Shimadzu Corporation

Junichi Taniguchi

Osamu Furuhashi

Daisuke Okumura

Eizo Kawato

Hiroto Itoi

A mass spectrometer () includes: an ionization section () configured to generate ions from a sample; a mass separation section () configured to separate ions generated by the ionization section according to mass-to-charge ratio; an ion detector () configured to detect an ion separated by the mass separation section; an ion capture section () configured to capture ions separated by the mass separation section; and an electron beam detection section () configured to detect an electron beam diffracted by ions captured within the ion capture section (). This mass spectrometer is capable of performing, in a single measurement operation, both a mass spectrometric analysis and an electron-beam diffraction measurement for distinguishing between isomers. The electron-beam diffraction measurement can be more efficiently performed than in a conventional device of this type.

Mass spectrometer

In a three-dimensional quadrupole-type ion trap, a shape and an arrangement of the ring electrode and the end cap electrodesandare shifted from an ideal state in which only a quadrupole electric field is formed, so that the polarities of the ratio of strength of an octupole electric field with respect to the strength of a quadrupole electric field and the ratio of strength of a dodecapole electric field with respect to the strength of the quadrupole electric field are different from each other, their absolute values are equal to or greater than 0.02, and the absolute value of the ratio of strength of the octupole electric field with respect to the strength of the dodecapole electric field is within the range of from 0.6 to 1.4.

Ion trap design method and ion trap mass spectrometer

A method of operating an electrode changeover switch which switches the connection state of electrodes, the electrode changeover switch is provided in the wiring path between eight electrodes through, arranged rotation-symmetrically about ion optical axis, and voltage generation switch which generates square wave high voltage &#xb1;V. When switch is switched as shown in the drawing, two circumferentially adjacent rod electrodes are connected to form one set, a square wave voltage of opposite phase is applied to circumferentially adjacent sets, and an effectively quadrupole electric field is formed. When switch is switched, a square wave voltage of opposite phase is applied to circumferentially adjacent rod electrodes and an octupole electric field is formed. In this way, by switching the switch according to the mass range, etc., it becomes possible to rapidly switch the number of poles of a multipole electric field and to suitably transport ions.

Mass spectrometer and method of driving ion guide

An electrostatic lens (), including five cylindrical electrodes (-) arrayed along an ion-optical axis (C) and an aperture plate () located on a common focal plane of two virtual convex lenses (Land L) formed under an afocal condition, is used as an ion-injecting optical system for sending ions into an orthogonal acceleration unit. The diameter of a restriction aperture () formed in the aperture plate () determines the angular spread of an exit ion beam. When voltages for making the electrostatic lens () function as an afocal system are set, a measurement with high mass-resolving power can be performed at a slight sacrifice of the sensitivity. When voltages for making the lens function as a non-afocal system having the highest ion-passage efficiency are set, a measurement with high sensitivity can be performed at a slight sacrifice of the resolving power.

Time-of-flight mass spectrometer

An electrode changeover switch which switches the connection state of electrodes is provided in the wiring path between eight electrodes through, arranged rotation-symmetrically about ion optical axis, and voltage generation switch which generates square wave high voltage &#xb1;V. When switch is switched as shown in the drawing, two circumferentially adjacent rod electrodes are connected to form one set, a square wave voltage of opposite phase is applied to circumferentially adjacent sets, and an effectively quadrupole electric field is formed. When switch is switched, a square wave voltage of opposite phase is applied to circumferentially adjacent rod electrodes and an octupole electric field is formed. In this way, by switching the switch according to the mass range, etc., it becomes possible to rapidly switch the number of poles of a multipole electric field and to suitably transport ions.

Ion guide and mass spectrometry device

In performing an isolation of specific ions or performing a dissociation operation by CID, ions are captured by applying a radio-frequency high voltage to a ring electrodeas before. In a cooling operation which is performed immediately before target ions are ejected toward a TOFMS unitwith the ions stored in an ion trap, a radio-frequency high voltage is not applied to the ring electrodebut to end cap electrodesandto capture the ions. In this operation, the frequency thereof is set to be higher than that of the voltage applied to the ring electrodeand the amplitude is also increased in order to assure a large pseudopotential and keep the low mass cutoff (LMC). This narrows the spatial distribution of the cooled ions, reducing the variation of the initial positions of the ions at the point in time when they are ejected, which increases the mass resolution. In addition, since an isolation of ions having a large m/z can be performed with a great qvalue as is conventionally done, a high mass selectivity can be assured.

When ions accumulated in the exit side end of ion guide are to be injected into ion trap as packets, the application of square wave high frequency voltage to ring electrode from main voltage generating unit is stopped. Once nearly all the ions have been injected into ion trap, the application of square wave high frequency voltage from main voltage generating unit to ring electrode is momentarily started, at which time the application of square wave high frequency voltage is started from a phase in the range of 90&#xb0;&#xb1;40&#xb0; or 270&#xb0;&#xb1;40&#xb0;. It is thereby possible to reduce the extent of spread of ions immediately after application of high frequency voltage and to improve the ion trapping efficiency.

Specific phase range for ion injection into ion trap device

An ion trap mass spectrometer with high sensitivity for detection in the high mass-to-charge ratio is provided. with separate measurement of square-wave voltages on the positive and negative electrode sides applied to a ring electrode in rectifying circuits and smoothing the measured voltages in integrating circuits, respectively, the areas of square-wave voltages on the positive and negative electrode sides are replaced with the peak values hand hof DC signals, respectively. A comparator circuit outputs the difference of said peak values as the error signal &#x394;, and variable delay circuits adjust the amount of delay of control signals so that the error signal &#x394; becomes zero. This changes the relative phase relation between control signals on the positive and negative electrode sides that turn on and off the switches, and renders the duty ratio of square-wave voltages nearly 50%.

Ion trap mass spectrometer

A technique for improving the mass-resolving power of an ion trap time-of-flight mass spectrometer is provided. At the final stage of a cooling process before the ejection of ions from an ion trap, the frequency of a rectangular-wave voltage applied to a ring electrode of the ion trap is increased for a few to several cycles. This operation reduces the confining potential depth of the ion trap and decelerates the captured ions. The turn-around time of the ions is shortened when the rectangular-wave voltage is halted and an accelerating electric field is created. Thus, the variation in the time of flight of the ions with the same mass-to-charge ratio is reduced. The time for increasing the frequency is determined so that a spread of the ions because of the depth reduction of the confining potential will fall within the range that can be corrected in the time-of-flight mass spectrometer.

Ion trap time-of-flight mass spectrometer

A technique for performing precursor isolation with a desired mass-to-charge ratio (m/z) in a digital ion trap while maintaining the q value at a substantially constant value is provided. A data obtained by digitizing an FNF signal having a notch is stored beforehand in an FNF waveform memory. In the process of precursor isolation, a main voltage timing controllerand a main voltage generatorgenerate a rectangular-wave voltage based on a reference clock signal CK. An auxiliary signal generatorreads data from the FNF waveform memoryand generates an FNF signal by performing digital-to-analogue conversion of the data in accordance with a clock signal synchronized with the reference clock signal CK. Under the command of a controller, a reference clock generatorproduces the reference clock signal CK having a frequency corresponding to the m/z value of a target ion. Accordingly, a change in the m/z of the target ion leads to a change in the frequency of the reference clock signal CK, which causes the frequency of the rectangular-wave voltage and the central frequency of the notch of the FNF signal to change in the same proportion.

A mass spectrometer according to the present invention includes: an ion source; a mass analyzer for analyzing ions generated by the ion source with their mass to charge ratio; an ion lens composed of platelet electrodes of an even number no less than four arranged radially and symmetrically around an ion optical axis connecting the ion source and the mass analyzer; and a voltage generator for applying a voltage composed of a DC voltage and an RF voltage to a group of alternately arranged platelet electrodes and for applying another voltage composed of the same DC voltage and another RF voltage having the same frequency and the opposite polarity to the other group of alternately arranged platelet electrodes. When ions are introduced into the ion traveling space defined by the inner surfaces of the platelet electrodes, the ions travel along the ion optical axis and converge to a rear focal point of the ion lens, while they are vibrated by the voltages applied to the platelet electrodes. By placing a small hole or orifice communicating to the next chamber at the rear focal point of the ion lens, larger number of ions can be sent to the next chamber, which enhances the sensitivity and precision of the mass spectrometer.

Ion lens for a mass spectrometer

In an ion trap mass spectrometer, between an ion supply source and an ion trap, there are disposed an entrance gate electrode, an ion storing section for holding ions by accumulating them near an exit side by means of an RF voltage with an axial electric potential inclined from an entrance side to the exit side, and an exit gate electrode. When the ions are accumulated near the exit side, the exit gate electrode is opened to thereby introduce the ions in the pulse state into the ion trap. At this point, a voltage is not applied to a ring electrode of the ion trap, so that repulsion due to the voltage of the ring electrode is eliminated. Thereafter, when maximum amount of ions stay inside the ion trap, ring RF voltage is suddenly applied. Thus, the maximum amount of the ions can be introduced into the ion trap.

When ions are introduced from outside into the ion trap space, a static electric field having equi-voltage surfaces concave to the entrance hole is formed in the ion trap space. For ions obliquely entering the ion trap space, such a static electric field makes the ions cross the equi-voltage surfaces at almost perpendicular angles. Owing to such configuration, ions are effectively decelerated, and enough time can be secured until ions of larger mass-to-charge ratios assuredly enter the ion trap space.

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Kyoto, Japan

Junichi Taniguchi