Biomedical subjects

Shou-Mei Wu

Publications and source records attributed to Shou-Mei Wu.

15 recordsLinked to original sources

PubMed2006

Direct and sensitive analysis of methamphetamine, ketamine, morphine and codeine in human urine by cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography.

Cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI-Sweep-MEKC) was directly used to test some abuse drugs in human urine, including morphine (M), codeine (C), ketamine (K) and methamphetamine (MA). First, phosphate buffer (50 mM, pH 2.5) containing 30% methanol was filled into uncoated fused silica capillary (40 cm, 50 microm I.D.), then high conductivity buffer (100 mM phosphate, 6.9 kPa for 99.9 s) was followed. Electrokinetic injection (10 kV, 500 s) was used to load samples and to enhance sensitivity. The stacking step and separation were performed at -20 kV and 200 nm using phosphate buffer (25 mM, pH 2.5) containing 20% methanol and 100 mM sodium dodecyl sulfate. Using CSEI-Sweep-MEKC, the analytes could be simultaneously analyzed and have a detection limit down to ppb level. It was unnecessary to have sample pretreatments. During method validation, calibration plots were linear (r>or=0.9982) over a range of 150-3,000 ng/mL for M and C, 250-5,000 n g/mL for MA, and 50-1,000 ng/mL for K. The limits of detection were 15 ng/mL for M and C, and 5 ng/mL for MA and K (S/N=3, sampling 500 s at 10 kV). Comparing with capillary zone electrophoresis, the results indicated that this stacking method could increase 6,000-fold sensitivity for analysis of MA. Our method was applied for analysis of 28 real urine samples. The results showed good coincidence with immunoassay and GC-MS. This method was feasible for application to detect trace levels of abused drugs in forensic analysis.

Cations↗

PubMed2006

Capillary electrophoresis combining field-amplified sample stacking and electroosmotic flow suppressant for analysis of sulindac and its two metabolites in plasma.

Field-amplified sample stacking with electroosmotic flow (EOF) suppressant in capillary electrophoresis was used to determine the concentration of sulindac (SU) and its two active metabolites, sulindac sulfide (SI) and sulindac sulfone (SO), in human plasma. After acidification, the analytes were extracted from the plasma with dichloromethane. Before sample loading, a water plug (0.5 psi, 3 s) was injected to contain sample anions and to permit field-amplified stacking. Electrokinetic injection at a reversed voltage (-6 kV, 99.9 s) was then used to introduce anions. Separation was performed using phosphate buffer (80 mM, pH 6.0) containing 2,6-di-O-methyl-beta-cyclodextrin (0.75 mM), and poly(ethylene oxide) (0.01%) as an EOF suppressant. The separation was performed at -30 kV and 200 nm. During method validation, calibration plots were linear (r > 0.994) over a range of 0.3-30.0 microM for SU and SO, and 0.5-30.0 microM for SI. During intra- and inter-day analysis, relative standard deviations (RSD) and relative errors (RE) were all less than 16%. The limits of detection were 0.1 microM for SU and SO, and 0.3 microM for SI (S/N = 4, sampling 99.9s at -6 kV). This method was feasible for determining SU and its metabolites in plasma. One female volunteer (27 years, 42 kg) was orally administered one SU tablet (Clinoril, 20 0 mg/tab), and blood samples were drawn at regular intervals over an 8h period. After pretreatment and analysis, the plasma levels of SU, SI and SO were monitored. The pharmacokinetic profile of SU was also investigated.

Adult↗

PubMed2006

Solid-phase extraction and large-volume sample stacking with an electroosmotic flow pump in capillary electrophoresis for determination of methotrexate and its metabolites in human plasma.

This paper describes approaches for large-volume sample stacking (LVSS) with an EOF pumpin CE for the determination of methotrexate (MTX) and its metabolites in human plasma. After pretreatment of plasma through a SPE cartridge, a large sample volume was loaded by hydrodynamic injection (3 psi, 70 s) into the capillary filled with phosphate buffer (70 mM, pH 6.0) containing 0.01% polyethylene oxide. Following removal of a large plug of sample matrix from the capillary using polarity switching (-25 kV), the separation of anionic analytes was subsequently performed without changing polarity again, achieving an improvement of sensitivity of around a 100-fold. The method was applied to therapeutic drug monitoring of MTX in one acute lymphoblastic leukemia patient. This study is one of very few applications showing the feasibility of LVSS in analysis of biological samples by CE.

Antimetabolites, Antineoplastic↗

PubMed2006

Cation-selective exhaustive injection and sweeping MEKC for direct analysis of methamphetamine and its metabolites in urine.

Direct analysis of methamphetamine, amphetamine, and p-hydroxymethamphetamine in urine was achieved by cation-selective exhaustive injection and sweeping micellar EKC. A bare fused-silica capillary (40 cm, 50 microm id) was filled with phosphate buffer (80 mM, pH 3, containing 20% ACN). Then a high-conductivity buffer (100 mM phosphate, pH 3; 6.9 kPa for 2.5 min) was injected. Samples were loaded using electrokinetic injection (10 kV, 600 s) which created long zones of cationic analytes. To enhance sensitivity by sweeping, the stacking step was performed using a phosphate buffer (50 mM, pH 3, containing 20% ACN and 100 mM SDS) at -20 kV before separation by MEKC. This method was capable of detecting the analytes at ppb levels. The calibration plots were linear (r(2) >or= 0.9948) over a range of 100-5000 ng/mL for methamphetamine, and 100-2000 ng/mL for amphetamine and p-hydroxymethamphetamine. The LODs (S/N = 3) were 20 ng/mL for methamphetamine, and 15 ng/mL for amphetamine and p-hydroxymethamphetamine. The method was applied to analysis of 14 urine samples of addicts and is suitable for screening suspected samples for forensic purposes. The results showed good agreement with fluorescence polarization immunoassay and GC-MS.

Amphetamine↗

PubMed2005

Simple fluorimetric liquid chromatographic method for the analysis of undecylenic acid and zinc undecylenate in pharmaceutical preparations.

A simple and selective liquid chromatographic method is described for the analysis of undecylenic acid (UA) and zinc undecylenate (ZnUA) in pharmaceutical preparations. The method is based on the derivatization of the analytes extracted from various samples with 2-(2-naphthoxy)ethyl 2-(piperidino)ethanesulfonate. The resulting derivative was analyzed by liquid chromatography with fluorimetric detection. The quantitation of the method is in the range of 3.0-50.0 microM UA with a detection limit of about 0.3 microM (S/N = 3 with 10 microl injection). We found that acetonitrile is a selective solvent for differentially dissolving UA from coexisted ZnUA in compound formulation. This results in the specific analysis of UA in the presence of ZnUA and simply analyzing the coexisted ZnUA by the value of total UA (UA+ZnUA) minus that of UA. Application of the method to the analysis of undecylenic acid and zinc undecylenate in ointment, powder and solution preparations proved feasible.

Chromatography, High Pressure Liquid↗

PubMed2005

High-performance liquid chromatography with electrochemical detection for analysis of gliclazide in plasma.

A sensitive HPLC-electrochemical detection method was developed for the analysis of gliclazide (GL) in human plasma. After deproteination of 100 microL of plasma by acetonitrile, evaporation, and reconstitution, GL was separated on a C18 column (150 mm x 4.6 mm) by the mobile phase (70 mM disodium tetraborate, pH 7.5, containing 26.5% of acetonitrile). The regression equations were linear (r> 0.9990) over the range of 50 nM to 4.00 microM. The precision and accuracy of intra- and inter-day analysis were less than 5.3 and 0.93% for relative standard deviation and relative error, respectively. The limit of detection for plasma was 10 nM for GL (S/N = 3, 10 microL injection). This newly developed method was applied for monitoring blood levels with one healthy volunteer dosing with a GL tablet.

Adult↗

PubMed2005

Enantiomeric analysis of (+)-menthol and (-)-menthol by fluorogenic derivatization and liquid chromatography.

A simple and sensitive liquid chromatography is described for the quantitative analysis of enantiomeric (+)-menthol and (-)-menthol that are lack of chromophore. The method is based on the derivatization of (+)-menthol and (-)-menthol with a fluorescent reagent, naproxen acyl chloride, in toluene. The resulting diastereomic derivatives were separated on a C8 column with methanol-water-tetrahydrofuran (80:18:2, v/v) as a mobile phase; they were sensitively monitored with a fluorimetric detector (excitation 235 nm and emission 350 nm). The linear range for the quantitation of the enantiomers was 5.0-50 microM with a detection limit (signal to noise ratio = 3, injected volume 10 microl) of about 1 microM. Application of the method to the enantiomeric analysis of menthol in mint plants proved simple and feasible. Toluene was used for the extraction of menthol from the leaves of mint, and the resulting toluene extract was directly used for subsequent derivatization without solvent replacement.

Chromatography, High Pressure Liquid↗

PubMed2005

Capillary zone electrophoresis for simultaneous determination of seven nonsteroidal anti-inflammatory drugs in pharmaceuticals.

A simple capillary zone electrophoresis (CZE) method has been developed for analyzing seven nonsteroidal anti-inflammatory drugs (NSAIDs)-sulindac (SU), ketoprofen (KE), indomethacin (IN), piroxicam (PI), nimesulide (NI), ibuprofen (IB), and naproxen (NA). The separation was run using borate buffer (60 mmol L(-1), pH 8.5) containing 13% (v/v) methanol at 20 kV, and detected at 200 nm. Several conditions were studied, including concentration and pH of borate buffer, methanol percentage, and separation voltage. In method validation, the calibration plots were linear over the range 40.0-500.0 micromol L(-1). In intra-day and inter-day analysis, relative standard deviations (RSD) and relative errors (RE) were all less than 5%. The limits of detection were 10 micromol L(-1) for SU, IN, PI, and 20 micromol L(-1) for KE, NI, IB, NA (S/N = 3, sampling 6 s by pressure). All recoveries were greater than 95%. This method was applied to the quality control of six NSAIDs in pharmaceuticals using NI as internal standard (IS). The assay results were within the labeled amount required by USP 25.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2005

An ionizable chromophoric reagent for the analysis of primary amine-containing drugs by capillary electrophoresis.

We found that ofloxacin acyl chloride is a potential chromophoric reagent for labeling amino analytes for capillary electrophoresis. Ofloxacin acyl chloride has a tertiary amino function in its structure and the derivatives from ofloxacin acyl chloride reacting with amino analytes can be ionized by an acid treatment and analyzed by simple capillary zone electrophoresis. Ofloxacin acyl chloride was used to derivatize model analytes (without chromophore) of amantadine (amino drug), tranexamic acid (non-protein amino carboxylic acid), glycine, and methionine (protein amino acids). The resulting derivatives were analyzed by capillary zone electrophoresis with ultraviolet detection (300 nm). The detection limits of the analytes studied were in the range of 1.0-2.5 microM (S/N = 3, injection 3 s). The precision (relative standard deviation) and accuracy (relative error) of the method for intra- and inter-day analyses of the analytes were respectively below 4.5% and 3.9%. Application of the method to the analysis of tranexamic acid in plasma proved feasible.

Amantadine↗

PubMed2005

Determination of mercaptopurine and its four metabolites by large-volume sample stacking with polarity switching in capillary electrophoresis.

This study describes approaches for stacking a large volume of sample solutions containing a mixture of mercaptopurine monohydrate, 6-methylmercaptopurine, thioguanine, thioguanosine, and thioxanthine in capillary electrophoresis (CE). After filling the run buffer (60 mM borate buffer, pH 8.5), a large sample volume was loaded by hydrodynamic injection (2.5 psi, 99.9 s), followed by the removal of the large plug of sample matrix from the capillary using polarity switching (-15 kV). Monitoring the current and reversing the polarity when 95% of current recovered, the separation of anionic analytes was performed in a run buffer < 20 kV. Around 44- to 90-fold improvement of sensitivity for five analytes was achieved by large-volume stacking with polarity switching when compared with CE without stacking. This method was feasible for determination of the analytes spiked in plasma. Removing most of electrolytes from plasma is a key step for performing large-volume sample stacking. Solid-phase extraction was used for pretreatment of biological samples. To our knowledge, this study is one of few applications showing the possibilities of this stacking procedure to analyze biological samples by large-volume sample stacking with polarity switching (LVSSPS) in CE.

Electrophoresis, Capillary↗

PubMed2005

Micellar electrokinetic chromatography for simultaneous determination of six corticosteroids in commercial pharmaceuticals.

We have developed a micellar electrokinetic chromatography (MEKC) method using bile salts for the simultaneous determination of six corticosteroids, including betamethasone, cortisone, prednisolone, 6alpha-methylprednisolone, triamcinolone, and prednisone. The separation was performed using borate buffer containing sodium cholate and sodium deoxycholate. Several parameters were studied, including bile salt concentrations, concentrations and pH of borate buffer, and analytical voltages. In method validation, calibration curves were linear over a range of 10-100 microM for each corticosteroid. The RSD (relative standard deviation) and RE (relative error) were all less than 5% for intra- and interday assays. The limit of detection of each analyte was 5 microM. The recoveries were greater than 95%. Application of this method for quality control of commercial tablets also proved to be feasible. All analytical values fall within the labeled amount of 90-110% for betamethasone and prednisolone, and of the labeled amount of 92.5-107.5% for 6alpha-methylprednisolone, as required by the United State Pharmacopeia 25 (USP 25).

Adrenal Cortex Hormones↗

PubMed2004

Simple and sensitive fluorimetric liquid chromatography method for the determination of valproic acid in plasma.

A simple and sensitive liquid chromatographic method is described for the analysis of valproic acid in human plasma. The method is based on the derivatization of valproic acid extracted from acidified plasma with 2-(2-naphthoxy)ethyl 2-(piperidino)ethanesulfonate. The resulting derivative is highly responsive to a fluorimetric detector (excitation at 230 nm and emission at 350 nm), giving a low detection limit of 0.6 microM (S/N = 3, 10 microl injected). The relative standard deviations of the method for intra- and inter-day analyses (n = 5) are below 3.3 and 4.1%, respectively. Toluene was used for the extraction of valproic acid from plasma and the toluene extract obtained was subjected to subsequent derivatization without solvent replacement. The simple method was applied to the analysis of valproic acid in plasma of dosed patients using only small amount of sample (10-50 microl plasma).

Adult↗

PubMed2004

Field-amplified sample stacking in capillary electrophoresis for the determination of clozapine, clozapine N-oxide, and desmethylclozapine in schizophrenics' plasma.

A method of field-amplified sample stacking in capillary electrophoresis is described for the simultaneous determination of clozapine (CZP) and its metabolites, clozapine N-oxide (CNO), and desmethylclozapine (DMC), in human plasma. Plasma (0.2 mL) was extracted with organic solvents (ethyl acetate/n-hexane/isopropyl alcohol, 8/1/1 by volume) and centrifuged. An aliquot of supernatant was evaporated and suitably reconstituted with water for CE analysis. An untreated fused-silica capillary was used (31.2 cm; effective length, 20 cm; 50 microm i.d.) for the analysis. The background buffer was phosphate buffer (400 mM, pH 3.0) containing 50% ethylene glycol. The separation voltage was 25 kV with a detection wavelength of 214 nm. In the method validation, the calibration curves were linear (r > or = 0.98) over a range of 50-800 ng/mL for CZP, 30-180 ng/mL for CNO, and 25-600 ng/mL for DMC. The relative standard deviation (R.S.D.) and relative error (R.E.) were all less than 11% for the intra- and inter-day assays. The limits of detection (S/N = 3, electric-driven injection, 99.9s) of CZP, DMC, and CNO were 5, 5, and 10 ng/mL, respectively. After continuing treatment with the CZP tablets, a blood sample from one male schizophrenic patient (41-year-old, 62 kg) who had been receiving ongoing treatment with the CZP tablets was prepared and analyzed. The levels of CZP, DMC, and CNO were determined and the feasibility of the method's application in clinical treatment was proven.

Clozapine↗

PubMed2003

Simultaneous determination of methotrexate and its eight metabolites in human whole blood by capillary zone electrophoresis.

A simple and selective capillary electrophoretic method was established for the simultaneous determination of methotrexate (MTX), 7-hydroxymethotrexate (7-OHMTX), 2,4-diamino-N10-methylpteroic acid (DAMPA), and polyglutamate derivatives [MTX-(Glu)n, n=2-7] in whole blood. After extraction, those analytes were separated by fused-silica capillary and a running buffer containing glycine (1.2 M, pH 9.3). The quantitative ranges were 10-50 microM for each analyte. The intra- and inter-day RSD and RE values were all less than 6 and 11%, respectively. The limits of detection (S/N= 3, injection 5 s) were found to be 1 microM for MTX, 7-OHMTX, MTX-(Glu)2, MTX-(Glu)3, and MTX-(Glu)4; 3 microM for MTX-(Glu)5 and MTX-(Glu)6; 5 microM for MTX-(Glu)7, and 8 microM for DAMPA. All recoveries were greater than 94%. This method was applied to blood MTX monitoring in a patient with acute lymphoblastic leukemia.

Antimetabolites, Antineoplastic↗

PubMed2002

Simple and sensitive analysis of long-chain free fatty acids in milk by fluorogenic derivatization and high-performance liquid chromatography.

A highly sensitive high-performance liquid chromatography (HPLC) method is described for the simultaneous determination of some important saturated and unsaturated fatty acids in milk, including lauric (dodecanoic), myristic (tetradecanoic), palmitic (hexadecanoic), stearic (octadecanoic), palmitoleic (hexadecenoic), oleic (octadecenoic), and linoleic acids (octadecadienoic acids). The fatty acids were fluorogenically derivatized with 2-(2-naphthoxy)ethyl 2-(piperidino)ethanesulfonate (NOEPES) as their naphthoxyethyl derivatives. The resulting derivatives were separated by isocratic HPLC and monitored with a fluorometric detector (lambdaex = 235 nm, lambdaem = 350 nm). The fatty acids in milk were extracted with toluene, and the extract with the fatty acids was directly derivatized with NOEPES without solvent replacement. Determination of long-chain free fatty acids in milk is feasible by a standard addition method. A small amount of milk product, 10 microL, is sufficient for the analysis.

Animals↗