Browsing by Author "Yang, Hao-Chun"

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Fizzy Extraction of Volatile Organic Compounds Combined with Atmospheric Pressure Chemical Ionization Quadrupole Mass Spectrometry
(2017-07-01)
Yang, Hao-Chun
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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
Chemical analysis of volatile and semivolatile compounds dissolved in liquid samples can be challenging. The dissolved components need to be brought to the gas phase, and efficiently transferred to a detection system. Fizzy extraction takes advantage of the effervescence phenomenon. First, a carrier gas (here, carbon dioxide) is dissolved in the sample by applying overpressure and stirring the sample. Second, the sample chamber is decompressed abruptly. Decompression leads to the formation of numerous carrier gas bubbles in the sample liquid. These bubbles assist the release of the dissolved analyte species from the liquid to the gas phase. The released analytes are immediately transferred to the atmospheric pressure chemical ionization interface of a triple quadrupole mass spectrometer. The ionizable analyte species give rise to mass spectrometric signals in the time domain. Because the release of the analyte species occurs over short periods of time (a few seconds), the temporal signals have high amplitudes and high signal-to-noise ratios. The amplitudes and areas of the temporal peaks can then be correlated with concentrations of the analytes in the liquid samples subjected to fizzy extraction, which enables quantitative analysis. The advantages of fizzy extraction include: simplicity, speed, and limited use of chemicals (solvents).
Microanalysis Using Acoustically Actuated Droplets Pinned Onto a Thread
(2019-01-01)
Yang, Tzu-Hsien
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Yang, Hao-Chun
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Chang, Cheng-Hao
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Prabhu, Gurpur Rakesh D.
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Urban, Pawel L.
An acoustic wave-assisted microscale assay platform is demonstrated. Liquid droplets containing samples and reagents are dispensed and pinned onto a hydrophobic thread, and actuated by sound waves. The transport of droplets is achieved by modulating sound emitted by two sources. The resulting sound intensity gradient pushes the droplets in one direction. The available distance of droplet actuation is related to droplet size. The moving droplets merge at the end of their actuation range, and the merged droplet travels further due to its greater size. Fluorometric analysis of the merged droplet is accomplished by positioning an excitation light source above a defined interrogation zone along the thread. The emitted light is analyzed by a miniature spectrometer positioned orthogonally to the excitation light beam. The sound sources and detection system are controlled by universal electronic modules (Raspberry Pi, Arduino). The system is operated automatically with the aid of a custom-developed graphical user interface. Here, we demonstrate its application in enzyme assays (trypsin, beta-galactosidase). In-droplet enzymatic reaction progress curves are readily obtained. The actuated droplets can be put in motion and stopped without a significant delay. Only microliter-range volumes of sample and reagent are consumed in every analysis, while sub-milliliter volumes of chemical waste are produced.
On-line coupling of fizzy extraction with gas chromatography
(2019-05-01)
Yang, Hao-Chun
;
Urban, Pawel L.
;
應用化學系
;
Department of Applied Chemistry
Fizzy extraction (FE) is carried out by first dissolving a carrier gas (typically, carbon dioxide) in a liquid sample at a moderate pressure (typically, 150kPa) and then rapidly depressurizing the sample. The depressurization leads to instant release of numerous microbubbles in the liquid matrix. The abruptly released gas extracts the volatile solutes and elutes them toward a detector in a short period of time. Here, we describe on-line coupling of FE with gas chromatography (GC). The two platforms are highly compatible and could be combined following several modifications of the interface and adjustments of the extraction sequence. The analytes are released within a short period of time (1.5s). Thus, the chromatographic peaks are satisfactorily narrow. There is no need to trap the extracted analytes in a loop or on a sorbent, as it is done in standard headspace and microextraction methods. The approach requires only minor sample pretreatment. The main parameters of the FE-GC-mass spectrometry (MS) method were optimized. The results of FE were compared with those of headspace flushing (scavenging headspace vapors), and the enhancement factors were in the order of 2 to 13 (for various analytes). The limits of detection for some of the tested analytes were lower in the proposed FE-GC-MS method than in FE combined with atmospheric pressure chemical ionization MS. The method was further tested in analyses of selected real samples (apple flavor milk, mixed fruit and vegetable juice drink, mango flavored drink, pineapple green tea, toothpaste, and yogurt).
The influence of UV filter and Al/Ag moisture barrier layer on the outdoor stability of polymer solar cells
(2020-03-15)
Weng, Chia-Ning
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Yang, Hao-Chun
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Tsai, Cheng-Yu
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Chen, Szu-Han
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Chen, Yan-Syun
The degradation of the polymer solar cells in the outdoor condition was studied. It was found that the devices with normal structure (ITO/PEDOT:PSS/PBDTTT-EFT:PC71BM/ZrOx/Al) show better stability than those with inverted device structure (ITO/ZnO/PBDTTT-EFT:PC71BM/MoO3/Ag). PBDTTT-EFT is poly[4, 8-bis(5-(2-ethylhexyl) thiophen-2-yl) benzo [1,2-b;4,5-b] dithiophene-2, 6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno [3,4-b] thiophene-) - 2-carboxylate-2-6-diyl)] and PC71BM is [6,6]-phenyl-C71-butyric acid methyl ester. The major cause of degradation was attributed to the ultraviolet (UV) part of the sunlight. When the UV filter with cut-off wavelength of 400 nm was used to protect the device, the decay rate was improved by 50 times and the protected device retains 95% of their initial power conversion efficiency after 13 days outside. In the meanwhile, the decay of device fabricated by toluene was found 8 times faster than device by chlorobenzene. Thin 20 nm of Ag capping layer can further improve the stability. Degradation under water immersion indicates that the major effect of Ag is to protect against the residual moisture inside the encapsulation.