Biomedical subjects

Cheng-Huang Lin

Publications and source records attributed to Cheng-Huang Lin.

31 records · Page 2Linked to original sources

PubMed2003

Identification of 2,5-dimethoxy-4-ethylthiophenethylamine and its metabolites in the urine of rats by gas chromatography-mass spectrometry.

A simple and specific method based on gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) for the analysis of in vivo metabolism of 2,5-dimethoxy-4-ethylthiophenethylamine (2C-T-2) in rats is described. Three male rats were administered 20 mg/kg of 2C-T-2 by intra-peritoneal injection, and 24 h urine fractions were collected before and after the administration for analysis. After acidic hydrolysis of the urine samples, the metabolites were liquid-liquid extraction and analyzed by a quadruple mass spectrometer in the selected ion monitoring mode. The findings show that four metabolites of 2-(4-ethylthio-2,5-dimethoxyphenyl)-ethanol (Mw: 242), 4-ethylthio-2,5-dimethoxyphenyl acetic acid (Mw: 256), 1-acetoamino-2-(2-hydroxy-4-ethylthio-5-methoxyphenyl)-ethane (Mw: 269) and 1-acetoamino-2-(2-methoxy-4-ethylthio-5-hydroxyphenyl)-ethane (Mw: 269) are present and the metabolic pathway for 2C-T-2 in the rat is proposed.

Animals↗

PubMed2003

Optimization of a simple method for the chiral separation of methamphetamine and related compounds in clandestine tablets and urine samples by beta-cyclodextrine modified capillary electrophoresis: a complementary method to GC-MS.

The chiral separation of (+/-)-methamphetamine, (+/-)-methcathinone, (+/-)-ephedrine and (+/-)-pseudoephedrine by means of beta-cyclodextrine modified capillary electrophoresis is described. The distribution of enantiomers in clandestine tablets and urine samples were identified. Several electrophoretic parameters such as the concentration of beta-cyclodextrin, temperature, the applied voltage and the amount of organic solvent required for successful separation were optimized. The method, as described herein, represents a good complementary method to GC-MS for use in forensic and clinical analysis.

Central Nervous System Stimulants↗

PubMed2003

Determination of corticosterone in mouse plasma by a sweeping technique using micellar electrokinetic chromatography.

The separation and on-line concentration of corticosterone in mouse blood was achieved by means of capillary electrophoresis/UV absorbance using sodium dodecyl sulfate (SDS) as a surfactant. The procedure involved the use of an on-line sample concentration method by sweeping-micellar electrokinetic chromatography (sweeping-MEKC). Optimal on-line concentration and separation conditions were determined. The detection limit for this method was 5 ng/ml (S/N=3) and photodiode array detection at 247 nm was used for identification. For the analysis of actual samples, corticosterones from blood samples of a non-stressed and stressed mouse were determined. The results show that only a minor amount of corticosterone was produced by a non-stressed mouse, whereas a significant amount was present in the blood sample from a stressed mouse. The method developed here can be used to examine corticosterone levels as a marker of stress in test animals and may also be used for estimating the effect of stress-release medications.

18-Hydroxycorticosterone↗

PubMed2003

Determination of riboflavin in urine by capillary electrophoresis-blue light emitting diode-induced fluorescence detection combined with a stacking technique.

A simple, inexpensive and reliable method for the simultaneous, routine analysis of riboflavin in urine by capillary electrophoresis-light emitting diode (LED)-induced fluorescence detection is described. Using a blue LED as the light source, the detection limit of riboflavin was determined to be 0.48 microg/ml and was improved to 20 ng/ml when a stacking technique was applied. In the analysis of an actual sample, various concentrations of riboflavin were distributed in the urine samples over a period of 9 h after the ingestion of a vitamin B(2) tablet.

Electrophoresis, Capillary↗

PubMed2003

Violet light emitting diode-induced fluorescence detection combined with on-line sample concentration techniques for use in capillary electrophoresis.

The first application of a violet light-emitting diode (LED) for fluorescence detection in capillary electrophoresis (CE) is described. The utility of violet LED (peak emission wavelength at 410 nm, approximately 2 mW) for fluorescence detection is demonstrated by examining reserpine and dopamine-labeled NDA (naphthalene-2,3-dicarboxaldehyde), respectively. The detection limit for reserpine was determined to be 2.5 x 10(-6) M by normal micellar electrokinetic capillary chromatography (MEKC) and this was improved to 2.0 x 10(-9) M and 2.0 x 10(-10) M when sweeping-MEKC and cation-selective exhaustive injection (CSEI)-sweep-MEKC techniques were applied, respectively. In addition, the detection limit of NDA-labeled dopamine was determined to be 6.3 x 10(-6) M by means of normal MEKC and this was improved to 3.0 x 10(-8) M when the sweeping-MEKC mode was applied.

Buffers↗

PubMed2003

On-line identification of lysergic acid diethylamide (LSD) in tablets using a combination of a sweeping technique and micellar electrokinetic chromatography/77 K fluorescence spectroscopy.

This work describes a novel method for the accurate determination of lysergic acid diethylamide (LSD) in tablets. A technique involving sweeping-micellar electrokinetic chromatography (MEKC) was used for the initial on-line concentration and separation, after which a cryogenic molecular fluorescence experiment was performed at 77 K. Using this approach, not only the separation of LSD from the tablet extract was achieved, but on-line spectra were readily distinguishable and could be unambiguously assigned. The results are in agreement with analyses by gas chromatography-mass spectrometry (GC-MS). Thus, this method, which was found to be accurate, sensitive and rapid, has the potential for use as a reliable complementary method to GC-MS in such analyses.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2003

Determination of lysergic acid diethylamide (LSD) in mouse blood by capillary electrophoresis/ fluorescence spectroscopy with sweeping techniques in micellar electrokinetic chromatography.

The separation and on-line concentration of lysergic acid diethylamide (LSD) in mouse blood was achieved by means of capillary electrophoresis/fluorescence spectroscopy using sodium dodecyl sulfate (SDS) as the surfactant. Techniques involving on-line sample concentration, including sweeping micellar electrokinetic chromatography (sweeping-MEKC) and cation-selective exhaustive injection-sweep-micellar electrokinetic chromatography (CSEI-sweep-MEKC) were applied; the optimum on-line concentration and separation conditions were determined. In the analysis of an actual sample, LSD was found in a blood sample from a test mouse (0.1 mg LSD fed to a 20 g mouse; approximately 1/10 to the value of LD(50)). As a result, 120 and 30 ng/mL of LSD was detected at 20 and 60 min, respectively, after ingestion of the doses.

Animals↗

PubMed2003

Chiral separation of 3,4-methylenedioxymeth- amphetamine and related compounds in clandestine tablets and urine samples by capillary electrophoresis/fluorescence spectroscopy.

The R-(-)- and S-(+)-isomers of 3,4-methylenedioxymethamphetamine (MDMA) and its metabolite 3,4-methylenedioxyamphetamine (MDA) were prepared, identified by gas chromatography/mass spectrometry (GC/MS) and then used as standards in a series of capillary electrophoresis (CE) experiments. Using these R-(-)- and S-(+)-isomers, the distribution of (RS)-MDA and (RS)-MDMA stereoisomers in clandestine tablets and suspect urine samples were identified. Several electrophoretic parameters, such as the concentration of beta-cyclodextrin used in the electrophoretic separation and the amount of organic solvents required for the separation, were optimized.

Designer Drugs↗

PubMed2002

Optimization of the separation of lysergic acid diethylamide in urine by a sweeping technique using micellar electrokinetic chromatography.

The separation and on-line concentrations of lysergic acid diethylamide (LSD), iso-lysergic acid diethylamide (iso-LSD) and lysergic acid N,N-methylpropylamide (LAMPA) in human urine were investigated by capillary electrophoresis-fluorescence spectroscopy using sodium dodecyl sulfate (SDS) as an anionic surfactant. A number of parameters such as buffer pH, SDS concentration, Brij-30 concentration and the content of organic solvent used in separation, were optimized. The techniques of sweeping-micellar electrokinetic chromatography (sweeping-MEKC) and cation-selective exhaustive injection-sweep-micellar electrokinetic chromatography (CSEI-sweep-MEKC) were used for determining on-line concentrations. The advantages and disadvantages of this procedure with respect to sensitivity, precision and simplicity are discussed and compared.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2002

Rapid analysis of 3,4-methylenedioxymethamphetamine: a comparison of nonaqueous capillary electrophoresis/fluorescence detection with GC/MS.

Because of the increasing use of 3,4-methylenedioxymethamphetamine (3,4-MDMA), a rapid and sensitive analytical technique is required for its detection and determination. Using nonaqueous capillary electrophoresis/fluorescence spectroscopy (NACE/FS) detection, it is possible to determine this drug at the level 0.5 ppm without any pre-treatment in less than 5 min. After liquid-liquid extraction, the sample can be condensed and a detection limit of 3,4-MDMA in urine of 50 ppb (S/N = 3) can be achieved. The precision of the method was evaluated by measuring the repeatability and intermediate precision of migration time and the corrected peak height by comparison with a 3,4-MDMA-D5 internal standard. With the conventional GC/MS method, it is necessary to derivatize the 3,4-MDMA before injection and the GC migration time also is in excess of 20 min. Therefore, NACE/FS represents a good complementary method to GC/MS for use in forensic analysis.

Electrophoresis, Capillary↗

PubMed2002

Ultra-low-temperature non-aqueous capillary electrophoretic separation--77 K fluorescence spectroscopic detection for the on-line identification of photo-converted analytes of trans-resveratrol.

We demonstrate here, for the first time, that non-aqueous capillary electrophoresis (NACE) can be interfaced with any ultra-low-temperature (ULT) separation method and 77 K fluorescence spectroscopy (FS). This novel ULT-NACE-FS system consists of a modular CE system, a dry ice bath, and instrumentation for 77 K fluorescence detection. The ULT-NACE method serves to separate structurally similar molecules by a combination of a low electrophoresis current and a high voltage at approximately -70 degrees C. When the ULT-NACE-separated analytes move into the quartz Dewar flask and traverse into the capillary detection window, liquid nitrogen was added, thus freezing the separating analyte zones, allowing the collection of 77 K fluorescence spectra for on-line spectral fingerprint identification. The first application of the ULT-NACE-FS system is described for the analysis of photo-converted analytes of trans-resveratrol; prospects and future applications of ULT-NACE-FS are also briefly addressed.

Cold Temperature↗

PubMed2002

Evolution of water chemistry in natural acidic environments in Yangmingshan, Taiwan.

In Yangmingshan National Park, located in the northern part of the Taiwan Island, there is a very rare area where fish (Channa asiatica) live in spite of acid environments. The origin of the acid in local acid ponds and rivers and the evolution of the water chemistry are discussed on the basis of sulfur stable isotope ratios and chemical equilibria. One of the sources of the acid is sulfuric acid, which is derived from the oxidation of hydrogen sulfide in volcanic gas gushing out from fumaroles around the area and from acid deposition supplied from Taipei City. It is also derived from the oxidation of pyrite: the sulfur stable isotope ratios of delta 34S of +1@1000 to +4@1000 (relative to CDT) of sulfate in acid pond waters (pH 3-4) could be related to those of hydrogen sulfide in volcanic gas, pyrite in local pond sediments and soils, and sulfate in rain water. One acid source is sulfuric and hydrochloric acids arising in springs from geothermal activity: the delta 34S values were characterised by +13@1000 to +17@1000 sulfate-S, which was provided by a disproportionation reaction of sulfur dioxide in the depths. Another acid source could be the oxidation of iron(II). Under acidic conditions, the water-rock reaction gives rise to high concentrations of aluminium and iron. While flowing down surface streams, iron(II) is oxidised to iron(III) and then hydrolysed to cause further acidification under oxic conditions. The concentrations of iron and aluminium are controlled by redox and dissolution equilibria.

Air Pollutants↗

PubMed2002

Simple and sensitive determination of citrinin in Monascus by GC-selected ion monitoring mass spectrometry.

A new method for the qualitative and quantitative analysis of citrinin in Monascus by gas-chromatography-selected ion monitoring (SIM) mass spectrometry has been developed. GC separation of citrinin in Monascus extract was achieved without the need for chemical derivatization, and could be detected as a single peak when the SIM mode selected 5 prominent fragmentations (m/z of 220, 205, 177, 105 and 91). The quantitative detection limit for citrinin was approximately 1 ppb. Finally, the GC-separated analyte from Monascus extract, at a retention time of 10.89 min, was examined by the method of pattern recognition by comparison with a citrinin standard. The results show that the 2 compounds had a 94% similarity when the SIM mode was used.

Ascomycota↗