Browsing by Author "Jen, Hsiu-Ping"

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Determination of cocaine and its metabolites using cation-selective exhaustive injection and sweeping-MEKC
(2008-11-01)
Su, Hsiu-Li
;
Feng, Lan-Ing
;
Jen, Hsiu-Ping
;
Hsieh, You-Zung
;
應用化學系
We have employed a high-sensitivity on-line preconcentration method, cation-selective exhaustive injection (CSEI) and sweeping MEKC, for the analysis of cocaine, benzoylecgonine, norcocaine, and cocaethylene. We monitored the effects of several of the CSEI-sweeping-MEKC parameters - including the pH, the concentrations of SDS and organic modifier, the injection length of the high-conductivity buffer, and the injection time of the sample - to optimize the separation process. The optimal BGE was 100 mM phosphoric acid (pH 1.8) containing 75 mM SDS with 10% 2-propanol and 10% tetrahydrofuran as the organic modifier. In addition, electrokinetic injection of the sample at 15 kV for 900 s provided both high separation efficiency and enhanced sweeping sensitivity. The sensitivity enhancements for cocaine, norcocaine, and cocaethylene ranged from 2.06 x 10(4) to 3.96 x 10(4); for benzoylecgonine it was 1.75 x 10(3); the coefficients of determination exceeded 0.9958. The LODs, based on an SIN ratio of 3:1, of sweeping-MEKC ranged from 33.5 to 52.8 ng/mL; in contrast, when using CSEI-sweeping-MEKC the sensitivity increased to range from 29.7 to 236 pg/mL. Under the optimal conditions, we analyzed cocaine in a human urine sample prepared using off-line SPE to minimize the influence of the matrix. The recovery of the SPE efficiency was satisfactory (ca. 74.9-87.6%). Our experimental results suggest that, under the optimal conditions, the CSEI-sweeping-MEKC method can be used to determine cocaine and its metabolites with high sensitivity in human urine.
Fabrication of a flexible and disposable microreactor using a dry film photoresist
(2006-06-01)
Tsai, Yuan-Chien
;
Yang, Shung-Jim
;
Lee, Hsun-Tsing
;
Jen, Hsiu-Ping
;
Hsieh, You-Zung
In this paper, we demonstrate that a low-cost flexible microreactor can be manufactured using a dry film photoresist in conjunction with photolithographic and hot roll lamination techniques. A microfluidic flow path and sample reservoir patterns were prefabricated in a dry film photoresist tape using traditional photolithographic methods. This tape was sandwiched between two plastic films - wells were prepouched on the cover film - that were bonded upon passage through a hot roll laminator. A simple Plexiglas reactor holder was designed and constructed to use in evaluating the flexible microchip reactor. We demonstrate a chemical synthesis of polyaniline that was performed with this polymeric microreactor using a hydrodynamic flow control system. The fabrication of this microreactor suggests that there is great potential for designing and prototyping disposable microscale reaction systems using dry film photoresist for a range of chemical and biochemical syntheses.
High-Performance Large-Scale Flexible Dye-Sensitized Solar Cells Based on Anodic TiO2 Nanotube Arrays
(2013-10-01)
Jen, Hsiu-Ping
;
Lin, Meng-Hung
;
Li, Lu-Lin
;
Wu, Hui-Ping
;
Huang, Wei-Kai
A simple strategy to fabricate flexible dye-sensitized solar cells involves the use of photoanodes based on TiO2 nanotube (TNT) arrays with rear illumination. The TNT films (tube length similar to 35 mu m) were produced via anodization, and sensitized with N719 dye for photovoltaic characterization. Pt counter electrodes of two types were used: a conventional FTO/glass substrate for a device of rigid type and an ITO/PEN substrate for a device of flexible type. These DSSC devices were fabricated into either a single-cell structure (active area 3.6 X 0.5 cm(2)) or a parallel module containing three single cells (total active area 5.4 cm(2)). The flexible devices exhibit remarkable performance with efficiencies eta = 5.40 % (single cell) and 4.77 % (parallel module) of power conversion, which outperformed their rigid counterparts with eta = 4.87 % (single cell) and 4.50 % (parallel model) under standard one-sun irradiation. The flexible device had a greater efficiency of conversion of incident photons to current and a broader spectral range than the rigid device; a thinner electrolyte layer for the flexible device than for the rigid device is a key factor to improve the light-harvesting ability for the TNT-DSSC device with rear illumination. Measurements of electrochemical impedance spectra show excellent catalytic activity and superior diffusion characteristics for the flexible device. This technique thus provides a new option to construct flexible photovoltaic devices with large-scale, light-weight, and cost-effective advantages for imminent applications in consumer electronics.
Using sweeping micellar electrokinetic chromatography to analyze Delta(9)-tetrahydrocannabinol and its major metabolites
(2009-04-17)
Su, Hsiu-Li
;
Feng, Lan-Ing
;
Jen, Hsiu-Ping
;
Hsieh, You-Zung
;
應用化學系
We have applied sweeping micellar electrokinetic chromatography (sweeping-MEKC) to the simultaneous determination of Delta(9)-tetrahydrocannabinol (THC) and its major metabolites, 11-hydroxy-Delta(9)-tetrahydrocannabinol (THC-OH) and 11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol (THC-COOH). We monitored the effects of several of the sweeping-MEKC parameters, including the proportion of organic modifier, the concentration of sodium dodecyl sulfate (SDS), the pH, and the sample injection volume, to optimize the separation process. The optimal buffer for the analysis of the three analytes was 25 mM citric acid/disodium hydrogenphosphate (pH 2.6) containing 40% methanol and 75 mM SDS. Under the optimized separation parameters, the enrichment factors for THC, THC-COOH, and THC-OH when using sweeping-MEKC (relative to MEKC) were 77,139, and 200, respectively. The limits of detection (LODs) for the three compounds in standard solutions ranged from 3.87 to 15.2 ng/mL. We combined the sweeping-MEKC method with solid-phase extraction to successfully detect THC, THC-COOH, and THC-OH in human urine with acceptable repeatability. The LODs of these analytes in urine samples ranged from 17.2 to 23.3 ng/mL. Therefore, this sweeping-MEKC method is useful for determining, with high sensitivity, the amounts of THC and its metabolites in the urine of suspected THC users. (C) 2008 Elsevier B.V. All rights reserved.