Browsing by Author "Meher, Anil Kumar"

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Analysis of volatile compounds by open-air ionization mass spectrometry
(2017-05-08)
Meher, Anil Kumar
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Chen, Yu-Chie
;
應用化學系
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Department of Applied Chemistry
This study demonstrates a simple method for rapid and in situ identification of volatile and endogenous compounds in culinary spice samples through mass spectrometry (MS). This method only requires a holder for solid spice sample (2-3 mm) that is placed close to a mass spectrometer inlet, which is applied with a high voltage. Volatile species responsible for the aroma of the spice samples can be readily detected by the mass spectrometer. Sample pretreatment is not required prior to MS analysis, and no solvent was used during MS analysis. The high voltage applied to the inlet of the mass spectrometer induces the ionization of volatile compounds released from the solid spice samples. Furthermore, moisture in the air also contributes to the ionization of volatile compounds. Dried spices including cinnamon and cloves are used as the model sample to demonstrate this straightforward MS analysis, which can be completed within few seconds. Furthermore, we also demonstrate the suitability of the current method for rapid screening of cinnamon quality through detection of the presence of a hepatotoxic agent, i.e. coumarin. (C) 2017 Elsevier B.V. All rights reserved.
Automatic Sampling and Analysis of Organics and Biomolecules by Capillary Action-Supported Contactless Atmospheric Pressure Ionization Mass Spectrometry
(2013-06-06)
Hsieh, Cheng-Huan
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Meher, Anil Kumar
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Contactless atmospheric pressure ionization (C-API) method has been recently developed for mass spectrometric analysis. A tapered capillary is used as both the sampling tube and spray emitter in C-API. No electric contact is required on the capillary tip during C-API mass spectrometric analysis. The simple design of the ionization method enables the automation of the C-API sampling system. In this study, we propose an automatic C-API sampling system consisting of a capillary (similar to 1 cm), an aluminium sample holder, and a movable XY stage for the mass spectrometric analysis of organics and biomolecules. The aluminium sample holder is controlled by the movable XY stage. The outlet of the C-API capillary is placed in front of the orifice of a mass spectrometer, whereas the sample well on the sample holder is moved underneath the capillary inlet. The sample droplet on the well can be readily infused into the C-API capillary through capillary action. When the sample solution reaches the capillary outlet, the sample spray is readily formed in the proximity of the mass spectrometer applied with a high electric field. The gas phase ions generated from the spray can be readily monitored by the mass spectrometer. We demonstrate that six samples can be analyzed in sequence within 3.5 min using this automatic C-API MS setup. Furthermore, the well containing the rinsing solvent is alternately arranged between the sample wells. Therefore, the C-API capillary could be readily flushed between runs. No carryover problems are observed during the analyses. The sample volume required for the C-API MS analysis is minimal, with less than 1 nL of the sample solution being sufficient for analysis. The feasibility of using this setup for quantitative analysis is also demonstrated.
Combination of Raman Spectroscopy and Mass Spectrometry for Online Chemical Analysis
(2016-09-20)
Meher, Anil Kumar
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Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Mass spectrometry (MS) and Raman spectroscopy are complementary analytical techniques used to provide information related to chemical structures and functional groups of target analytes. Each instrument provides specific chemical information. If these two analytical tools are coupled online, comprehensive structural information can be simultaneously collected from the analytes of interest without losing any important chemical information. Nevertheless, exploring a suitable interface for coupling of these analytical tools, which are governed with different operation principles, remains challenging. In this study, we used a small piece of tissue paper as an: interface for hyphenating a Raman spectroscope and a mass spectrometer online. The paper played multiroles as sample loading substrate and an emitter to generate electrospray. Furthermore, it can facilitate surface-enhanced Raman spectroscopic analysis to improve analyte signals in Raman spectra. A sample droplet was placed on the tissue paper located close to the laser of the Raman spectroscope and the inlet of mass spectrometer. Raman spectra were first collected by the Raman spectroscope through laser irradiation followed by generation of electrospray on the edge of the paper for MS analysis. Positional isomers were used as model samples to demonstrate the effectiveness of the hyphenated analytical tool in distinguishing isomers. The feasibility of using this Raman-MS hyphenated technique for monitoring chemical reactions online in real time was also investigated.
Online monitoring of chemical reactions by polarization-induced electrospray ionization
(2016-09-21)
Meher, Anil Kumar
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Polarization-induced electrospray ionization (PI-ESI) is a simple technique for instant generation of gas-phase ions directly from a microliter-sized droplet for mass spectrometric analysis. A sample droplet was placed over a dielectric substrate and in proximity (2-3 mm) to the inlet of a mass spectrometer. Owing to the polarization effect induced by the high electric field provided by the mass spectrometer, the droplet was polarized and the electrospray was generated from the apex of the droplet. The polarization-induced electrospray could last for tens of seconds, which was sufficiently long to monitor fast reactions occurring within few seconds. Thus, we demonstrated the feasibility of using the droplet-based PI-ESI MS for the online monitoring of fast reactions by simply mixing two droplets (5-10 mu L) containing reactants on a dielectric substrate placed in front of a mass spectrometer applied with a high voltage (-4500 V). Schiff base reactions and oxidation reactions that can generate intermediates/products within a few seconds were selected as the model reactions. The ionic reaction species generated from intermediates and products can be simultaneously monitored by PI-ESI MS in real time. We also used this approach to selectively detect acetone from a urine sample, in which acetone was derivatized in situ. In addition, the possibility of using this approach for quantitative analysis of acetone from urine samples was examined. (C) 2016 Elsevier B.V. All rights reserved.
Polarization induced electrospray ionization mass spectrometry for the analysis of liquid, viscous and solid samples
(2015-03-01)
Meher, Anil Kumar
;
Chen, Yu-Chie
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
In this study, a polarization-induced electrospray ionization mass spectrometry (ESI-MS) was developed. A micro-sized sample droplet was deposited on a naturally available dielectric substrate such as a fruit or a stone, and then placed close to (similar to 2mm) the orifice of a mass spectrometer applied with a high voltage. Taylor cone was observed from the sample droplet, and a spray emitted from the cone apex was generated. The analyte ion signals derived from the droplet were obtained by the mass spectrometer. The ionization process is similar to that in ESI although no direct electric contact was applied on the sample site. The sample droplet polarized by the high electric field provided by the mass spectrometer initiated the ionization process. The dielectric sample loading substrate facilitated further the polarization process, resulting in the formation of Taylor cone. The mass spectral profiles obtained via this approach resembled those obtained using ESI-MS. Multiply charged ions dominated the mass spectra of peptides and proteins, whereas singly charged ions dominated the mass spectra of small molecules such as amino acids and small organic molecules. In addition to liquid samples, this approach can be used for the analysis of solid and viscous samples. A small droplet containing suitable solvent (5-10 mu l) was directly deposited on the surface of the solid (or viscous) sample, placed close the orifice of mass spectrometer applied with a high voltage. Taylor cone derived from the droplet was immediately formed followed by electrospray processes to generate gas-phase ions for MS analysis. Analyte ions derived from the main ingredients of pharmaceutical tablets and viscous ointment can be extracted into the solvent droplet in situ and observed using a mass spectrometer. Copyright (c) 2015 John Wiley & Sons, Ltd.
Tissue paper assisted spray ionization mass spectrometry
(2015-01-01)
Meher, Anil Kumar
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Electrospray ionization mass spectrometry (ESI-MS) has been widely utilized in the analysis of analytes with a wide mass range. A metal ESI emitter, which is usually applied with a high voltage, is required in the setup of ESI-MS. Nevertheless, electrospray can be induced simply by the electric field provided by the mass spectrometer without applying electric contact on the ESI emitter. In this work, we demonstrate a simple and straightforward ionization technique for MS analysis by utilizing tissue paper as the sampling substrate and the ESI emitter. The fine fibers on the paper can work as ESI-like emitters to facilitate the generation of electrospray. When a small piece of tissue paper (diameter: similar to 4 mm) loaded with a few microliters of the sample solution was positioned in the proximity of the inlet of a mass spectrometer applied with a high voltage, the analyte ions were readily generated and obtained by the mass spectrometer. Although no electric contact was made on the paper, the high voltage applied at the inlet of the mass spectrometer induced the formation of electrospray for MS analysis. This approach is applicable to the analysis of various samples including organic compounds, peptides, proteins, and complex samples. Additionally, tissue paper is flexible and can be used to sample trace amounts of samples from surface of solid objects such as drug tablets simply through wiping. The tissue with a trace amount of samples then can be readily placed close in front of the inlet of mass spectrometer followed by solvent deposition for MS analysis. Additionally, we also examined the feasibility of using this approach for quantitative MS analysis.