Search results for "Chloroform"
showing 10 items of 414 documents
Halogen-bonded solvates of tetrahaloethynyl cavitands
2017
The formation and structures of halogen-bonded solvates of three different tetrahaloethynyl cavitands with acetone, chloroform, acetonitrile, DMF and DMSO were prepared and investigated. The inclusion and host–guest behaviour of the resorcinarene cavitands was found to be highly dependent on the flexibility of the ethylene-bridging unit.
Chiral determination of amphetamine and related compounds using chloroformates for derivatization and high-performance liquid chromatography
1999
The enantiomeric determination of amphetamine and various amphetamine-type compounds by liquid chromatography after chiral derivatization with 9-fluorenylmethyl chloroformate-L-proline (FMOC-L-Pro) is reported. The results obtained were compared with those achieved after achiral derivatization with 9-fluorenylmethyl chloroformate and subsequent separation of the derivatives on a beta-cyclodextrin chiral stationary phase. Conditions for the derivatization of amphetamines with FMOC-L-Pro were investigated, including the effect of the derivatization reagent concentration, pH and reaction time, using amphetamine, ephedrine and pseudoephedrine as model compounds. On the basis of these studies, p…
Characterization of bile acids and fatty acids from ox bile in oil paintings by gas chromatography?mass spectrometry*1
2004
Characterization of ox bile, traditionally used in painting, is of interest in the fields of archaeometry and conservation and restoration of works of art. Bile acids, fatty acids (F), and cholesterol found in ox bile have been identified using a derivatization method that combines the formation of ethyl esters from the carboxylic groups and the trimethylsilyl ethers from hydroxyl groups. This method of analysis is consistent with these others proposed by the authors to analyze drying oils, proteins, and diterpenic resins usually used as binders and varnishes by the painters. Bile acids from binary samples such as animal glue/ox bile, casein/ox bile and Arabic gum/ox bile have been successf…
Liquid chromatographic determination of aliphatic amines in water using solid support assisted derivatization with 9-fluorenylmethyl chloroformate
2002
A simple and sensitive method has been developed for the liquid chromatographic determination of short-chain aliphatic amines in water. Analytes are retained in solid-phase extraction (SPE) cartridges, and then derivatized by drawing an aliquot of the fluorogeneic reagent 9-fluorenylmethyl chloroformate (FMOC) through the cartridges. After a certain reaction time the derivatives formed are desorbed with acetonitrile. The collected extracts are then chromatographed on a LiChrospher 100 RP18 125 mm×4 mm i.d., 5 μm, column using an acetonitrile-water gradient. The influence of experimental conditions (SPE material, volume of sample, concentration of FMOC, time of reaction and pH) has been inve…
Extractive Spectrophotometric Determination of Ondansetron by Ion-Pair Formation with Bromocresol Green
1996
Abstract An empirical spectrophotometric procedure for the determination of the antiemetic ondansetron is carried out. The method is based on the formation of a 1:1 ion pair with bromocresol green in the pH range over 3.2 – 4.4, extraction into chloroform layer and spectrophotometric measurement at 420.8 nm. The calibration graph is linear over the range 0.1 – 20 μg ml−1 ondansetron, with a relative standard deviation of 2.7%; the influence of foreign substances is also studied. The method is applied to ondansetron determination in human urine.
Lipid hydroperoxides determination in milk‐based infant formulae by gas chromatography
2003
A simple gas chromatograph using a flame ionization detector and a polar capillary column method is proposed for determining hydroperoxides in the lipid fraction of milkbased infant formulas. Tricosanoic acid is used as internal standard. The method includes the following steps: a) the extraction of fat with chloroform/methanol (2:1, v/v), b) the reduction of hydroperoxide acids to hydroxide acids with hydrogen gas and palladium as a catalyst, c) the transmethylation to obtain the methyl esters with acetyl chloride and methanol/ hexane (4:1, v/v), and d) an acetylation with acetic anhydride/ pyridine (4:1, v/v) to obtain an acetoxy derivate of the hydroxide present. Two chromatography runs,…
Liquid chromatography-Fourier transform infrared spectrometric determination of cholesterol in animal greases
1997
Abstract Stearic acid, cholesterol and cholesteryl palmitate have been separated in less than 14 min by liquid chromatography on a column (3.9 mm i.d.×150 mm) of Nova-Pack C 18 (5 μm) using chloroform–acetonitrile (45 : 55) as mobile phase pumped at 0.5 ml min −1 ; Fourier transform infrared (FTIR) spectrometry was employed for both, general detection at 2868 or 2855 cm −1 and selective detection at 3285 cm −1 for stearic acid and 3526 cm −1 for cholesterol. In all cases a baseline established at 3900 cm −1 , 9-point smoothing and chromatographic peak height measurements were used. The method has been validated by application to the determination of cholesterol in animal greases and fish oi…
Suppression of pigment interference in the gas chromatographic analysis of proteinaceous binding media in paintings with EDTA.
2004
A method to suppress the interference of pigments in the analysis of proteinaceous media used in paintings is presented in this paper. This method is based on the formation of metallic ion-ethylenediaminetetraacetic acid (EDTA) complexes previous to the derivatisation process, using ethyl chloroformate (ECF), to transform the amino acids in N(O,S)-ethoxycarbonyl (EOC) ethyl esters. Test specimens, containing different proteinaceous media such as albumin, porcine gelatine and casein mixed with lead white, chalk, verdigris and raw Sienna have been prepared for carrying out this study. Different pH conditions have been probed for the different pigments studied. Values of peak area ratio of ami…
Identification of diterpenes in canvas painting varnishes by gas chromatography-mass spectrometry with combined derivatisation.
2004
A derivatisation method that combines the formation of ethyl esters from the carboxylic groups and trimethylsilyl ethers from hydroxyl groups of the components of diterpenic resins is presented in this paper. This methodology involves two experimental steps: (1) formation of ethyl esters using ethyl chloroformate; and (2) the esterified compounds are lead to react with trimethylsilylimidazole to form the corresponding trimethylsilyl ethers. The main advantage of the proposed method is the possibility of performing simultaneously the analysis of amino acids from proteins, fatty acids from drying oils, and diterpenic compounds from natural resins usually found in works of art. This methodolog…
Study of Burseraceae resins used in binding media and varnishes from artworks by gas chromatography–mass spectrometry and pyrolysis-gas chromatograph…
2005
In the present work, a study attempting to characterize the Manila elemi and Mexican copal resins from the Burseraceae family, which are used as components of varnishes and binding media of artworks, has been carried out. A new GC-MS method involving the use of methyl chloroformate as derivatisation reagent has been proposed. A second method which uses pyrolysis-GC-MS and hexamethyldisilazane as derivatization reagent has also been applied. Characterization of the main components of the mono-, sesqui- and triterpenoid fractions occurring in the raw materials has been achieved. Both alpha- and beta-amyrin have been established as the major triterpenoid compounds occurring in these resins tog…