Browsing by Author "Urban, Pawel L."

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A compact 3D-printed interface for coupling open digital microchips with Venturi easy ambient sonic-spray ionization mass spectrometry
(2015-01-01)
Hu, Jie-Bi
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Chen, Ting-Ru
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Chang, Chia-Hsien
;
Cheng, Ji-Yen
;
Chen, Yu-Chie
Digital microfluidics (DMF) based on the electrowetting-on-dielectric phenomenon is a convenient way of handling microlitre-volume aliquots of solutions prior to analysis. Although it was shown to be compatible with on-line mass spectrometric detection, due to numerous technical obstacles, the implementation of DMF in conjunction with MS is still beyond the reach of many analytical laboratories. Here we present a facile method for coupling open DMF microchips to mass spectrometers using Venturi easy ambient sonic-spray ionization operated at atmospheric pressure. The proposed interface comprises a 3D-printed body that can easily be "clipped" at the inlet of a standard mass spectrometer. The accessory features all the necessary connections for an open-architecture DMF microchip with T-shaped electrode arrangement, thermostatting of the microchip, purification of air (to prevent accidental contamination of the microchip), a Venturi pump, and two microfluidic pumps to facilitate transfer of samples and reagents onto the microchip. The system also incorporates a touch-screen panel and remote control for user-friendly operation. It is based on the use of popular open-source electronic modules, and can readily be assembled at low expense.
A hybrid nanoparticle matrix for mass spectrometry
(2013)
Li, Po-Han
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Huang, Shin-Yi
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Chen, Yu-Chie
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Urban, Pawel L.
;
應用化學系
We demonstrate hybrid inorganic-organic nanoparticles -based on silicon dioxide and 9-aminoacridine- which can enhance mass spectrometric analysis and imaging in the negative-ion mode. The nanoparticles bind to the surface of cells while still in the liquid phase, which is followed by a controlled release of the organic matrix molecules triggered by alkaline ammonia vapours delivered to the specimen in a closed chamber. First, the method was optimized and tested using standard compounds as analytes. Second, the spatial resolution was verified using a natural fibre (diameter similar to 20 mu m). Third, the method was used in the imaging of molecules present in the outer layer of large algal cells (Closterium acerosum). An important advantage of this method is that nanoparticles loaded with organic matrix can be applied to the biological cells as aqueous suspensions; hence, the release and spreading of metabolites can be limited during sample preparation for MALDI-MS. In addition, since this method does not involve spraying, exposure of experimenters to toxic aerosols is decreased.
A pinch-valve interface for automated sampling and monitoring of dynamic processes by gas chromatography-mass spectrometry
(2014)
Ting, Hsu
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Hu, Jie-Bi
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Hsieh, Kai-Ta
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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.
Advances in ultrasensitive mass spectrometry of organic molecules
(2013)
Kandiah, Mathivathani
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Urban, Pawel L.
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應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
Ultrasensitive mass spectrometric analysis of organic molecules is important for various branches of chemistry, and other fields including physics, earth and environmental sciences, archaeology, biomedicine, and materials science. It finds applications - as an enabling tool - in systems biology, biological imaging, clinical analysis, and forensics. Although there are a number of technical obstacles associated with the analysis of samples by mass spectrometry at ultratrace level (for example analyte losses during sample preparation, insufficient sensitivity, ion suppression), several noteworthy developments have been made over the years. They include: sensitive ion sources, loss-free interfaces, ion optics components, efficient mass analyzers and detectors, as well as "smart'' sample preparation strategies. Some of the mass spectrometric methods published to date can achieve sensitivity which is by several orders of magnitude higher than that of alternative approaches. Femto- and attomole level limits of detection are nowadays common, while zepto- and yoctomole level limits of detection have also been reported. We envision that the ultrasensitive mass spectrometric assays will soon contribute to new discoveries in bioscience and other areas.
Agarose-Based Gel-Phase Microextraction Technique for Quick Sampling of Polar Analytes Adsorbed on Surfaces
(2019-11-19)
Liao, Pei-Han
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Urban, Pawel L.
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應用化學系
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Department of Applied Chemistry
Sampling and extraction of chemical residues present on flat or curved surfaces as well as touch-sensitive objects are challenging. Hydrogels are characterized by high mechanical flexibility and water content. Thus, they are an ideal medium for transferring water-soluble analytes from a sampled surface to the next stage of an analytical workflow. Here, we demonstrate gel-phase microextraction (GPME), in which disks of blended hydrogels are utilized to lift traces of water-soluble substances adsorbed on surfaces. The protocol has been optimized in a series of tests involving fluorometric and mass spectrometric measurements. Compared with the pure agarose hydrogel, most of the tested blended hydrogels provide a higher efficiency for the sampling/extraction of a model analyte, fluorescein. The blended hydrogel disks are incorporated into three-dimensional (3D)-printed acrylonitrile-butadiene-styrene chips to create easy-to-use sampling probes. We exemplify the suitability of this improved GPME approach in sampling chemical residues present on the skin, glass, and daily use objects. In these tests, the extracts were analyzed on a triple quadrupole mass spectrometer fitted with an electrospray ion source operated in the positive- and negative-ion modes. The method enabled the detection of diclofenac on excised porcine skin fragments exposed to a topical nonsteroidal anti-inflammatory drug and sweat residues (lactic acid) left on surfaces touched by humans. The limits of detection for diclofenac and lactic acid in hydrogel extract were 6.4 x 10(-6) and 2.1 x 10(-5) M, respectively. In a model experiment, conducted using the presented approach, the amount of lactic acid on a glass slide with fingerprints was estimated to be similar to 1.4 x 10(-7) mol cm(-2).
Analysis of single algal cells by combining mass spectrometry with Raman and fluorescence mapping
(2013)
Fagerer, Stephan R.
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Schmid, Thomas
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Ibanez, Alfredo J.
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Pabst, Martin
;
Steinhoff, Robert
In order to investigate metabolic properties of single cells of freshwater algae (Haematococcus pluvialis), we implement matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) in combination with microspectroscopic mapping. Straightforward coupling of these two detection platforms was possible thanks to the self-aliquoting properties of micro-arrays for mass spectrometry (MAMS). Following Raman and fluorescence imaging, the isolated cells were covered with a MALDI matrix for targeted metabolic analysis by MALDI-MS. The three consecutive measurements carried out on the same cells yielded complementary information. Using this method, we were able to study the encystment of H. pluvialis - by monitoring the adenosine triphosphate (ATP) to adenosine diphosphate (ADP) ratio during the build-up of astaxanthin in the cells as well as the release of beta-carotene, the precursor of astaxanthin, into the cytosol.
Automated Dual-Chamber Sampling System to Follow Dynamics of Volatile Organic Compounds Emitted by Biological Specimens
(2018-12-04)
Chang, Cheng-Hao
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Urban, Pawel L.
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應用化學系
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Department of Applied Chemistry
Growth of microorganisms is often accompanied by the release of volatile organic compounds (VOCs). The released VOCs may qualitatively or quantitatively reflect the physiological states of microbial cultures. A number of VOCs are produced during microbial degradation of organic matter accompanying food spoilage. In order to characterize the dynamics of microbial VOC production, and enable time-dependent analysis, we have constructed a dual-chamber sampling system and coupled it online with mass spectrometry (MS). The biological specimen is placed in a gas-tight sampling chamber. A carrier gas is introduced to the chamber periodically to transfer the VOCs present in the specimen headspace to the atmospheric-pressure chemical-ionization interface of a triple-quadrupole mass spectrometer. A control or blank spectrum is recorded before the specimen spectrum is recorded at each time point, enabling signal comparison and subtraction. The custom-made electronic control unit, incorporating three Arduino microcontrollers, operates six pinch valves and a miniature air compressor and triggers MS-data acquisition. The automated dual-chamber sampling system was first tested using standard mixtures to verify its analytical performance. To demonstrate the usefulness of this system in the studies of microbial volatomes, we implemented it in real-time monitoring of the growth of bakers yeast (Saccharomyces cerevisiae), fructification of golden oyster mushroom (Pleurotus citrinopileatus), and microbial degradation of a food-related sample (Pacific white shrimp, Litopenaeus vannamei). The recorded VOC signals show characteristic temporal profiles with transient bands or plateaus corresponding to different stages of microbial growth and putrefaction processes.
Automated on-line liquid-liquid extraction system for temporal mass spectrometric analysis of dynamic samples
(2015-09-24)
Hsieh, Kai-Ta
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Liu, Pei-Han
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Urban, Pawel L.
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應用化學系
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應用化學系分子科學碩博班
Most real samples cannot directly be infused to mass spectrometers because they could contaminate delicate parts of ion source and guides, or cause ion suppression. Conventional sample preparation procedures limit temporal resolution of analysis. We have developed an automated liquid-liquid extraction system that enables unsupervised repetitive treatment of dynamic samples and instantaneous analysis by mass spectrometry (MS). It incorporates inexpensive open-source microcontroller boards (Arduino and Netduino) to guide the extraction and analysis process. Duration of every extraction cycle is 17 min. The system enables monitoring of dynamic processes over many hours. The extracts are automatically transferred to the ion source incorporating a Venturi pump. Operation of the device has been characterized (repeatability, RSD = 15%, n = 20; concentration range for ibuprofen, 0.053-2.000 mM; LOD for ibuprofen, similar to 0.005 mM; including extraction and detection). To exemplify its usefulness in real-world applications, we implemented this device in chemical profiling of pharmaceutical formulation dissolution process. Temporal dissolution profiles of commercial ibuprofen and acetaminophen tablets were recorded during 10 h. The extraction-MS datasets were fitted with exponential functions to characterize the rates of release of the main and auxiliary ingredients (e.g. ibuprofen, k = 0.43 +/- 0.01 h(-1)). The electronic control unit of this system interacts with the operator via touch screen, internet, voice, and short text messages sent to the mobile phone, which is helpful when launching long-term (e.g. overnight) measurements. Due to these interactive features, the platform brings the concept of the Internet-of-Things (IoT) to the chemistry laboratory environment. (C) 2015 Elsevier B.V. All rights reserved.
Automated system for extraction and instantaneous analysis of millimeter-sized samples
(2014)
Hu, Jie-Bi
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Chen, Ssu-Ying
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Wu, June-Tai
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Chen, Yu-Chie
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Urban, Pawel L.
Adequate sample treatment is critical when employing mass spectrometry (MS) in the analyses of complex biological matrices. Despite various improvements, it is generally difficult to automate the process of preparing solid biological samples for MS analysis. Here we demonstrate a facile approach for automation of the whole analysis (from an untreated sample to the final result). The proposed platform enables disruption and extraction of relatively small samples (individual fruit flies, fragments of tea leaves, powdered drug sampled with a cotton bud), and almost simultaneous analysis of the obtained extract within less than 10 min, and with very little intervention of the analyst. The operation is straightforward: once a sample is placed in the sample chamber, the analyst only needs to press a button on the touch screen of the user interface. The programmed open-source electronic device triggers addition of a small amount of solvent, and subsequent mechanical disruption/extraction of the specimen under controlled conditions (thermostated chamber). A small volume of the extract is directed to the ion source of the mass spectrometer incorporating a Venturi pump. During the operation of the instrument, fluorescence intensities (excitation wavelength windows: 320-380 and 460-500 nm) as well as MS extracted ion currents are recorded simultaneously. In the case of fruit fly samples, similar to 70 signals were recorded in both modes while the analysis of green tea leaves yielded similar to 30 signals. The resulting data reveal time-resolved extraction profiles characterizing every sample.
Automation of mass spectrometric detection of analytes and related workflows: A review
(2020-02-01)
Elpa, Decibel P.
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Prabhu, Gurpur Rakesh D.
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Wu, Shu-Pao
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Tay, Kheng Soo
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Urban, Pawel L.
The developments in mass spectrometry (MS) in the past few decades reveal the power and versatility of this technology. MS methods are utilized in routine analyses as well as research activities involving a broad range of analytes (elements and molecules) and countless matrices. However, manual MS analysis is gradually becoming a thing of the past. In this article, the available MS automation strategies are critically evaluated. Automation of analytical workflows culminating with MS detection encompasses involvement of automated operations in any of the steps related to sample handling/treatment before MS detection, sample introduction, MS data acquisition, and MS data processing. Automated MS workflows help to overcome the intrinsic limitations of MS methodology regarding reproducibility, throughput, and the expertise required to operate MS instruments. Such workflows often comprise automated off-line and on-line steps such as sampling, extraction, derivatizadon, and separation. The most common instrumental tools include autosamplers, multi-axis robots, flow injection systems, and lab-on-a-chip. Prototyping customized automated MS systems is a way to introduce non-standard automated features to MS workflows. The review highlights the enabling role of automated MS procedures in various sectors of academic research and industry. Examples include applications of automated MS workflows in bioscience, environmental studies, and exploration of the outer space.
Bioparticles, Molecules, and Complexes Analyzed by "Chromatography" Without a Stationary Phase
(2017-10-01)
Urban, Pawel L.
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Goodall, David M.
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應用化學系
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Department of Applied Chemistry
Blotting paper as a disposable tool for sampling chemical residues from skin surface
(2019-04-01)
Wu, Pei-Chi
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Dutkiewicz, Ewelina P.
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Liao, Pei-Han
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Chiu, Hsien-Yi
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Urban, Pawel L.
Capillary Action-Supported Contact less Atmospheric Pressure Ionization for the Combined Sampling and Mass Spectrometric Analysis of Biomolecules
(2011-04-15)
Hsieh, Cheng-Huan
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Chang, Chia-Hsien
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Urban, Pawel L.
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Chen, Yu-Chie
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應用化學系
It is proposed that a short tapered capillary can be utilized as a nanoliter-volume sampling tool and sample emitter for generation of gas-phase ions in front of the mass spectrometer, without the need for using an additional electric power supply, a gas supply, or a syringe pump. A wide range of molecules can be analyzed in pure solutions and complex matrixes (cell extract, urine, and plant tissue) with no or minimum sample preparation. Singly and multiply charged ions can be detected in either positive or negative-ion mode. Because of the nanoliter-volume sampling and low spectral background, the mass detection limit for bradykinin is in the low attomole range. Other advantages include simplicity, disposability, and low cost. The putative mechanism of the ion formation in this capillary-action supported contactless spray emitter is discussed.
Capillary hydrodynamic chromatography reveals temporal profiles of cell aggregates
(2016-03-03)
Tang, Ya-Ru
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Huang, Hsin-Yi
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Hu, Jie-Bi
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Rattinam, Rajesh
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Li, Chun-Hsien
Microbial cells are known to form aggregates. Such aggregates can be found in various matrices; for example, functional drinks. Capillary hydrodynamic chromatography (HDC) enables separation of particles by size using nanoliter-scale volumes of samples. Here we propose an approach based on HDC for characterisation of real samples containing aggregated and non-aggregated bacterial and fungal cells. Separation of cells and cell aggregates in HDC arises from the parabolic flow profile under laminar flow conditions. In the presented protocol, hydrodynamic separation is coupled with different on-line and offline detectors (light absorption/scattering and microscopy). The method has successfully been applied in the monitoring of dynamic changes in the microbiome of probiotic drinks. Chromatographic profiles of yogurt and kefir samples obtained at different times during fermentation are in a good agreement with microscopic images. Moreover, thanks to the implementation of an area imaging detector, capillary HDC could be multiplexed and used to profile spatial gradients in cell suspensions, which arise in the course of sedimentation of cells and cell aggregates. This result shows compatibility of sedimentation analysis and capillary HDC. We believe that the approach may find applications in the profiling of functional foods and other matrices containing aggregated bioparticles. (C) 2016 Elsevier B.V. All rights reserved.
Carbon-13 labelling strategy for studying the ATP metabolism in individual yeast cells by micro-arrays for mass spectrometry
(2011)
Urban, Pawel L.
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Schmidt, A. Mareike
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Fagerer, Stephan R.
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Amantonico, Andrea
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Ibanez, Alfredo
Isotopic labelling of cellular metabolites, used in conjunction with high-density micro-arrays for mass spectrometry enables observation of ATP metabolism in single yeast cells.
Chemical clocks, oscillations, and other temporal effects in analytical chemistry: oddity or viable approach?
(2018-08-07)
Prabhu, Gurpur Rakesh D.
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Witek, Henryk A.
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Urban, Pawel L.
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交大名義發表
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應用化學系
Most analytical methods are based on analogue inputs from sensors of light, electric potentials, or currents. The signals obtained by such sensors are processed using certain calibration functions to determine concentrations of the target analytes. The signal readouts are normally done after an optimised and fixed time period, during which an assay mixture is incubated. This minireview covers anotherand somewhat unusualanalytical strategy, which relies on the measurement of time interval between the occurrences of two distinguishable states in the assay reaction. These states manifest themselves via abrupt changes in the properties of the assay mixture (e.g. change of colour, appearance or disappearance of luminescence, change in pH, variations in optical activity or mechanical properties). In some cases, a correlation between the time of appearance/disappearance of a given property and the analyte concentration can be also observed. An example of an assay based on time measurement is an oscillating reaction, in which the period of oscillations is linked to the concentration of the target analyte. A number of chemo-chronometric assays, relying on the existing (bio)transformations or artificially designed reactions, were disclosed in the past few years. They are very attractive from the fundamental point of view butso faronly few of them have be validated and used to address real-world problems. Then, can chemo-chronometric assays become a practical tool for chemical analysis? Is there a need for further development of such assays? We are aiming to answer these questions.
Clarifying Misconceptions about Mass and Concentration Sensitivity
(2016-06)
Urban, Pawel L.
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應用化學系
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Department of Applied Chemistry
This commentary discusses differences between the so-called "mass sensitivity" and "concentration sensitivity". These terms are freely used in analytical chemistry literature to characterize operation of analytical techniques and methods. The type of sensitivity in an analytical method delimits the method\'s applications (e.g., in analysis of volume-limited and concentrated, or large-volume but dilute samples). It is helpful to instruct students how to distinguish between mass-sensitive and concentration-sensitive methods. Introduction of mass and concentration sensitivity can. be included in graduate courses related to instrumental analysis, and, if time is available, also in the upper-level undergraduate courses.
Coffee-ring effects in laser desorption/ionization mass spectrometry
(2013-03-05)
Hu, Jie-Bi
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Chen, Yu-Chie
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Urban, Pawel L.
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應用化學系
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Department of Applied Chemistry
This report focuses on the heterogeneous distribution of small molecules (e.g. metabolites) within dry deposits of suspensions and solutions of inorganic and organic compounds with implications for chemical analysis of small molecules by laser desorption/ionization (LDI) mass spectrometry (MS). Taking advantage of the imaging capabilities of a modern mass spectrometer, we have investigated the occurrence of "coffee rings" in matrix-assisted laser desorption/ionization (MALDI) and surface-assisted laser desorption/ionization (SALDI) sample spots. It is seen that the "coffee-ring effect" in MALDI/SALDI samples can be both beneficial and disadvantageous. For example, formation of the coffee rings gives rise to heterogeneous distribution of analytes and matrices, thus compromising analytical performance and reproducibility of the mass spectrometric analysis. On the other hand, the coffee-ring effect can also be advantageous because it enables partial separation of analytes from some of the interfering molecules present in the sample. We report a "hidden coffee-ring effect" where under certain conditions the sample/matrix deposit appears relatively homogeneous when inspected by optical microscopy. Even in such cases, hidden coffee rings can still be found by implementing the MALDI-MS imaging technique. We have also found that to some extent, the coffee-ring effect can be suppressed during SALDI sample preparation. (C) 2013 Elsevier B.V. All rights reserved.
Compartmentalised chemistry: from studies on the origin of life to engineered biochemical systems
(2014-01-01)
Urban, Pawel L.
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應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
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Institute of Molecular science
The origin of life on Earth has been the subject of inquiry since the early days of philosophical thought. The main questions are centred around the formation of protocells capable of metabolism and replication. Research studies have been carried out to simulate the conditions on early Earth. They have led to a proposal that the first cells could have emerged through self-assembly of molecules such as phospholipids. When such structures split pre-metabolic mixtures into small-volume aliquots, biochemical reactions could be "digitised\'\' giving rise to self-sustaining entities. Since then compartmentalisation has remained instrumental to biology and biochemistry. It prevents dispersion of metabolic intermediates, and facilitates molecular interactions by means of confinement. Eukaryotic organisms are highly compartmentalised on various levels (subcellular, cellular, and organ levels). Apart from cell-level compartmentalisation, metabolism relies on the separation of biochemical pathways into subcellular organelles. Whilst in vitro studies in chemical and synthetic biology generally use homogeneous mixtures of reactants and biocatalysts, a faithful mimicry of biochemical systems requires introduction of metabolic compartments. In fact, the compartmentalised structure of biological tissues can serve as a blueprint in applied research (e.g. biochemical engineering). Three-dimensional arrays of interconnected microdroplet compartments can already be engineered. It is envisioned that compartmentalisation will play a key role in emerging biotechnologies, including those related to in vitro growth of tissues and organs, offering new possibilities in regenerative medicine, as well as the construction of intelligent and miniaturised systems for multi-step biosyntheses and biocomputing.
Cool Mist Scavenging of Gas-Phase Molecules
(2017-10-01)
Wu, Pei-Chi
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Dutkiewicz, Ewelina P.
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Urban, Pawel L.
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應用化學系
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Department of Applied Chemistry
The purpose of analytical extractions is to simplify sample matrix without losing analyte molecules. Here we present a technique of extracting volatile compounds by scavenging gas-phase molecules with tiny liquid droplets (<10 mu m). A cool mist of the extracting solvent is generated by an ultrasonic transducer, transferred to the headspace of the sample chamber under atmospheric conditions, and pushed by a small pressure difference toward a condenser. By slowly passing over the sample, the microdroplets extract volatile species present in the sample headspace, and they coalesce in a cooled zone. The condensed liquid is collected for analysis by direct infusion mass spectrometry or chromatography coupled with mass spectrometry. Due to the high surface-to-volume ratio of the microdroplets, the mist depletes a great share of the volatile organics present in the headspace. Other advantages of cool mist scavenging include: selective extraction of gas-phase molecules, the extracting solvent can be miscible with the sample solvent, simplicity, high speed, and no requirement for heating that could potentially decompose the sample. In this study, cool mist scavenging was first tested on artificial samples containing esters. The relationship between the sample concentration and the extract concentration was verified theoretically and experimentally. Some of the possible confounding effects were tested and discussed. The technique was subsequently applied to qualitative analysis of selected complex samples in liquid and solid phase as well as an esterification reaction.