RU2564443C2 - Device of orthogonal introduction of ions into time-of-flight mass spectrometer - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: invention relates to the field of time-of-flight mass spectrometry and will find wide application in solving problems of organic and bioorganic chemistry, toxicology, criminalistics, immunology and medicine when ionising molecules of investigated substances with methods of electronic shock, "electrospray". The device of orthogonal introduction of ions into a time-of-flight mass spectrometer (TFMS) includes a channel for transportation of a continuous beam of ions arriving from a source, being formed by two electrodes, aligned in parallel to the direction of movement of the continuous ion beam and designed for development of a pulse electric field, which pushes the ions in direction perpendicular to the continuous beam, and electrodes for electrostatic acceleration of ions arranged outside the specified channel. Into a gap between electrodes forming the channel of charged particles transportation there are additional electrodes introduced, which are aligned in parallel to the direction of movement of a continuous ion beam, and static electric potentials applied to these electrodes provide for compression of a continuous ion beam in direction of pulse pushing of ions from the channel.

EFFECT: increased sensitivity of TFMS.

3 dwg

Description

The invention relates to the field of time-of-flight mass spectrometry and will find wide application in solving problems of organic and bioorganic chemistry, toxicology, forensic science, immunology and medicine in the ionization of molecules of the studied substances by electron impact, electrospray, etc.

The vast majority of the sources currently used in mass spectrometry create continuous ion beams. To coordinate time-of-flight mass spectrometers (VPMS) with such sources, a continuous ion beam is converted into short pulsed ion packets. The most effective and widely used method for creating ion packets of short duration is the acceleration of charged particles in an orthogonal ion input device in the IMSS with a periodically generated pulsed electric field in the direction perpendicular to the direction of motion of the continuous ion beam.

A prototype of the invention is an orthogonal input device [1], schematically represented in figure 1, a. In the above scheme, a continuous ion beam 1 enters from a source into a transport channel formed by two electrodes 2 and 3 oriented in the yz plane parallel to the z direction of the continuous beam motion. The electrode 3 has a window covered by a conductive grid. Outside the transport channel, electrodes 4 are also located, also having windows, some of which are tightened with conductive nets.

In the time intervals between the pulse ejection of ions from the channel, the electrodes 2 and 3 are grounded and there is no electrostatic field in the transport channel. At certain time intervals, a pulse electric voltage is applied to the electrode 2, and a uniform electric field is formed in the transport channel, pushing out the ions received at these time intervals into the channel through the window in the electrode 3 in the x direction, perpendicular to the z direction of the continuous beam. The ions pushed out of the channel are accelerated to the required energy in the x direction by an electric field created using a set of electrodes 4.

The disadvantage of the prototype is due to the presence of angular dispersion of the directions of movement of the free expansion of a continuous ion beam in the transport channel in the x direction at time intervals between pulsed ejection, as shown in figure 1, b. The width of the transport channel is limited by the requirement to achieve a certain magnitude of the buoyant field strength at the maximum achievable amplitude of the pulse voltage at the electrode 2. Moreover, the indicated free expansion of the ion beam leads to partial emission of ions from the transport channel through the window in the electrode 3 into the region of the electric field formed by the set of electrodes 4 Such ions reach the VPMS detector at an arbitrary time and become a source of a noise signal that reduces sensitivity HDI.

There are analogues of the described prototype [2-4], in which the electrode 3 and electrodes 4 are gridless, however, these analogues have the indicated drawback.

The objective of the invention is the spatial compression coming from the source of a continuous ion beam in the transport channel of the device orthogonal input of ions into the IMSS in the x direction of ejection of ions and, as a result, increase the sensitivity of the IMSS.

The problem is solved in that additional electrodes are introduced into the transport channel of the device for orthogonal ion input into the IMSC, oriented in parallel with the direction of motion of the continuous ion beam, to which static electric voltages are applied. In this case, unlike the prototype, a static inhomogeneous electric field is created in the ion transport channel, which acts on the ions and prevents the expansion of the continuous ion beam in the x direction.

The invention is illustrated by drawings, where in Fig.2 shows a diagram of the invention with one example of the geometry of additional electrodes (Fig.2, a) and the type of ion trajectories in the planes xz (Fig.2, b) and yz (Fig.2, c), figure 3 presents a diagram of the invention with another example of the geometry of the additional electrodes (Fig 3, a) and the type of ion trajectories in the planes xz (Fig 3, b) and yz (Fig 3, c).

The proposed device for orthogonal ion input into the HPMC (Fig. 2, a) consists of a channel formed by two electrodes 2 and 3, into which a continuous beam of ions 1, a set of electrodes for accelerating ions 4, and additional electrodes 5 located in the transport channel enter. In the presented in figure 2, and the option for additional electrodes 5 applied the same voltage.

The proposed device operates as follows. A continuous beam of ions 1 enters the transport channel formed by electrodes 2 and 3, which are grounded in the accumulation mode. A static electric voltage U _{1 is} applied to the additional electrodes 5, which forms an electric field in the channel, which is close to quadrupole in the region of movement of the ion beam. This field has a focusing effect on the ion beam in the xz plane (FIG. 2, b) and, thus, compresses the beam in the x direction and prevents the possibility of ions escaping through the window in the electrode 3 at time intervals between the ejection pulses. The action of the considered static field is defocusing on the ion beam in the yz plane (Fig. 2, c), however, a slight increase in the size of the ion beam in the y direction does not affect the properties of the IMSS. When a pulse voltage is applied to the electrode 2 for ejecting ions, the presence of voltages on the electrodes 5 leads only to a slight distortion of the structure of the ejecting electric field, which does not affect the properties of the IMSS, since the strength of the static field required to compress a continuous ion beam is much lower than the strength of the pulse ejecting field.

Figure 3, a presents a diagram of the invention with another example of the geometry of additional electrodes introduced into the channel for transporting a continuous ion beam. In the embodiment shown in FIG. 3, as an embodiment, two pairs of additional electrodes 5 and 6 are introduced into the channel, to which the static electric potentials U ₁ and U _{2 of} opposite signs are applied. In this case, it is possible to realize spatial compression of a continuous ion beam in the transport channel in the transport channel in two mutually perpendicular planes xz and yz. Figures 3, b and 3, c show the trajectories of ions in these planes in the case when a static electric potential U _{1 is} applied to the additional electrodes 5, which compresses the ion beam in the x direction.

Thus, the introduction of additional electrodes into the transportation channel of the device for orthogonal ion input of ions, oriented parallel to the direction of motion of the continuous ion beam, to which static electric potentials are applied, contributes to the task of increasing the sensitivity of the IMSS.

Information sources

1. Dodonov A.F., Chernushevich I.V., Dodonova T.F., Raznikov V.V., Talroze V.L. The method of time-of-flight mass spectrometric analysis of continuous ion beams. // A.S. 1681340 A1. 1987.

2. Franzen J. Gridless time-of-flight mass spectrometer for orthogonal ion injection. // US Patent 0011703 A1. 2001.

3. Makarov A.A. A time of flight mass spectrometer including an orthogonal accelerator. // Patent WO 01/11660 A1. 2000.

4. Pomozov T.B., Yavor M.I. Meshless orthogonal accelerator for multi-reflective time-of-flight mass analyzers. // Scientific instrument making. 2012.V.22. Issue 1. S.113-120.

Claims (1)

A device for orthogonal ion input into a time-of-flight mass spectrometer (VPMS), including a channel for transporting a continuous ion beam coming from a source, formed by two electrodes oriented parallel to the direction of motion of the continuous ion beam and designed to create a pulsed electric field pushing the ions in the direction perpendicular to the continuous beam , and electrodes for electrostatic acceleration of ions located outside the specified channel, characterized in that in simple anstvo between the electrodes forming the transport path, introduced additional electrodes oriented parallel to the direction of movement of the continuous ion beam to which are applied a static electric potentials.

Images