Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
  • G01N27/64—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J49/00—Particle spectrometers or separator tubes
  • H01J49/004—Combinations of spectrometers, tandem spectrometers, e.g. MS/MS, MSn
  • H01J49/0045—Combinations of spectrometers, tandem spectrometers, e.g. MS/MS, MSn characterised by the fragmentation or other specific reaction
  • H01J49/0059—Combinations of spectrometers, tandem spectrometers, e.g. MS/MS, MSn characterised by the fragmentation or other specific reaction by a photon beam, photo-dissociation
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J49/00—Particle spectrometers or separator tubes
  • H01J49/26—Mass spectrometers or separator tubes
  • H01J49/34—Dynamic spectrometers
  • H01J49/42—Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons
  • H01J49/4205—Device types
  • H01J49/424—Three-dimensional ion traps, i.e. comprising end-cap and ring electrodes

Definitions

• the subject of the present invention is a device and a method for analyzing by mass spectrometry of molecules, implementing, on the one hand, a quadrupole ion trap and, on the other hand, a UV or visible laser beam, ensuring photodissociation of ionized molecules that are trapped inside the quadrupole trap.
• an ion trap makes it possible, on the one hand, to trap ions in the form of a stable ion cloud and, on the other hand, to carry out their mass analysis.
• the general principle of a quadrupole ion trap and the mass analysis method implementing such a trap have been described in US Pat. Nos. 3,527,939 and 4,650,999.
• a quadrupole ion trap is equipped with an input for the injection of the molecules in ionized form to be analyzed and an output for the ejection of the ions to be detected, and comprises an electrode system which makes it possible to generate a three-dimensional quadrupole field capable of selecting the molecules under ionized form to be analyzed, according to their mass-to-charge ratio (m / z) and to trap them in a trapping volume. It is the variations applied to the quadrupole field that make it possible to select and trap ionized molecules whose m / z ratio has been predetermined and to eject the other ions. The selected molecules are then ejected to detection means allowing their mass analysis.
• the method and the device described in this patent do not allow the differentiation of molecules of the same m / z ratio.
• Tandem mass spectrometry which consists of isolating a mass and then breaking it up by colliding with a gas and analyzing the fragments obtained in bulk, is described in US Pat. No. 4,736,101. implanted in commercial ion traps and is widely used in proteomics, in particular.
• This analytical technique called “Collision Induced Dissociation” (CID) has, however, several drawbacks:
• Louris et al. J. Mass Spectrom Ion Processes, 1987, 75, 345) have proposed to use a UV laser to carry out photodissociation of trapped ions.
• the injection of the UV laser, inside the trap is performed by means of an optical fiber.
• the use of an optical fiber allows an interface between the laser production means and the simple trap. Nevertheless, the laser beam obtained at the output of the optical fiber is divergent, and high energy densities are necessary to obtain a satisfactory photodissociation.
• the use of a fiber The optical system is not adapted to laser beams in the form of ultra-low pulses, in the order of a few femtoseconds.
• the laser injected inside the trap, can interact with the walls of the trap and cause parasite generation.
• Gabryelski and Li also used an experimental setup using a laser for photodissociation, which leads to low mass resolution.
• the high power laser used generates a very large number of parasitic ions within the trap. More recently, Weinkauf et al. (Phys Chem Chem 2004, 6,
• the present invention aims to provide a device and a method of mass analysis of a sample using a quadrupole ion trap, to perform a photo-induced dissociation by a visible or ultraviolet laser beam. , which allows dissociation much more specific than the CID or dissociation. multi-photon infrared and which does not have the disadvantages of the prior art.
• the present invention therefore relates to a device for mass analysis of molecules comprising a quadrupole ion trap equipped with an input for injecting the molecules in ionized form to be analyzed and an output for the ejection of the ions to to detect, comprising an electrode system that generates a three-dimensional quadrupole field, capable of selecting the molecules in ionized form to be analyzed, in according to their mass-to-charge ratio (m / z) and trapping them in a trapping volume, said trap being coupled to a UV or visible laser beam ensuring the dissociation of the molecules in ionized form to be analyzed, characterized in that the beam laser is introduced into the trap, without passage through an optical fiber, through an opening, arranged in one of the electrodes, separate from the inlet for injection of the molecules in ionized form to be analyzed and the outlet for ejection ions to be detected, and sealingly closed by a window passing the laser beam, the size of the window being chosen so that the laser beam covers the entire trapping volume
• Another aspect of the invention relates to a method of mass analysis of molecules implementing an injection of the molecules in ionized form to be analyzed in a quadrupole trap, a selection of the molecules in ionized form to be analyzed, according to their mass-to-charge ratio (m / z) and their trapping in a trapping volume, by means of a three-dimensional quadrupole field generated by an electrode system, a dissociation of the molecules in ionized form to be analyzed trapped in the trapping volume, by means of a UV or visible laser beam, then an ejection of the ions to be detected, characterized in that the dissociation laser beam is introduced into the trap, without passing through an optical fiber, through an opening, arranged in the one of the electrodes, distinct from the input for the injection of the molecules in ionized form to be analyzed and the output for the ejection of the ions to be detected, and closed in a manner sealed by a window passing the laser beam and so that the laser beam covers the entire trapping volume
• the fîg. 1 and 2 illustrate examples of device according to the invention.
• the fg. 3 shows a sectional view of a part of the device according to FIG. 2.
• the fîg. 4 to 8 relating to spectra obtained with the device illustrated in FIG. 2 will be detailed in the part of the description relating to the example.
• the device I uses a quadrupole ion trap 1 equipped with an inlet 2 for injecting the molecules in ionized form to be analyzed and an outlet 3 for the ejection of the ions to be detected, comprising an electrode system 4 which allows to generate a three-dimensional quadrupole field, capable of selecting the molecules in ionized form to be analyzed, according to their mass-to-charge ratio (m / z) and trapping them in a trapping volume 5.
• the input 2 is connected to a series of means 6 allowing first of all to ionize a sample of interest and to inject the ionized molecules obtained inside the trap 1.
• a quadrupole ion trap 1 equipped with an inlet 2 for injecting the molecules in ionized form to be analyzed and an outlet 3 for the ejection of the ions to be detected, comprising an electrode system 4 which allows to generate a three-dimensional quadrupole field, capable of selecting the molecules in ionized form to be analyzed, according to their mass-to
• these means 6 consist of an electrospray source 7 coupled to a pair of octopoles 8 connected to the inlet 2 of the trap 1, means conventionally used in commercial devices.
• the quadrupole trap 1 is also coupled, at the output 3 for the ejection of the ions to be detected, to means 9 for detecting ejected ions.
• These detection means 9 are, for example, constituted by a conversion dynode coupled to an electron multiplier, all of these detection means being able to be protected by a Faraday cage.
• the electrode system 4 may be composed of a central annular electrode delimiting a cavity in which the trapping volume 5 and two cap electrodes 11 and 12 situated on either side of the cavity delimited by the electrode are located.
• annular 10 as shown in fig. 2.
• Q spacers for example quartz, are positioned so that the electrode system delimits a closed cavity.
• the inlet 2 for the injection of the molecules in ionized form to be analyzed can be arranged in one of the cap electrodes 11, the outlet 3 for the ejection of the ions to be detected being arranged in the other cap electrode 12.
• the inlet 2 and the outlet 3 will be positioned facing each other, so that the axis of injection of the molecules in ionized form to be analyzed and the axis of ejection of the ions to be detected coincide on an axis x.
• the diameters of the inlet 2 and the outlet 3 are very small, of the order of a few hundred microns.
• the device I comprises electronic means for controlling and adjusting the quadrupole field making it possible to maintain and vary the generated quadrupole field and thus ensure the selection, trapping and / or ejection of molecules of mass m / z given.
• an opening 13 is provided in one of the electrodes for the passage of the laser beam L which will be used for photodissociation of the ions.
• This opening is sealingly sealed by a permeable material (that is to say transparent) to the laser beam in the form of a window 14, the position of the shutter and the y-direction of propagation of the laser beam L being chosen so that the laser beam L does not interact inside the trap with the injection of the molecules in ionized form to be analyzed, nor with the ejection of the ions to be detected and directly reaches the trapping volume 5.
• the opening 13 is equipped with sealing means ensuring the seal between the window 14 and the electrode in which the opening 13 is arranged.
• the size of the opening 13 or, more precisely, of the window 14 is, for its part, chosen so that the laser beam covers the entire trapping volume.
• the diameter of the laser beam L is effectively directly related to the size of the window 14.
• the dimension of the opening and especially the passage size for the laser beam is therefore determined at the most accurate compared to that of the trapping volume 5, in such a way that the value of the cross-section of the laser beam L with respect to the y-axis is preferably between the value of the cross section of the trapping volume 5 with respect to the y-axis and the value of this section + 5%.
• Sealed sealing means that the opening is closed by a portlight system 14, for example, so that the pressure conditions and the electrostatic trapping conditions inside the trap 1 are not modified at the same time.
• the sealing of the window 14 and the dimensions of the opening 13 make it possible to ensure that the introduction of the laser beam L does not come to modify the electrostatic field lines in which are trapped the molecules in ionized form.
• the window 14 is in a material passing the laser beam, for example fused silica (UV quality) or sapphire.
• a source 15 generating a laser beam L is therefore positioned upstream of the window 14.
• the opening 13 is sufficiently distant from the inlet and the outlet of the ions, so that the source 15 can be positioned, taking into account the size of the ionization means 6 and injection means of the ionized molecules on the one hand and the detection means 9 on the other hand.
• the opening 13 for introducing the laser will advantageously be arranged in the ring electrode.
• the laser beam L is introduced in a direction y perpendicular to the injection and ejection direction x when they are parallel and aligned.
• the laser beam L is not injected via an optical fiber, which allows a great adaptability of the device according to the invention to different types of laser beam.
• the implementation of an optical fiber often leads to a divergent beam, especially in the case of high power UV laser, and can operate only with a range of wavelengths.
• the use of an optical fiber for the introduction of a UV laser with a wavelength of less than 220 nm is, at present, almost excluded.
• solarization leading to a reversible degradation of the fiber is noted.
• the device I according to the invention can, in turn, operate with a wide range of wavelengths, from visible to UV.
• the invention is particularly adapted to the implementation of a UV laser of a wavelength, in particular between 193 and 450 nm.
• the laser used preferably has a power of at least 10 mW and preferably between 10 and 100 mW.
• lasers in the form of very short pulses may be used. In particular it is possible to inject ultrashort pulses controlled in phase and amplitude.
• the device is equipped with means for aligning the laser beam L on the trapping volume 5.
• means for aligning the laser beam L on the trapping volume 5 before injecting the molecules to be analyzed, a step of alignment of the laser beam on the trapping volume will be performed.
• alignment means it is possible to use, for example, a photodiode positioned on the selected y-axis which is centered on the trapping volume 5, or means as illustrated by FIG. 2, and detailed in the example which follows.
• a low-power visible laser source 16 injected via an optical fiber 17, along the determined y-axis centered on the trapping volume 5 and, in the illustrated example, perpendicular to the x-axis d injection and ejection of ions.
• This visible beam thus exits through the opening 13 arranged for the introduction of the laser beam L which will be used for photodissociation and makes it possible to locate the y axis at the output, using two pinholes 18 and 19 positioned centrally on the latter.
• the laser beam L will then be able to be aligned on this axis y by means of two mirrors 20 and 21.
• a sealed aperture 23 sealed by a permeable element to the laser beam used is arranged in the quadrupole trap 1, so as to allow the output of the trap 1 of the laser beam L introduced.
• the output of laser beam L introduced into the trap 1 is ensured, which avoids, especially in the case of a UV laser, to pollute the analysis results by the presence of desorbed ions of the material constituting the inner walls of the trap .
• the opening 22, arranged for the implementation of the alignment means 15, coincides with that 23, arranged for the evacuation of the laser L out of the trap 1, since these two openings 22 and 23 must be in the y axis.
• FIG. 3 illustrates sealing means of the opening 13, which can be adapted to the openings 22 and 23.
• the sealing system illustrated fig. 3, consists of a cylindrical tip 24 of an insulating material, for example, inserted into the opening and having a porthole 14 sapphire (opening 13) or fused silica UV quality (opening 22).
• the sealing means therefore comprise, in the illustrated example, a tube 24 made of an insulating material whose one end is closed by a porthole 14 in sapphire or fused silica of UV quality.
• the tube 24 is engaged in a bore, arranged at the outer surface of the electrode being centered on the opening 13, so that the window 14 is aligned with the opening 13.
• the assemblies of the tube 24 and port 14, and the tube 24 and the electrode 10 are then made to be sealed.
• the tube 24 has a length greater than the thickness of the window 14 and the diameter of the window 14 is greater than the diameter of the opening 13.
• control means 25 are, for example, consisting of a photon detector.
• the device I according to the invention also comprises means 26 ensuring the synchronization between the introduction of the laser beam into the trap and trapping of the ionized form molecules to be analyzed.
• means 26 ensuring the synchronization between the introduction of the laser beam into the trap and trapping of the ionized form molecules to be analyzed.
• These means 26 will allow to modulate the duration of the interaction of the molecules to be analyzed with the laser.
• various electronic control means on the one hand of the quadrupole field, on the other hand the laser beam, so that these means of synchronization, will enable to perform MS n-type experiments, by successive photodissociations.
• At least one following sequence is implemented: by setting the three-dimensional quadrupole field generated by the electrode system, selecting molecules in ionized form to be analyzed after the dissociation previous, as a function of their mass-to-charge ratio (m / z) and trapping of the latter in the trapping volume, then dissociation of the molecules in selected ionized form. It is also possible to couple the method according to the invention with an upstream CID analysis.
• the quadrupole trap 1, as well as other elements of the device are arranged in an enclosure E, in which the pressure conditions necessary for the detection must be maintained. Therefore, the different connections made at the enclosure, for the introduction of the laser, its output for the alignment means must be perfectly sealed, so as not to disturb the pressure conditions inside the trap.
• the device I and the method according to the invention are suitable for many applications: - in photophysical chemistry, for dissociation spectrum measurements, the realization of MS N spectra by photodissociation, for photofragmentation cross section measurements;
• the device and the method according to the invention make it possible to obtain a wide range of fragments, including fragments of very small size, which will allow to increase the efficiency of identification of proteins or peptides.
• Mass and laser optical absorption spectrum will provide unambiguous identification of many chemical or bacteriological pollutants in wastewater and gases, among others;
• thermo electron thermo electron
• Two mirrors were used to align the laser beam.
• the laser beam passes through two pinholes 1 mm in diameter, before entering, through a quartz window, into the chamber of the device, in which a reduced pressure of 10 -5 mbar is maintained. the trap is made by crossing the central ring electrode.
• the central ring electrode was pierced with two diametrically opposed holes 3 mm in diameter, in which were glued two ends, as illustrated in fig. 3.
• the first tip is used for laser injection. It is a tube of insulating material, at the bottom of which a sapphire window has been glued. The diameter used allows the laser to completely cover the cloud of ions.
• the second tip is used for laser output and alignment procedure. It also consists of a tube of insulating material with, on one side, a collimating lens on 3 cm and, on the other, an SMA connection for optical fiber.
• the two tips are perfectly aligned and glued, perpendicular to the axis of the electrode which coincides with the axis x injection and ejection of ions.
• the attachment of the end pieces is performed with a high degree of tightness, in order to obtain a modification of the assembly which does not alter the helium pressure in the part, necessary for its optimal operation. No changes to the calibration, mass resolution, and trapping capabilities of the device are induced by changes to the ring electrode.
• an optical fiber transmitting UV to near infrared (SENTRONIC), connects the second tip to an empty passage for optical fiber (SENTRONIC). A second fiber is connected to the output of this passage.
• a visible laser used for alignment (helium, neon).
• a visible laser is injected through the optical fiber. Its output, through the two windows, defines an optical axis that passes through the center of the trap and, therefore, by the trapping volume that corresponds to the cloud of ions that will be trapped. The two pinholes are then aligned on this axis.
• the laser for the photodissociation is then aligned on the optical axis defined above, thanks to the two mirrors. He must cross the two pinholes.
• the detection of photons at the output of optical fiber allows a fine adjustment of the alignment of the laser at the center of the trap. This detection also allows a relative measurement of the power of the injected laser.
• the temporal synchronization between the injection of the laser into the trap and the radio frequency voltages applied to the trap electrodes is achieved by means of an electromechanical shutter controlled by a delay generator controlled on the trap electronics.
• the laser-induced test dissociation sequences consist of injecting ions from the electrospray source, isolating a given mass ion m / z in the trap, ejecting the other masses, and then injecting them for a given time. , the photodissociation laser.
• the ions, resulting from the fragmentation are then mass analyzed by the standard procedure.
• the assembly and the synchronization used make it possible to carry out experiments of the MS N type by photodissociation (isolation of a mass, photo fragmentation, isolation of a fragment, photodissociation ...) -
• Tryptophan was used as a test molecule.
• the fij. Figure 5 shows the photodissociation spectrum of tryptophan as a function of the wavelength of the laser.
• the spectrum was normalized according to the laser power.
• the fg. 6A and 6B show the evolution of the branching ratio measured for the main tryptophan fragmentation products, as a function of the wavelength of the photodissociation laser.
• Figs. 7A to 7F show the dissociation spectra laser-induced MS 3.
• the irradiation time of the laser for each dissociation step is 300 ms.

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• 2004
  • 2004-12-16 FR FR0413396A patent/FR2879744B1/fr not_active Expired - Fee Related
• 2005
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