Determination of (R)- and (S)-phenprocoumon in human plasma by enantioselective liquid chromatography/electrospray ionisation tandem mass spectrometry

Phenprocoumon is a commonly used oral anticoagulant of the coumarin type, and has found extensive clinical use in the treatment of thrombophlebitis, pulmonary embolism and atrial fibrillation. In the course of a clinical study to investigate the influence of genetic polymorphisms of the CYP2C9 enzyme on phenprocoumon metabolism, we developed a new enantioselective liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/MS/MS) method to quantify (R)- and (S)-phenprocoumon in human plasma. HPLC separation of the enantiomers was achieved on a Chira-Grom-2 column under isocratic conditions using a water/acetonitrile/formic acid eluent. For detection and quantification a triple-quadrupole MS system was used in the selected reaction monitoring (SRM) mode. As an internal standard the structurally homologous compound warfarin was chosen. The detector response was linear with a correlation coefficient of 0.988-0.999 for (R)-phenprocoumon and 0.989-0.999 for (S)-phenprocoumon in the investigated concentration range between 62.5 and 1000 ng/mL (per enantiomer). The limit of detection (LOD) was 12.5 ng/mL.     

Radioanalytical quality control of11C,18F and123I-labelled compounds and radiopharmaceuticals

Radiochemical quality control using high performance high pressure liquid chromatography and, to some extent, gas chromatography is described for a variety of carrier-free¹¹C-,¹⁸F-and¹²³I-labelled compounds and radiopharmaceuticals. The particular problems associated with the handling of carrier-free compounds labelled with short-lived radionuclides are outlined, and chromatographic data are given for the separation and purification of such products.     

Quencing of perylene fluorescence by Ag+ ions via exciplex formation

The fluorescence of perylene in alcoholic solution is dynamically quenched by AgClO₄ resulting in a new emission band with its maximum around 480 nm. Analysis of fluorescence decay curves at various emission wavelengths proves the formation of a perylene/Aa⁺ ion exciplex in the quenching reaction.     

Time dependence of shear and normal stresses of polystyrene and poly(ethylene oxide) solutions

The time dependence of shear and normal stresses during constant shearing of some polystyrene and poly(ethylene oxide) solutions in Aroclor 1248 was measured by means of a Weissenberg rheogoniometer. The stresses of the poly(ethylene oxide) solutions first increase rapidly with the increase of strain, then decrease to a value lower than the value in the stationary state, pass another maximum smaller than the first one, and finally reach a steady value. At the end of the shearing of these solutions at high shear rates, the formation of aggregates was clearly evident. The polystyrene solutions became time-dependent only after a certain shear rate and then showed a rheopectic behavior. The difference in behavior is explained qualitatively by the differing tendencies of these polymer chains to form a network.     

Angularly resolved coherent Raman spectroscopy (ARCS) in gases

We report here the development of a Coherent Anti-Stokes Raman Scattering (CARS) configuration which takes advantage of the phasematching criterion to produce simultaneous spatially-separated signals from different constituents within a gas. In particular, we have show that separate CARS beams from nitrogen monoxide may be simultaneously observed from a single sample volume.