Search results for "Spectrometry"

2018

Abstract. Here we present a sensitive method to analyze lignin oxidation products (LOPs) in speleothems and cave drip water to provide a new tool for paleo-vegetation reconstruction. Speleothems are valuable climate archives. However, compared to other terrestrial climate archives, such as lake sediments, speleothems contain very little organic matter. Therefore, very few studies on organic biomarkers in speleothems are available. Our new sensitive method allows us to use LOPs as vegetation biomarkers in speleothems. Our method consists of acid digestion of the speleothem sample followed by solid-phase extraction (SPE) of the organic matter. The extracted polymeric lignin is degraded in a m…

The Influence of the Amide Linkage in the FeIII-Binding Properties of Catechol-Modified Rosamine Derivatives

2015

The two new fluorescent ligands RosCat1 and RosCat2 contain catechol receptors connected to rosamine platforms through an amide linkage and were synthesized by using microwave-assisted coupling reactions of carboxyl- or amine-substituted rosamines with the corresponding catechol units and subsequent deprotection. RosCat1 possesses a reverse amide, whereas RosCat2 has the usual oriented amide bond (HNCO vs. CONH, respectively). The ligands were characterized by means of NMR spectroscopy, mass-spectrometry, and DFT calculations and X-ray crystallography studies for RosCat1. The influence of the amide linkage on the photophysical properties of the fluorescent ligands was assessed in different …

Polyunsaturated fatty acids and Plasmalogens in diabetics

2012

Purpose Plasmalogens (PLS) are phospholipids characterized by a vinyl ether bond and a preferential esterification of polyunsaturated fatty acids (PUFA). We have previously shown that the lack of PLS leads to retinal hyper-capillarization. We hypothesize that PLS are negative regulators of vascular development, and aimed to check their circulating levels in diabetic patients. Methods Blood samples were collected from 88 patients and 14 control subjects. Among diabetics we had 14 patients without diabetic retinopathy (DR), 12 with a mild non proliferative DR, 12 with a moderate non proliferative DR, 22 with a severe non proliferative DR and 24 with a proliferative DR (PDR). Erythrocytes were…

ChemInform Abstract: Synthesis of Fluorinated Allylic Amines: Reaction of 2-(Trimethylsilyl)ethyl Sulfones and Sulfoxides with Fluorinated Imines.

2008

A new synthesis of fluorinated allylamines through the reaction of 2-(trimethylsilyl)ethyl sulfones and sulfoxides (as vinyl anion equivalents) with imines and imino esters has been described. The process includes a TBAF-mediated fragmentation of 2-(trimethylsilyl)ethyl sulfones to afford the desired allylic amines. When the reaction is performed with the corresponding sulfoxides, the fragmentation takes place under the addition conditions, affording the final products in a single step.

Trace element determination in sediments: a comparative study between neutron activation analysis (NAA) and inductively coupled plasma-mass spectrome…

2000

An inductively coupled plasma-mass spectrometry (ICP-MS) method has been employed for trace element determination in five real sediment samples and a standard reference material. These samples were mineralized by dry ashing at 550°C and fused at 1100°C for 30 min with lithium metaborate. Dissolved samples were measured by a semiquantitative methodology with external calibration and with Rh as an internal standard. More than 50 elements have been measured. As a reference technique, a direct analysis of the solid samples was carried out by neutron activation analysis. Results obtained by ICP-MS have been compared with those obtained by neutron activation analysis (NAA) by applying the paired …

Single and Multiple Additions of Dibenzoylmethane onto Buckminsterfullerene (Eur. J. Org. Chem. 35/2013)

2013

Nano‐Powdered Calcium Carbonate Reference Materials: Significant Progress for Microanalysis?

2019

Field Desorption Mass Spectra of Gastrine Peptides and Glutathione Derivatives

1979

Oligopeptides comprising the sequence of the C-terminal tetrapeptide of gastrine, Trp-Met-Asp-Phe-NH2, and several derivatives of glutathione, γ-Glu-Cys(SR)-Gly, were characterized by field desorption mass spectrometry. The field desorption mass spectra obtained at various field ion emitter temperatures reveal abundant molecular ions and fragmentation reactions that yield partial sequence information. In the series of glutathione derivatives investigated, characteristic ions formed by cleavage of the γ-Glu-Cys peptide bond determine the substituent at the Cys residue and can therefore be used to identify corresponding conjugation products of drug metabolites with glutathione.

Massenspektrometrische Untersuchungen an Edukten für die Synthese H2-aktiver Substanzen

1982

Unter den Bedingungen der Elektronenstosionisation wurden 4-[(2-Aminoethoxy)-methyl]-5-methyl-imidazo (1), die Imidazolderivate mit N-substituierter Ethylendiamin-Struktur 2–5 sowie die Imidazolcarboxamide 6–8 massenspektrometrisch untersucht. Der Mechanismus der konkurrierenden Bindungsspaltungen und der Umlagerungsprozesse wird formuliert. Die Wechselwirkung der funktionellen Gruppen sowie deren Einflus auf das Fragmentationsverhalten der Substanzen wird beschrieben und ein Schema der Hauptfragmentierungswege vorgeschlagen. Mess Spectrometry of Reactants for the Synthesis of H2-Active Compounds 4-[(2-Aminoethoxy)methyl]-5-methylimidazole (l), the imidazoles 2-5 with N-substituted ethylene…

Validation of Methylmercury Determinations in Aquatic Systems by Alkyl Derivatization Methods for GC Analysis Using ICP-IDMS

2001

Isotope dilution mass spectrometry (IDMS), using an inductively coupled plasma quadrupole mass spectrometer (ICPMS) and a species-specific methylmercury spike was applied to validate the commonly used GC method for methylmercury (MeHg+) determination, which is based on the formation of volatile methylethylmercury by derivatization with NaBEt4. The spike compound, Me201Hg+, was synthesized by reaction of 201Hg-enriched mercury chloride with methylcobalamin. By analyzing different environmental aquatic samples, it was found that in most cases, transformation of MeHg+ into elemental mercury (Hg0) took place. From investigations of synthetic solutions, it could be followed that halide ions are …