Search results for "Column chromatography"

Practical Syntheses of Terrylene Chromophores from Naphthalene and Perylene Building Blocks

2017

A facile and efficient method to synthesize terrylene imides, a unique class of chromophores, and their derivatives from commercially available naphthalene and perylene building blocks is reported. We developed an extremely efficient Suzuki/C-H-arylation coupling cascade with Pd2(dba)3/PCy3 (dba = dibenzylidenacetone, Cy = cyclohexyl) as the catalyst and highly soluble naphthalene derivatives as starting materials. This efficiency allows purification via precipitation and crystallization, avoiding time-consuming column chromatography. For the first time, the highly soluble 3,4,11,12-terrylene tetraester was prepared in gram scale with yields up to 75 % which thus becomes a versatile startin…

Newest Strategies in the Search for Bioactive Saponins from the Tropical Plant Biodiversity.

2016

This review will focus on newest results leading to the discovery of new bioactive saponins by using a combination of successive advanced procedures in extraction, isolation, structure elucidation and bioassays. Microwave- and ultrasonic-assisted extractions, two recent advanced methods have been increasingly used in the last decade. Then, a multistep purification procedure was achieved by flash chromatography, vacuum liquid chromatography, low, medium- and high-pressure liquid chromatography on silica gel and reversed-phase silica gel RP-18 (VLC, LPLC, MPLC, HPLC). These successive chromatographic steps have been implemented in the author's laboratory in order to avoid the time-consuming t…

Cheese flavour : instrumental techniques

2004

This chapter discusses instrumental techniques to analyze cheese flavor. It focuses on recent advances made to study and identify the taste-active components present in the water-soluble fraction of cheese. A general procedure for the preparation of fractions involves an extraction of grated cheese by water followed by a fractionation scheme, generally adapted from the fractionation protocol used to isolate cheese nitrogen fractions in the study of proteolysis in cheese during ripening. However, as sub-fractions have to be evaluated sensorially to assess their relative sensory impact and try to link it to their chemical composition, a suitable eluent has to be used in the chromatographic st…

Evaluation of taste compounds in water-soluble extract of goat cheeses

2000

Abstract The water-soluble fractions of two goat cheeses — one denomination of origin commercial trade mark (crottin de Chavignol®) and one bought in a local cheese making establishment (Bouton de culotte®) — containing many taste and flavour molecules were studied. Ultrafiltration with a 1000 Da threshold membrane, followed by gel filtration on Toyopearl HW-40S gel using water as eluent, led to the production of edible fractions. Physicochemical and sensory analysis of these fractions showed that the most tasty fractions contained, essentially, the free amino acids and mineral salts. Some of these tasty fractions also imparted some flavours. The quantity of small peptides (MW

Isocratic high-performance liquid chromatographic determination of tryptophan in infant formulas.

1996

The application to infant formulas of a method for tryptophan determination by isocratic HPLC with UV detection at 254 nm, after derivatization with phenyl isothiocyanate, was studied. Protein was hydrolysed by barium hydroxide at 120 degrees C for 8 h, followed by derivatization with phenyl isothiocyanate, HPLC and UV detection at 254 nm. The optimum chromatographic conditions (pH, ionic strength of elution solvent and eluent ratio) were established. The analytical parameters (linearity, precision, accuracy of derivatization and limits of detection and quantification) were determined. The values obtained demonstrated that the method is useful for determining the tryptophan content of infan…

Zeolithe als Adsorbentien für die Trennung, Reinigung und Konzentrierung von organischen Wertprodukten in der präparativen Säulen-Flüssig-Chromatogra…

1995

Comparative column chromatographic estimations of phenylalanine in plasma, whole blood, native and paper-dried capillary blood of healthy children an…

1984

The concentration of phenylalanine in plasma, whole venous and capillary blood, and paper-dried blood of 75 probands (25 healthy adults, 27 healthy children, and 23 patients with hyperphenylalaninaemia) were measured by use of a sensitive short column chromatography method. The comparison of the values in each group of probands by several statistic methods showed an excellent correlation of the phenylalanine concentration in paper-dried whole blood to those measured in venous plasma. Evaluation of the analytical method revealed a high sensitivity and accuracy by use of a sample volume of 50 microliter. We would therefore suggest that the estimation of phenylalanine for the diagnosis and the…

Automated Determination of Fluvoxamine in Plasma by Column-Switching High-Performance Liquid Chromatography

1992

Abstract A column-switching system with high-performance liquid-chromatographic separation and ultraviolet detection is described for automated determination of fluvoxamine in human plasma or serum. Samples were injected and the drug was retained in a clean-up column [20 x 4.6 mm (i.d.)] filled with C8 reversed-phase material (10-micron particles). After unwanted material was washed out, the drug was eluted and separated with an analytical chromatography column, 4.6 x 250 mm (i.d.), filled with Nucleosil 100 CN (5-micron particles) with an acetonitrile:methanol:0.01 mol/L phosphate buffer eluent (188:578:235 by vol) at a flow rate of 1.5 mL/min for < 20 min and detected by spectromet…

Automated Determination of Ziprasidone by HPLC With Column Switching and Spectrophotometric Detection

2005

An isocratic high-performance liquid chromatography (HPLC) method with column switching and ultraviolet (UV) detection is described for quantitative analysis of the new antipsychotic drug ziprasidone. After centrifugation of serum or plasma samples and addition of fluperlapine as internal standard, the samples were injected into the HPLC system. On-line sample clean-up was conducted on a column (10 x 4.0 mm ID) filled with silica C8 material (20-microm particle size) using 8% (vol/vol) acetonitrile in deionized water as eluent. Ziprasidone was eluted and separated on ODS Hypersil C18 material (5 microm; column size 250 x 4.6 mm ID) using acetonitrile-water-tetramethylethylendiamine (50:49.6…

Determination of barbiturates in urine by micellar liquid chromatography and direct injection of sample.

2000

Abstract A liquid chromatographic procedure for the determination of six barbiturates (barbital, diallyl barbituric acid, phenobarbital, butabarbital, amobarbital and pentobarbital) in urine samples is described. The proposed system uses a Spherisorb octadecyl-silane ODS-2 C 18 analytical column and a guard column of similar characteristics. The UV detector was set at 240 nm. A study to select adequate composition of the micellar mobile phase for the separation of these compounds in urine samples is performed. Maximum resolution was achieved with a 0.07 M sodium dodecylsulphate-0.3% propanol at pH 7.4 eluent. Limits of detection at 240 nm were ranged between 0.13 μg ml −1 for diallyl barbit…