JP2827010B2 - Method and apparatus for introducing effluent to mass spectrometers and other gas or particle detectors - Google Patents

Description

The present invention relates to a method and an apparatus for introducing an effluent into a mass spectrophotometer or other gas or particle detector.

BACKGROUND OF THE INVENTION Suitable liquid sample introduction for gas or particle detectors depends on the interface between the liquid stream and the detector. The coexistence of continuous liquid sample introduction and normal operation requirements for a gas phase detector raises compatibility issues. Adapting material flow from a liquid stream into a detector often involves difficulties. In addition, decomposition of the thermally labile sample components may occur during the evaporation step prior to gas phase detection. For example, in the case of a gas phase detector such as a mass spectrophotometer in which detection is performed under reduced pressure, vacuum locking and pumping are requirements to be considered. The general requirements for the interface between the liquid stream and the gas phase detector are as follows: (1) the sample must be evaporated before detection; (2) minimal thermal decomposition during the sample evaporation step (3) The transport efficiency of the sample must be high enough to adhere to sufficient sensitivity; (4) the normal operating conditions of the detector must be maintained during sample introduction; (5) For the interface The composition of the sample must be maintained as it is transported (eg, minimum chromatographic bandwidth). The success rate of interfacing a liquid stream to a gas phase detector depends on how well the requirements are met.

The main use of the device according to the invention for gas-phase detection of liquid streams is to introduce the effluent from a liquid chromatograph into a mass spectrophotometer. The interface between liquid chromatography (LM) and mass spectrophotometry (MS) is called LC-MS. Although the present invention relates to the general field of liquid sample introduction to gas phase or particle detectors, most previous work in this area has focused on LC-MS. This is a significant obstacle to interface design. Therefore, the study of this prior art concentrates on LC-MS.

Complex gas phase detectors (ie, mass spectrometers) detect gas phase ions formed by various mechanisms. Electron impact (EI) ionization and chemical ionization (CI) are the most commonly performed methods. When EI ionization is used, a sample gas of 10 ^-3 to 10 ^-6 Torr is bombarded with electrons of sufficient energy (generally 70 eV) to excite the electron energy level of the sample molecules to be higher than the ionization potential, and the electrons are sampled. It is removed from the molecule to make it a cation. In the formation of sample ions in the EI mode, excess energy applied to sample molecules from impacting electrons causes bond cleavage or fragmentation. The characteristic and reproducible nature of EI fragmentation, which suggests a molecular structure, provides a technique with a wide range of uses for analyzing samples with unknown composition. In contrast, the CI method operates at a higher pressure (typically 1 Torr) compared to the EI method, and thus ionization occurs by collision of sample molecules with gas ions of the reagent. Analytical applications for CI are generally found when molecular weight information is present.
In the case of CI, limited and non-reproducible fragmentation of the sample molecules is a major drawback. It should be emphasized that the ionization step ultimately determines the qualitative information obtained on the mass spectrophotometer. Other ionization techniques are atmospheric pressure ionization (API) at 760 Torr and field ionization at 10 ^-4 Torr. To get the maximum information for a given sample,
Preferably, various ionization techniques are used, including EI and CI. Furthermore, LC-MS that limits ionization conditions
The technique is limited only to the sample information obtained for a given analysis.

The mass spectra of many compounds (compounds that are generally ionized under EI conditions) have been compiled as archives in a large computerized database, and these were combined with spectra (fragment ions) obtained from samples of unknown composition. Then compare. Therefore, utilizing this type of spectral archive is a significant advantage of LC-MS instruments, since computer comparisons can be made in seconds. Therefore, for widespread use, it is necessary to use the EI ionization method for the LC-MS device. Unfortunately, only a few of the prior art devices have been developed for thermally labile and / or non-volatile compounds.
It is reported that it does not have the ability to generate EI spectra.

Effluent from either the liquid chromatograph or the liquid process stream must be processed by mass spectrophotometer interface technology. As noted above, the pressure requirements for ionization depend on the mode of ionization and are limited by the mass flow to the ionization region of the mass spectrophotometer and the pumping capability of the mass spectrophotometer. Evaporation of a liquid flowing at 1-2 ml / min can produce a gas sample of about 1 per minute under standard conditions, this amount can be reduced to 10 ⁸ gas per minute at 10 ^-5 Torr (ie EI condition). Correspondingly, this is far beyond the pumping capabilities of conventional mass spectrometers. Ionization techniques that occur at pressures of 1 mm Torr or higher, such as CI, require lower pumping power, but generally pose significant ion-molecule reaction chemistry problems, which provide less structural fragmentation information. . Due to the low pressure requirements for EI ionization, direct introduction of a continuous stream of liquid from a liquid chromatograph is difficult to achieve without very high capacity pumping systems such as, for example, cryogenic pumping.

Evaporation or desorption steps that convert the sample to a gas can also result in thermal degradation (pyrolysis), reaction or rearrangement of the initial sample molecules. These sample losses are generally greatest for sample components that are thermally unstable and / or non-volatile, separated by liquid chromatography. Mass spectrometry of these thermally sensitive and / or non-volatile molecules is generally limited by the inability of these compounds to generate complete gas phase ions. Therefore, it is important to develop an interface between LC and MS that vaporizes the sample with minimal degradation or loss of analyte.

There are various ways to interface LC with MS,
This study has been studied extensively (see References 1, 2 below,
3, 4). The common purpose of all interface technologies is
Efficiency in the generation of gas phase sample ions.

Direct liquid introduction (DLI) is one of the easiest ways to interface LC with MS. In the case of DLI, the effluent from the liquid chromatograph flows through a small circular aperture or tube having a diameter on the order of 3-10 μm. A high velocity cylindrical liquid jet is directed into the ionization chamber. There are many types of designs using this method, all of which have the same basic configuration (discussed in references 5 and 6). The jet may pass through a heated desolvation zone before entering the ionization zone to promote solvent evaporation. Typically, this technique has been limited to LC flow rates of micropores of less than 100 μm per minute.
To effect direct introduction of liquid into the ion source, a cryogenic pump is used to trap excess sample on a cold surface outside the ion source. Normal LC flow rate, i.e. 1-2 ml / mi
In the case of n, the effluent is disrupted leaving only part of the sample to be sampled in the mass spectrophotometer. Another limitation of the DLI technique is that the spectra obtained give little CI data. That is, little or no structural information is obtained compared to EI. In addition, costly differential pumps are required to keep the mass analyzer pressure low enough. In practice, DLI has the problem that micro-sized orifices repeatedly block, complicating and significantly delaying the process. Matching and instability in small size liquid jets also makes DLI experimentally difficult in that the data obtained is noisy and non-reproducible. However, an advantage of this technique is that no thermal decomposition occurs when analyzing thermolabile compounds. Further discussion of this technology can be found in U.S. Pat. No. 3,997,298, issued Dec. 14, 1976, and U.S. Pat. No. 4,403,147, issued Sep. 6, 1983.

Mechanical transport (MT) is an LC-MS in which the effluent from the LC is deposited on a transfer surface, such as a wire or belt.
Is the law. Heat can be applied to the sample to remove the solvent, and mechanically transported to the low pressure ion source of the mass spectrophotometer through a series of vacuum locks on the desolvated sample and wires or belts. Both EI and CI mass spectrophotometers have been obtained by this technique. A limitation of this technique is that the sample must be evaporated or desorbed from the moving surface before ionization. Pyrolysis can occur during the thermal evaporation process. The operation of mechanical transport equipment is often cumbersome due to design complexity and obstacles in moving parts. The chromatographic profile of the sample can be degraded by uneven application of the sample to the moving surface. This method is described in detail in U.S. Pat. No. 4,055,987, issued Nov. 1, 1977.

Thermal spraying (TSY) is one of the most widely used methods for LC-MS. The effluent from the LC flows into the heated vaporization chamber in the ion source region of the MS via the thermal vaporizer. The thermal vaporizer converts the sample into an ion vapor plasma in a vaporization chamber. A small percentage of the ion vapor is sampled through a small aperture into the ion optical area of the mass spectrophotometer. The efficiency with which the analyte is collected through the sampling aperture is very low. Most of the ion vapor is exhausted via a miscellaneous path connected to the vaporization chamber. As in the case of DLI, a costly differential pump between the ion optics area and the mass analyzer area is needed to maintain sufficient vacuum. The vaporization step generates gas phase reagent ions as a buffer solution, such as aqueous ammonium acetate, is pumped through a thermal vaporizer. This ionization method, known as thermal spray ionization, produces a spectrum similar to CI. Under normal operating conditions, pyrolysis was observed with the use of a thermal vaporizer. However, a number of thermolabile compounds have been analyzed by this technique with minimal degradation. TSY has several limitations, most notably the absence of structural information, such as that obtained under EI ionization conditions. The response of various compounds depends on the chemistry of the substance being analyzed. As a result, it is often difficult to predict the response to poorly characterized samples. Thermal spraying is
The details are described in Canadian Patent No. 1,162,331 filed on August 14, 1984 and U.S. Patent Application No. 527,751 filed on August 30, 1985 and its continuation applications.

Monodisperse aerosol generation interface (MAGI) for combining liquid chromatography with mass spectrometry
C) LC pumping the effluent through a small orifice or tube to form a stable liquid jet
-A method for MS. The liquid jet is broken into uniformly sized or monodispersed droplets. These droplets are dispersed with a dispersing gas in a desolvation chamber at a pressure close to the atmospheric pressure, and this dispersing gas prevents rapid aggregation of the droplets and introduces thermal energy to the droplets, thereby causing rapid desolvation. . This method requires a large-diameter desolvation chamber close to atmospheric pressure to enable efficient desolvation. The effect of reducing the pressure in the desolvation chamber at the rate of solvent evaporation is theoretically handled by Fuchs and Stutgen (16). The evaporation rate of the droplets decreases significantly with decreasing pressure. In the absence of a dispersing gas, the droplets receive insufficient thermal energy, preventing their complete desolvation. A sufficiently high pressure is maintained in the desolvation chamber using a flow rate of the dispersing gas of greater than 1 per minute. After desolvation, the solute particles from which the solvent has been removed are accelerated through a nozzle into a decompression chamber to form a high-speed aerosol beam. In contrast to heavier solute particles, the lighter solvent vapor and dispersing gas expand outwardly from the axis of the aerosol beam, resulting in a collimated particle beam that is free of gaseous components. The gas component of the aerosol beam is
It is removed in a two-stage pressure reduction step performed by directing the particle beam to two successive skimmers separating two successive reduced pressure chambers. The solute particle beam enters the ion source region via the skimmer, where the concentrated solute is thermally desorbed from the surface in the ion source region and ionized by conventional CI or EI ionization techniques.

The MAGIC method for LC-MS has the advantage of ionizing solutes under EI conditions. However, the need for near-atmospheric desolvation significantly reduces the solute transport efficiency of a mass spectrophotometer for low pressure ion sources. The addition of a high flow of dispersing gas causes turbulence in the nozzle and
Significant reductions in transport efficiency are observed due to impacts on the skimmer and nozzle surfaces and the walls of the desolvation chamber.
In addition, the need for large volumes of gas also tends to entail the use of two-stage separation devices that cause solid angular expansion of the particle beam and are inefficient. Due to these conditions, the efficiency of solute transport into the ion source is generally on the order of 5%. In the case of MAGIC, the composition of the mobile phase does not affect the response for various analytes, similar to thermal spray techniques, which in some cases require mobile phase additives due to the sensitive response. Furthermore, if EI ionization is the only method used, no differential pump is required for this technique. More 19 details on this technology
It is described in US Patent Application No. 623,711, filed June 23, 1986 and filed by Willowby and Browner, and its continuation applications.

MAGIC can be considered as a particle beam introduction technology. To study this, the introduction of the particle beam accelerates the aerosol into the decompression chamber sequentially through the nozzle, skimmes the aerosol particles on the axis, forms a particle beam, and changes the gas component of the aerosol beam from the axis. It is considered to be a pumping removal technique. The result of this method is an efficient separation of aerosol particles from the gaseous material, where the particles are more efficiently transported into the low pressure region due to the higher moment of the particles compared to gas molecules. Conventional particle beam introduction techniques for mass spectrometry have been applied to two areas: (1) real-time aerosol monitoring (7-9); and (2) the aerosol generation process precedes the particle beam introduction. Introduction of liquid sample (References 10 to 14). MAGIC technology is an example of the latter. Furthermore, the present invention also includes a particle beam solute concentration step when applied to sample introduction into a mass spectrophotometer.

The performance of particle beam introduction technology depends on the nature of the aerosol. The solid angular dispersion of the particle beam is the size of the solute particles,
Depends on the pressure from the aerosol source and the shape of the nozzle. Israel and Friedlander (Ref. 15)
The relationship of these parameters to particle beam dispersion was experimentally shown. The results show that: (1)
The angular dispersion of the particle beam increases with the pressure of the aerosol source: (2) The angular dispersion of the particle beam decreases with increasing particle size: (3) The expansion of the particle beam is reduced by using a capillary for the converging nozzle. It becomes more uniform as the particle size changes. Therefore, the nature of the aerosol generation process as well as the gas flow rate and pressure as well as the particle size and distribution ultimately determine the efficiency of particle beam introduction.

Various aerosol generators have been used for particle beam methods for introducing liquid samples into mass spectrophotometers. These include the monodisperse aerosol generators of Berglundori (8, 10-14), the monodisperse aerosol generators of Willoughby Browner (14), and the Devilbiss and ultrasonic nebulizers (10-10). A major limitation with conventional particle beam beads has been the difficulty in desolvating aerosol droplets after aerosol generation. The prior art required a desolvation chamber to remove solvent from the droplets or increased the gas load. The generation of droplets greater than about 10 μm in diameter with conventional aerosol generation techniques tends to result in greater particle loss in the desolvation chamber and nozzle due to impact or settling processes. The aerosol generation method of the present invention is designed to allow precise control over aerosol properties including droplet size, directionality and evaporation rate. Improved control over the aerosol generation and desolvation steps increases the efficiency of particle transport for various detectors.

The solid angular dispersion of a particle beam has been shown to increase with increasing aerosol source pressure [15]. Thus, conventional particle beam technologies that require high gas loads for aerosol generation or desolvation tend to have more divergent particle beams. This requires that only a part of the particle beam cross section can be sampled via the axial skimmer. This is because the pressure in the subsequent chamber exceeds the upper limit pressure of the detector. Thus, theoretically, the entire cross section of the smaller divergent particle beam can be recovered at the same skimmer diameter, and
The same detector pressure could be maintained. The result of the less divergent particle beam allows for more efficient sample transport to the detector. As a result, the purpose of the device according to the invention is to reduce the gas load from the aerosol generation step and to improve the sample transport efficiency.

The use of particle beam technology for sample introduction into a mass spectrophotometer has demonstrated the ability to generate spectra under potential impact ionization conditions (7-14). The main purpose of the device according to the invention is to improve the ability to vaporize particles after the particle beam has entered the ion source area of the mass spectrophotometer. The purpose is to form a complete gas phase molecular species derived from the particles. In a conventional particle beam sample introduction device, it is difficult to form complete molecular ions because thermal fragmentation of molecules occurs during evaporation from a heated surface (Reference 8). The particle vaporization process depends on the equilibrium surface vapor pressure of molecules from the particles, the temperature and material of the particle beam collection surface, and the presence of other components in the particle matrix. Control of these factors is essential to the performance of the device according to the invention.

Other uses for introducing liquid samples for gas or particle detectors include light scattering (17), flame ionization (18),
Atomic absorption or emission spectrophotometry (19) has been reported. The improved control of aerosol generation, desolvation and solute concentration by the device of the present invention can be applied to various types of detectors.

The documents cited in the above prior art are as follows: 1. PJ Alpino, journal chromatography,
Volume 323, page 3 (1985).

2. DE game, advanced chromatography,
Volume 21, Page 1 (1983) 3. CG Edmond, JA Macroski, VA Edmond, Biomed Mass Spectrophotometry, Volume 10, Page 237 (1
983) 4. RC Willowby, RF Browner, Trace Analysis, Volume 2, page 69, edited by JF Lawrence, Academic Press (1982).

5. WMA Niessen, Chromatography, Volume 21, page 5 (1986).

6. WMA Niessen, Chromatography, Volume 21, Page 5 (1986).

7. JJ Stoffels, "A Direct Air Sampling Inlet for Surface Ionization Mass Spectrometry of Air-Supported Particles", submitted to the ASMS 24th Annual General Meeting in San Diego, CA, 1976.

8. MP Singha, CE Griffin, DG Norris and S.
K. Friedlander, "Analysis of Aerosol Particles by Mass Spectrophotometry," submitted to the 28th ASMS Annual Meeting in New York, NY, 1980.

9. J. Allen and RK Gould, Review Science, Instruments, Volume 52, Issue 6, June 1981
Moon.

10. FT Green, Particle Impact Mass Spectrophotometry, 197
Submitted to ASMS's 23rd Annual Meeting in Houston, Texas for 5 years.

11. FT Gree, Mass Spectrophotometry of Non-Volatile Materials and Solutions by Particle Impact Technology, submitted to the 24th Annual Meeting of ASMS in San Diego, California, 1976.

12. FT Green, "Development of Particle Impact Mass Spectrometry", 1980, AS in New York, NY
Submitted to MS's 29th Annual Meeting.

13. FT Green, "Current State of Particle Impact Mass Spectroscopy", 1981, ASMS in Minneapolis, MN
Submitted to the 29th Annual General Meeting.

14. RC Willowby, "Study on aerosol generation interface between liquid chromatography and mass spectrophotometry", Georgia Tech University doctoral dissertation, 1983.

15. GW Israel and SK Friedlander, Journal Colloid Interface Science,
Vol. 24, p. 330 (1967) 16. NA Fuchs and AG Stugen, "Highly dispersed aerosol", Annual Arbor, Science, Ann.
Arbor (1970).

17. JW Jorgenson, SL Smith and M. Novotney, Journal Chromatography, 142, 233
Page (1977).

18. E. Harkti and T. Nikkali, Acta Chemica Scandinavia, Vol. 17, p. 2565 (1963).

19. RF Browner and AW Bone, Analytical Chemistry, 56/7, 787A (1984).

 The disclosures of these references are incorporated herein by reference.

SUMMARY OF THE INVENTION The present invention is a method and apparatus for introducing a process stream, a liquid injection stream or an effluent from a liquid chromatograph into a gas phase or particle detector into an analyzer. It has applications in introducing liquid samples into mass spectrophotometers, flame ionization detectors, light scattering detectors and other devices suitable for characterizing analytes in the gas phase or in particulate form. Can be.

The basic processes that occur in the device of the present invention are the generation and desolvation of aerosols, the concentration of solutes, and the detection of solutes with a suitable gas or particle detector.

Aerosol generation according to the present invention is a liquid flow (inside flow)
And a gas flow (outside flow). The gas is heated by direct contact with a heat source (generally a heating tube that seals the gas). The tube is heated by controlled resistance heating of the tube or direct contact of the tube with the cartridge heater. By precisely controlling the flow of gas into the outer tube, the flow of liquid into the inner tube, the dimensions of both tubes, and the power to the heat source, the nature of the aerosol is accurately determined.
The heat is introduced via a gaseous medium, so that the thermal conductivity of the gas is preferably high (eg hydrogen, helium).

The amount of heat supplied to the liquid via the gaseous medium determines the degree of solvent removal or evaporation of the solvent that occurs during the aerosol generation step. Gas supply is 2 in aerosol generation
Performs two functions. First, it provides the heat required for desolvation. Second, it encloses or seals the aerosol particles, preventing them from widespread dispersion,
An expansion shock is applied to the chamber wall. The apparatus of the present invention does not require a desolvation chamber since the evaporation of the solvent occurs entirely within the inner tube of the aerosol generator.

Controlled aerosol generation and desolvation by the apparatus of the present invention effectively separates the solvent from the solute, as the solute generally has a lower volatility than the solvent. The solvent is in the gas phase and the solute is kept in a particulate state.

After phase separation, the solute is concentrated by one of two methods. The first method of solute enrichment is to separate the solvent from the solute in a particle beam or moment separator, where higher moment solute particles are effectively introduced into successive low pressure regions separated by a skimmer aperture. It is carried in. The device of the invention can be used in one stage or two
Utilize particle beam pressure reduction in any of the stages. The configuration of the particle beam in the device of the present invention transports most solutes to the low pressure detection zone and removes more than 99% of the solvent. A second method of solute enrichment separates the solvent from the solute by the mobility of the particles relative to the gas. The gaseous solvent component of the aerosol having higher mobility interacts significantly with the cold surface and is trapped on the surface (ie, a cryogenic trap). The solute in particulate form is carried in the gas stream by a less condensable carrier gas such as, for example, helium or hydrogen, leaving solvent vapors. A combination of cryogenic trapping and particle beam solute enrichment is a third alternative.

The detection of the concentrated solute by the apparatus of the present invention is performed by various means. One embodiment of the present invention uses particle beam enrichment to direct solute particles to the ionization source of a mass spectrophotometer. The particle beam intersects various means surrounding the primary ion beam, laser beam, discharge plasma, electron beam, electric or magnetic field. Under these operating conditions, the energy of solute evaporation and ionization is provided directly to the solute particles during flight. Other embodiments use a target surface to collect solute particles. The target surface is generally composed of a controlled temperature inert material and plays a role in supplying heat to the particles to achieve rapid solute vaporization. After the solute has been vaporized, conventional gas phase methods such as, for example, electron bombardment or chemical ionization, result in ionization. Neutral ions or an electron beam can collide with the target surface having the recovered particles to generate gas phase ions from the target surface. Alternatively, solutes are collected on a cold target surface for a predetermined period of time before heating the target, and the sample is concentrated to reduce the detection limit. The heat of vaporization is also determined using a measurement of the power supplied to the target.

The use of other gas phase detectors, such as, for example, a flame ionization detector (FID), requires a cryogenic pump for solute concentration and hydrogen as atomizing gas. This embodiment operates with atmospheric or low pressure flames.

In addition, embodiments of the particle beam are used in laser scattering or continuous light scattering measurements and serve as universal liquid chromatography detectors.

EXAMPLES Hereinafter, the present invention will be further described with reference to the accompanying drawings with reference to examples.

The apparatus of the present invention comprises three components: an aerosol generator 14, a solute concentrator, and a solute collector or detector.

The first of these parts, the aerosol generator 14, will be described in detail with reference to FIGS.
Liquid flows from source 30 and gas flows from source 31 into aerosol generator 14. The gas flows through tube 11,
And the liquid flows through the tube 10. Aerosol generator 14
What is important for the operation of this embodiment is that heat is supplied coaxially to the flowing liquid in the tube 10 via the flowing gas medium between the tubes 10 and 11. The dimensions of these tubes and the flow rates of gas, liquid and heat determine the nature of the aerosol generated.

Liquid source 30 for aerosol generator according to the present invention
Are effluents from liquid process streams, liquid chromatographs or liquid injection streams (ie effluents containing dissolved analytes of interest in addition to other naturally occurring or intentionally added low volatility components) It is. Fused silica capillary 10
Functions as a nozzle for confining the flow of the effluent. The tube 10 restricts the flow of the liquid, increasing the linear side of the liquid flow and increasing the surface contact between the liquid per unit volume and the heated wall of the fused silica capillary. The inner diameter of the fused silica capillary 10 has dimensions determined by the flow rate requirements of the liquid for a given application. The minimum inner diameter of the tube 10 is determined by the upper pump pressure of the liquid supply 30. The flow rate, length and inner diameter of the liquid in the tube 10 has an effect on the liquid supply pressure. 0.1-2.0ml per minute
Typical dimensions of the fused silica capillaries for liquid flows in the range are 50 μm inner diameter and 250 μm outer diameter. Tube 1
The inner diameter of 0 is 10 μm, 25 μm, 50 μm, 75 μm and 1
Testing at 00 μm has been successful. The length of the fused silica capillary is long enough to allow heat transfer to the liquid stream. A typical length is 20cm. The maximum length of the fused silica capillary 10 is determined by the pressure limit of the liquid pump system.

The gas source 31 for the aerosol generator 14 comprises a compressed or spontaneous controlled gas source of a conductive gas or gas mixture. A coaxial metal capillary 11 seals the fused silica tube 10, restricts the flow of the atomizing gas supplied from the controlled gas supply 31, and provides a precision valve.
35 (see FIG. 3). The inner diameter of the metal capillary 11 and the gas flow rate from the supply source 31 determine the linear velocity of the gas flowing through the metal capillary 31 and, consequently, the linear velocity of the concentric sealing gas 33 in the aerosol generation step. The concentric gas flow serves two functions in the device according to the invention. First
Next, the aerosol flowing out of the fused silica capillary 10 is sealed. Second, it acts as a conductive medium for heat transfer from the heated outer metal capillary 11 to the inner fused silica capillary 10.

The heat supply of the aerosol generator according to the invention is a metal capillary
It consists of 11 electrical resistors, which heat the tube. FIG. 1 shows a means for increasing the temperature of the capillary tube 11 by supplying heat by supplying an electric current. The tube is the resistive heating part of the heating circuit. The length, composition and wall thickness of the outer tube 11 determine the power requirements of the heating power supply 20, which is controlled by the heater controller 23. The heating circuit is controlled by maintaining a constant resistance in the circuit or maintaining a constant temperature by thermocouple feedback 24. The heated outer tube 11 is preferably composed of a pure metal such as, for example, nickel or platinum. This is because the temperature is proportional to the resistance of this kind of pure metal, or of many other pure metals. This relationship is
Allows control of heat supply or temperature by direct resistance feedback measurement without the need for thermocouple feedback control. Furthermore, the device according to the invention can also use thermocouple feedback for heat supply control and resistively heated alloys other than pure metals. The resistive heating circuit is electrically insulated from the ground by any suitable means, such as, for example, insulators indicated by reference numerals 12 and 13. The inner diameter of the heated metal capillary 11 is slightly larger than the outer diameter of the inner fused silica capillary 10. A typical range for the inner diameter of tube 11 is 300-400 μm. In this range the gas velocity is
At position 32 it is high enough to entrain the liquid jet or aerosol emanating from the fused silica capillary 10. Further, the gap spacing is small enough to allow efficient heat transfer through the gas to the fused silica capillary 10. Not part of a resistance-heated circuit and an electrically insulating union 12
Thus, there is a portion of the capillary tube 11 connected to the heated portion of the tube 11. The area surrounding the outer metal capillary 11 heats the inner fused silica tube at a slower rate than the rate of heat transfer.
Guide to 10. As a result, the outer tube is insulated by air space, insulating material or reduced pressure, ensuring heat transfer to the flowing liquid stream.

FIG. 2 shows an alternative means of supplying heat to the metal capillary 11 by heating the cartridge. Cartridge heater
26 is inserted into a metal block that is in thermal contact with the metal capillary 11. If a cartridge heater is used, the control means for heater power supply 20 is thermocouple feedback 24 to controller 23.

The heating portion of the aerosol generator is contained within a protective housing 28 which serves to direct the aerosol generator and protect the operator from voltage burns or electrical shock. The aerosol generator is attached to the aerosol expansion chamber via a connection 29 which can be a gasket and / or an O-ring seal.

Aerosol generation by the device of the present invention is obtained by precisely controlling the coaxial flow of liquid, gas and heat. The aerosol is generated at a location 32 and is confined by a sealing gas 33 along an axis in the direction of flow. Coaxial heat transfer to the flowing liquid is controlled by an electrical feedback circuit and gas flow between the outer heated metal tube 11 and the inner fused silica capillary 10, which is the conductive medium passing through the interstitial space. The thermal conductivity of the gas is a critical parameter in the transfer of heat to the inner fused silica tube 10. Preferably, the gas supply comprises a highly conductive gas such as, for example, hydrogen or helium, but this does not preclude other gases or gas mixtures with low conductivity.

Preferred operating conditions of the aerosol generator according to the invention are:
Depends on the required aerosol properties for a given application. The range of aerosol properties varies from pneumatic nebulized solvent-rich aerosols with relatively large diameter droplets to hot nebulized solvent-removed aerosols with relatively small diameter droplets. The combination of pneumatic and thermal spraying results in an aerosol in which the droplet size variation, the degree of desolvation of the droplets and the direction of flow of the generated aerosol have been adjusted, which has been removed as a vapor. It functions to produce solute particles.

The aerosol generated by the device of the present invention requires a solute concentration step in embodiments where the presence of a relatively large amount of solvent makes detection of the solute worse. The device according to the invention is particularly generally applied to effluents in which the solute is less volatile than the relevant solvent or solution. The difference in volatility between the solvent and the solute results in a solute that is primarily present in the particulate portion of the aerosol and a solvent that is primarily present in the vapor portion of the aerosol. 3 to 5 show an embodiment of the present invention based on aerosol generation, particle beam solute concentration and mass spectrophotometric detection. FIG. 6 shows an embodiment of the present invention relating to aerosol generation, solvent cryogenic trapping for solute concentration and flame ionization detection. Although the use of the device according to the invention for aerosol generation, solute enrichment and detection by other detection modes is not shown, the modifications necessary to do this are the techniques of introducing a liquid sample into a gas phase or particle detector. It will be apparent to those skilled in the art from the disclosed embodiments.

FIG. 3 shows an embodiment of the present invention relating to one-stage particle beam solute enrichment. The device is mounted via a flange vacuum joint 62 to an ion source chamber 60 of the mass spectrophotometer. The aerosol generator described above is attached to the aerosol expansion chamber 40 by the sealing joint 29.
The expansion chamber 40 provides sufficient space for the high speed aerosol generated at the location 32 to slow down to the viscous flow range and travel in the directions indicated by the dashed and arrows. The pressure in the expansion chamber can vary from near atmospheric to 1 Torr, depending on the material flow rate from the aerosol generator. The solute particles and the solvent vapor are accelerated in the nozzle 42 to form a high velocity aerosol beam along the longitudinal axis between the nozzle 42 and the skimmer 43. Due to the pressure drop between the expansion chamber 40 and the decompression chamber 41, a beam is formed. Decompression chamber 41
Is reduced by a pump 44, typically at 400 / min
Is a mechanical pump having a large pump capacity such as a rotary pump. Nozzle 42 and skimmer 43 aligned in the axial direction
In the region between, the solvent vapor from the aerosol and the conductive gas expand much more rapidly than the solute particles. As a result of the differential expansion between the gas and the particles, the particles are highly concentrated at the axis of the expanded aerosol beam. The concentrated solute particles are sampled through the skimmer 43 into the ion source chamber of the mass spectrophotometer. A concentrated solute particle beam is formed from the skimmer to the ionization region 61 of the mass spectrophotometer.
The distance between the point where the aerosol beam is formed at the nozzle 42 and the ionization region should be kept to a minimum, generally between 5 and 10 cm.

FIG. 4 shows an embodiment of the present invention relating to a two-stage solute beam enrichment. As described with reference to FIG. 3, the apparatus is mounted via a flange joint 62 to the ion source chamber 60 of the mass spectrophotometer. The aerosol generator is mounted in the aerosol expansion chamber 40 by the sealing joint 29. The aerosol expands axially from the aerosol generator at location 32 and travels down the axis of the expansion chamber in the direction indicated by the dashed lines and arrows. The aerosol is accelerated in the nozzle 42 to form a high-speed aerosol beam between the nozzle 42 and the skimmer 43. This aerosol beam is formed by a pressure drop between the expansion chamber 40 and the first decompression chamber 41. The second vacuum chamber 46 provides a higher degree of solute enrichment by pumping further solvent vapors in the region between the skimmer 43 and the skimmer 49. 1st decompression chamber
41 is depressurized by a pump 44, and the second decompression chamber is a pump
Depressurized by 45. Pumps 44 and 45 have sufficient pumping capacity to remove most of the solvent vapor introduced by the aerosol generator. Nozzle 42 and skimmers 43 and 49 are similarly axially aligned to permit sampling of the concentrated solute particles into a progressively decreasing pressure zone. The distance between the nozzle 42 where the aerosol beam is formed and the ionization region 61 is minimized to ensure the solute particle transfer efficiency. This distance is generally between 1 and 10 cm.

FIG. 5 shows an embodiment of the present invention relating to a two-stage solute particle beam enrichment alternative to the embodiment shown in FIG. This device is removable from the ion source chamber 60 of the mass spectrophotometer via a standard gate valve 64. The insertion probe portion 65 of the device is inserted into a gate valve 64, which opens and closes automatically, and the ionization region 61 of the mass spectrophotometer.
Are aligned in the axial direction. The aerosol generator is mounted in the aerosol expansion chamber 40 at the sealing joint 29. The aerosol expands axially from the aerosol generator at location 32 and travels down the axis of expansion chamber 40 in the direction indicated by the dashed lines and arrows. Aerosol nozzle 42
To form a high-speed aerosol beam between the nozzle 42 and the skimmer 43. This aerosol beam
It is formed by the pressure drop between the expansion chamber 40 and the first decompression chamber 41. The second vacuum chamber 46 provides a higher degree of solute enrichment by pumping out additional solvent vapor in the area between the skimmer 43 and the skimmer 49. The first decompression chamber 41 is depressurized by a pump 44, and the second decompression chamber is depressurized by a pump 45. Pumps 44 and 45 have sufficient pumping capacity to remove most of the solvent vapors and conductive gases introduced by the aerosol generator. Nozzle 42 and skimmers 43 and 49 are similarly axially aligned to allow for the sampling of concentrated solute particles into a progressively decreasing pressure zone. The distance between the nozzle 42 where the aerosol beam is formed and the ionization region 61 is minimized to ensure the transport efficiency of the solute particles. However, in this embodiment, an additional length for the intervening probe 65 is required. This distance is generally in the range of 20-40 cm.

FIG. 5 further shows an optional mounting 67 which can be introduced into the ion chamber 60 which is close to and surrounds the ionization area 61 for special purposes. For example, the mounting 67 can be a laser, which allows the laser beam to be focused on the surface of the target 61 and the beam to be subjected to photoionization and laser desorption analysis. Further, the mounting portion 67
Can also constitute an electron source for chemical ionization or a high voltage source to ionize particles and molecules by discharge or field ionization.

Still further, the mounting portion 64 may comprise a cryogenic trap for collecting solvent vapor on the cold surface and passing solute particles through the cold trap for later detection. Another form of mounting 67 is an apparatus for providing an optical region transverse to the axis of the particle beam to perform light scattering measurements on the beam. Attachment 67 may further comprise a support for the moving target (ie, belt 68 shown in dashed lines), which collects solute particles as a function of time and incorporates devices ( Ie separate device)
Locates and analyzes surface measurements such as SIMS, infrared, x-ray, ultraviolet or visible spectrophotometric scanning, or chromatographic contours received, for example, by reflection or transmission measurement techniques. In addition, the belt 68 can also collect highly purified solute crystals for subsequent structural analysis. The belt 68 or its equivalent (eg, a disk or a moving band) can be heated to perform on-line continuous thermal analysis. In this case, the mounting 67 may further comprise means for heating the target, controlling this heat and accurately measuring the thermal energy consumed by evaporation or desorption of solutes from the target.

Attachment 67 can constitute an apparatus for generating a high energy discharge having sufficient energy to charge the surface of the particles in the beam and thereby increase ion desorption or particle cleavage at clonogenic forces. .
The mountings 67 can be self-contained, or preferably easily removable, and a plurality of mountings 67 can be located within the chamber 60 in operative proximity to the target and the area 61, thus providing It can be used alone or in combination as desired.

The concentrated particle beam generated by the embodiment shown in FIGS. 3-5 converts solute particles into gas phase ions as well.
In each of these devices, the solute particles are collected on the target surface 50. The target surface 50 is a surface heated by resistance, and vaporizes solute molecules by supplying thermal energy to minute solute particles. The target is inserted into the gate valve 63 to cause solute vaporization to occur in the ionization region 61 of the mass spectrophotometer. The temperature of the target surface 50 is determined by the thermocouple feedback 53
And a power supply 51.
The recovered solute particles are heated at a low temperature for heat sensitive compounds and at a high temperature for non-volatiles and sprays. The operating temperature range of the target surface 50 is generally 100 ° C to 300 ° C.
It is in the range of ° C. Ionization of gas phase solute molecules is performed by conventional ionization methods such as, for example, electron impact or chemical ionization.

The ionization process that occurs in the apparatus described with reference to FIGS. 3 to 5 is not limited to gas phase ionization alone. The solute particle beam is further collected on the target surface 50, for example, rapid atom bombardment, secondary ion mass spectrometry, electric field desorption,
Ionization is accomplished by conventional surface ionization techniques such as thermal ionization, plasma desorption and laser desorption as described with reference to FIG. These techniques require introducing an alternative energy source at the target surface. In addition to the surface ionization method, the device according to the invention can also introduce energy directly into the solute particle beam without collecting particles on the surface before ionization. According to this embodiment, the target surface 50 need not be present. When in flight, the solute particle beam intersects the primary ion beam, primary atom beam, laser beam or high electric field region.

FIG. 6 illustrates an embodiment of the present invention with solvent cryogenic trapping to provide solute particle concentration. The aerosol generator is attached to the aerosol expansion chamber 40 at the sealing joint 29. The conductive gas used for aerosol generation according to this embodiment is hydrogen gas. The aerosol expands axially from the aerosol generator at location 32 and travels down the axis of the expansion chamber in the direction indicated by the dashed lines and arrows. The walls of the expansion chamber 40 are cryogenically cooled to trap solvent vapor. Solute particles and hydrogen gas pass through the expansion chamber more efficiently than solvent vapor. The concentrated solute particles and hydrogen gas are introduced into the burner chamber 71 through the inlet 70. Here, the particles are burned by the hydrogen flame, and the ions in the generated flame are collected on the electrode grid 73. Air or oxygen is introduced into burner chamber 71 via inlet 72.

While the present invention has been described in terms of particular embodiments so that those skilled in the art would readily understand it, this should not be understood as implying unnecessary limitations. The cited prior art patents, literature and patent applications are intended to assist those skilled in the art in understanding the present invention and are not intended to limit the invention in any way.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a thermal concentric aerosol generator using resistance heating of a conductive aerosol generating gas, and FIG. 2 is a schematic sectional view of a thermal concentric aerosol generating apparatus using a cartridge heating of a conductive aerosol generating gas. FIG. 3 is a schematic cross-sectional view of a thermal concentric aerosol generator and one-stage particle beam solute enrichment interface to the ion source chamber flange of a conventional mass spectrophotometer, and FIG. 4 is a conventional mass spectrophotometer. FIG. 5 is a schematic cross-sectional view of a thermal concentric aerosol generator and a two-stage particle beam solute concentrator interfacing with the ion source chamber flange of the meter; FIG. 5 shows the thermal interface with the ion source chamber gate valve of a conventional mass spectrophotometer; FIG. 6 is a schematic cross-sectional view of an alternative concentric aerosol generator and two-stage particle beam solute enrichment; To a flame ionization detector is a schematic illustration of a heat concentric aerosol generator and a solvent cryogenic trapping solute concentrated to Intasuesu. 10 ... Inner fused silica capillary 11 ... Outer metal capillary 14 ... Aerosol generator, 40 ... Expansion chamber 41 ... First decompression chamber, 46 ... Second decompression chamber 52 ... Control room

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-148245 (JP, A) JP-A-53-90992 (JP, A) JP-A-62-40149 (JP, A) JP-A-60-1985 44 (JP, A) JP-B-58-43692 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) G10N 27/62-27/70

Claims (18)

(57) [Claims] A thermal concentric aerosol generator for obtaining solvent-removed solute particles having micron and submicron dimensions from a liquid sample containing a volatile solvent and a less volatile solute in a well-defined direction. Wherein: (a) an inner capillary; (b) a liquid stream into the capillary containing the solvent containing a solute less volatile than the solvent; (c) while the solvent is flowing through the capillary. Heating means coupled to said capillary to raise its temperature sufficient to cause substantially all of the phase of said solvent to change from a liquid to a gas before said solvent flows out of said capillary outlet; A tube outside the capillary, containing a gaseous substance flowing in the same direction as the solvent; (e) the solvent gas and the solute in particulate form, wherein the gaseous substance flowing out of the outlet of the tube is separated from the capillary outlet Enclose An expansion chamber receiving the outlet of the tube and the capillary in which the tube and the capillary are disposed so as to be inserted therein; (f) an outlet of the expansion chamber located away from an outlet of the capillary; and (g) an expansion chamber. The gas and solute particles reach the outlet of the expansion chamber almost simultaneously and are introduced, so that the solute particles are sufficiently guided by the gas and gaseous substance. Pressure and motion into the interior of the expansion chamber to prevent the majority of the solute particles from impinging on the outlet of the capillary, the inner wall of the expansion chamber and the inner surface of the outlet of the expansion chamber. . 2. The heating means comprises an electric circuit,
2. The thermal concentric aerosol generator according to claim 1, wherein said tube is a heating member of said circuit, and said outer tube is made of a high-purity metal having a relatively high linear relationship between temperature and resistance. 3. An expansion chamber which is coaxial with said capillary outlet to provide sufficient space for high velocity gas and particles, and to provide an internal velocity without significant sample loss due to particle bombardment or sedimentation. The thermal concentric aerosol generating device according to claim 1, wherein the temperature is reduced. 4. A supply means for heating the expansion chamber,
4. The thermal concentric aerosol generator according to claim 3, further comprising control means for controlling the supply means, and detection means for monitoring the temperature of the expansion chamber. 5. An expansion chamber outlet comprising a nozzle restriction downstream of the expansion chamber and coaxial with the inner capillary, from which the flow of the solute particles is accelerated in the nozzle. 5. The thermal concentric aerosol generator according to claim 4, which forms a high-speed particle beam. 6. A low pressure chamber downstream from said nozzle, solute particles,
A solvent gas and a gaseous substance discharged from the nozzle at a high velocity, further expanding a flow of a beam emitted from the nozzle outwardly from an axis of the nozzle, further separating the gaseous substance and the solvent gas from each other. 6. The concentric aerosol generator of claim 5 including pump means for removing from the beam. 7. A thermal concentric aerosol generator according to claim 6, further comprising means for collecting solvent vapor on a cold surface and passing solute particles through the cold trap for later detection. 8. A thermal concentric aerosol generator according to claim 1, including coupling means for directly fixing to the housing of the mass spectrophotometer. 9. The thermal aerosol generator according to claim 8, further comprising an insertion probe which can be easily attached to and detached from an ion source region of the mass spectrophotometer through a flange pressure reducing joint in combination with the mass spectrophotometer interface. 10. The thermal aerosol generator according to claim 9, further comprising a heating target aligned in the axial direction so as to collect the solute particles, wherein the target rapidly evaporates the collected solute particles or detaches the collected solute particles by flash. 11. A method for attaching and detaching a solute from said heating target and / or
Or further comprising a control means for controlling the evaporation: (a) evaporating the collected solute particles in a state of being completely desorbed as a molecular substance before ionization by an electron impact or chemical ionization step; (C) thermally ionizing the solute particles from the surface as complete molecular ions, or (c) thermally decomposing the recovered solute particles on the surface of the target to form gas phase thermal fragments, for example, by electron impact or chemical ionization. 11. The thermal concentric aerosol generation device according to claim 10, wherein the target is made ionizable by a conventional method, and the temperature of the target is adjusted so as to control and remove the solute from the target. 12. A method for generating, transporting, collecting, analyzing, introducing a sample into a detection device, introducing a sample into a detection device, condensing the solute, or purifying the solute from a solution containing a low volatility solute. (A) introducing and transporting a liquid stream containing said solvent containing a solute less volatile than the solvent into the inner capillary, and (b) transferring the thermally conductive gaseous medium to the inner capillary. Introducing the gaseous medium into a tube concentrically surrounding the capillary tube and transporting the same through the tube, thereby causing the gaseous medium to flow in the same direction as the solvent; and (c) sufficiently heating the gaseous medium, and (D) moving the solvent from a liquid to a gas while the energy is recovered in the solvent and flowing through the capillary; (E) containing the gaseous medium and solute The gaseous solvent is sufficiently decelerated while moving in the expansion chamber, minimizing disturbances in the expansion chamber to a substantial extent, while the solute particles are centrally defined by the gaseous medium and the gas flow. Almost concentrated in the passage, most of the solute particles diverge from the capillary outlet because they are guided by the gas flow and the gaseous medium, and to the inner wall of the expansion chamber and the inner surface of the expansion chamber outlet Avoiding the collision of the above. 13. The method for generating a highly dispersed aerosol according to claim 12, further comprising a separation step of pumping the solvent vapor in a direction non-axial to the direction of movement of the solute particles in the expansion chamber. 14. The method of claim 1, further comprising the step of collecting the solvent-removed solute particles on a target surface for subsequent analysis, the analysis comprising the following steps: (a) evaporation and ionization for mass spectrophotometric analysis;
Or (b) X-ray diffraction analysis or other techniques for examining crystals or solid particles, or (c) optical analysis such as infrared reflection or transmission or other optical techniques using any suitable wavelength, filter or monochromator. 14. The method of generating a highly dispersed aerosol according to claim 13, comprising one or more selected steps. 15. A thermal concentric aerosol generator for obtaining solvent-removed solute particles having micron and submicron dimensions from a liquid sample containing a volatile solvent and a less volatile solute in a well-defined direction. (A) an inner capillary; (b) means for supplying a liquid stream containing said solvent containing a solute less volatile than the solvent into said capillary; (c) a tube concentrically surrounding said capillary; Means for introducing a thermally conductive gaseous substance into the tube and moving the same in the same direction as the solvent, (d) the temperature of the gaseous substance, and the heat conduction through the gaseous substance, whereby the solvent and Heating means for raising the temperature of the solute enough to cause substantially all of the phase of the solvent to change from a liquid to a gas phase before the solvent flows out of the outlet of the capillary; Escaping gas An expansion chamber receiving the outlet of the tube and the capillary, wherein the tube and the capillary are arranged such that a substance surrounds and guides the solvent gas and particles from the solute away from the outlet of the capillary; The gaseous substance, the solvent gas and the solute particles are discharged from the expansion chamber when the outlet of the expansion chamber located apart from the outlet of the capillary tube to collect them when flowing out, the interior of the expansion chamber, Disturbance in the expansion chamber is minimized to a substantial extent, and the gaseous medium and solute particles and solvent gas are decelerated and, when they reach the outlet of the expansion chamber, move at approximately the same speed, (G) The solute particles are maintained at a pressure such that they are concentrated substantially at the center of the gaseous substance and the solvent gas flow. (G) The gaseous substance and the solvent are drawn from the solute particles downstream of the expansion chamber. At least for One stage, and (h) located downstream of said step, said generator comprising an analysis chamber, which are exposed to high vacuum to recover the solute particles. 16. A thermal concentric aerosol generator for obtaining solvent-free solute particles having micron and submicron dimensions from a liquid sample containing a volatile solvent and a less volatile solute in a well-defined direction. Wherein: (a) an inner capillary for recovering the pressure of the liquid solvent containing a solute less volatile than the solvent; (b) a tube concentrically surrounding the capillary and introducing a thermally conductive gaseous substance into the tube. Means for moving the solvent in the same direction as the solvent; (c) substantially all of the phase of the solvent passing therethrough before the solvent flows out of the outlet of the capillary changes phase from a liquid to a gas. Supplying sufficient thermal energy to the capillary tube to raise its temperature enough to cause the gaseous material passing through the tube to cool the temperature of the solvent gas before it exits the opening surrounding the outlet. Also high (D) surrounding and guiding particles from the solvent gas and the solute remote from the outlet of the capillary tube. An expansion chamber receiving the opening of the tube and the outlet of the capillary so as to: (e) a high vacuum stage downstream of the expansion chamber; (f) the gaseous substance, solvent gas and solute particles from the expansion chamber. The passage for the flow of the gas, the arrangement of the inside of the expansion chamber, the deceleration of the gaseous substance, the solvent gas and the solute particles substantially avoid the disturbance in the expansion chamber, and reduce the flow of the solute particles by the gaseous substance. And concentrates relatively centrally with respect to the solvent gas, thereby reducing the chance of the solute particles being trapped in a high vacuum stage downstream of the expansion chamber, where the gaseous and solvent gases are The solute particles passing through the high vacuum stage It shall be as desorbed, the generator comprising a. 17. The method of claim 12, further comprising the step of removing solvent vapor from the aerosol by cryogenic trapping of the vapor and transporting the dried solute particles for subsequent detection. 18. The method for generating a highly dispersed aerosol according to claim 17, further comprising flame ionization detection of the particle stream.