SU957318A1

SU957318A1 - Quadruple mass spectrometer

Info

Publication number: SU957318A1
Application number: SU802875355A
Authority: SU
Inventors: Александр Федорович Кузьмин
Priority date: 1980-01-28
Filing date: 1980-01-28
Publication date: 1982-09-07

Description

(54) КВАДРУПОЛЬНЫЙ МАСС-СПЕКТРОМЕТР(54) QUADRUPOLE MASS SPECTROMETER

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Изобретение относитс к масс-спектрометрии , а именно к квадрупольным массспектрометрам дл анализа молекул рных пучков.The invention relates to mass spectrometry, namely quadrupole mass spectrometers for analyzing molecular beams.

Известны квадрупольный масс-спектрометры , содержащие источник молекул рного 5 пучка, ионизатор, анализатор с полеобразующими электродами, приемник ионов и устройство дл улавливани молекул рного пучка 1.Quadrupole mass spectrometers are known, which contain a source of molecular 5 beam, an ionizer, an analyzer with field-forming electrodes, an ion receiver and a device for capturing molecular beam 1.

В этих масс-спектрометрах молекул рный пучок направл ют перпендикул рно оси анализатора, ввод т в ионизатор, ионизируют пучком зар женных частиц, формируют полученные ионы в узкий направленный пучок, вывод т ионный пучок из ионизато- 15 ра и ввод т в раздел ющее поле анализатора .In these mass spectrometers, the molecular beam is directed perpendicular to the axis of the analyzer, introduced into the ionizer, ionized with a beam of charged particles, the resulting ions are formed into a narrow directional beam, the ion beam is removed from the ionizer 15 and inserted into the separation field analyzer.

От момента выхода из ионизатора до момента входа в анализатор (а точнее в ту область анализатора, где его раздел ю- ° щее поле вл етс строго гиперболичным) ионный пучок проходит так называемое краевое поле анализатора. Как известно, краевое поле на входе квадрупольного анализатора ведет к потере чувствительности и дискриминации по массам.From the moment of exit from the ionizer to the moment of entry into the analyzer (or more precisely in that area of the analyzer, where its division of the field is strictly hyperbolic), the ion beam passes through the so-called edge field of the analyzer. As is known, the marginal field at the input of a quadrupole analyzer leads to a loss of sensitivity and discrimination by masses.

В этом поле тер етс основна дол ионов, выход щих из ионизатора, особенно при высокой разрешающей способности анализатора , причем дол потер нных ионов различна дл ионов различных масс. .In this field, the main fraction of the ions leaving the ionizer is lost, especially at high resolution of the analyzer, and the proportion of lost ions is different for ions of different masses. .

Известн также квадрупольный массспектрометр , содержащий источник молекул рного пучка, ионизатор, анализатор с полеобразующими электродами и расположенный за ним приемник ионов 2.A quadrupole mass spectrometer is also known, which contains a source of molecular beam, an ionizer, an analyzer with field-forming electrodes and an ion receiver 2 located behind it.

В известном масс-спектройетре на входе ионного пучка в анализатор предусмотрены средства дл уменьщени вли ни краевого пол на ионный пучок. Однако полностью устранить вли ние краевого пол принципиально невозможно.Means are provided in the known mass spectrometer at the entrance of the ion beam to the analyzer to reduce the influence of the edge field on the ion beam. However, it is fundamentally impossible to completely eliminate the influence of the marginal field.

Цель изобретени - увеличение чувствительности и точности анализа.The purpose of the invention is to increase the sensitivity and accuracy of the analysis.

Claims

This goal is achieved by the fact that in a quadrupole mass spectrometer containing a molecular beam source, an ionizer, an analyzer with field-forming electrodes and an ion receiver located behind it, the molecular beam source is connected to the analyzer through a collimator, and the optical axis of the ionizer intersects the optical axis of the analyzer inside the latter is outside the marginal fields of the analyzer at a distance greater than the radius of the floor of the analyzer. The optical axes of the source of the molecular beam and the collimator may coincide with the optical axis of the analyzer or intersect it at an acute angle at the point of its intersection with the optical axis of the ionizer. FIG. 1 and 2 depict the proposed mass spectrometer. The mass spectrometer contains a source of 1 molecular beam, a collimator 2, an analyzer 3, an ionizer 4, a receiver 5 ions. optical axes 6, 7, 8 and 9, respectively, of the source of the molecular beam, collimator, analyzer and ionizer, the molecular beam with the point 10 of intersection of the optical axes of the collimator, analyzer and ionizer. Mass spectrometer works as follows. The molecular beam is directed from the source of the molecular beam 1 through the collimator 2 to the analyzer 3 along the axis 8 of the latter. The required speed of movement of the ions along the axis 8 of the analyzer, which in known quadrupole mass spectrometers is created by ion acceleration by the electric fields of the ionizer 4, in the proposed mass spectrometer is achieved by directing the molecular beam along the ion-optical axis of the analyzer. As is known, in a molecular beam, all molecules that form it already have a directional initial velocity, which can be quite substantial, as, for example, in the case of a supersonic jet. This velocity in the order of magnitude corresponds to the required ion velocity along the analyzer. Due to the fact that the molecules are neutral, they pass the edge field of the analyzer without loss and discrimination. The ionization of these molecules is carried out inside the analyzer on its axis beyond the influence of its edge fields, for example, by laser radiation from the ionizer. The ions thus formed retain the initial velocities possessed by the initial molecules, move in the field of the analyzer, are separated by masses, and are recorded. The effect of the edge fields of the analyzer can be neglected inside the analyzer at a distance equal to or greater than the radius of the analyzer's floor (the latter is equal to half the distance between its opposite electrodes). Therefore, it is advisable to ionize the molecular beam inside the analyzer 3 at a distance from its entrance, somewhat larger than the radius of the field of the analyzer, i.e., that the optical axes 8 and 9 of the analyzer and ionizer intersect inside the analyzer 3 at a distance from its entrance, more. radius of the analyzer field 3. It is most convenient to ionize the molecular beam inside the analyzer with a photon beam, such as a high-density laser beam, since photons are not affected by the floor of the analyzer. In this case, the sensitivity of the molecular beam analysis can be increased by using a narrow flat light beam intersecting the axis of the analyzer with its plane. For ionization, high-energy charged particle beams capable of crossing the analyzer field with little or no deviation from their original direction can be used. The component of the initial velocity of molecules in a molecular beam will be directed along the axis of the analyzer from its entrance to its exit and in the event that Introduce the beam into the analyzer at an acute angle to the axis of the analyzer, i.e., at an angle less than 90 °. In this case, the optical axes 6 and 7 of the source of the molecular beam and the collimator must coincide and ne ... the optical axis 8 of the analyzer below at its intersection point 10 with the optical axis 9 of the ionizer (Fig. 2). In all cases, it is advisable to ionize the molecular beam on the axis of the analyzer or near the axis. In this case, the coordinates of the nucleation of ions are minimal; therefore, the amplitudes of stable oscillations of these ions in the analyzer are minimal and the sensitivity of the analysis is maximal. Thus, in the proposed quadrupole mass spectrometer, the maximum sensitivity of the analysis is achieved by eliminating ion losses in the edge field of the analyzer and the accuracy of the analysis is improved, since a different level of ion losses in the edge field of the analyzer is excluded depending on the molecular weight of these ions. Claim 1. A quadrupole mass spectrometer comprising a molecular beam source, an ionizer, an analyzer with field-forming electrodes and an ion receiver located behind it, characterized in that, in order to increase the sensitivity and accuracy of the analysis, the molecular beam source is connected to the analyzer through a collimator and the optical axis of the ionizer intersects the optical axis of the analyzer inside the latter outside the boundary fields of the analyzer at a distance greater than the radius of the field of the analyzer.