Abstract:
A method of detecting specified target microbes in different types of sample uses only one to two cultivation steps for the enrichment of the target microbes from the sample, preferably in selective culture media, combined with a mass spectrometric detection method that identifies the target microbes in mixtures with other microbes even if the target microbes account for only a small proportion of the mixture. The sample may be a food sample, a sample from bodies of water used for bathing, a soil sample, a swabbed sample, a stool sample, an impactor sample with collected aerosol particles, amongst many others. The detection method is several days faster than standard methods and less expensive.
Abstract:
In a Kingdon ion trap in which harmonic ion oscillation in a potential well in a longitudinal direction is completely decoupled from ion oscillation in a direction transverse to the longitudinal direction, ions enter the trap via an entrance tube extending through, but electrically insulated from, one of the Kingdon trap housing electrodes and located outside the minimum of the potential well in the longitudinal direction. The geometry of the Kingdon trap is arranged so that the oscillating ions introduced through the entrance tube cannot return to the entrance tube until they have performed several longitudinal oscillations during which time heavy ions can be introduced into the trap.
Abstract:
The invention relates to measuring devices of an electrostatic Fourier transform mass spectrometer and measurement methods for the acquisition of mass spectra with high mass resolution. The measuring device includes electrostatic measuring cells according to the Kingdon principle, in which ions can, when appropriate voltages are applied, orbit on circular trajectories around the cylinder axis between two concentric cylindrical surfaces, which are composed of specially shaped sheath electrodes, insulated from each other by parabolic gaps, and can harmonically oscillate in the axial direction, independently of their orbiting motion. In the longitudinal direction, the two cylindrical surfaces of the measuring cell are divided by the parabolic separating gaps into different types of double-angled and tetragonal sheath electrode segments. Appropriate voltages at the sheath electrode segments generate a potential distribution between the two concentric cylindrical surfaces which forms a parabolic potential well in the axial direction for orbiting ions. The ion clouds oscillating harmonically in the axial direction in this potential well induce image currents in suitable electrodes, from which the oscillation frequencies can be determined by Fourier analyses.
Abstract:
Microorganisms, particularly bacteria, are identified and characterized on the basis of a mass spectrometric measurement of their protein profiles with ionization by matrix-assisted laser desorption. In order to measure the microbial resistance to antibiotics, the protein profiles of microorganisms are measured after cultivation for a short time duration in nutrient media containing the antibiotics.
Abstract:
The invention relates to ions guided by gas flows in mass spectrometers, particularly in RF multipole systems, and to RF quadrupole mass filters and their operation with gas flows in tandem mass spectrometers. The invention provides a tandem mass spectrometer in which the RF quadrupole mass filter is operated at vacuum pressures in the medium vacuum pressure regime, utilizing a gas flow to drive the ions are through the mass filter. Vacuum pressures between 0.5 to 10 pascal are maintained in the mass filter. The mass filter may be enclosed by a narrow enclosure to guide the gas flow. The quadrupole mass filter may be followed by an RF multipole system, operated at the same vacuum pressure, serving as fragmentation cell to fragment the selected parent ions. The fragmentation cell may be enclosed by the same enclosure which already encloses the mass filter, so the ions may be driven by the same gas flow at the same vacuum pressure, greatly simplifying the required vacuum pumping system in tandem mass spectrometers. There are many other applications utilizing gas flows including supersonic gas jets in mass spectrometry.
Abstract:
The invention relates to measuring devices of an electrostatic Fourier transform mass spectrometer and measurement methods for the acquisition of mass spectra with high mass resolution. The measuring device includes electrostatic measuring cells according to the Kingdon principle, in which ions can, when appropriate voltages are applied, orbit on circular trajectories around the cylinder axis between two concentric cylindrical surfaces, which are composed of specially shaped sheath electrodes, insulated from each other by parabolic gaps, and can harmonically oscillate in the axial direction, independently of their orbiting motion. In the longitudinal direction, the two cylindrical surfaces of the measuring cell are divided by the parabolic separating gaps into different types of double-angled and tetragonal sheath electrode segments. Appropriate voltages at the sheath electrode segments generate a potential distribution between the two concentric cylindrical surfaces which forms a parabolic potential well in the axial direction for orbiting ions. The ion clouds oscillating harmonically in the axial direction in this potential well induce image currents in suitable electrodes, from which the oscillation frequencies can be determined by Fourier analyses.
Abstract:
The invention relates to acquisition techniques for time-of-flight mass spectra with ionization of the analyte substances by matrix assisted laser desorption. Generally speaking, these acquisition techniques involve adding together a large number of individual time-of-flight spectra, each with restricted dynamic measuring range, to form a sum spectrum. The invention provides a method that improves, in particular, the reproducibility, the concentration accuracy and therefore the ability to quantify the mass spectra. Particular embodiments also increase the dynamic range of measurement. For this purpose, multiple series of mass spectra are acquired, whereby the energy density in the laser spot is increased in discrete steps. As a result, many ion signals saturate the detector and can therefore no longer be evaluated. However, it is possible to employ a technique in which the ion beam is increasingly defocused, or, secondly, to replace parts of the spectrum that are subject to saturation by intensity extrapolations from mass spectra acquired with lower energy density. In the first case, hundreds or thousands of individual mass spectra must be added together in order to increase the dynamic measuring range. In the second case, the finally acquired mass spectrum, with its replacements, forms a mass spectrum with a high dynamic measuring range, improved reproducibility and better concentration accuracy. The gradient of the increasing intensities of the ion signals, as a function of the energy density, supplies additional information about the proton affinity of the analyte ions. The concentration accuracy is enhanced because the increase in the number of proton donors in the ionization plasma leads to an increase in the ionization of those analyte substances that have a lower proton affinity.
Abstract:
The mobility of mass-selected ions in gases is measured at pressures of a few hectopascal by selecting the ions under investigation in a quadrupole filter according to their mass-to-charge ratio m/z, measuring their mobility in a drift region at a pressure of a few hundred Pascal under the influence of a DC electric field and then filtering the measured ions by means of a quadrupole field in order to eliminate, or detect changes in, the mass-to-charge ratio. Several embodiments for the drift region are disclosed, in which the ions are kept in the axis of the drift region by RF fields. As these drift regions can also be utilized for a collision-induced decomposition of the ions, the device can additionally be used as a so-called triple quadrupole mass spectrometer.
Abstract:
Ions entrained in a gas are transported into the vacuum system of an ion user, such as a mass spectrometer, from an ion source located outside the vacuum. The gas and ions pass through a nozzle that connects the ion source to the vacuum system and is shaped to form a supersonic gas jet in a first vacuum chamber of the vacuum system. In the first vacuum chamber, ions entrained in the supersonic gas jet are extracted electrically or magnetically and are collected, for example, by an RF ion funnel and transmitted to the ion user. The supersonic gas jet travels on and, after passing through the first vacuum chamber, the supersonic gas jet is directed into a separate pump chamber out of which the gas is pumped.
Abstract:
The invention relates to instruments for storing ions in more than one ion storage device and to the use of the storage bank thus created. The ion storage bank includes several storage cells configured as RF multipole rod systems, where the cells contain damping gas and are arranged in parallel. Each pair of pole rods is used jointly by two immediately adjacent storage cells such that the ions collected can be transported from one storage cell to the next by briefly applying DC or AC voltages to individual pairs of pole rods. The ions can thus be transported to storage cells in which they are fragmented or reactively modified, or from which they can be fed to other spectrometers. In particular, a circular arrangement of the storage cells on a virtual cylindrical surface makes it possible to accumulatively fill the storage cells with ions of specific fractions from temporally sequenced separation runs.