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Time-of-flight mass spectrometre

IPC classes for russian patent Time-of-flight mass spectrometre (RU 2381591):

H01J49/40 - Time-of-flight spectrometers (H01J0049360000 takes precedence);;

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FIELD: physics.

SUBSTANCE: proposed invention relates to mass spectrometry with orthogonal entry of ions and is widely used in organic and bioorganic chemistry, immunology, biotechnology and medicine when ionising analysed substances using an electron impact method, electrospray etc. The time-of-flight mass spectrometre consists of an electrospray type ion source, an orthogonal ion accelerator (pulser), which includes regions for accumulation and acceleration of ions, field-free drift space, two-stage mirror and detector. The accumulation region of the pulser is made in form of a monopole whose grounded electrode edge is combined with the grounded grid of the acceleration region. There is an ion exit slit in the grounded electrode edge of the monopole.

EFFECT: increased resolution of the time-of-flight mass spectrometre.

2 cl, 3 dwg

The present invention relates to the field of mass spectrometry with orthogonal input ions and will find wide application in solving problems in organic and Bioorganic chemistry, immunology, biotechnology and medicine during ionization of the compounds under investigation by electron impact, "electrospray" and others. At the existing time-of-flight mass spectrometers with orthogonal input ions there are several factors limiting the resolution of the device, two of which are essential for time-of-flight mass spectrometer with orthogonal input, the first due to the width of the ion beam in the area of accumulation, and the other by the range of ion velocities at the moment of start. In other words, the decisive factor limiting resolution time-of-flight instruments, is the presence of non-zero phase volume (φ=ΔvΔx) of the ion beam in the area of accumulation of the orthogonal accelerator (PALSAR).

Orthogonal to the velocity dispersion of the ions in the field of accumulation Pulsera leads to time reversal (turn around time), which cannot be compensated by any analyzers, containing only homogeneous field and bespravie intervals. Therefore, time reversal is the main factor limiting resolution time-of-flight instrument with orthogonal input ion PU is CA.

Known time-of-flight mass spectrometer [1], consisting of a pulsed ion source, bespolovogo drift space, a two-stage electrostatic mirror and the detector, which is good enough (to second order) is compensated by the variation of the initial energies of the ions of the same type. However, it is not possible to obtain a higher degree of ion focusing on energy, and consequently, to achieve a significant increase resolution without significantly increasing the dimensions of the device.

Also known time-of-flight mass spectrometer [2], consisting of a pulsed ion source, bespolovogo drift space, two flat net capacitors inhibitory fields separated by the second bespaleva interval, and the ion detector. This mass spectrometer is achieved by focusing the third order energy, however, and its resolution is significantly limited uncompensated effect of time reversal ions in the orthogonal input method.

The closest of the known devices is time-of-flight mass spectrometer MX 5303 [3] with orthogonal input ion beam, selected as a prototype. It consists of an ion source for producing ions of Bioorganic substances used method of extraction of ions from solutions at atmospheric pressure (electrospray"); system of differential pumping with a cooling gas transport and focusing quadrupole systems; orthogonal accelerator (pulser) with a uniform electrostatic field in the area of accumulation of ions (from the plate with U_Pusha grounded grid), and their acceleration (from a grounded grid to the electrode with U_Acc); span bespolovogo space, two-stage mirror and the detector. The disadvantage of the prototype is not sufficiently high resolution (R₀~ 10000), which is organic, a large time spread of the ions when they are orthogonal acceleration Pulsera with a homogeneous field.

Object of the invention is the reduction of the time-reversal and, consequently, an increased resolution time-of-flight mass spectrometer.

The problem is solved due to the fact that in the known time-of-flight mass spectrometer comprising an ion source of the type "electrospray"orthogonal accelerator (PALSAR), including the area of accumulation and ion acceleration, bespolovogo span space, two-stage mirror and the detector, the area of accumulation Pulsera made in the form of a monopole, the edge of the grounded electrode which is combined structurally combined with the grounded grid area of acceleration.

Offer vremjaproletnyj the th mass spectrometer differs from the prototype in that in the field of accumulation Pulsera using monopole creates an inhomogeneous electrostatic field, which first generates a temporary focus on the field boundary for strictly parallel beam and, secondly, it greatly reduces the time reversal ions for weakly diverging beam that despite a slight increase in the energy spread in the ion package gives the effect of increasing the resolution is approximately two times at a constant geometrical and electrical parameters of the device.

The invention is explained in mathematical calculations and drawings, in which figure 1 is a schematic representation of a mass spectrometer Pulsera with inhomogeneous field figa presents the monopole in the scheme of orthogonal accelerator (PALSAR), figb presents the orthogonal accelerator (PALSAR), creating a uniform electrostatic field - pulser prototype.

Consider the work of the proposed mass spectrometer.

The proposed new device (figure 1) consists of an ion source 1, creating a continuous ion beam, orthogonal accelerator (PALSAR), including the area of accumulation 2 and acceleration 3 ions, bespolovogo drift space 4, the first mirror 5 with a retarding potential, the second mirror 6 having potential, and the ion detector 7.

The proposed device works follow the way.

Continuous ion beam generated in the source 1, falls in the region of accumulation Pulsera 2, where when applying a pulsed potential U_Pushcreates an inhomogeneous electrostatic field, which cuts out a continuous beam and orthogonal to the original direction accelerates the ion packet, which, falling into the acceleration region with a homogeneous electrostatic field 3, accelerated to an energy of qU_Accthat flies in the fieldless span the space of 4; slowing field of the first mirror 5, is reflected in the second mirror 6; accelerated in the field of the first mirror 5, is flying in fieldless space 4 and falls on the detector 7. It is assumed that the velocity vector of the ion package is a small angle with the axis X, as in the prototype.

Let us prove that the proposed device has the effect of reducing the time reversal, bringing with it an increased resolution of the instrument is approximately two times.

In the absence of an electrostatic field of a continuous ion beam is injected along the Z-axis in the region of accumulation Pulsera as close to the rod monopole strictly parallel to the edge of the grounded electrode of the monopole and perpendicular to the X axis pulser. When submitting eject U_Pushpulse to hyperbolic (or cylindrical) electrode monopole and pull pulse U_Pullnext after aseminae grid electrode ion package is accelerated first to the ground potential in a two-dimensional field of the monopole, and then to the accelerating potential in a uniform field. Orthogonal accelerated ions enter into the mass analyzer, the parameters of which are identical to the parameters of the prototype.

When submitting eject pulse U_Pushat the core of the monopole in the field of accumulation palser, i.e. in the space between the electrodes of the monopole, is a two-dimensional field, the potential distribution which is determined by the expression (I):

where U_Push- eject the potential on the rod monopole,

anddistance from the rod to the ribs grounded electrode monopole.

The electric field and its components are defined by the relations:

In the field with the potential (1) can be easily integrated the exact equations of motion for ions:

where m, q are the mass and charge of the ion. The solutions of the equations (4) will be:

where x₀, y₀and V_0xV_0y- the initial coordinates and the components of the initial velocity of the ion along the axes X and Y, respectively,

For strictly parallel beam, i.e. beam, in which all ions have no tangential component of the velocity (V_0x=0), system (5) takes the form:

From the system (6) shows that for any initial coordinates (x₀, y₀) all ions even from the ribbon beam, and not just a narrow cylindrical, get in the plane of the exit slit of the accumulation area (x=0) at the same time, spending time, defined by the expression (7):

This indicates the presence of intermediate temporary focus on the output of the inhomogeneous field of the proposed device.

Time reversal in an inhomogeneous field, τ is determined from the first equation of system (5).

Putting the arctangent of the expression (8) in a Taylor series, keeping only the first member and given that x₀≈and, we obtain the expression (9)connecting time reversal for heterogeneous τ and uniform τ₀fields:

Thus, as (ΔT, ΔT₀)<<τ, T≈T₀, the resolution R of the proposed mass spectrometer with Pulsera-monopole with respect to time reversal is approximately two times larger than that of the prototype R₀, that is, a mass spectrometer with Pulsera with a homogeneous field:

and, thus, the execution of the field of accumulation Pulsera in the form of a monopole contributes to the achievement of the objectives.

Literature

1. Veerathai, Bagamery, Dwick. A new principle focus of IO is different packets in flight mass spectrometers. // ZH - 1971 - v.41, V, s-1501.

2. Ukhalov, Navkrishna, Roublev. // Russian Federation patent No. 2295797. Application for invention No. 2005119734 priority from 16.06.2005 G., "time-of-Flight mass spectrometer.

3. Time-of-flight mass spectrometer with elektrorazpredelenie MX 5303. // Prospectus of the Institute for analytical instrumentation RAS. http://www.iai.rssi.ru

1. Time-of-flight mass spectrometer comprising an ion source of the type "electrospray"orthogonal accelerator (PALSAR), span bespolovogo space, two-stage mirror and the detector, characterized in that the area of accumulation Pulsera made in the form of monopole, creating a quadratic electrostatic field, and the edge of the grounded electrode monopole combined with grounded grid fostering Pulsera with a homogeneous field.

2. Time-of-flight mass spectrometer according to claim 1, characterized in that the edge of the grounded electrode monopole has a slot exit of ions.