Search results for "deriva"

Method for determination of formaldehyde in air in the pptv-range by HPLC after extraction as 2,4-dinitrophenyl-hydrazone

1982

The derivatization of formaldehyde with 2,4-dinitrophenylhydrazine and the extraction of the product formalhydrazone is studied. The determination is carried out by HPLC. Applying a cryogenic sampling technique and a sampling volume of 300l of air the detection limit of formaldehyde in air is 30 pptv and this is suitable for measurements of formaldehyde in the atmosphere. (IFU)

Gaschromatographisch-massenspektrometrische identifizierung der durch umsetzung von aminen mit isocyanaten gebildeten harnstoffderivate

1977

Abstract Gas chromatographic-mass spectrometric identification of urea derivatives formed by the reaction of amines with isocyanates N,N′-Di- and N,N′,N′-trisubstituted ureas constitute suitable derivatives for the gas chromatographic (GC) determination of primary and secondary amines. The GC identification of N- tert. -butyl-,N′,N′-alkyl urea derivatives presented in the first communication has been succesfully confirmed by mass spectrometry (MS) and mass fragmentometry. The reproduced mass spectra of six N- tert. -butyl-,N′,N′-alkyl ureas were interpreted according to the decomposition mechanisms of less complicated alkyl ureas known from the literature. Using combined GC-MS the detection…

Characterization of proteinaceous glues in old paintings by separation of the o-phtalaldehyde derivatives of their amino acids by liquid chromatograp…

2005

A HPLC-fluorescence method for characterization of proteinaceous glues from binding media used in pictorial works of art prior to conservation or restoration treatment is proposed. Fluorescence derivatization of amino acids released by acid hydrolysis of standard proteins is studied. The derivatization reagent was o-phtalaldehyde with 2-mercaptoethanol as catalyst. Mobile phase was a programmed gradient among two eluents (water buffered at pH 5.8 wit 5% THF, and methanol) and is able to satisfactorily resolve the amino acid derivatives in 45min. Peak area ratios among amino acid derivatives and the leucine derivative are useful to characterize the proteins. The method shows good sensitivity…

Determination of the absolute configuration of (−)-abietic acidviaits (4R,5R,9R,10R)-7,13-abietadien-18-ylp-bromobenzoate derivative

2006

The absolute configuration of the title bromo derivative of abietic acid, C27H35BrO2, has been determined. The structural analysis confirms the absolute stereochemistry for (−)-abietic acid proposed by Bose & Struck [(1959). Chem. Ind. (London), pp. 1628–1630] on the basis of optical rotatory dispersion measurements. The mol­ecule exhibits a trans anti 6/6/6 tricyclic hydro­carbon skeleton, with the cyclo­hexane ring in the expected chair form and the two cyclo­hexene rings, the double bonds of which are conjugated, in half-chair conformations.

Infusion mass spectrometry as a fingerprint to characterize varnishes in oil pictorial artworks.

2007

Mass spectrometry methodology to characterize drying oil used as binding media and varnishes in pictorial artworks, prior to conservation or restoration treatment, is proposed. The analytical treatment requires prior basic hydrolysis of the samples to release the fatty acids : caprylic, pelargonic, capric, sebacic, azelaic, suberic, eicosanoic, lauric, mirystic, palmitic, linolenic, linoleic, oleic and stearic, followed by separation from the matrix by a hexane/water extraction. After removing the solvent, the remaining solid is dissolved in potassium hydroxide, propanol and methanol. The mixture is directly infused into a mass spectrometer without any previous derivatization or separation …

Pyrolysis of humic acids from digested and composted sewage sludge

2000

Humic acids (HAs) were extracted from four digested sewage sludge samples composted for four months, one, two and four years. HAs were pyrolyzed at three different temperatures applying both conventional and in situ methylation (ISM) pyrolysis. The pyrolysates were analyzed using gas chromatography-mass spectrometry (GC/MS). Derivatization (ISM) and pyrolysis temperature had dramatic effects on the composition and relative amounts of the pyrolysates. Among the derivatized HA fragments aliphatic compounds prevailed under all the pyrolysis conditions tested. Aromatic substances consisting mainly of guaiacyl-type compounds were detected in higher abundances only at elevated temperatures. Witho…

Biofiltration of ethylbenzene vapours: influence of the packing material.

2006

In order to investigate suitable packing materials, a soil amendment composed of granular high mineralized peat (35% organic content) locally available has been evaluated as carrier material for biofiltration of volatile organic compounds in air by comparison with a fibrous peat (95% organic content). Both supports were tested to eliminate ethylbenzene from air streams in laboratory-scale reactors inoculated with a two-month conditioned culture. In pseudo-steady state operation, experiments at various ethylbenzene inlet loads (ILs) were carried out. Maximum elimination capacity of about 120 g m(-3) h(-1) for an IL of 135 g m(-3) h(-1) was obtained for the fibrous peat. The soil amendment re…

A nitric oxide induced “click” reaction to trigger the aggregation induced emission (AIE) phenomena of a tetraphenyl ethylene derivative: A new fluor…

2020

Abstract An Aggregation Induced Emission (AIE) transduction mechanism has been used to detect nitric oxide (NO). A new tetraphenylethylene derivative functionalized with alkyne moieties has been prepared to work as a fluorescent probe. A “click” reaction was chosen because NO is able to generate the required catalytic species by reducing Cu(II) to Cu(I).

Fullerene polymers: synthesis and properties

2007

Mimicking photosynthesis: covalent [60]fullerene-based donor–acceptor ensembles

2004

Abstract Within the context of exploring photophysical properties of [60]fullerene-based donor–acceptor ensembles, we highlight in this contribution an approach towards the synthesis of a novel series of donor-bridge-acceptor, C 60 –wire– ex TTF , ensembles that incorporate p -phenylenevinylene oligomers, in which the conjugation length has been systematically increased, as bridges that connect π-extended tetrathiafulvalenes (exTTF) (electron donor) with [60]fullerene (electron acceptor). This molecular design allows probing the effects of distance and rate, at which electron transfer processes occur, as well as the molecular-wire behavior of the oligo-PPV fragments.