Frank H. Laukien

Pulsed-Gas Glow Discharge for Ultrahigh Mass Resolution Measurements with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

A new pulsed-gas glow discharge (GD) source has been developed for use with an external ion source Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. With pulsed argon gas introduction into the GD source, the gas load and pressure in the mass analyzer region were greatly reduced; this resulted in improved mass resolution. Mass resolution of greater than 1u2009450u2009000 (fwhm) has been achieved for Cu(+) ions from a brass sample, the highest reported for any type of GD mass spectrometer. The pulsed-gas GD source promises analytical usefulness for ultrahigh resolution measurements in GD mass spectrometry.

Ultrahigh mass resolution glow discharge mass spectrometry : direct analysis of heavy isotope mixtures

Abstract A number of advantages can be realized in the coupling of glow discharge (GD) sources to Fourier transform ion cyclotron resonance (FTICR) mass spectrometers. Foremost among these is mass resolving power in the range of 1 part in 200 000–700 000, a considerable improvement over all currently available commercial instrumentation, which has a maximum resolution of 20000. At the higher resolving power, closely spaced isotopic pairs such as 238 U and 238 Pu, 198 Hg and 198 Pt, and 204 Pb and 204 Hg can be analyzed without the conventional time consuming chemical separation step that normally precedes an isotopic measurement.

Method for the reduction of radiation damping during signal acqusition in NMR experiments

A method of reducing radiation damping during free induction decay in NMR measurements of samples having a narrow line width uses the active switching of the quality factor value of the coil circuit of an NMR detection probe. After application of an excitation pulse to the sample, data acquisition is accomplished in periodic samples. The Q of the coil circuit is set to a high value while each sample is being taken, but is reduced significantly in between samples by detuning the coil circuit. Minimization of the high-Q state of the coil circuit and maximization of the difference between the high Q value and the low Q value greatly decrease the detrimental effects of radiation damping on free induction decay. The coil circuit Q is modified automatically by the application of a Q switching signal generated by a controller, such as a computer which controls other aspect of the NMR experiment.

NMR spectroscopy with radial pulses. p- and n-type selection COSY

Abstract A novel NMR probe geometry is introduced and shown to have advantages for coherence pathway selection. The probe can generate rf fields with two distinct symmetries, a normal homogeneous rf field, and a “radial” rf field. One field can be used to both excite and detect the spin magnetization while the other is used to introduce spatially varying coherence pathway transformations. The detection process will select only that magnetization that preserves the symmetry of the detection coil. A single acquisition quadrature-detected COSY experiment is shown as an example of this principle.

Pulse sequence and method for creating a radio-frequency magnetic field gradient with a spatially independent phase for NMR experiments

A composite RF pulse is created from a sequence of conventional homogeneous RF pulses and conventional gradient RF pulses and the composite pulse generates a gradient magnetic field with a spatially varying amplitude, but a spatially independent phase. In one embodiment of the invention, the pulse sequence consists of four conventional gradient RF pulses interspersed with two conventional homogeneous RF pulses. In another embodiment of the invention, a conventional gradient RF pulse is combined with a conventional homogeneous RF pulse and the pulse pair is repeated in order to generate an effective magnetic field with a spatially varying amplitude, but a spatially independent phase.

Automated spray extraction of volatile organic compounds from aqueoud systems

A new sampling technique is described, where volatile organic compounds are extracted from an aqueous phase into the gas phase using a spray process. The formation of droplets during this spray process enormously increases the total interfacial area between the liquid and the gaseous phase. Using a spray extractor, volatile organic compounds dissolved in water can be sampled to perform. gas chromatographic / mass spectrometric analysis.