SU1267512A1 - Method of analyzing charged particles in three-dimensional trap-type hyperboloid mass spectrometer - Google Patents

Abstract

This invention relates to the field of mass spectrometry. It can be used to create hyperbolic mass spectrometers such as three-dimensional traps with high resolution and sensitivity. The purpose of the invention is to increase the accuracy of the analysis. The method is to follow up. With the help of source 3 through the through channel in the ring electrode 2 into the working volume of the analyzer, limited by electrodes 1 and 2, during ionization the electron flow 4 is introduced. The molecules are ionized near the center of the system, after which they are sorted in a high-frequency constant. the floor To achieve this goal, after the sorting process has been completed, the charged particles are accelerated in the direction of the end electrodes 1, and after they pass through the lead electrodes, the charged particles are decelerated by a potential difference determined by the ratio shown in the materials of the invention. To achieve a positive effect, it is sufficient during the output to apply a potential difference of 80-90 V. between the ring and end electrodes. In this case, the molecular ions are easily separated. A device for implementing the method also contains additional

Description

grid 5, detector of charged particles; circles denote positive charged particles. This method allows simple means to significantly suppress the peaks of fragment ions in the mass spectra without reducing the intensity of the peaks of molecular ions. 2 Il.

one

The invention relates to the field of mass spectrometry, and more specifically to hyperboloid mass spectrometry, and can be used to create hyperbolic mass spectrometers of the type of three-dimensional trap with high resolution and sensitivity.

The purpose of the invention is to improve the accuracy of the analysis.

The amplitude of oscillations of charged particles in hyperboloid mass analyzers depends on the initial coordinates (Eq) and the velocities (TO) of the latter. With increasing (Y) and (Y ,,), the amplitude of oscillations increases.

Usually in hyperboloid mass spectrometers of the type of three-dimensional trap molecules and gas atoms ionize near the center of the system :. In this case, if the ionizing electron flow is introduced through the ring electrode, then the initial coordinate for the formation of ions along the axis (Q) of symmetry turns out to be rather small. Therefore, mainly the amplitude of oscillation will be determined by the initial velocity (Zo). charged particles along this axis. Molecular ions are formed during ionization, as is well known, with low thermal initial velocities. Therefore, the oscillation amplitude of these ions is small and during sorting they are localized (along the Z axis) near the center of the system (origin Z 0). Fragmentation ions in the formation have for the most part large initial energies. As a result, when sorting they are distributed over the entire working volume of the analyzer. In other words, if you are interested in their position along the Z axis, you can say that they are distributed along the entire axis from Z 0 to Z C1, where 4 is the distance from the center of the system to end electrode. If a

during the output in the analyzer a constant accelerating field is created along the Z axis (for example, during the output the potentials on the electrodes are constant and the positive potential of the ring electrode is higher than the potential of the end electrodes), then, depending on the position of the particles at the moment of the start of the output, they pass through face

electrode will have different speeds. Those ions that at the time of the start of the input were located in the center of the system will acquire greater speed in the field. If the decelerating grid is now located behind the front end electrode, then it can be used to pass only fast ions towards the detector, i.e. those that at the time of the beginning of the withdrawal were near the beginning

coordinates (in this case, molecular ions). Thus, in the analyzer itself, during the extraction, molecular ions can be selectively accelerated compared to fragmentation,

using lix location in the analyzer volume during sorting.

As a result of acceleration of charged particles in the analyzer and their braking outside the analyzer, a

the positive effect is that the relative height of the peaks of fragment ions decreases sharply (by a factor of 3–5) in comparison with the height of the peaks of the molecular ions. With

This way, if one chooses the braking potential difference correctly, then the spectrum is largely depleted in the peaks of fragment ions.

To achieve a positive hey.

It is sufficient to apply a potential difference of 80-90 V. between the annular and end electrodes during the extraction. The molecular ions are easily separated.

Claims (1)

Fig. 1 is a diagram of a device implementing the proposed 3 method; Fig. 2 is a diagram showing the potential distribution along the Z axis during acceleration and deceleration of charged particles. A device that implements the proposed method contains end 1 and ring 2 analysis electrodes; Thor, source 3 of ionizing electron flow, ionizing electron flow 4, additional grid 5, detector 6 of charged particles. In addition, in FIG. 1, circles denote positive charged particles (ions). The method is carried out as follows. With the help of source 3 through the squared channel (not shown) in the annular electrode 2 into the working volume of the analyzer, limited by electrodes 1 and 2, during ionization, an electron beam 4 is introduced. The molecules ionize near the center of the system (Z 0), after which sorting them in a high-frequency constant field. After the sorting process is completed, a constant potential UK is fed to the ring electrode 2, and a constant potential UT is fed to the end electrodes 1, and the sorted charged particles are accelerated along axis 1. Particles pass through the end electrode (through channels for output of particles in the end electrode are not shown) at a speed along axis 1, which basically corresponds to the position of the particle at the beginning of the output. In such a case, if by the end of the particle sorting time, the small coordinates along axis 2 (Z,), then these particles, passing through the end electrode, will have a greater speed along axis 1. Now, if the output ions behind the end electrode are braked by a potential difference uU equal to / order / U center - 1} ring / and center / - potential of the center of the working volume /., Then only ions located in the direction of the detector can pass; the moment the output begins near the center of the system, i.e. The ions formed during ionization with small initial coordinates are molecular ions. The required decelerating potential difference l 1 /, opr is determined by the ratio 12 h, 1 CR „-P / - where O is the potential of the ring electrode at the output time, UT is the potential of the end electrode at the time of the output. -3 PO and XD and g - the distance from the center of the analyzer to the surface of the ring - electrode along the axis X and Z, is the distance from the center of the analyzer to the surface of the end electrode along the axis Z. In the case of an axisymmetric analyzer XQ, Q Gd and Rd 1. An experimental verification of the method was carried out using an axisymmetric analyzer such as a three-dimensional trap with a Gd of 19 mm and a distance between the end electrodes of 38 mm. An assembly of microchannel plates was used as an ion detector. When and 250 V, 1} 163 V, lithorm 3 V (as compared with the case of d1)), the relative height of the peaks is 18, 28,32,40 amu. remained unchanged, and the height of the peaks 29,27,39, 43,44 decreased by 3-4 times. The proposed method allows using simple means to significantly suppress the peaks of fragment ions in the mass spectra (by a factor of 3.-5) without reducing the intensity of the peaks of the molecular ions and, thus, greatly facilitate the analysis of the molecular composition of the analyzed gas mixture. DETAILED DESCRIPTION A method for analyzing charged particles in a three-dimensional trap-type hyperboloid mass spectrometer with one ring and two end electrodes, according to which charged particles are introduced into the working volume of the analyzer, sorted by specific charges and detected the fact that, in order to increase Accuracy, after the termination of sorting, the charged particles are accelerated by a constant time field the direction of the end electrodes, and after the passage of the ends of the electrodes by them, the charged particles are decelerated by the intensity of the potentials, determined by the ratio Ch .-- PTGp-- -. where DH is the potential applied to the ring electrode during acceleration. AT, 1267512 and -potential supplied to end electrodes during acceleration, B, (2: -. Р.г: / х Xd and Yq are the distances from the center of the analyzer to the surface of the ring electrode along the axis X, Y, Zg is the distance from the center of the analyzer to the surface of the end electrode along axis 2.