Browsing by Author "Liao, Pei-Han"

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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).
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.
Facilitating chemical and biochemical experiments with electronic microcontrollers and single-board computers
(1970-01-01)
Prabhu, Gurpur Rakesh D.
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Yang, Tzu-Hsien
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Hsu, Chun-Yao
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Shih, Chun-Pei
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Chang, Chun-Ming
Since the advent of modern science, researchers have had to rely on their technical skills or the support of specialized workshops to construct analytical instruments. The notion of the 'fourth industrial revolution' promotes construction of customized systems by individuals using widely available, inexpensive electronic modules. This protocol shows how chemists and biochemists can utilize a broad range of microcontroller boards (MCBs) and single-board computers (SBCs) to improve experimental designs and address scientific questions. We provide seven example procedures for laboratory routines that can be expedited by implementing this technology: (i) injection of microliter-volume liquid plugs into microscale capillaries for low-volume assays; (ii) transfer of liquid extract to a mass spectrometer; (iii) liquid-gas extraction of volatile organic compounds (called 'fizzy extraction'), followed by mass spectrometric detection; (iv) monitoring of experimental conditions over the Internet cloud in real time; (v) transfer of analytes to a mass spectrometer via a liquid microjunction interface, data acquisition, and data deposition into the Internet cloud; (vi) feedback control of a biochemical reaction; and (vii) optimization of sample flow rate in direct-infusion mass spectrometry. The protocol constitutes a primer for chemists and biochemists who would like to take advantage of MCBs and SBCs in daily experimentation. It is assumed that the readers have not attended any courses related to electronics or programming. Using the instructions provided in this protocol and the cited material, readers should be able to assemble simple systems to facilitate various procedures performed in chemical and biochemical laboratories in 1-2 d. This protocol provides a set of seven customizable example procedures for using microcontroller boards (MCBs) and single-board computers (SBCs) for applications in chemical and biochemical research.
On-Line Coupling of Simultaneous Distillation-Extraction Using the Likens-Nickerson Apparatus with Gas Chromatography
(2020-01-07)
Liao, Pei-Han
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Yang, Hui-Hsien
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Wu, Pei-Chi
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Abu Bakar, Noor Hidayat
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Urban, Pawel L.
Simultaneous distillation-extraction (SDE) using the Likens-Nickerson apparatus is a convenient technique used to isolate volatile organic compounds (VOCs) from complex liquid matrices. The technique combines steam distillation with solvent extraction. While analytical extractions are normally followed by off-line separation/detection, it is advantageous to couple extractions on-line with separation and detection systems that are employed in the same analytical workflow. Here, we have coupled the Likens-Nickerson apparatus on-line with a gas chromatograph hyphenated with a mass spectrometer. For that purpose, we have devised an automated liquid transfer setup comprising a peristaltic pump, control unit, customized transfer vial with a drain port, and an autosampler arm to deliver liquid extract aliquots at defined time points. The on-line SDE-GC/MS system enables one to record real-time extraction profiles. These profiles reveal extraction kinetics of various VOCs present in the extracted samples. The data sets were fitted with the first order kinetic equation to obtain numeric values characterizing the extraction process (rate constants ranging from 0.21 to 0.01 min(-1) for the ethyl esters from C-6 to C-19). A comparison of on-line and off-line results reveals that the on-line system is more dependable, while the off-line analysis leads to artifacts. To demonstrate the operation of the on-line SDE-GC/MS system, we performed analyses of selected real samples (beer). The real-time data sets revealed extraction kinetics for VOCs present in these samples. The devised extraction-analysis system allows the analysts to make an evidence-based decision on the extraction time for different groups of analytes in order to maximize extraction yield and minimize analyte losses.