Browsing by Author "Ting, Hsu"

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A pinch-valve interface for automated sampling and monitoring of dynamic processes by gas chromatography-mass spectrometry
(2014)
Ting, Hsu
;
Hu, Jie-Bi
;
Hsieh, Kai-Ta
;
Urban, Pawel L.
;
應用化學系
Gas chromatography (GC) is frequently used in qualitative and quantitative analysis of volatile organic molecules. In its most common embodiment, samples are prepared in the laboratory, and injected into the capillary column using an autosampler. Analytes are separated, and detected by one of several available detection systems, including mass spectrometry (MS). However, this mode of operation is not convenient when monitoring dynamic chemical systems - for example, reaction mixtures. Here we present a facile approach for automated sampling, and subsequent introduction of samples to a GC apparatus in order to enable monitoring of dynamic chemical processes in real time. The proposed system incorporates two pinch valves, a peristaltic pump, a thermoshaker, and an electronic control unit (Raspberry Pi microcomputer) with several relays. The device facilitates dosing small volumes of liquid samples to the injection port of a commercial GC-MS apparatus. A program in C language controls the operation of the pump (on/off, direction of flow) and actuation of the pinch valves, and it initiates GC-MS runs. The system has been characterised with artificial samples, and successfully used in the monitoring of transesterification reactions catalysed by single microbeads containing immobilised lipase, as well as in the monitoring of the extraction of natural products from plant tissue samples. We believe that - following further improvements - this automated approach may be adapted for monitoring industrial processes and environmental analysis.
Recording temporal characteristics of convection currents by continuous and segmented-flow sampling
(2012)
Li, Po-Han
;
Ting, Hsu
;
Chen, Yu-Chie
;
Urban, Pawel L.
;
應用化學系
Despite the fact that the natural distribution of chemical substances in the three-dimensional world is far from homogeneous, most liquid-phase chemistry involves operations on homogeneous solutions. Here we describe two facile methods for real-time monitoring of liquid-phase chemical heterogeneity induced by convection in millilitre-range volumes. The liquid medium was continuously aspirated from the vial (acting as a "convection chamber''), and driven to online detectors either using continuous or discontinuous (segmented) hydrodynamic flow. In one embodiment, after the initial passage through a flow-through optical detector, the sample was driven to an electrospray ion source-set in front of the orifice of an ion trap mass spectrometer. The system recorded the emergence of chemical waves produced as a result of convection currents from the test substances introduced to the vial. Both variants of the method (using continuous and segmented flow) revealed fluctuations of the analyte concentration before an equilibrium was reached, and the mixture became homogeneous. We believe that this analytical scheme can further be used to study spatiotemporal characteristics of various dynamic chemical systems in liquid phase.
Spatiotemporal effects of a bioautocatalytic chemical wave revealed by time-resolved mass spectrometry
(2014)
Ting, Hsu
;
Urban, Pawel L.
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
Mass spectrometry has been implemented as an on-line detection tool to monitor transmission of chemical signals due to natural processes such as diffusion and convection as well as a bienzymatic autocatalytic process. It was found that the enzyme-accelerated chemical wave propagates faster than the chemical wave propelled by other processes. The two enzymes (pyruvate kinase and adenylate kinase), involved in the process, work co-operatively catalysing production of adenosine diphosphate (ADP) and adenosine triphosphate (ATP), and induce formation of a front propagating along a high-aspect-ratio drift cell towards the ion source of an ion trap mass spectrometer. Isotopically labelled C-13-ATP was used as the trigger of the accelerated chemical wave. Using this substrate, one could easily distinguish between the two chemical waves (passive and accelerated) in a single experiment, reducing the bias due to the inherent experimental instabilities. We think that - following further improvements - the process described in this report may find applications in bioengineered systems, in which chemical signals need to be transmitted over macroscopic distances.