and a cationic surfactant, cetyltrimethylammonium hydroxide, was added to the electrolyte to reverse the EOF. On the basis of the resolution of the neighboring peaks, different parameters (i.e., the pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF-MEKC separation of eight GA standards. Under optimum conditions, a baseline separation of GA standards, including GA1, GA3, GA5, GA6, GA7, GA9, GA12, and GA13, was accomplished within 25 min. Satisfactory results were obtained in terms of precision (RSD of migration time below 0.9%), sensitivity (LODs in the range of 0.8-1.9 microM) and linearity (R2 between 0.981 and 0.997). MS/MS with multiple reaction monitoring (MRM) detection was carried out to obtain sufficient selectivity. PF-MEKC-MS/MS allowed the direct identification and confirmation of the GAs presented in coconut water (CW) sample after SPE, while, the quantitative analysis of GAs was performed by PF-MEKC-MS approach. GA1 and GA3 were successfully detected and quantified in CW. It is anticipated that the current PF-MEKC-MS method can be applicable to analyze GAs in a wide range of biological samples.

ACS Style

Liya Ge; Jean Wan Hong Yong; Swee Ngin Tan; Lin Hua; Eng Shi Ong. Analyses of gibberellins in coconut (Cocos nucifera L.) water by partial filling-micellar electrokinetic chromatography-mass spectrometry with reversal of electroosmotic flow. ELECTROPHORESIS 2008, 29, 2126 -2134.

AMA Style

Liya Ge, Jean Wan Hong Yong, Swee Ngin Tan, Lin Hua, Eng Shi Ong. Analyses of gibberellins in coconut (Cocos nucifera L.) water by partial filling-micellar electrokinetic chromatography-mass spectrometry with reversal of electroosmotic flow. ELECTROPHORESIS. 2008; 29 (10):2126-2134.

Chicago/Turabian Style

Liya Ge; Jean Wan Hong Yong; Swee Ngin Tan; Lin Hua; Eng Shi Ong. 2008. "Analyses of gibberellins in coconut (Cocos nucifera L.) water by partial filling-micellar electrokinetic chromatography-mass spectrometry with reversal of electroosmotic flow." ELECTROPHORESIS 29, no. 10: 2126-2134.