Browsing by Author "Jen, HP"

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Fabrication of microfluidic devices using dry film photoresist for microchip capillary electrophoresis
(2006-04-14)
Tsai, YC
;
Jen, HP
;
Lin, KW
;
Hsieh, YZ
;
應用化學系
An inexpensive, disposable microfluidic device was fabricated from a dry film photoresist using a combination of photolithographic and hot roll lamination techniques. A microfluidic flow pattern was prefabricated in a dry film photoresist tape using traditional photolithographic methods. This tape became bonded to a poly(methyl methacrylate) (PMMA) sheet with prepouched holes when passed through a hot roll laminator. A copper working electrode and platinum decoupler was readily incorporated within this microchip. The integrated microchip device was then fixed in a laboratory-built Plexiglas holder prior to its use in microchip capillary electrophoresis. The performance of this device with amperometric detection for the separation of dopamine and catechol was examined. The separation was complete within 50 s at an applied potential of 200 V/cm. The relative standard deviations (RSD) of analyte migration times were less than 0.71%, and the theoretical plate numbers for dopamine and catechol were 3.2 x 10(4) and 4.1 x 10(4), respectively, based on a 65 min separation channel. (c) 2005 Elsevier B.V. All rights reserved.
On-line preconcentration and determination of ketamine and norketamine by micellar electrokinetic chromatography - Complementary method to gas chromatography/mass spectrometry
(2006-04-14)
Jen, HP
;
Tsai, YC
;
Su, HL
;
Hsieh, YZ
;
應用化學系
We have investigated a rapid, simple, and highly efficient on-line preconcentration method using in micellar electrokinetic chromatography (MEKC) for the analysis of abused drugs. Ketamine is an anesthetic that has been abused as a hallucinogen. We applied the sample sweeping technique first to ketamine and its major metabolite, norketamine, and separated the analytes with MEKC. Several of the sweeping MEKC parameters to effect successful separations, such as the concentration of sodium dodecyl sulfate (SIDS), the injection time, and the applied voltage were optimized. The improvements in the number of theoretical plates under the different separation conditions are presented clearly in a three-dimensional representation. The limits of detection were 2.8, 3.4, and 3.3 ng/mL for ketamine, norketamine, and ketamine-D-4, respectively. The enrichment factor for each compound was within the range of 540-800. Experimental results are in agreement with those of analysis conducted by gas chromatography/mass spectroscopy (GC/MS). Therefore, we believe that sweeping, combined with MEKC, represents a suitable complementary method to GC/MS for use in clinical and forensic analyses of ketamine and norketamine. (c) 2005 Elsevier B.V. All rights reserved.
Sweeping technique combined with micellar electrokinetic chromatography for the simultaneous determination of flunitrazepam and its major metabolites
(2006-03-31)
Huang, CW
;
Jen, HP
;
Wang, RD
;
Hsieh, YZ
;
應用化學系
A sweeping technique, in conjunction with micellar electrokinetic chromatography, for the simultaneous determination of flunitrazepam and its major metabolites, 7-aminoflunitrazepam and N-desmethylflunitrazepam, is described. The optimized conditions for the sweeping and separation were a pH 9.5 buffer, 25 mM borate, 50 mM cetyltrimethylammonium bromide, 30% MeOH (v/v), and a 151-mm injection length. The calibration functions were all linear with the coefficient of determination (r(2)) exceeding 0.996 for the three target compounds. Using the sweeping procedure, the limits of detection were determined to be 13.4, 5.6, and 12.0 ng/mL for flunitrazepam, 7-aminoflunitrazepam, and N-desmethylflunitrazepam, respectively, and the sensitivity enhancement for each compound was within the range of 110-200 fold. The RSDs for the retention time and the peak area were less than 4.10%. The optimized sweeping method was also used to examine a spiked urine sample. We conclude that sweeping with micellar electrokinetic chromatography has considerable potential use in clinical and forensic analyses of flunitrazepam and its metabolites. (c) 2006 Elsevier B.V. All rights reserved.