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Results 401 - 450 of 1645
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Ranz A - - 2006
In the present study, a derivatization method for the determination of acidic herbicides has been investigated. This procedure involves the methylation with the quaternary ammonium salt trimethylanilinium hydroxide (TMAH) directly in the gas chromatographic auto-sampler vial for analysis by gas chromatography combined with mass spectrometry. The derivatization reaction has been ...
Li Baozhi - - 2006
A new method has been established to convert triptolide (1) into tripchlorolide (2) directly in the Chinese herbal drug Tripterygium wilfordii Hook F. and the influences of reaction times and pH values have been investigated. It was found that 1 could be most efficiently converted into 2 using a hydrochloric ...
Li Qing - - 2006
A high performance liquid chromatography (HPLC) method was developed for the first time to quantify simultaneously the six major active ingredients in Acanthopanax senticosus (Rupr. et Maxim.) Harms, namely protocatechuic acid, syringin, chlorogenic acid, caffeic acid, liriodendrin and isofraxidin. The analysis was performed by a reverse phase gradient elution with ...
Uematsu Yoko - - 2006
A simple method for the determination of magnesium stearate in capsule- or tablet-type supplements was developed. Free stearic acid in the sample was removed by extraction with tetrahydrofuran. The remaining stearate was converted to stearic acid by reaction with a cation-exchange resin. The resulting stearic acid was determined by gas ...
Fiamegos Yiannis C - - 2006
The gas chromatographic determination of amino acids via their simultaneous extraction, preconcentration and pentafluorobenzylation is reported. Using phase-transfer catalysis (PTC), the amino acids under study were transformed to their pentafluorobenzyl adducts. The method was tested for different catalysts and tetrabutylammonium bromide provided favorable features in comparison to the other PTCs. ...
Zhou Limin - - 2006
The current study intends to provide an improved quality control analysis for Danshen product-a representative herbal product with known active components that are both hydrophilic and lipophilic in nature. A simple HPLC method with photodiode-array (PDA) ultraviolet detection was developed for the simultaneous determination of three major lipophilic components (cryptotanshinone, ...
Himanen Marina - - 2006
Concentration of low-weight carboxylic acids (LWCA) is one of the important parameters that should be taken into consideration when compost is applied as soil improver for plant cultivation, because high amounts of LWCA can be toxic to plants. The present work describes a method for analysis of LWCA in compost ...
McDonald Gene D - - 2006
The relative abundance of the protein amino acids has been previously investigated as a potential marker for biogenicity in meteoritic samples. However, these investigations were executed without a quantitative metric to evaluate distribution variations, and they did not account for the possibility of interdisciplinary systematic error arising from inter-laboratory differences ...
Sakurai Hiroki - - 2006
A rapid sample-digestion method for the determination of toxic metals, cadmium, chromium, and lead, in polyethylene and polyvinyl chloride has been developed by using a microwave oven for household use. An appropriate amount of the sample taken in a PTFE decomposition vessel was mixed with nitric acid or nitric and ...
Moliner-Martínez Y - - 2006
This work has evaluated the influence of humic acid and/or surfactants in the quantification of ammonium in waters with the indophenol-type reaction method. Thymol has been employed with the colorimetric method for sample ammonium concentrations between 0.25 and 1mgL(-1). In addition, SPE/diffuse reflectance method has been used for quantification of ...
Goodwin Michael B - - 2006
Quantitative analysis of cellular small molecule organic acids of intermediary metabolism can provide critical insight into bacterial metabolic pathways. The concentration of these metabolites in culture supernatant varies at different growth stages or under particular environmental conditions reflecting both the energy and the biosynthetic needs, yielding metabolic information about the ...
Hou Rui-Zhen - - 2006
A new route was employed to synthesize RGD. First, Gly-Asp dipeptide was synthesized by a novel chemical method in two steps, including chloroacetylation of L-aspartic acid and ammonolysis of chloroacetyl L-aspartic acid. Second, Nalpha-Z- L-Arginine was reacted with Gly-Asp to synthesize RGD by the N-carboxyanhydride method. Less protected amino acids ...
Jakmunee Jaroon - - 2006
A simple sequential injection analysis (SIA) with spectrophotometric detection for an assay of acidity in fruit juice was investigated. An alkaline reagent (sodium hydroxide), a sample and an indicator (phenolphthalein) were first aspirated and stacked as adjacent zones in a holding coil. With flow reversal through a reaction coil to ...
Herrler Andreas - - 2006
OBJECTIVE: To develop a method of freezing small amounts of spermatozoa in polymerized alginic acid drops, which can be liquified after thawing for recovery of the spermatozoa. DESIGN: Prospective clinical study. SETTING: Medical School, RWTH Aachen, Aachen Germany. PATIENT(S): None. INTERVENTION(S): Validation of the encapsulation method with bovine sperm; cryopreservation ...
Ng Chuen-How - - 2006
Functional properties of the amino polysaccharides, chitin and chitosan, vary significantly with their acetyl content. The acid hydrolysis-HPLC method offers good accuracy and precision to assay the acetyl content regardless of the solubility of the sample. In this research, the hydrolysis parameters were changed, and the analytical method was counterchecked ...
Janssen Hans-Gerd - - 2006
The use of lipase D (Rhizopus delemar) immobilised on microporous polypropylene as a replacement for the standard pancreatic lipases used in the stereospecific sn-2 position analysis of triacylglycerols from edible oils and fats is studied. Excellent hydrolysis characteristics are obtained in hexane/methanol solvents at reaction temperatures up to 60 degrees ...
Zhai Qing-Zhou - - 2006
A new catalytic kinetic spectrophotometric method was proposed for determining trace oxalic acid based on the catalytic effect of oxalate on the oxidation of potassium dichromate with rhodamin B in 0.10 M of sulfuric acid. Good linearity is obtained over the concentration range 0.40-6.0 microg/mL of oxalic acid. After the ...
Liu Ai-Hua - - 2006
A high-performance liquid chromatographic method was applied to the determination of danshensu, protocatechuic aldehyde, rosmarinic acid, lithospermic acid, salvianolic acid B and salvianolic acid A in the roots of Salvia miltiorrhiza and four related traditional Chinese medicinal preparations. The six phenolic acids were simultaneously analyzed with a Zorbax Extend C18 ...
Li Xiu-Qin - - 2005
Fatty acid of the root of the medicinal plant of Bupleurum Chinense DC in China has been investigated by gas chromatography combined with mass spectroscopy. After methyl-esterification, eight fatty acid compositions were identified by GC-MS. A simple and rapid determination of the fatty acid has been firstly developed by GC-FID. ...
Mondal Jayanta K - - 2005
The present paper describes the application of a solid phase extraction system in order to separate traces of calcium from glass and ceramics for its spectrophotometric determination. The method is based on the extraction of calcium from sodium hydroxide solution by tri-n-butyl phosphate (TBP) loaded polyurethane foam (PUF), followed by ...
Wadsak Wolfgang - - 2006
Nucleophilic aromatic substitution is a challenging task in radiochemistry. Therefore, a thorough evaluation and optimisation of this step is needed to provide a satisfactory tool for the routine preparation of [(18)F]fluorinated aromatic amino acids. Two methods, already proposed elsewhere, were evaluated and improved. The yields for the radiofluorination were increased ...
Cech Nadja B - - 2006
Extracts of the plant Echinacea purpurea are widely used for medicinal purposes. Effective quality control of these extracts requires rapid methods to determine their chemical composition. A new method for analysis of caffeic acid derivatives and alkamides from Echinacea extracts has been developed. With this method, isomeric isobutylamides and 2-methylbutylamides ...
Thurnhofer Saskia - - 2005
A method using gas chromatography/electron ionization-mass spectrometry (GC/EI-MS) in the selected ion monitoring (SIM) mode was developed for the analysis of fatty acids as methyl esters (FAMEs) in order to determine their percentage contribution to the fatty acid profile in food. In the GC/EI-MS-SIM mode, saturated fatty acids were determined ...
Han Suqin - - 2005
A capillary electrophoresis with chemiluminescence method has been developed for the determination of rutin and chlorogenic acid based on its enhancing effect on the luminol-ferricyanide system. Under the optimum conditions, the analytes could be separated within 5 min, and the detection limits of the proposed method were 0.22 microg/ml for ...
W?jciak-Kosior Magdalena - - 2005
HPTLC combined with densitometric method was used to determine the content of oleanolic acid in acetone extract from the Lamii albi flos L. The plant extract was separated on Si 60 HPTLC plates and determined with the use of two densitometric methods: measurement of fluorescence and absorbance. The content of ...
Yan Shikai - - 2006
High-performance liquid chromatography coupled with photo diode array detection and evaporative light scattering detection (HPLC/DAD/ELSD) was established to simultaneously determine nine ingredients in Qingkailing injection. Four wavelengths at 240, 254, 280 and 330 nm, respectively, were chosen as the monitoring wavelength to determine two nucleosides (uridine and adenosine), geniposide, baicalin ...
Ghorbani R - - 2006
A simultaneous conductometric titration method for determination of mixtures of acetic acid, monochloroacetic acid and trichloroacetic acid based on the multivariate calibration partial least squares is proposed. It is possible to obtain an adjustable model to relate squared concentration values of the mixtures used in the calibration range by conductance. ...
Cristiano D V - - 2005
A comparative study on acid and hydrothermal methods as ways to reduce interlamellar charge has been carried out on a vermiculite. This study showed that the application of the hydrothermal treatment as a previous step to pillaring the vermiculites, reported here for the first time, is a new route to ...
Shishehbore Masoud Reza - - 2005
This study reports a sensitive kinetic spectrophotometric method for the determination of trace amounts of thiocyanate. In acidic solution, Methylene Blue (MB) is oxidized by bromate to form a colorless compound. The reaction is accelerated by trace amounts of thiocyanate and can be followed by measuring the absorbance at 664 ...
Rozman Marko - - 2005
The most stable charge-solvated (CS) and zwitterionic (ZW) structures of sodiated and cesiated leucine and isoleucine were studied by density functional theory methods. According to the Boltzmann distribution in gas phase, both forms of LeuNa+ and IleNa+ exist, but in LeuCs+ and IleCs+, the ZW forms are dominant. Results for ...
Chen Sheng-Pei - - 2005
Based on ion chromatography (IC) technology, we have developed a new method that combines ion chromatography with a conductivity detector to separate and determine the substances of glyoxal, glycolic acid, oxalic acid and glyoxylic acid. The ion chromatography was applied for the first time in quantitative determination of substances involved ...
Isar Jasmine - - 2006
The most influential parameters for succinic acid production obtained through one at a time method were sucrose, tryptone, magnesium carbonate, inoculum size and incubation period. These resulted in the production of 7.0 g L(-1) of succinic acid in 60 h from Escherichia coli W3110 under anaerobic conditions. Based on these ...
Reychler G - - 2005
INTRODUCTION: Home-nebulizers are a potential source of bacterial infection of the respiratory tract in patients suffering from cystic fibrosis. Recommendations for disinfecting this equipment are often arbitrary and sometimes contradictory. OBJECTIVE: To assess in vitro the effectiveness of 5 methods of disinfecting this equipment. METHODS: 160 mouthpieces and 160 masks ...
Lukasewycz Marta T - - 2005
Accurate measurement of organic carbon (OC) and black carbon (BC) in sediments requires the complete removal of coexisting inorganic carbonates from the sample before instrumental analysis. The removal of carbonates from sediments is achieved with acidification, which causes the dissolution and decomposition of carbonates with accompanying effervescence. This effervescence, or ...
Ansari Tariq Mahmood - - 2005
In this study, a simple, fast, accurate and sensitive spectrophotometric method has been developed for the determination of tranexamic acid in bulk and pharmaceutical preparations. The method is based on the reaction of ninhydrin with the primary amino group of tranexamic acid in the basic medium at pH 8.0. The ...
Larsen Erik - - 2005
A simple, reliable, and gentle saponification method for the quantitative determination of carotenoids in green vegetables was developed. The method involves an extraction procedure with acetone and the selective removal of the chlorophylls and esterified fatty acids from the organic phase using a strongly basic resin (Ambersep 900 OH). Extracts ...
Song H-K - - 2006
This paper describes a method for preparing substrates with micropatterns of positive guidance cues for the purpose of stimulating the growth of neurons. This method uses an oxidizing potential, applied to a micropattern of indium tin oxide in the presence of pyrrole and polyglutamic acid, to electrodeposit a matrix consisting ...
Dutra Elizângela Abreu - - 2006
In this work, a simple and reliable method for the simultaneous analysis of alpha-hydroxy acids such as tartaric, glycolic and lactic acids in cosmetic products was developed using capillary electrophoresis with indirect UV detection at 254 nm. A buffer solution containing 10 mmoll(-1) potassium phthalate (pH 4.1) and 0.5 mmoll(-1) ...
Taniyasu Sachi - - 2005
Fluorotelomer alcohols and fluorotelomer acids have been proposed as a source of the perfluorinated carboxylic acids found in remote marine locations. To examine the sources and fate of perfluorinated acids in the environment, a method to determine a wide range of poly- and perfluorinated acids in environmental and biological matrices ...
Dabek-Zlotorzynska Ewa - - 2005
Urban fine airborne particulate matter (PM2.5) and vehicle emission samples were studied for water-soluble low-molecular-weight carboxylic acids using CE with indirect UV detection. Further identification of these acids was achieved using GC-MS as their butyl esters (after derivatization with BF3/butanol). Several dicarboxylic acids in the range C2-C10 including straight-chain, branched-chain, ...
Li Li Na - - 2005
A simple, sensitive and rapid flow-injection chemiluminescence method has been developed for the determination of ferulic acid based on the chemiluminescence reaction of ferulic acid with potassium permanganate in a nitric acid medium. A strong chemiluminescence signal was observed when ferulic acid was injected into an acidic potassium permanganate solution ...
Masood Athar - - 2005
Conventional sample preparation for fatty acid analysis is a complicated, multiple-step process, and gas chromatography (GC) analysis alone can require >1 h per sample to resolve fatty acid methyl esters (FAMEs). Fast GC analysis was adapted to human plasma FAME analysis using a modified polyethylene glycol column with smaller internal ...
Thompson Crista - - 2005
Biological materials can release amino acids during the course of bacterial mutation testing. Low levels of released amino acids from soluble materials can cause moderate increases in the number of revertant colonies on the plate, whereas higher levels lead to overgrowth of the background lawn, making counting of revertant colonies ...
Gerencsér János - - 2005
We describe here an efficient and versatile method for the preparation of 3-imidazo[1,2-a]pyridin-3-yl-propionic acids involving, as a key step, a three-component Michael-type reaction. The extended and validated procedure allowed us to prepare various acids with three diversity points. The method was easily adaptable for parallel synthesis and an approximately 2000-membered ...
Carvalho Ana P - - 2005
Assays for fatty acid composition in biological materials are commonly carried out by gas chromatography, after conversion of the lipid material into the corresponding methyl esters (FAME) via suitable derivatization reactions. Quantitative derivatization depends on the type of catalyst and processing conditions employed, as well as the solubility of said ...
Zhao Yan - - 2005
We compare the performance of four recently developed DFT methods (MPW1B95, MPWB1K, PW6B95, and PWB6K) and two previous, generally successful DFT methods (B3LYP and B97-1) for the calculation of stacking interactions in six nucleic acid bases complexes and five amino acid pairs and for the calculation of hydrogen bonding interactions ...
Kaiser Mary A - - 2005
Perfluorooctanoic acid is a completely fluorinated carboxylic acid that is usually used in the ammonium salt form as a processing aid in the production of many fluoropolymers and fluoroelastomers. Ammonium perfluorooctanoate readily dissociates in water to give the ammonium and perfluorooctanoate ions. Perfluorooctanoate has been reported to be present in ...
Noroozifar Meissam - - 2005
A new and simple flow injection method followed by atomic absorption spectrometry has been developed for the indirect determination of ascorbic acid. The proposed method is based on oxidation of ascorbic acid to dehydroascorbic acid using a solid-phase manganese dioxide (30% m/m suspended on silica gel beads) reactor. The flow ...
Murado Miguel Anxo - - 2005
The most common method in the routine determination of uronic acids, the m-hydroxydiphenyl reaction, recently adapted to rapid microplate analysis, has as a main inconvenience, in any one of their modalities, interferences due to the frequent presence of proteins and neutral carbohydrates in the samples. Corresponding corrections in the literature ...
Attin T - - 2005
The study describes the suitability of a colorimetric method (malachite green procedure) for detection of minimal amounts of phosphate (7.3-29.1 micromol/L) in different acidic solutions (hydrochloric acid, oxalic acid, maleic acid, perchloric acid, tartaric acid, citric acid, lactic acid and acetic acid) adjusted to pH 2.0. A mixture of the ...
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