Bruker-franzen Analytik Gmbh

US Government As Represented by the Secretary of the Army

Reemt-Holger Gabling

Jochen Franzen

Gerhard Heinen

Gerhard Weiss

Yang Wang

The invention relates to methods and devices for the effective introduction of ions, which are stored in an RF ion guide into a quadrupole ion trap. The invention consists of arranging a switchable ion lens between the RF ion guide and the quadrupole ion trap, and introducing the ions into the quadrupole ion trap by a suitable connection of the ion lens only during the filling period, while otherwise the ions are reflected back into the RF ion guide. The filling period can be divided up and limited to the capture intervals of the quadrupole ion trap during each RF period. Measurement of the filling rate can be made by switching open the ion lens longer then the admission interval of the quadrupole ion trap, and measuring the flow of the ions passing through on the detector.

Method and device for the introduction of ions into quadrupole ion traps

A method is disclosed for chemical ionization of the molecules of an analysis gas or analysis gas mixture or for studying ion-molecule reactions in ion traps. Specifically, by superposing a quadrupole field with a dipolar introduced frequency mixture in which there are accurately selected frequency gaps in the ionization phase of the analysis, the only ions which are stored are those which are on the selected reaction path of the reactant gas ions for making the proper reactant ions for the desired ion-molecule reaction. All the other ions are eliminated from storage by excitation of their secular oscillations. In a second phase, by switching off the dipolar introduced frequency mixture, all the ions can be stored in a wide range of mass-to-charge ratios, and therefore also the product ions of the desired ion-molecule reactions of the analysis gas. In a third phase the spectrum of the product ions is scanned.

Method of selecting reaction paths in ion traps

A method and a device for the mass selective excitation of the secular oscillations of selected ion types in an RF quadrupole ion trap, including the simultaneous excitation of more than one ion type, is disclosed. The secular oscillation frequency is excited by resonances with specific frequencies of the frequency bands of the additional alternating fields, the frequency bands being generated digitally at a basic pulse rate .OMEGA.. Interfering frequency side bands .OMEGA.-.omega., .OMEGA.+.omega., 2.OMEGA.-.omega., 2.OMEGA.+.omega., etc. arise, however, for each frequency .omega. within the frequency bands. These side bands can excite and eliminate other ions, which are not to be eliminated, in an undesired manner. The invention comprises forming the side bands in such a way that they only excite the selected ions. This is done by making the basic pulse rate for digital generation of the frequency bands for the additional alternating voltage identical with the frequency of the drive voltage of the ion trap or with an integral multiple of it and coupling the basic pulse rate to it in locked phase relation.

Method and device for the digital generation of an additional

The measuring process for generating mass spectra using a sequentially-scanned quadrupole ion trap mass spectrometer, is improved by controlling the measurement of the ion packages ejected from the ion trap so that measurement takes place starting at the anticipated exit times of the ion packages and measurement continues only as far as possible for a time duration corresponding to the length of the ion packages. Measuring only during ion package ejection enables a measurement for the total number of ejected ions having a selected mass to be obtained by means of digital addition of the individual package measurements. Subsequent processing of the data can be carried out with practically only the fluctuations of normal ion counting statistics.

Method and device for in-phase measuring of ions from ion trap mass

An improved scanning method used in an ion trap mass spectrometer comprises controlling the amplitude of the excitation RF during the mass scan to produce a smooth, nonlinear, highly suitable function. A smooth function is a function with a steady derivative. According to one embodiment of the invention, the excitation amplitude is set proportionally to the square root of the storage amplitude, thus making the excitation amplitude proportional to the root of the mass number.

Method and device for control of the excitation voltage for ion ejection

For mass-spectroscopic examinations of gas mixtures a mass spectrometer is used which comprises a quistor in which ions of the gas mixture whose charge-to-mass ratio is located in a predetermined range are stored by generating an electromagnetic field. By varying the field parameters, the ions are forced successively to leave the ion trap. The intensity of the ion flow leaving the ion trap is measured as a function of the variation of the field parameters. For improving the resolution, one uses a quistor of the type where the distance-related ratio Q of the radii of the inscribed vertex circles of the electrodes comply with the condition Q.ltoreq.3.990, wherein ##EQU1## R.sub.e being the radius of the cross-section of the vertex of the end electrodes (3,5);

Method for mass-spectroscopic examination of a gas mixture and mass

A method for the measurement of mass spectra by three dimensional quadrup fields (QUISTORs) is presented, in which the ions are mass-to-charge selectively ejected by a selected nonlinear resonance effect in an inharmonic QUISTOR. In order to enhance scan speed and mass resolution, the ejection of a single kind of ions can be confined to a very small time interval, either by the generation of ions within a small volume outside the field center, or by an excitation of the secular amplitudes by an additional RF voltage across the end electrodes, shortly before the ions encounter the sum resonance condition. An instrument for this method is described.

Method and instrument for mass analyzing samples with a quistor

In a quadrupole ion store (QUISTOR), a sample is analyzed by increasing the mplitude of the harmonic, or 'secular', oscillations of selected stably trapped ions so that they leave the trapping field. In a preferred embodiment, deviations from the ideal electrode geometry are incorporated into the QUISTOR to produce resonance phenomena between the r and z secular oscillations, thereby increasing the amplitude of oscillations in the z direction.

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Bremen, Germany

Reemt-Holger Gabling