Browsing by Author "Wu, Pei-Chi"

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Biodegradation of soil-applied polycyclic aromatic hydrocarbons by sulfate-reducing bacterial consortium
(2009)
Kumar, Mathava
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Wu, Pei-Chi
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Tsai, Jen-Chieh
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Lin, Jih-Gaw
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環境工程研究所
In the present study, the potential of polycyclic aromatic hydrocarbons (PAHs) biodegradation by sulfate-reducing bacterial consortium enriched from piggery wastewater was investigated. The batch experiments of soil-applied PAH biodegradation were conducted with a mixture of PAHs, i.e., naphthalene, fluorene, phenanthrene, fluoranthene and pyrene, at a concentration of 50 mu g of each PAH per g of soil. A central composite design (CCD) was applied to determine the experimental conditions of each batch assay. The pH, biomass and ethanol concentrations were selected as independent variables and the PAH removal percentage was considered as a dependent variable. The optimal conditions for PAH biodegradation were found to be a pH between 4 and 6.5, an ethanol concentration less than 35 mg/L and a biomass concentration greater than 65 mg/L. Bench scale experiments were carried out at the optimal conditions. At the end of experiment (27 d), total PAH removals by biodegradation and volatilization were around 74% and 20%, respectively. The order of PAH removal was naphthalene, phenanthrene, fluorene, fluoranthene, and pyrene. Throughout the study, PAH biodegradation was in good correlation with sulfate reduction. Results of the kinetics study indicated a competitive inhibition between PAHs investigated.
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.
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.
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.