CN102568996A - Ionization device for mass spectrometer - Google Patents

Abstract

The invention provides an ionization device for a mass spectrometer. The ionization device comprises an ionization chamber and at least one lamp filament arranged in the ionization chamber. The ionization device further comprises at least one pair of radio-frequency electrodes arranged oppositely, wherein the at least one pair of radio-frequency electrodes has the radio-frequency frequency of 10<6>-10<9> Hz and voltage of 1-2000 V. According to the invention, a strong electromagnetic field can be generated by adjusting the radio-frequency frequency and the voltage applied on the radio-frequency electrodes, so that an electron movement path can be increased to enough length; that is to say, increase of ionization efficiency cannot be limited by the intensity of a magnetic field; therefore, the ionization efficiency is beneficial to being increased greatly; and simultaneously, because the radio-frequency frequency and the voltage applied on the radio-frequency electrodes can be adjusted, the ionization device provided by the invention can be applied to all kinds of different samples and has a wide application range.

Description

Be used for mass spectrometric ionization device

Technical field

The present invention relates to a kind of mass spectrometric ionization device that is used for.

Background technology

Mass spectrometer mainly is used for measuring the quality of microcosmic particle.Because the quality of microcosmic particle is very little, in order to measure their quality, at first to make electric charge on the microcosmic particle band, just can control their motion then through electromagnetic field, just can measure the quality of microcosmic particle through certain calculating.Therefore, mass spectrometer all must be provided with the ionization device that can sample ionization be become ion.

In ionization device, make the process of electric charge on the sample band of being analyzed be called ionization process.To different samples different ioning methods is arranged, wherein electronic impact method is to use ionization techniques the most widely at present, and this technology is mainly used in the ionization of volatile samples.Generally speaking, sample molecule gets into chamber with the state of gas, and from microcosmic angle, the distance between each sample molecule is very big, therefore can collide electronics and that the collision probability of ionization takes place is very low, and promptly Ionization Efficiency is low.In order to improve Ionization Efficiency, the method for taking usually is the length that increases the flight path of electronics.After ionization chamber vacuumizes, send into low pressure sample gas.Like vacuum degree in the ionization chamber is 10 ^-4Pascal, the about 10mm of the width of ionization chamber is 10mm so electronics passes across the straight line distance of ionization chamber, in fact because electronics walks is curve, so length can be greater than 10mm.Because air pressure is very low; This moment electronics the about 200m of mean free path, in other words, electronics will fly 200 meters just can collide sample molecule; So from probability; Need sample molecule of about 20000 electronics ability ionization success, ionization probability is very little, and the electronics utilance is very low in other words.Air pressure certain with the electronics condition that just energy is fixed under, the mean free path of electronics is fixed.Therefore, if we increase from getting into the during this period of time length of the flight path of interior electronics of ionization chamber to the ionization chamber that flies out; Perhaps prolong the time of staying of electronics in the ion chamber, can make electronics be more prone to run into sample molecule, thereby improve the probability of electrons hit sample molecule.

As depicted in figs. 1 and 2, the ion source in the mass spectrometer comprises set of lenses and ionization device.Set of lenses comprise coaxial installation repeller electrode 1, introduce the utmost point 2, condenser lens 3, extraction pole 4 etc.The effect of set of lenses mainly is to make the sample molecule with going up electric charge to be got in the mass analyzer smoothly by ionization device.Traditional ionization device mainly comprises ionization chamber 5, be located at the N utmost point 6 and the S utmost point 7 of positioned opposite in the ionization chamber 5 and be arranged on the N utmost point 6 and the S utmost point 7 between two filaments 8; And between the repeller electrode 1 and the introducing utmost point 2 of two filaments 8 in ion source, the N utmost point 6 can be processed by permanent magnet or electromagnet with the S utmost point 7.

The filament 8 of ionization device is heated the back and produces electronics, and electronics is quickened the back from filament 8 ejaculations by 70 electron-volts voltage.The S utmost point 6 and the N utmost point 7 generation magnetic fields, the simulaed path of electronics is as shown in Figure 2 under the action of a magnetic field, becomes helix shape.So the path that electronics moves in ionization chamber 5 is elongated, the time has also extended, and therefore, electron collision has increased considerably to the probability of analytic sample molecule, has promptly improved Ionization Efficiency.

The tradition ionization device has following two drawbacks: the one, and the magnetic field intensity of general permanent magnet is about 300 Gausses, and produce high-intensity magnetic field needs superconductor, and cost is very high, can have side effects to mass spectrometric Circuits System if use electromagnet to produce magnetic field.This length that just makes the electron motion path to increase is very limited, i.e. the raising of Ionization Efficiency is restricted; And magnetic field intensity is unadjustable, and to a permanent magnet, its magnetic field intensity is specific, can not change along with the demand of sample, so its narrow application range.The 2nd, magnetic field intensity is inhomogeneous, thereby trajectory of electron motion is difficult to accurate Calculation, and the Lorentz force equation of motion of electron motion can not be found the solution, so people are difficult to accurately predicting electronic motion track.

Summary of the invention

The object of the present invention is to provide a kind of mass spectrometric ionization device that is used for, to solve the inhomogeneous and uncontrollable technical problem of magnetic field intensity in the above-mentioned prior art.

For solving the problems of the technologies described above, the present invention adopts following technical scheme:

Of the present inventionly be used for mass spectrometric ionization device; Comprise ionization chamber, be located at least one filament in the said ionization chamber; Wherein, said ionization device also comprises the radio frequency electrode of at least one pair of positioned opposite, and the rf frequency that is added in said at least one pair of radio frequency electrode is 10 ⁶-10 ⁹Hertz, voltage is the 1-2000 volt.

The circular frequency of said at least one pair of radio frequency electrode satisfies inequality:

wherein; ω representes circular frequency; The initial velocity of v (0) expression electron motion; L representes the half the of distance between two said radio frequency electrodes; N representes that electronics runs into the number of times of the simple harmonic vibration of doing before the wall of said ionization chamber in said ionization chamber, and x (0) representes the initial position of electron motion.

The voltage of said at least one pair of radio frequency electrode satisfies inequality: wherein V representes voltage; L representes the half the of distance between two said radio frequency electrodes; M representes the quality of electronics; ω representes circular frequency; N representes that electronics runs into the number of times of the simple harmonic vibration of doing before the wall of said ionization chamber in said ionization chamber, and q representes the electric weight of electron institute band.

The quantity of said filament is a pair of, is arranged symmetrically in the said ionization chamber.

Said radio frequency electrode is that plane tabular or curved surface are tabular.

The quantity of said radio frequency electrode is two pairs, is evenly arranged in the said ionization chamber.

Can know that by technique scheme advantage and the good effect that is used for mass spectrometric ionization device of the present invention is: of the present inventionly be used for mass spectrometric ionization device, comprise the radio frequency electrode of at least one pair of positioned opposite, and the rf frequency that is added in radio frequency electrode is 10 ⁶-10 ⁹Hertz, voltage is the 1-2000 volt.So; Be added in rf frequency and voltage on the radio frequency electrode through adjusting; Can produce very strong electromagnetic field; Thereby can make the electron motion path be increased to sufficient length, that is to say that the raising of Ionization Efficiency can not be restricted because of magnetic field intensity, this helps increasing substantially Ionization Efficiency.Simultaneously; Because the rf frequency and the voltage that are added on the radio frequency electrode can be regulated, the structure that therefore needn't change ionization device just can obtain needed field strength values at an easy rate, so; Ionization device of the present invention can be used in various sample, and is applied widely.In addition; Because the uniform electromagnetic field that radio frequency electrode produces; So being easy to accurate Calculation, trajectory of electron motion comes out; And the Lorentz force equation of motion of electron motion can be found the solution, so people are easy to accurately predicting electronic motion track, and this helps improving the overall measurement accuracy of mass spectrometer.

With reference to the accompanying drawing description of a preferred embodiment, above-mentioned and other purpose of the present invention, feature and advantage will be more obvious through following.

Description of drawings

Fig. 1 representes the perspective view in traditional mass spectrometer intermediate ion source;

Fig. 2 representes the simulaed path sketch map of electronics in traditional mass spectrometric ionization device;

Fig. 3 representes the perspective view that is used for first kind of embodiment of mass spectrometric ionization device of the present invention, and its expression has the structure of a pair of radio frequency electrode;

Fig. 4 representes the mass spectrometric ionization device that is used for shown in Figure 3, the simulaed path sketch map of electronics;

Fig. 5 representes the mass spectrometric ionization device that is used for of the present invention, velocity of electrons decomposing schematic representation;

Fig. 6 representes the structural representation that is used for second kind of embodiment of mass spectrometric ionization device of the present invention, and its expression has the structure of two pairs of radio frequency electrodes;

Fig. 7 representes the structural representation that is used for mass spectrometric the third embodiment of ionization device of the present invention, the structure when its expression radio frequency electrode is curved slab;

When Fig. 8 represented to use traditional mass spectrometric ionization device analytic sample, the concentration of 1.0 μ L was the signal strength map of the every microlitre octafluoro naphthalene of 1 pik-isooctane solution sample;

Fig. 9 representes of the present invention when being used for mass spectrometric ionization device analytic sample, and the concentration of 1.0 μ L is the signal strength map of the every microlitre octafluoro naphthalene of 1 pik-isooctane solution sample.

Embodiment

To combine accompanying drawing to describe specific embodiment of the present invention in detail below.Should be noted that the embodiments described herein only is used to illustrate, be not limited to the present invention.

Like Fig. 3 and shown in Figure 4, of the present inventionly be used for mass spectrometric ionization device, comprise ionization chamber 5, be located at two filaments 8 and the plane tabular radio frequency electrode 11,12 of a pair of positioned opposite in the ionization chamber 5.The rf frequency that is added in a pair of radio frequency electrode 11,12 is 10 ⁶-10 ⁹Hertz, voltage is the 1-2000 volt.In the use, can regulate the voltage of the rf frequency of radio frequency electrode 11,12, thereby obtain desirable magnetic field intensity to the sample characteristics according to the characteristics of sample to be analyzed.The quantity of filament 8 can be selected one or more for use according to actual conditions.

Of the present inventionly be used for mass spectrometric ionization device, through increase electronics in ionization chamber the length through the path prolonged the time of electronics in the ion chamber, thereby improved ionizing efficiency effectively.Meanwhile, the voltage of the radio frequency electrode that generates an electromagnetic field and frequency can be controlled respectively, have increased the control ability to electron motion.

Among the present invention, be added in radio frequency electrode and produce alternating electric field in the space, Newton's second law is satisfied in the motion of electronics in this alternating electric field:

$\stackrel{\&RightArrow;}{f}=m\stackrel{\&RightArrow;}{a}=\stackrel{\&RightArrow;}{E}q---\left(1\right)$

Being write as the differential equation is exactly

$m\frac{d^{2}x}{{\mathrm{<figure-callout\; id="2"\; label="dt"\; filenames="HSA00000413170400011.png,HSA00000413170400032.png"\; state="\{\{state\}\}">dt</figure-callout>}}^2}=\stackrel{\&RightArrow;}{E}q---\left(2\right)$

Wherein, M is an electron mass; Q is an electron charge, and is electric field strength.

Electric field strength is the ratio of distance between voltage and two radio frequency electrodes

$\stackrel{\&RightArrow;}{E}=\frac{V}{D}---\left(3\right)$

Wherein, D is a distance between two radio frequency electrodes

So the electronic motion differential equation is exactly:

$m\frac{d^{2}x}{{\mathrm{<figure-callout\; id="2"\; label="dt"\; filenames="HSA00000413170400011.png,HSA00000413170400032.png"\; state="\{\{state\}\}">dt</figure-callout>}}^2}=-\frac{V}{L}\sin \left(\mathrm{\&omega;t}\right)q---\left(4\right)$

Wherein, L is the half the of distance B between the radio frequency electrode, and ω is the circular frequency of alternating current.In order to find the solution this equation, we take the integration way.The acceleration of electron motion is:

$a\left(t\right)=-\frac{V}{\mathrm{Lm}}\sin \left(\mathrm{\&omega;t}\right)q---\left(5\right)$

Speed is that acceleration was quadratured to the time

$v\left(t\right)={\&Integral;}_0^{t}a\left(t\right)\mathrm{dt}=-\frac{\mathrm{Vq}}{\mathrm{Lm\&omega;}}\cos \left(\mathrm{\&omega;t}\right)+v\left(0\right)---\left(6\right)$

Displacement is that speed was quadratured to the time

$x\left(t\right)={\&Integral;}_0^{t}v\left(t\right)\mathrm{dt}=\frac{\mathrm{Vq}}{\mathrm{Lm}{\mathrm{\&omega;}}^2}\sin \left(\mathrm{\&omega;t}\right)+v\left(0\right)t+x\left(0\right)---\left(7\right)$

We hope, on the x direction of principal axis, electronics had been done n simple harmonic vibration before the wall of running into ionization chamber 5, then during this period of time in, following inequality establishment is arranged:

$\frac{L-x\left(0\right)}{v\left(0\right)}\&GreaterEqual;\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HSA00000413170400011.png,HSA00000413170400032.png"\; state="\{\{state\}\}">n</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&omega;}}---\left(8\right)$

So, can obtain inequality to the alternating current circular frequency

$\mathrm{\&omega;}\&GreaterEqual;\frac{2\mathrm{n\&pi;v}\left(0\right)}{L-x\left(0\right)}---\left(9\right)$

We turn to electronics the function of initial velocity and kinetic energy distribution factor in the speed of radio frequency electrode direction

$\mathrm{\&omega;}\&GreaterEqual;\frac{2\mathrm{n\&pi;}\sqrt{\frac{2\mathrm{\&alpha;}{E}_K}{m}}}{L-x\left(0\right)}---\left(10\right)$

For the general ionogenic size and the first energy of electronics, can obtain the order of magnitude that this frequency approximately is a megahertz.

We can find out from the time expression formula (7) of displacement, and the amplitude of vibrational term is

$\frac{\mathrm{Vq}}{\mathrm{Lm}{\mathrm{\&omega;}}^2}---\left(11\right)$

We also hope amplitude is claimed, if amplitude is too big, then electronics can knock the wall of ion chamber in vibration.So we hope that amplitude is smaller, at least less than n/one of L.

$\frac{\mathrm{Vq}}{\mathrm{Lm}{\mathrm{\&omega;}}^2}\&le;\frac{L}{n}---\left(12\right)$

So the voltage that we must be added on the radio frequency electrode preferably satisfies condition:

$V\&le;\frac{{\mathrm{<figure-callout\; id="2"\; label="mL"\; filenames="HSA00000413170400011.png,HSA00000413170400032.png"\; state="\{\{state\}\}">mL</figure-callout>}}^2{\mathrm{\&omega;}}^2}{\mathrm{nq}}---\left(13\right)$

Certainly, even do not satisfy the following formula condition, the wall that has a spot of electronics in motion process, to bump against ionization chamber influences little, also is feasible.

As shown in Figure 4; Of the present inventionly be used for mass spectrometric ionization device; The moving line of electronics in the electromagnetic field that radio frequency electrode 11,12 produces becomes helix shape, and promptly route increases, so the probability that is bumped by sample molecule in the air inlet pipe 9 entering ionization chambers 5 and electronics increases considerably.

Fig. 5 is illustrated in electronic motion situation in the ionization chamber, and the length of hypotenuse is represented the size of electronics general speed, the component velocity after the length of two right-angle sides is represented to decompose.Concerning any electronics, the length of hypotenuse all is the same, but the length of two right-angle sides can change, and this initial angle that changes with the electronics outgoing has relation.The horizontal kinetic energy of electronics and the ratio α of total kinetic energy satisfy: α=sin ²Φ, wherein, Φ is the angle between longitudinal velocity vector and the general speed vector.Calculating shows, Φ less than 26 degree situation under, all electronics can be rebuffed.

Fig. 6 representes the structural representation that is used for second kind of embodiment of mass spectrometric ionization device of the present invention; The difference of the ionization device of itself and first embodiment only is: the quantity of radio frequency electrode is two pairs; Adopt two pairs of radio frequency electrodes, not only can retrain, increase the length of electron motion route at the swing-around trajectory of fore-and-aft direction to electronics; But also can retrain at the swing-around trajectory of left and right directions to electronics, increased the length of electron motion route.Structure identical with the ionization device of first embodiment among this embodiment repeats no more here.

Fig. 7 representes the structural representation that is used for mass spectrometric the third embodiment of ionization device of the present invention, and the difference of the ionization device of itself and first embodiment only is: radio frequency electrode is a spherical shape.When adopting the spherical shape radio frequency electrode; Because the shape of electrode itself just has the effect of shrouding electronics; Make that electronics is difficult to from electric field region, escape away, help guaranteeing the electron amount in ionization chamber internal ionization zone, thereby increase the probability of electronic impact sample molecule.Certainly radio frequency electrode also can adopt other curve forms, like parabolic shape etc.Structure identical with the ionization device of first embodiment among this embodiment repeats no more here.

Experimental example 1

As shown in Figure 8, be octafluoro naphthalene-isooctane solution 1.0 μ L of concentration 1pg/ μ L for sample, use traditional mass spectrometer ionization device as shown in Figure 1, magnetic field intensity is under 350 Gausses' the condition, adopts the full scan mode, obtaining signal strength signal intensity is 150.

For same sample, ionization device as shown in Figure 3 is analyzed among use the present invention.Half L of distance is 10 between the radio frequency electrode 11,12 ^-2Rice, the frequency n of the simple harmonic vibration that power taking is done in ionization chamber is 100, the initial position x (0) of electron motion gets 0, then according to formula (10)

can calculate minimum circular frequency value:

Simultaneously can calculate the minimum voltage value that is added on the radio frequency electrode according to formula (13) is:

As shown in Figure 9, being 24 volts at voltage V is 9 * 10 with circular frequency ω ⁷Under the hertz condition, adopt the full scan mode, the signal strength signal intensity that obtains becomes 300, and than having increased by 100% under traditional mass spectrometer ionization device condition, therefore, the instrument index has remarkable lifting.

Though described the present invention with reference to several exemplary embodiments, should be appreciated that used term is explanation and exemplary and nonrestrictive term.Because the present invention's practical implementation and do not break away from the spirit or the essence of invention in a variety of forms; So be to be understood that; The foregoing description is not limited to any aforesaid details; And should in enclose spirit that claim limited and scope, explain widely, therefore fall into whole variations and remodeling in claim or its equivalent scope and all should be the claim of enclosing and contain.

Claims (6)

1. one kind is used for mass spectrometric ionization device; Comprise ionization chamber (5), be located at least one filament (8) in the said ionization chamber (5); It is characterized in that: said ionization device also comprises the radio frequency electrode (11 of at least one pair of positioned opposite; 12) rf frequency that, is added in said at least one pair of radio frequency electrode (11,12) is 10 ⁶-10 ⁹Hertz, voltage is the 1-2000 volt.

2. as claimed in claim 1ly be used for mass spectrometric ionization device; It is characterized in that: said at least one pair of radio frequency electrode (11; 12) circular frequency satisfies inequality:

wherein; ω representes circular frequency; The initial velocity of v (0) expression electron motion, L are represented the half the of distance between two said radio frequency electrodes (11,12); N representes that electronics runs into the number of times of the simple harmonic vibration of doing before the wall of said ionization chamber (5) in said ionization chamber (5), and x (0) representes the initial position of electron motion.

3. as claimed in claim 2ly be used for mass spectrometric ionization device; It is characterized in that: said at least one pair of radio frequency electrode (11; 12) voltage satisfies inequality:

wherein V representes voltage; L representes two said radio frequency electrodes (11; 12) distance is half the between, and m representes the quality of electronics, and ω representes circular frequency; N representes that electronics runs into the number of times of the simple harmonic vibration of doing before the wall of said ionization chamber (5) in said ionization chamber (5), and q representes the electric weight of electron institute band.

4. as claimed in claim 1ly be used for mass spectrometric ionization device, it is characterized in that: the quantity of said filament is a pair of, is arranged symmetrically in the said ionization chamber (5).

5. as claimed in claim 1ly be used for mass spectrometric ionization device, it is characterized in that: said radio frequency electrode is that plane tabular or curved surface are tabular.

6. as claimed in claim 1ly be used for mass spectrometric ionization device, it is characterized in that: the quantity of said radio frequency electrode is two pairs, is evenly arranged in the said ionization chamber (5).

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