Search results for "Ethyl chloroformate"
showing 10 items of 10 documents
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…
Reaction of Diphenyldiazomethane withN-Methyloxy- andN-Ethyloxycarbonyl-N-(2,2,2-trichloroethylidene)amines
1999
Reaction of the title imines with diphenyldiazomethane gives a Δ3-1,3,4-triazoline, which leads, after loss of dinitrogen, to a transient azomethine ylide. Subsequent elimination of ethyl or methyl chloroformate gives the unexpected 1,1-diphenyl-4,4-dichloro-2-aza-1,3-butadiene.
Separation of the enantiomers of primary and secondary amphetamines by liquid chromatography after derivatization with (−)-1-(9-fluorenyl)ethyl chlor…
2003
The chiral reagent (−)-1-(9-fluorenyl)ethyl chloroformate (FLEC) has been evaluated for the enantioselective analysis of amphetamines by liquid chromatography. For separation of the FLEC diastereomers conventional reversed-phase conditions were used. The conditions affording the best enantiomeric resolution and sensitivity were determined for amphetamine, methamphetamine, ephedrine, pseudoephedrine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), and 3,4-methylenedioxyethylamphetamine (MDE). All the amphetamines assayed could be separated with resolution factors ranging from 0.91 to 1.92. Although FLEC is typically used as a fluorogenic reagent, it was shown t…
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…
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…
ChemInform Abstract: Reaction of Diphenyldiazomethane with N-Methyloxy- and N-Ethyloxycarbonyl-N-(2,2,2-trichloroethylidene)amines.
2010
Reaction of the title imines with diphenyldiazomethane gives a Δ3-1,3,4-triazoline, which leads, after loss of dinitrogen, to a transient azomethine ylide. Subsequent elimination of ethyl or methyl chloroformate gives the unexpected 1,1-diphenyl-4,4-dichloro-2-aza-1,3-butadiene.
Identification by GC-FID and GC-MS of amino acids, fatty and bile acids in binding media used in works of art.
2001
GC-FID was used as single methodology for the identification and differentiation of proteins, lipids and ox bile from binders used in artistic paintings. The samples were hydrolyzed by HCl. Subsequently, the simultaneous formation of volatile derivatives of the amino, fatty and bile acids with ethyl chloroformate was performed quickly and safely in an aqueous medium. The derivatives were separated by capillary GC and characterized by GC-MS. The ageing of drying oils was studied, identifying pelargonic acid among other degradation products. Proteinaceous and lipoid binding media were characterized by means of the quotients between the areas of the peaks for each amino or fatty acid with resp…
Analytical study of proteinaceous binding media in works of art by gas chromatography using alkyl chloroformates as derivatising agents.
2001
In this work, we present the results obtained in an analytical study of the different types of proteinaceous binding media most commonly used in paintings, using GC-FID as the technique of analysis and GC-MS as a confirmatory technique. The application of this methodology requires prior hydrolysis of the proteins in the binding media to obtain free amino acids and then volatile derivatives, in this case by reaction with chloroformates due to advantages of speed, safety and the aqueous medium in which the reaction occurs. The method proposed for the proteinaceous binding media study is to calculate the proportions of the different amino acids with respect to alanine. This method provided goo…
Study of binding media in works of art by gas chromatographic analysis of amino acids and fatty acids derivatized with ethyl chloroformate
1997
The aim of this work is to identify proteinaceous and oil binding media used in paintings from art collections in the Region of Valencia (Spain). This information is extremely useful for conservation and restoration work. The proposed procedure involves protein and glyceride hydrolysis from sub-milligram samples by treatment with hydrochloric acid, followed by neutralization, partition with chloroform and derivatization with ethyl chloroformate (ECF) of both the aqueous and the organic phases. The ECF derivatives of amino acids and azelaic, myristic, palmitic and stearic acids are separated by capillary gas chromatography. Amino acids are mainly found in the aqueous phase and long chain fat…
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…