Wilfried Ma Niessen

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The alkaloids from CINCHONA LEDGERIANA shoot cultures and from CINCHONA ROBUSTA shoot cultures and a compact globular structure (CGS) culture were analyzed by thermospray liquid chromatography/mass spectrometry (TSP LC/MS). Because of the relative stability of the alkaloids under TSP discharge ionization conditions, a protonated molecule was observed in the(More)
Unknown compounds that were not amenable to GC/MS were found during routine benzodiazepine HPLC screening in a postmortem case. The apparent thermolability made the application of liquid chromatography with mass spectrometry mandatory. The moving-belt interface was used because of its value for identification based on the use of both electron impact and(More)
A number of potential matrix candidates were investigated with regard to the importance of the pH in the matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) analysis of non-covalently bound protein complexes. The matrices examined were 2,5-dihydroxybenzoic acid (DHB), 4-hydroxy-alpha-cyanocinnamic acid (HCCA), 2-aminonicotinic acid(More)
Supercritical fluid chromatography (SFC) has become a valuable tool in analytical chemistry. In the past few years considerable progress has been made in bioanalytical applications of both capillary and packed column SFC. Progress in this respect has especially been made with combined SFC-mass spectrometry, an important alternative to combined liquid(More)
A specific method for the determination of erythromycin 2'-ethylsuccinate (EM-ES) in plasma is described. The method involves a liquid-liquid extraction procedure followed by the analysis of extracts using phase-system switching (PSS) continuous-flow fast atom bombardment (CF-FAB) liquid chromatography-mass spectrometry (LC-MS). In PSS EM-ES is enriched(More)
Pig kidney diamine oxidase was purified to homogeneity. The reaction product of the cofactor with p-nitrophenylhydrazine (pNPH) was liberated with pronase treatment and purified. 1H NMR, uv/vis, and electrospray tandem mass spectroscopy revealed it to be a dipeptide with the sequence topaquinone-pNPH and aspartate. No heterogeneity was observed, indicating(More)
The application of a continuous-flow dialysis system, consisting of a membrane dialyser and a trace enrichment column, in on-line combination with tandem mass spectrometry via a thermospray interface is described. The method is applied to the quantitation of drugs in complex biological matrices containing macromolecular interferences. The potential of the(More)
The sulfate ester of the liver carcinogen N-hydroxy-4'-fluoro-4-(acetylamino)biphenyl (FAABP-N-sulfate) is believed to be a reactive intermediate in the male rat liver in vivo. After reaction of FAABP-N-sulfate with double-stranded calf thymus DNA in vitro, 30% of the adducts was identified as N-(deoxyguanosin-8-yl)-4'-fluoro-4-(acetylamino)biphenyl(dG-C8-(More)
The analysis of intact neutral oligosaccharides by on-line liquid chromatography/thermospray mass spectrometry is described. Molecular-weight information on oligomers up to a degree of polymerization of 10 is obtained using an aqueous mobile phase containing 10(-4) mol/L sodium acetate, which was found to be compatible with thermospray interfacing and(More)