Device for determining the mass of a particle in suspension or in solution in a fluid

0001The present invention relates to mass spectrometry of particles in suspensions or solutions in liquids, in particular, which applies to mass spectrometry of neutral or ionized species.

0002Traditional mass spectrometry (MS) is a general-purpose chemical or biological analysis tool, based on four essential components; an injection system, an ionization source, a mass spectrometer and an ion detector. .. These components are placed in a housing with a pump to create a vacuum.

0003The result of mass spectrometric measurements is a spectrum that reflects the abundance of the species type as a function of the mass / charge of the species in the mixture. Each peak in the spectrum is characteristic of a mono-charged or multi-charged ion; and species identification is accomplished by a pre-prepared databank.

0004The techniques described are now the norm for many applications. However, it has some drawbacks: -This technique is relatively long-running and not very sensitive: many biological materials are needed to make measurements; -All commercial mass spectrometers are extremely large: they occupy volumes on the order of several cubic meters; and they are expensive: they cost hundreds of thousands of euros; and-this technology is Generally 100 kDa (1.66 × 10)^-22It is not possible to measure significant masses in excess of kg) (mass for which the measurement resolution is completely inadequate).

0005This latter drawback is mainly due to the difficulty of accelerating heavy particles sufficiently and gives enough energy to reach the ion detector. However, due to its fundamental importance in the field of biomedical medicine, it has a mass of 100 kDa (1.66 × 10).^-22It is important to be able to measure particles larger than kg): they may be, for example, viruses, bacteria, organelles, protein complexes or cells.

0006Another technique for detecting mass using NEMS (ie, nano-electro-mechanical systems) has also been proposed. And NEMS, which is based on a resonator, has a detection limit below QCM, that is, a commercially available quartz crystal microbalance.¹²It is made to be a time. In this regard, the following documents can be referred to. :: KL Ekinci, XMH Huang and ML Roukes, 2004, "Ultrasensitive nanoelectromechanical mass detection", Applied Physics Letters 84 (22): 4469. Doi: 10.1063 / 1.1755417 Michae L. Roukes and Kamil L. Ekinci, 2004, "Apparatus and method for ultrasensitive nanoelectromechanical mass detection" US 6 722 200

0007like this<u style="single">NEMS</u>The principle of the base resonator will be explained later.

0008Mass m_pParticles precipitate in NEMS (stiffness k, effective mass m), increasing their total mass. The new resonant frequency of the device is equal to:<maths num="1"><img id="000002" he="11" wi="22" file="JP6352004B2_D0001.tif" img-format="tif" img-content="drawing" /></maths>Frequency response peak (open loop) is mass m_pShift by the amount of Δf before and after the deposition of. this is,<maths num="2"><img id="000003" he="11" wi="18" file="JP6352004B2_D0001.tif" img-format="tif" img-content="drawing" /></maths>It is almost the same as. When the device is used in a closed loop, the resonant frequency can be monitored in real time using electrical conversion means and loop closing means.

0009Thus, during adsorption to the resonating NEMS, the individual particles of the specimen or groups of such particles deplete the resonance frequency of the NEMS. Then, the mass of the particles or groups of particles can be estimated from the measurement of the frequency jump Δf.

0010The frequency jump Δf depends on the mass of the particle or group of particles (see the value of Δf above). However, it also depends on the location of the particles or groups of particles anchored to the surface of the NEMS. If the position of particle adsorption on the NEMS cannot be determined accurately-and this is the most common case-the single frequency jump information is not sufficient. The recourse can then refer to a statistical approach, which is: -Measuring multiple events, where each event corresponds to the appearance of a single particle or set of particles associated with a frequency jump, and -Assuming equal probability of NEMS surface position.

0011In this regard, the following documents can be referred to. :: AK Naik, MS Hanay, WK Hiebert, XL Feng and ML Roukes, 2009, "Towards single-molecule nanomechanical mass spectrometry", Nature Nanotechnology 4: 445-450. Doi: 10.1038 / NNANO.2009.152

0012Another solution is to measure the frequency of two or more modes of the same NEMS in real time. Some of the information is available thereby. In this regard, the following documents can be referred to. :: S. Dohn, W. Svendsen, A. Boisen and O. Hansen, 2007, "Mass and position determination of attached particles on cantilever based mass sensors", Review of Scientific Instruments 78: 103303. Doi: 10.1063 / 1.2804074.

0013Mass measurement by this NEMS means has led to the use of them to perform mass spectrometry, which is known as NEMS-MS. In this technique, the mass distribution of all particles present in the mixture is measured and, in order to measure, they are sent one after the other on the surface of the NEMS. This allows biological mass spectrometry at the level of individual particles and has the following advantages: -Due to the integrability of NEMS, which can be manufactured in large quantities and in bulk on semiconductor wafers, NEMS-MS is a very parallel isable technology that makes measurements very fast; It will be possible to envision the manufacture of portable and inexpensive NEMS-MS equipment; -Mass detection using NEMS for weighing is affected by both ions and neutral particles; measurement efficiency is improved by several orders of magnitude; and -Weight detection provides constant mass resolution over the entire measurement range and, unlike prior art, provides excellent resolution at high masses.

0014Figure 1 of the previously mentioned AK Naik et al. Paper shows a known NEMS-MS system, the structure of which is similar to that of conventional mass spectrometers: liquid phase biological particles. Infused and under vacuum, exactly 10^-5mTorr (10^-6Pa) Under order pressure, it is transmitted to the NEMS as efficiently as possible.

0015To do so, commercially available components are used :, the injection source utilizes ESI, an electrospray ionization that atomizes and ionizes the species being analyzed. The latter goes through several differential exhaust and ion guidance stages (using hexapoles). Finally, it arrives at the NEMS zone.

0016Such known systems have various drawbacks that do not enable optimal use of all the benefits provided by NEMS-MS technology: -In this known system, the injection source and the NEMS are very far apart from each other to allow differential exhaust; there is a considerable loss of species between the injection source and the NEMS; -This distant distance forces the species to NEMS; and in this system only ionized species are guided; neutral particles are lost in the system; and -It is very difficult to concentrate the ion beam on a surface area of less than a few square millimeters at such a distance; therefore, a very low percentage of the particles actually settle on the NEMS. , Its surface area is generally on the order of a few square micrometers.

0017All of these drawbacks do not make this known system very inefficient and make it possible to fully benefit from the benefits of NEMS-MS. In particular, potential advantages can be seen in use in systems that specialize in neutral and / or similarly ionized species. In fact, the ion-optical (and electromagnetic field means) transmission of heavy species in general, especially those targeted by NEMS-MS (organelles, viruses, bacteria, protein complexes, etc.) is very difficult. In order to transfer these heavy particles with the correct efficiency, it is necessary to have a highly charged state that has the effect of denaturing them and no longer allows them to be measured in their natural state.

0018Resonators using NEMS are also known through the following literature: S. Hentz's WO 2012/034949, S. Hentz et al.'S WO 2012/034951, and S. Hentz's WO 2012/034990.

<p num="0019"> An object of the present invention is to solve the shortcomings of the known NEMS-MS system described above by combining a device for injecting neutral and / or ionized seeds, a guidance device and a NEMS type detector, and various of these. It is preferred that the entire components are in close proximity.</p><p num="0020"> To be precise, the subject of the present invention is a device for detecting the mass of at least one particle in a suspension or solution in a liquid: -A first device that atomizes a liquid to obtain a flux containing at least one of the particles. -A second device that includes an inlet and an outlet to receive the flux and guides and aerodynamically focuses the flux, and -A second device that includes at least one weight detector located opposite the outlet of the second device to receive the at least one particle and measures the mass of the at least one particle by frequency measurement. It is characterized by being equipped with three devices.</p><p num="0021"> The apparatus, which is the subject of the present invention, measures the mass of each particle or set of particles in a suspension or solution, depending on the flow rate of the flux used and the type of sample containing the particles being analyzed. to enable. It is clear that "particle" means an individual particle or a collection of particles.</p><p num="0022"> According to a particular embodiment of the device which is the subject of the present invention, the second device is electrically neutral.</p><p num="0023"> Such an electrically neutral device has the advantage of transmitting cations and anions in the same way as neutral particles.</p><p num="0024"> The second device may have an aerodynamic lens.</p><p num="0025"> The aerodynamic lens may be coupled to the opening at the outlet.</p><p num="0026"> Preferably, the device that is the subject of the present invention is: -A predetermined pressure zone, including the first device, and -At least one vacuum enclosure or first that contacts the zone and includes at least a portion of the second device and is provided to have a first pressure lower than the pressure in the zone. Including the housing, further.</p><p num="0027"> "Predetermined pressure" means air pressure (atmospheric pressure) or the pressure of another gas depending on the assumption of application to the present invention.</p><p num="0028"> Further, in order to arrange the zone in contact with the first housing, the second device further provides a capillary tube having an inlet opening in the zone and an outlet opening in the first housing. It may be included.</p><p num="0029"> In this case, the second device may have an aerodynamic lens facing the inlet and / or outlet opening of the capillary tube.</p><p num="0030"> Therefore, flux concentration or focusing can occur at the inlet and / or outlet opening of the capillary tube as well.</p><p num="0031"> According to certain embodiments, the device of subject matter of the present invention further comprises another vacuum enclosure or second enclosure provided to be a second pressure. The second pressure may be lower than the first pressure, and the second housing includes the third device and the first through a first opening facing the weight detector. Contact the chassis of.</p><p num="0032"> The weight detector is selected from nanoelectromechanical systems, microelectromechanical systems, quartz crystal microbalances, SAW (surface acoustic wave) resonators, BAW (bulk ultrasonic) resonators, and impact detectors. May be done.</p><p num="0033"> The first device may be selected from an ultrasonic nebulizer, a microwave induction spray device, a microcapillary array nebulizer, and a surface acoustic wave nebulizer.</p>

0034<figref num="1">It is the schematic of the specific embodiment of the apparatus which is the subject of this invention.</figref><figref num="2">It is a figure which shows roughly the principle of an aerodynamic focusing lens.</figref><figref num="3">It is a figure which shows typically an example of a complete aerodynamic focus system.</figref><figref num="4">It is a figure which shows roughly and partially a simple example of the aerodynamic focus device which can be used in this invention.</figref>

0035The present invention will be better understood by reading the description of examples of embodiments described below with reference to the accompanying drawings. The examples of embodiments are shown merely as indicators and are by no means limited.

0036FIG. 1 is a schematic representation of a particular embodiment of an apparatus for measuring the mass of particles in a suspension or solution in a liquid. The device is: -A device for atomizing the liquid, i.e., a specimen that deposits in the form of droplets 4 in the example shown, to obtain a flux containing at least the particles 2. -A device that includes an aerodynamic focusing lens 6 with an inlet 8 and an outlet 10 to guide and aerodynamically focus the flux, and -The device 12 includes at least one weight detector 14 arranged to face the outlet 10 of the aerodynamic focus lens 6 to receive the particles, and measures the mass of the particles by frequency measurement.

0037The device shown in Figure 1 is: -Including sprayer 2, given pressure, eg atmospheric pressure (approximately 10)⁵Pa) Zone 16 and -Contact zone 16 and include device 6 to establish a primary vacuum, i.e., using the primary pump represented by arrow 20 10²Includes a vacuum enclosure 18 that provides Pa-order residual pressure.

0038The flux guide and aerodynamic focusing device is a capillary tube (straight line) having an inlet opening 24 in the zone 16 and an outlet opening 26 in the housing 18 for arranging the zone 16 in contact with the housing 18. ) 22 is provided. The flux guide and the inlet of the aerodynamic focusing device are composed of the inlet opening 24 of the capillary tube 22, and the flux guide and the outlet of the aerodynamic focusing device are the outlets of the aerodynamic focus lens 6. It consists of 10.

0039Capillary tubes 22 have been pointed out to allow desolvation of particles in suspensions or solutions.

0040In the device shown in FIG. 1, a secondary vacuum is established, i.e. by the turbomolecular pumping means represented by arrow 3010.^-2It comprises another housing 28 in which a Pa-order residual pressure is achieved (however, in another embodiment of the invention, the housing 18 and the housing 28 may have the same pressure).

0041The housing 28 includes the device 12 and communicates with the housing 18 through an opening 32 facing the detector 14.

0042As shown in FIG. 1, the detector 14 is mounted on a micro-positioning wafer 34 mounted on a sealed feedthrough 36.

0043The capillary tube 22 is aligned with the opening 32, and the device 6 is configured between the opening 32 and the output opening 26 of the capillary tube 22.

0044Therefore, in the example of FIG. 1, the sample is present in the liquid phase, and a part of the liquid is atomized by the device 2. Device 2 produces a very small droplet aerosol that is predominantly neutral and contains a sample, some of which can be potentially ionized. Due to the pressure difference between the zone 16 and the housing 18, the aerosol is sucked into the inlet capillary tube 22. On the opposite side, an aerodynamic focus lens 6 capable of similarly guiding neutral seeds and ions to a detector 14 located in the secondary vacuum housing 28 is arranged.

0045The example of the invention shown in FIG. 1 comprises an apparatus according to the invention comprising two differential pump chambers, ie, housings 18 and 28, but with two or more differential pump chambers or a single chamber. It is also possible to produce.

0046In the example of FIG. 1, the detector 14 comprises one NEMS, but it is also possible to produce an apparatus according to the invention, wherein the detector comprises a number of such NEMS.

0047Means for reading and controlling the detector 14 are not shown here. The detector 14 may or may not be temperature controlled. The same applies to the inlet capillary tube 22.

0048It is advantageous to use NEMS for detection; however, any other weigh scale detector (MEMS, QCM, SAW, BAW) may be used, and more generally, an inertial force detector. In particular, an impact detector may be used. Regarding the latter, the following documents can be referred to. :: Jonghoo Park, Hua Qin, Mark Scalf, Ryan T. Hilger, Michael S. Westphall, Lloyd M. Smith and Robert H. Blick, 2011, "A Mechanical Nanomembrane Detector for Time-of-Flight Mass Spectrometry", Nano Letters 11: 3681-3684.

0049The aerodynamic focus lens 6 is more simply known as the "aerodynamic lens". The latter is known to actually consist of a series of simple aerodynamic lenses. Aerodynamic lens An example of a lens will be described later.

0050In the present invention, the use of such lenses makes it possible to guide certain neutral species in order to maximize measurement efficiency. Therefore, the kind of electrostatic guidance used in ion optics is not used.

0051It is recalled that an aerodynamic lens contains a series of apertures that make up a simple aerodynamic lens. The openings may have the same size (see FIG. 3, see below), or may have different sizes, eg, become smaller and smaller (see FIG. 2, see below). .. Through these openings, the diluted aerosol is sucked up. Most of the light, particle-free carrier gas (and most of the water molecules sucked up by the capillary tube 22 used in the example of FIG. 1) diffuses in the volume at the outlet of the lens, whereas Heavy particles (compared to gas molecules), such as biomolecules, gain sufficient momentum to be collected in the form of very fine jets through the outlet flux. Under certain conditions, the jet can be focused on one point (focus).

0052Aerodynamic lenses are typically used in mass spectrometers for the purpose of measuring particles present in aerosols, but in the latter case, the lens is because the seeds are always ionized after being introduced into the mass spectrometer. , Not used to guide and collect particles in the detector. : Lens is used for concentration and classification of the species to be measured before the species to be measured passes through the analyzer.

0053In detailed form, the focusing device (see FIG. 2) that can be used in the present invention is aerodynamic consisting of an inlet opening 38 that allows control of flux and differential pressure and a series of simple lenses 41. Includes lens 40 and. The series of simple lenses 41 makes it possible to compress the magnetic flux lines of the particles as they travel along the device. At the outlet of a series of simple lenses 41, an aperture 42 may be placed that allows a collimated beam of heavy particles to be captured, while light molecules (eg, solvent molecules) are volume diffusion. And run away.

0054In this regard, the following documents can be referred to. :: US2008 / 0024853, "Aerodynamic lens particle separator", invention of P. Ariessohn

0055FIG. 3 may be used in the present invention, an aerodynamic focus apparatus having a continuous 43 of an aerodynamic lens or a simple aerodynamic lens 44 and a channel 45 at the continuous outlet of the simple lens. Here is another example of. The channel 45 (or acceleration nose) may be a convergent channel or a convergent / divergent channel, depending on the velocity of the particles, to help the particles focus.

0056It is pointed out that only some of the components of the apparatus of FIG. 3 may be used in the present invention. Technical documentation provided by Aerodyne Research can be referred to for the device shown in Figure 3, in particular: ARI Aerosol Mass Spectrometer, Operation Manual, page 9 may be referenced.

0057Even if the aerodynamic lens 40 of FIG. 2 (the aerodynamic lens 43 of FIG. 3) is apparently coupled with a capillary tube of type 22 of the capillary tube 22 located at the inlet and / or outlet of the aerodynamic lens. It may or may be combined with an opening of type 42 in FIG.

0058FIG. 4 is a schematic partial view of another device of the present invention, in which the aerodynamic focus device simply goes to the inlet capillary tube 22, its outlet opening 26, and the secondary vacuum enclosure 28 in which the NEMS 14 is located. It is composed of the entrance opening 32 of. In FIG. 4, the direction of circulation of the longitudinal fluxes is reversed as compared to FIG. Arrow 48 also represents the radial flux of light molecules at the outlet of the capillary 28.

0059In the present invention, any type of spraying device may be used, in particular an ultrasonic nebulizer, a microwave induction spraying device or a microcapillary array nebulizer.

0060Advantageously, SAWNs (ie, surface acoustic wave nebulizers) are used. In this regard, the following documents can be referred to. :: David R. Goodlett, Scott R. Heron and Jon Cooper, 2011, "Ions generated by surface acoustic wave device detected by mass spectrometry", WO 2011/060369 A1.

0061In this case, it is necessary to use a surface acoustic wave resonator in which a droplet containing a sample is arranged. The surface acoustic waves produced by the resonator then dissipate its energy in the atomized liquid.

0062This spraying means has the benefit of ionizing a very small portion of the specimen, even at very low ionization energies. In addition, all water droplets and biological particles over a wide range of mass can be eliminated. Moreover, such a spraying device is integrable. It may be obtained by a holistic micro-manufacturing method. And when such an integrable device is used, it may be assumed that all the structures of the present invention are integrated.

0063In the example of the invention described above, the guide and focusing device are electrically neutral. This indicates that the electromagnetic field is not applied to or generated by the device.

0064Desirably, such an electrically neutral device is used for guiding and focusing. Nevertheless, electrically non-neutral guides and focusing devices, more precisely, to separate neutral species from ionic species, or vice versa, can focus only on neutral species. In order to polarize the device for obtaining an electromagnetic field, a device whose sides are polarized at a specific voltage can be used.

0065In the example of FIG. 1, the aerodynamic lens 6 is coupled to the capillary tube 22. However, one embodiment of the invention may be envisioned in which the second device for guiding the flux and performing aerodynamic focusing has a diaphragm or opening instead of the capillary.