Biomedical subjects

Shang-Da Huang

Publications and source records attributed to Shang-Da Huang.

9 recordsLinked to original sources

PubMed2006

Dynamic hollow fiber protected liquid phase microextraction and quantification using gas chromatography combined with electron capture detection of organochlorine pesticides in green tea leaves and ready-to-drink tea.

The dynamic hollow fiber protected liquid phase microextraction (DHFP-LPME) technique was evaluated for the extraction of organochlorine pesticides (OCPs) in green tea leaves and ready-to-drink tea prior to gas chromatography combined-electron capture detection (GC-ECD) analysis. A conventional microsyringe with a 1.5 cm length of hollow fiber attached to its needle was connected to a syringe pump to perform the extraction. The microsyringe was used as both the microextraction device and the sample introduction device for GC-ECD analysis. In this work, the organochlorine pesticides were extracted and condensed to a volume of 3 microl of organic extracting solvent (1-octanol) confined within a 1.5 cm length of hollow fiber. The effects of extraction solvent, extraction time, sample agitation, plunger speed, and extraction temperature and salt concentration content on the extraction performance were also investigated. Good enrichments were achieved (34-297-fold) with this method, and good repeatabilities of extraction were obtained, with full name (RSDs) below 12.57%. Detection limits were much below 1 microg l(-1) for ready-to-drink tea and much below 1 microg g(-1) for green tea leaves.

1-Octanol↗

PubMed2006

Coupled two-step microextraction devices with derivatizations to identify hydroxycarbonyls in rain samples by gas chromatography-mass spectrometry.

Coupling a two-step liquid-phase microextraction (LPME) with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine/bis(trimethylsilyl)trifluoroacetamide (PFBHA)/(BSTFA) derivatization was developed to detect hydroxycarbonyls in rainwater samples using gas chromatography-mass spectrometry (GC-MS). LPME provides a fast and inexpensive pre-concentration, and miniaturized extraction to analyze the target compounds rainwater samples. Derivatization techniques offer a clear method to identify target compounds. The hydroxycarbonyls were determined using two-step derivatizations. Dynamic-LPME was applied in the first derivatization, and head-space single drop derivatization was employed in the second reaction. The LODs varied from 0.023 to 4.75 microg/l. The calibration curves were linear for at least two orders of magnitude with R2>or=0.994. The precision was within 6.5-12%, and the relative recoveries in rainwater were more than 89% (the amount added ranged from 0.3 to 15 microg/l). A field sample was found to contain 2.54 microg/l of hydroxyacetone and 0.110 microg/l of 3-hydroxy-2-butanone. Hydroxyacetone was also detected in one of the tested samples at a concentration of 2.39 microg/l.

Calibration↗

PubMed2006

Extraction of hydroxyaromatic compounds in river water by liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase.

Liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase technique is described for the extraction of six hydroxyaromatic compounds in river water using a disposable and ready to use hollow fiber. Separation and quantitative analyses were performed using LC with UV detection at 254 nm. Analytes were extracted from the acidified sample solution (donor phase) into the organic solvent impregnated in the pores of the hollow fiber and then back extracted into the alkaline solution (acceptor phase) inside the lumen of the hollow fiber. The fiber was held by a conventional 10 microL LC syringe. The acceptor phase was sandwitched between the plunger and a small volume of the organic solvent (microcap). The acceptor solution was repeatedly moved in and out of the hollow fiber using a syringe pump. This movement provides a fresh acceptor phase to come in contact with the organic phase and thus enhancing extraction kinetics thereby leading to the improvement in enrichment of the analytes. The microcap separates the acceptor phase and the donor phase in addition to being partially responsible for mass transfer of the analytes from the donor solution to the acceptor solution. Under stirring, a fresh donor phase will enter through the open end of the fiber that will also contribute to the mass transfer. Various parameters affecting the extraction efficiency viz type of organic solvent, extraction time, stirring speed, effect of sodium chloride, and concentration of donor and acceptor phases were studied. RSD (3.9-5.6%), correlation coefficient (0.995-0.997), detection limit (2.0-51.2 ng/mL), enrichment factor (339-630), relative recovery (93.2-97.9%), and absolute recovery (33.9-63.0%) have also been investigated. The developed method was applied for the analysis of river water.

Automation↗

PubMed2006

Analysis of organochlorine pesticides in wine by solvent bar microextraction coupled with gas chromatography with tandem mass spectrometry detection.

A solvent bar microextraction (SBME) technique combined with gas chromatography/tandem mass spectrometry (GC/MS/MS), for the determination of selected organochlorine pesticides (OCPs) in wine samples, is described. In this work the OCPs were extracted and dissolved in a 2-microL aliquot of organic extraction solvent (n-tetradecane) confined within a 1.7-cm length of hollow fiber. Both ends of the hollow fiber (solvent bar) were sealed, and it was placed in an aqueous sample solution for extraction. The effects of solvent selection, sample agitation, extraction time, extraction temperature, and salt concentration on the SBME performance were optimized. The influence of aqueous sample/organic solvent phase ratio was further investigated in detail. High enrichments (1900-7100-fold) could be obtained at an aqueous sample/organic solvent volume ratio of 20 mL/2 microL in this study. Good extraction reproducibility was obtained with relative standard deviation (RSD) values below 12.6%. Comparisons of sensitivity and precision between SBME and dynamic hollow-fiber liquid-phase microextraction were also investigated.

Chemical Fractionation↗

PubMed2005

Liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase for the extraction of phenoxyacetic acids prior to liquid chromatography detection.

A simple liquid-liquid-liquid microextraction with automated movement of the acceptor and the donor phase (LLLME/AMADP) technique is described for the quantitative determination of five phenoxyacetic acids in water using a disposable and ready to use hollow fiber. The target compounds were extracted from the acidified sample solution (donor phase) into the organic solvent residing in the pores of the hollow fiber and then back extracted into the alkaline solution (acceptor phase) inside the lumen of the hollow fiber. The fiber was held by a conventional 10-microl syringe. The acceptor phase was sandwiched between the plunger and a small volume of the organic solvent (microcap). The acceptor solution was repeatedly moved in and out of the hollow fiber assisted by a programmable syringe pump. This repeated movement provides a fresh acceptor phase to come in-contact with the organic phase and thus enhancing extraction kinetics leading to high enrichment of the analytes. The microcap separates the aqueous acceptor phase and the donor phase in addition of being partially responsible for mass transfer of the analytes from donor solution (moving in and out of the hollow fiber from the open end of the fiber) to the acceptor solution. Separation and quantitative analyses were then performed using liquid chromatography (LC) with ultraviolet (UV) detection at 280 nm. Various parameters affecting the extraction efficiency viz. type of organic solvent used for immobilization in the pores of the hollow fiber, extraction time, stirring speed, effect of sodium chloride, and concentration of donor and acceptor phases were studied. Repeatability (RSD, 3.2-7.4%), correlation coefficient (0.996-0.999), detection limit (0.2-2.8 ng ml(-1)) and enrichment factors (129-240) were also investigated. Relative recovery (87-101%) and absolute recoveries (4.6-13%) have also been calculated. The developed method was applied for the analysis of river water.

Acetates↗

PubMed2005

Simultaneous derivatization and extraction of primary amines in river water with dynamic hollow fiber liquid-phase microextraction followed by gas chromatography-mass spectrometric detection.

A one-step derivatization and extraction technique for the determination of primary amines in river water by liquid-phase microextraction (LPME) is presented. In this method the primary amines are derivatized with pentafluorobenzaldehyde (PFBAY) in aqueous solution and extracted by dynamic hollow fiber-protected-LPME (HF-LPME) simultaneously. The effects of solvent selection, sample agitation, extraction time, extraction temperature and salt concentration on the extraction performance are investigated. High enrichments (172-244-fold) and good repeatabilities (RSD less than 7.2%) were obtained. Linearity in this developed method was ranging from 1 to 500 ng/ml, and the correlation coefficients (R2) were between 0.992 and 0.998. Comparisons of sensitivity and precision between dynamic HF-LPME and single-drop liquid-phase microextraction (SDME) were also made.

Amines↗

PubMed2005

Quantitative detection of ketamine, norketamine, and dehydronorketamine in urine using chemical derivatization followed by gas chromatography-mass spectrometry.

A repeatable and highly sensitive analytical method using gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring mode (SIM) is developed for the simultaneous detection of ketamine (KT), norketamine (NK), and newly introduced dehydronorketamine (DHNK) in urine. The test specimen along with the deuterium analogues as internal standards (IS): d4-KT for KT and d4-NK for NK/DHNK, was extracted on an automatic solid-phase extraction (SPE) apparatus. The extracted eluate then was dried and derivatized with N-methyl-bis(trifluoroacetamide) (CF3CONCH3COCF3, MBTFA). Finally, the cooled derivatized solution was directly injected into the GC-MS system for analysis. The proposed process achieves high sensitivity for the detection of KT, NK, and DHNK. Correlation coefficients derived from typical calibration curves in the range of 20-2000 ng/mL are 1.000 for KT and NK, 0.999 for DHNK. The limits of detection (LODs) and limits of quantitation (LOQs) are 0.5-1.0 and 1.5-3.0, respectively. The overall method recoveries of KT, NK, and DHNK are 82.2-93.4. The intra- and inter-day run deviations are smaller than 5.0%. The analytical scheme was also applied to the determination of KT, NK, and DHNK in 20 KT suspected urine specimens, and the results reconfirm that DHNK is a main metabolite of KT.

Anesthetics, Dissociative↗

PubMed2003

Solid-phase microextraction coupled with high-performance liquid chromatography for the determination of phenylurea herbicides in aqueous samples.

Solid-phase microextraction coupled with high-performance liquid chromatography was successfully applied to the analysis of nine phenylurea herbicides (metoxuron, monuron, chlorotoluron, isoproturon, monolinuron, metobromuron, buturon, linuron, and chlorbromuron). Polydimethylsiloxane-divinylbenzene (PDMS-DVB, 60 microm) and Carbowax-templated resin (CW-TPR, 50 microm) fibers were selected from four commercial fibers for further study because of their better extraction efficiencies. The parameters of the desorption procedure were studied and optimized. The effects of the properties of analytes and fiber coatings, carryover, duration and temperature of absorption, pH, organic solvent and ionic strength of samples were also investigated. External calibration with an aqueous standard can be used for the analysis of environmental samples (lake water) using either PDMS-DVB or CW-TPR fibers. Good precisions (1.0-5.9%) are achieved for this method, and the detection limits are at the level of 0.5-5.1 ng/ml.

Calibration↗

PubMed2002

One step and highly sensitive headspace solid-phase microextraction sample preparation approach for the analysis of methamphetamine and amphetamine in human urine.

A fiber-stable, repeatable and highly sensitive headspace solid-phase microextraction (HS-SPME) method was developed for the analysis of methamphetamine (MA) and amphetamine (AM) in urine using gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring mode. For sample preparation, the test specimen was placed in a 7 ml vial along with the additives (KOH and NaCl) and the internal standards (d8-MA and d8-AM), a glass insert containing heptafluorobutyric anhydride (HFBA) and heptafluorobutyric chloride (HFBCl) as derivatizing reagents was inserted into the vial, the vial was then sealed tightly. A SPME device with a 100 microm polydimethylsiloxane fiber was inserted into the vial and the fiber was exposed to the headspace in the insert, then the vial was heated and stirred at 100 degrees C and 600 rpm for 20 min for evaporation/adsorption/derivatization. The vaporized analytes (AM and MA) in the vial diffused into the glass insert though the holes on the insert, they absorbed onto the fiber, and then interacted with the vapor of the derivatizing reagent. Some of the analytes in the headspace of the glass insert may react with the vapor of the derivatizing reagent first, and then adsorb onto the fiber. The needle was finally removed and inserted into the injection port to desorb the analytes with the fiber exposed to the liner of the GC-MS system for analysis. By combining HFBCl and HFBA as derivatizing reagents and placing them in an insert, the HS-SPME method achieves high sensitivity for the analysis of AM and MA. Correlation coefficients derived from typical calibration curves in the 1.0-1700 ng ml(-1) range are 0.998 for MA and 0.994 for AM. The limits of detection and the limits of quantitation using a sample size of 1 ml are 0.3 and 1.0 ng ml(-1), respectively, for both MA and AM in urine specimens. Because the water hydrolysis of derivatizing reagent is much faster than the acylation reaction of the primary and secondary amines with the derivatizing reagent, the amphetamines cannot be acylated effectively over heated aqueous solution, and therefore this study provides a new acylation design in moisture surroundings. The proposed process also simplifies the procedure for urine sample preparation, and makes the automation of SPME possible.

Amphetamine↗