Browsing by Author "Yang, Hui-Hsien"

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Dry ice fog extraction of volatile organic compounds
(2019-01-25)
Yang, Hui-Hsien
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Urban, Pawel L.
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應用化學系
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Department of Applied Chemistry
Extraction of volatile organic compounds (VOCs) into a condensed phase requires maximizing the surfaceto-volume ratio of the extracting medium. In the case of the solid-phase extracting media, the surfaceto-volume ratio can be increased by implementing porous monoliths or particles with different size. In the case of the liquid-phase extracting media, the surface-to-volume ratio can be increased by generating microbubbles or aerosol microdroplets. Here, we propose dry ice fog extraction (DIFE) approach. Briefly, aerosol microdroplets are generated by inserting dry ice into the extraction solvent. The produced fog, containing high-density microdroplets, is directed toward the sample headspace, where the gas-liquid extraction occurs. The microdroptets, containing the extracted VOCs, subsequently coalesce on a cold surface. The movement of the microdroplets is facilitated by a small pressure difference between the fog generator and the extract collector. Within several minutes, a few hundred microliters of the extract are collected, which is sufficient for chromatographic and mass spectrometric analyses. In this proof-ofconcept study, the DIFE approach was characterized by using gas chromatography coupled with electron ionization mass spectrometry (MS), as well as direct infusion atmospheric pressure chemical ionization MS. The limits of detection for linalool and menthol were 2.0 x 10(-6) and 4.7 x 10(-5) M, respectively. The method was further applied in analyses of VOCs emanating from a variety of liquid and solid matrices (ecigarette "vapor", cinnamon branch, curly spearmint leaves, lily petal, garlic bulb, ginger root, mouthwash, shampoo, spoiled seafood, toothpaste, and red wine). D1FE effectively isolated the VOCs associated with these complex matrices. (C) 2018 Elsevier B.V. All rights reserved.
Kinetic study of continuous liquid-liquid extraction of wine with real-time detection
(2018-11-30)
Yang, Hui-Hsien
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Dutkiewicz, Ewelina P.
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Urban, Pawel L.
;
應用化學系
;
Department of Applied Chemistry
Kinetic optimization of continuous liquid-liquid extraction (CLLE) can shorten sample preparation times and reduce losses of labile or volatile analytes. Here, we coupled a downscaled CLLE apparatus with atmospheric pressure chemical ionization interface of triple quadrupole mass spectrometer. Real-time sampling was guided by an Arduino-based programmable logic controller. The recorded datasets were processed to compute the extraction rate constants for the target analytes. The extraction time in subsequent on-line experiments was set to 180 min as a compromise between the reduction of the analysis time and maximizing its yield. Interestingly, off-line analysis of the extract produced different results than on-line analysis pointing to the immanent degradation of the collected extract aliquots. Next, we implemented this hyphenated system in the analysis of red wine samples, which were stored during different periods of time after opening the bottle. The results reveal differences in the depletion of the volatile wine components during storage. (C) 2018 Elsevier B.V. All rights reserved.
On-Line Coupling of Simultaneous Distillation-Extraction Using the Likens-Nickerson Apparatus with Gas Chromatography
(2020-01-07)
Liao, Pei-Han
;
Yang, Hui-Hsien
;
Wu, Pei-Chi
;
Abu Bakar, Noor Hidayat
;
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.