Abstract:
Embodiments of the invention relate to a device for analyzing a sample surface Comprising an outlet and a frame. The outlet is for forming a jet of gas, the jet forming a sampling region for receiving one or more sample surfaces, and the frame holding the outlet and being adapted to receive a detector means. The detector means has an inlet. In use, the jet produces desorbed sample from sample surfaces received in the sample area. At least a portion of the desorbed sample is ionized to produce one or more sample ions. The frame holds the outlet with respect to the sample ions and produce a signal indicative of the composition of the sample ions.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of International Application No. PCT/US2008/052768, filed Feb. 1, 2008, which claims priority to and benefit of U.S. Provisional Patent Application Ser. No. 60/887,897, filed Feb. 2, 2007, U.S. Provisional Patent Application Ser. No. 60/911,566, filed Apr. 13, 2007 and U.S. Provisional Patent Application Ser. No. 60/941,004, filed May 31, 2007. The entire contents of these applications are incorporated herein by reference. 
    
    
     STATEMENT WITH RESPECT TO FEDERAL SPONSORSHIP 
     The present invention was made without Federal sponsorship or funds. 
     FIELD OF THE INVENTION 
     The present invention relates to a device and method for analyzing the surface of a sample. 
     BACKGROUND OF THE INVENTION 
     Ion analysis devices such as mass spectrometers have been used to great effect to analyze and characterize samples both simple and complex. Such devices require samples to be ionized so that mass to charge ratio (m/z) may be measured by various methods of manipulation of the ions. Early ion sources involved such methods as the bombarding of samples with electrons. These methods, however, often caused ions to be produced with very high energy, which left them liable to fragment. Later, so called “soft” ionization techniques, notably electrospray, atmospheric pressure chemical ionization (APCI) and matrix assisted laser desorption ionization (MALDI), were developed, each of which enabled sample ion fragmentation to be better controlled, and for sample ions to be detected in their entirety. 
     The analysis of solid samples and surfaces with on analysis devices has always provided particular challenges, as traditional soft ionization techniques are appropriate only to the analysis of liquid samples or samples held in solution. Certain industries however, such as food, homeland security, and forensics, would find great benefit in a source able to effectively produce molecular or pseudo molecular ions from a solid sample without significant damage to the surface. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention relate to a device for analysing a sample surface comprising an outlet and a frame. The outlet is for forming a jet of carbon dioxide, the jet forming a sampling region for receiving one or more sample surfaces, and the frame holding the outlet and being adapted to receive a detector means. The detector means has an inlet. 
     In use, the jet produces desorbed sample from sample surfaces received in the sample area. At least a portion of the desorbed sample is ionized to produce one or more sample ions. The frame holds the outlet with respect to the sampling area and the inlet to allow the detector means to receive the sample ions and produce a signal indicative of the composition of the sample ions. 
     Preferably, the device further comprises a detector having an inlet configured to receive the sample ions. Preferably, the inlet is held at an elevated potential. More preferably, the inlet is held at a potential between 50V and 100V. 
     Preferably, the device further comprises a heater in thermal communication with the inlet. The inlet is preferably maintained at a temperature of between 70° C. and 200° C. 
     In preferred embodiments, the detector means is selected from the group comprising: mass spectrometer, ion mobility spectrometer. 
     In some embodiments, the outlet is held at elevated potential. 
     In some preferred embodiments, the device further comprises a discharge member held by the frame proximal to the outlet, for affecting a discharge such that at least a further portion of the desorbed sample is ionized to produce further sample ions. The discharge member is preferably held at a potential of 2000V to 6000V. Preferably, a resistor is provided in electrical series with the discharge member. The resistor preferably provides a resistance of 100MΩ to 6000MΩ. Alternatively the discharge member may be attached to a current regulated high voltage supply. 
     In other preferred embodiments, the device further comprises an aerosol source proximal to the outlet for directing an aerosol toward the sampling region. 
     The aerosol source may comprise a pneumatic nebuliser. In some embodiments the aerosol comprises methanol or water-methanol mixtures and in further embodiments the aerosol may further comprise acetic acid or acetic acid-water mixtures. In a further embodiment, the aerosol source may consist simply of a source of heated nitrogen or other inert gas. 
     In other preferred embodiments, the device further comprises an electrospray needle secured to the frame. The electrospray needle is for directing charged solvent droplets toward said sampling region, such that at least a further portion of the desorbed sample is ionized to produce further sample ions. 
     In other preferred embodiments, the device further comprises a lamp secured to the frame. The lamp provides electromagnetic radiation to the sampling region. Preferably, the device also comprises a dopant outlet secured to the frame. The dopant outlet provides a dopant to the sampling region, wherein the dopant is ionized by the electromagnetic radiation to produce dopant ions. The dopant ions ionize a further portion of desorbed sample to produce further sample ions. Preferably, the electromagnetic radiation comprises ultra-violet radiation. 
     Preferably, the device is operated at atmospheric pressure. 
     Preferably, the jet is subject to a Joule-Thomson expansion. 
     Preferably, the outlet is movable, enabling optimization of signal strength produced by the detector. 
     Preferably, an insulating jacket surrounds the outlet. 
     Other preferred embodiments of the present invention relate to a device for analysing a sample surface comprising an outlet and a frame. The outlet is for forming a jet of a Joule-Thomson cooling gas, the jet forming a sampling region for receiving one or more sample surfaces, and the frame holding the outlet and being adapted to receive a detector means. The detector means has an inlet. 
     In use, the jet produces desorbed sample from sample surfaces received in the sample area. At least a portion of the desorbed sample is ionized to produce one or more sample ions. The frame holds the outlet with respect to the sampling area and the inlet to allow the detector means to receive the sample ions and produce a signal indicative of the composition of the sample ions. 
     Preferably, the Joule-Thomson cooling gas comprises N 2 O. 
     Other preferred embodiments of the present invention relate to a device for analysing a sample surface comprising an outlet, a detector and a frame. The outlet is for forming a jet of carbon dioxide, the jet forming a sampling region for receiving one or more sample surfaces. The detector means has an inlet. The frame holds the outlet and the detector means. 
     In use, the jet produces desorbed sample from sample surfaces received in the sample area. At least a portion of the desorbed sample is ionized to produce one or more sample ions. The frame holds the outlet with respect to the sampling area and the inlet to allow the detector means to receive the sample ions and produce a signal indicative of the composition of the sample ions. 
     Further embodiments of the invention relate to a device for analysing a sample surface comprising an outlet and a frame. The outlet is for forming a jet of gas, the jet forming a sampling region for receiving one or more sample surfaces, and the frame holding the outlet and being adapted to receive a detector means. The detector means has an inlet. 
     In use, the jet produces desorbed sample from sample surfaces received in the sample area. At least a portion of the desorbed sample is ionized to produce one or more sample ions. The frame holds the outlet with respect to the sampling area and the inlet to allow the detector means to receive the sample ions and produce a signal indicative of the composition of the sample ions. Preferably, the gas is selected from the group comprising: carbon dioxide, nitrous oxide, propane, ethane, ethylene, Freon 11, Freon 21, Freon 22, Freon 23, Freon 152A 1,1-difluoroethane. 
     Further embodiments of the invention relate to a device for analysing a sample surface comprising an outlet and a frame. The outlet is for forming a jet of gas, the jet forming a sampling region for receiving one or more sample surfaces, and the frame holding the outlet and being adapted to receive a detector means. The detector means has an inlet. 
     In use, the jet produces desorbed sample from sample surfaces received in the sample area. The frame holds the outlet with respect to the sampling area and the inlet to allow the detector means to receive the desorbed sample and produce a signal indicative of the composition of the sample. Preferably, the gas is selected from the group comprising: carbon dioxide, nitrous oxide, propane, ethane, ethylene, Freon 11, Freon 21, Freon 22, Freon 23, Freon 152A 1,1-difluoroethane. Preferably the detector means is selected from the group comprising gas chromatographs, Fourier Transform Infrared spectroscopes, and detectors based on amplifying fluorescent polymers. 
     Other preferred embodiments relate to a method of ionizing a sample comprising the steps of: 
     (i) Providing an outlet, a detector and a frame. The outlet is for forming a jet of carbon dioxide, the jet forming a sampling region for receiving one or more sample surfaces and said frame holding said outlet and the detector means. The detector means has an inlet. 
     (ii) Positioning a sample in the sampling region. 
     (iii) Forming a jet of carbon dioxide such that the jet produces desorbed sample from the sample surfaces received in the sampling region. At least a portion of the desorbed sample is ionized to produce one or more sample ions. The frame holds the outlet with respect to the sampling region and the inlet to allow the detector means to receive the sample ions and produce a signal indicative of the composition of the sample ions. 
     In some preferred embodiments, the method further comprises the steps of: 
     (i) Providing a discharge member secured to the frame proximal to the outlet. 
     (ii) Applying a potential to the discharge member to affect a discharge such that a further portion of the desorbed sample is ionized to produce further sample ions. 
     Preferably, the step of applying a potential to the discharge member comprises applying a voltage of 2000V to 6000V to the discharge member. 
     In other preferred embodiments, the method further comprises the steps of: 
     (i) Providing an aerosol source secured to the frame proximal to the outlet. 
     (ii) Directing an aerosol from the aerosol source toward the sampling region. 
     In other preferred embodiments, the method further comprises the steps of: 
     (i) Providing an electrospray needle secured to the frame proximal to the outlet. The electrospray needle is for directing charged solvent droplets toward the sampling region. 
     (ii) Applying a potential to the electrospray needle. 
     (iii) Directing charged solvent droplets towards the sampling region such that at least a further portion of desorbed sample is ionized to produce further sample ions. 
     In other preferred embodiments, the method further comprises the steps of: 
     (i) Providing a lamp secured to the frame and a dopant outlet secured to the frame. The lamp is to provide electromagnetic radiation to the sampling region and the dopant outlet is to provide a dopant to the sampling region; 
     (ii) Directing a dopant towards the sampling region such that the dopant is ionized by the electromagnetic radiation to produce dopant ions. The dopant ions ionize a further portion of desorbed sample to produce further sample ions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a preferred embodiment of the invention. 
         FIG. 2  shows a preferred embodiment of the invention. 
         FIG. 3  shows a preferred embodiment of the invention. 
         FIG. 4  shows a preferred embodiment of the invention. 
         FIG. 5  shows a preferred embodiment of the invention. 
         FIG. 6  shows a mass spectrum of Benadryl provided by a device according to the present invention. 
         FIG. 7  shows a mass spectrum of Benadryl provided by a device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     At ambient temperatures, carbon dioxide exists as a liquid when held under pressures around 43 atmospheres and above. When this liquid is allowed to flow through an orifice and expand into a region at atmospheric pressure, the process of Joule-Thomson expansion occurs. 
     Joule-Thomson expansion is the process by which a fluid changes temperature in response to a change in pressure. Some fluids, including carbon dioxide, decrease in temperature when allowed to expand into a region of atmospheric pressure. In the case of carbon dioxide, the cooling is so pronounced when expanding from high pressure conditions, such as when stored as a liquid, to atmospheric pressure, that solid carbon dioxide may be formed. 
     The inventors have discovered that the aiming of a beam of a rapidly expanding beam of carbon dioxide at a surface produces ions representative of that surface or of compounds on that surface. The ions formed are typically pseudo-molecular ions of the (M+H)+, where the neutral species M is ionized by addition of a proton H+. Such (M+H)+ pseudo-molecular ions are also commonly formed in ionization techniques such as laser desorption ionization, often used in conjunction with mass spectrometry devices. 
     Accordingly, embodiments of the present invention relate to devices and methods of ionizing samples from or on a given surface and detecting those ions to produce a signal indicative of their identity. 
     A first embodiment of the invention is shown in  FIG. 1 . A device  100  comprises a frame  102  holding an outlet  104 . Outlet  104  may comprise, for example, a tube, pipe or capillary, and is in fluid communication with valve  116 , in turn in fluid communication with fluid source  106 . Preferably, fluid source  106  contains carbon dioxide under elevated pressure. Valve  116  controls the release of carbon dioxide from fluid source  106  through outlet  104  to affect a jet  114  which forms a sampling region  120 . Frame  102  is adapted to receive detector  108  having an inlet  110 . Heater  118  is held in thermal communication with inlet  110 . Frame  102  may be secured to detector  108  by such means as bolts  112 , or by other such means as known in the art. In certain embodiments, an insulating jacket surrounds outlet  104 , preventing the build-up of frost. In other preferred embodiments, outlet  104  is movably secured to said frame such that the direction of jet  114  may be adjusted to affect ionization efficiency. 
     In operation, a sample  122  is placed in sample region  120 . Sample  122  may be presented on a surface. Alternatively, sample  122  may be a surface part of a surface itself. 
     Valve  116  is opened to emit a jet  114  of carbon dioxide from outlet  104  toward sample region  120 . Jet  114  of carbon dioxide undergoes Joule-Thomson cooling which causes at least a portion of the jet  114  to form solid carbon dioxide. At least a portion of the sample is desorbed, with a portion of the desorbed sample being ionized to form sample ions. In preferred embodiments, outlet  104  is held at ground potential while emitting jet  114 . In other preferred embodiments, outlet  104  is held at elevated potential while emitting jet  114 . 
     A potential may be applied to inlet  110 . Preferably, the potential applied to inlet  110  is between 50V and 100V. Heater  118  applies heat to inlet  110 , preventing build-up of frost which could prevent sample ions from efficiently entering detector  108 . Detector  108  is operated at a lower pressure than the sampling region, causing the sample ions to drift through inlet  110 . 
     In some preferred embodiments, detector  108  is a mass spectrometer. In other preferred embodiments, detector  108  is an ion mobility spectrometer. Detector  108  is operated to produce a signal indicative of the identity of the sample ions. Ion mobility spectrometers that operate at ambient pressure are also known and can likewise be used to analyze ions produced by this invention. 
     A further embodiment of the invention is shown in  FIG. 2 . A device  100  comprises a frame  102  holding an outlet  104 . Outlet  104  may comprise, for example, a tube, pipe or capillary, and is in fluid communication with valve  116 , in turn in fluid communication with fluid source  106 . Preferably, fluid source  106  contains carbon dioxide under elevated pressure. Valve  116  controls the release of carbon dioxide from fluid source  106  through outlet  104  to affect a jet  114  which forms a sampling region  120 . Frame  102  is adapted to receive detector  108  having an inlet  110 . Heater  118  is held in thermal communication with inlet  110 . Frame  102  may be secured to detector  108  by such means as bolts  112 , or by other such means as known in the art. Discharge member  124  is secured to frame  102  to extend approximately between outlet  104  and inlet  110 . In electrical series with discharge member  124  is resistor  126  and power supply  128 . 
     In operation, a sample  122  is placed in sample region  120 . Sample  122  may be presented on a surface. Alternatively, sample  122  may be a surface part of a surface itself. 
     Valve  116  is opened to emit a jet  114  of carbon dioxide from outlet  104  toward sample region  120 . Jet  114  of carbon dioxide undergoes Joule-Thomson cooling which causes at least a portion of the jet  114  to form solid carbon dioxide. At least a portion of the sample is desorbed, with a portion of the desorbed sample being ionized to form sample ions. Power supply  128  elevates discharge member  124  to a potential between 2000V and 6000V. Resistor has a resistance between 100MΩ and 6000MΩ, keeping current during discharge in the μA range. Discharge member  124  causes ionization of a further portion of the desorbed sample. Alternatively, discharge member  124  may be driven by a current regulated high voltage supply (not shown). 
     In preferred embodiments, outlet  104  is held at ground potential while emitting jet  114 . In other preferred embodiments, outlet  104  is held at elevated potential while emitting jet  114 . 
     A potential may be applied to inlet  110 . Preferably, the potential applied to inlet  110  is between 50V and 100V. Heater  118  applies heat to inlet  110 , preventing build-up of frost which could prevent sample ions from efficiently entering detector  108 . Detector  108  is operated at a lower pressure than the sampling region, causing the sample ions to drift through inlet  110 . 
     In some preferred embodiments, detector  108  is a mass spectrometer. In other preferred embodiments, detector  108  is an ion mobility spectrometer. Detector  108  is operated to produce a signal indicative of the identity of the sample ions. Ion mobility spectrometers that operate at ambient pressure are also known and can likewise be used to analyze ions produced by this invention. 
     A further embodiment of the invention is shown in  FIG. 3 . A device  100  comprises a frame  102  holding an outlet  104 . Outlet  104  may comprise, for example, a tube, pipe or capillary, and is in fluid communication with valve  116 , in turn in fluid communication with fluid source  106 . Preferably, fluid source  106  contains carbon dioxide under elevated pressure. Valve  116  controls the release of carbon dioxide from fluid source  106  through outlet  104  to affect a jet  114  which forms a sampling region  120 . Frame  102  is adapted to receive detector  108  having an inlet  110 . Heater  118  is held in thermal communication with inlet  110 . Frame  102  may be secured to detector  108  by such means as bolts  112 , or by other such means as known in the art. Aerosol source  130  is secured to frame  102  such that an aerosol  132  may be directed towards sampling region  120 . 
     In operation, a sample  122  is placed in sample region  120 . Sample  122  may be presented on a surface. Alternatively, sample  122  may be a surface part of a surface itself. 
     Valve  116  is opened to emit a jet  114  of carbon dioxide from outlet  104  toward sample region  120 . Jet  114  of carbon dioxide undergoes Joule-Thomson cooling which causes at least a portion of the jet  114  to form solid carbon dioxide. At least a portion of the sample is desorbed, with a portion of the desorbed sample being ionized to form sample ions. Aerosol source  130  emits aerosol  132  towards sampling region  120 , to blanket the area impacted by jet  114 , preventing frost build-up over prolonged use. Aerosol  132  may comprise methanol nebulized with nitrogen gas. Additionally, aerosol source  130  may be replaced by a source of heated nitrogen gas directed towards sampling region  120 . 
     In preferred embodiments, outlet  104  is held at ground potential while emitting jet  114 . In other preferred embodiments, outlet  104  is held at elevated potential while emitting jet  114 . 
     A potential may be applied to inlet  110 . Preferably, the potential applied to inlet  110  is between 50V and 100V. Heater  118  applies heat to inlet  110 , preventing build-up of frost which could prevent sample ions from efficiently entering detector  108 . Detector  108  is operated at a lower pressure than the sampling region, causing the sample ions to drift through inlet  110 . 
     In some preferred embodiments, detector  108  is a mass spectrometer. In other preferred embodiments, detector  108  is an ion mobility spectrometer. Detector  108  is operated to produce a signal indicative of the identity of the sample ions. Ion mobility spectrometers that operate at ambient pressure are also known and can likewise be used to analyze ions produced by this invention. 
     A further embodiment of the invention is shown in  FIG. 4 . A device  100  comprises a frame  102  holding an outlet  104 . Outlet  104  may comprise, for example, a tube, pipe or capillary, and is in fluid communication with valve  116 , in turn in fluid communication with fluid source  106 . Preferably, fluid source  106  contains carbon dioxide under elevated pressure. Valve  116  controls the release of carbon dioxide from fluid source  106  through outlet  104  to affect a jet  114  which forms a sampling region  120 . Frame  102  is adapted to receive detector  108  having an inlet  110 . Heater  118  is held in thermal communication with inlet  110 . Frame  102  may be secured to detector  108  by such means as bolts  112 , or by other such means as known in the art. Electrospray needle  134  is secured to frame  102  such that it may spray a charged solvent  136  from solvent source  138  towards a region between sample region  120  and inlet  110 . Power supply  140  is connected in electrical series with electrospray needle  134  to hold electrospray needle at elevated potential. 
     In operation, a sample  122  is placed in sample region  120 . Sample  122  may be presented on a surface. Alternatively, sample  122  may be a surface part of a surface itself. 
     Valve  116  is opened to emit a jet  114  of carbon dioxide from outlet  104  toward sample region  120 . Jet  114  of carbon dioxide undergoes Joule-Thomson cooling which causes at least a portion of the jet  114  to form solid carbon dioxide. At least a portion of the sample is desorbed, with a portion of the desorbed sample being ionized to form sample ions. Electrospray needle  134  is operated to spray charged solvent  136  towards a region between sample region  120  and inlet  110 . Charge is transferred from the solvent to a further portion of desorbed sample. 
     In preferred embodiments, outlet  104  is held at ground potential while emitting jet  114 . In other preferred embodiments, outlet  104  is held at elevated potential while emitting jet  114 . 
     A potential may be applied to inlet  110 . Preferably, the potential applied to inlet  110  is between 50V and 100V. Heater  118  applies heat to inlet  110 , preventing build-up of frost which could prevent sample ions from efficiently entering detector  108 : Detector  108  is operated at a lower pressure than the sampling region, causing the sample ions to drift through inlet  110 . 
     In some preferred embodiments, detector  108  is a mass spectrometer. In other preferred embodiments, detector  108  is an ion mobility spectrometer. Detector  108  is operated to produce a signal indicative of the identity of the sample ions. Ion mobility spectrometers that operate at ambient pressure are also known and can likewise be used to analyze ions produced by this invention. 
     A further embodiment of the invention is shown in  FIG. 5 . A device  100  comprises a frame  102  holding an outlet  104 . Outlet  104  may comprise, for example, a tube, pipe or capillary, and is in fluid communication with valve  116 , in turn in fluid communication with fluid source  106 . Preferably, fluid source  106  contains carbon dioxide under elevated pressure. Valve  116  controls the release of carbon dioxide from fluid source  106  through outlet  104  to affect a jet  114  which forms a sampling region  120 . Frame  102  is adapted to receive detector  108  having an inlet  110 . Heater  118  is held in thermal communication with inlet  110 . Frame  102  may be secured to detector  108  by such means as bolts  112 , or by other such means as known in the art. Lamp  142  is secured to frame  102  such that it may provide electromagnetic radiation to sampling region  120 . Dopant outlet  144  is secured to frame  102  to supply dopant compound  146  from dopant source  148  to sampling region  120 . Dopant compound  146  is selected to be susceptible to ionization under electromagnetic radiation. Preferably, dopant compound  146  is selected to be susceptible to ionization under ultra-violet radiation. 
     In operation, a sample  122  is placed in sample region  120 . Sample  122  may be presented on a surface. Alternatively, sample  122  may be a surface part of a surface itself. 
     Valve  116  is opened to emit a jet  114  of carbon dioxide from outlet  104  toward sample region  120 . Jet  114  of carbon dioxide undergoes Joule-Thomson cooling which causes at least a portion of the jet  114  to form solid carbon dioxide. At least a portion of the sample is desorbed, with a portion of the desorbed sample being ionized to form sample ions. Lamp  142  is operated to provide electromagnetic radiation to sampling region  120 , while dopant outlet  144  provides dopant compound  146  to sampling region  120 . Dopant compound  146  is ionized by exposure to electromagnetic radiation from lamp  142 , and transfers charge to further desorbed sample to produce further sample ions. In preferred embodiments, outlet  104  is held at ground potential while emitting jet  114 . In other preferred embodiments, outlet  104  is held at elevated potential while emitting jet  114 . 
     A potential may be applied to inlet  110 . Preferably, the potential applied to inlet  110  is between 50V and 100V. Heater  118  applies heat to inlet  110 , preventing build-up of frost which could prevent sample ions from efficiently entering detector  108 . Detector  108  is operated at a lower pressure than the sampling region, causing the sample ions to drift through inlet  110 . 
     In some preferred embodiments, detector  108  is a mass spectrometer. In other preferred embodiments, detector  108  is an ion mobility spectrometer. Detector  108  is operated to produce a signal indicative of the identity of the sample ions. Ion mobility spectrometers that operate at ambient pressure are also known and can likewise be used to analyze ions produced by this invention. 
     In another preferred embodiment, the device  100  comprises a frame  102  holding an outlet  104 . Outlet  104  may comprise, for example, a tube, pipe or capillary, and is in fluid communication with valve  116 , in turn in fluid communication with fluid source  106 . Preferably, fluid source  106  contains fluid under elevated pressure. Valve  116  controls the release of fluid from fluid source  106  through outlet  104  to affect a gas jet  114  which forms a sampling region  120 . Frame  102  is adapted to receive detector  108  having an inlet  110 . Heater  118  is held in thermal communication with inlet  110 . Frame  102  may be secured to detector  108  by such means as bolts  112 , or by other such means as known in the art. In certain embodiments, an insulating jacket surrounds outlet  104 , preventing the build-up of frost. In other preferred embodiments, outlet  104  is movably secured to said frame such that the direction of jet  114  may be adjusted to affect sample vaporization efficiency. 
     In operation, a sample  122  is placed in sample region  120 . Sample  122  may be presented on a surface. Alternatively, sample  122  may be a surface part of a surface itself. 
     Valve  116  is opened to emit a gas jet  114  from outlet  104  toward sample region  120 . At least a portion of the sample is desorbed, to produce gaseous sample. Gaseous sample is the admitted into detector  108 . Detector  108  may comprise gas chromatographs, Fourier Transform Infrared spectroscopes, and detectors based on amplifying fluorescent polymers such as are used in the detector called Fido sold by Nomadics, Inc of Stillwater, Okla. 
     The exact mechanisms of ionization in the embodiments described above are not all known. It is likely, however, that the water vapor content of normal ambient room air, which typically may vary between 30 and 60 percent, is needed to supply the protons to create pseudomolecular ions. In 0 per cent humidity environments, some water vapor may need to be supplied. This could be done by adding water vapor to the sample environment, for example by a second jet or a water reservoir. 
     Alternatively, liquid water could be premixed with the gas or liquid carbon dioxide prior to jet formation. It is also possible that in some embodiments, other species may usefully contribute to ionization. 
     It will be recognized that since the desorption induced by the gas jet is localized, that images of localized sample concentrations may be obtained either by scanning the jet or the sample. 
     it will also be recognized that in some cases if the sample is sufficiently thin, that it may be useful to have the jet impact the sample on the opposite side of the sample from the mass spectrometer inlet. 
     More generally, it is recognized that substances which exist as gases at atmospheric pressure, can be caused to exist as liquids under pressure, and can be caused to exit from said pressurized environment such that they exist transiently as liquids or solids, may provide a useful means and method for converting solid samples to a vapor phase where they may be conveniently subjected to analysis. The term “gas jet” as used herein is intended to include such jets of such substances. 
     Examples of such substances may comprise some or all of those listed below. 
     
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                   
                   
                 P vap   
                   
                   
                   
                   
               
               
                   
                   
                 BP 
                 (psia @ 
                 Tc 
                 Pc 
                 0.75 Tc 
                 0.75 Pc 
               
               
                 substance 
                 Formula 
                 (° C.) 
                 25° C.) 
                 (° C.) 
                 (psia) 
                 (° C.) 
                 (psia) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Carbon 
                 CO 2   
                 −78.5 
                 860 
                 31.1 
                 1070 
                 −45.0 
                 803 
               
               
                 dioxide 
               
               
                 Nitrous oxide 
                 N 2 O 
                 −88.5 
                 700 
                 36.5 
                 1051 
                 −41.0 
                 788 
               
               
                 Propane 
                 C 3 H 8   
                 −42.1 
                 130 
                 96.7 
                 616 
                 4.2 
                 462 
               
               
                 Ethane 
                 C 2 H 6   
                 −88.7 
                 570 
                 32.3 
                 709 
                 −44.1 
                 531 
               
               
                 Ethylene 
                 C 2 H 4   
                 −103.8 
                 NA 
                 9.3 
                 731 
                 −61.4 
                 548 
               
               
                 Freon 11 
                 CCl 3 F 
                 23.8 
                 15 
                 198.1 
                 639 
                 80.3 
                 480 
               
               
                 Freon 21 
                 CHCl 2 F 
                 8.9 
                 24 
                 178.5 
                 750 
                 65.6 
                 562 
               
               
                 Freon 22 
                 CHClF 2   
                 −40.8 
                 140 
                 96.1 
                 722 
                 3.8 
                 541 
               
               
                 Freon 23 
                 CHF 3   
                 −82.2 
                 630 
                 26.1 
                 700 
                 −48.7 
                 525 
               
               
                 Freon 152A 
                 C2H4F2 
                 −24.9° C. 
               
               
                 1,1- 
               
               
                 difluoroethane 
               
               
                   
               
             
          
         
       
     
     Additionally it is recognized that while embodiments for the processes heretofore described occur at or near atmospheric pressure, it is possible that it may also be advantageous sometimes to carry out these processes at somewhat or substantially reduced pressures. This may result in increased sensitivity as it may eliminate some of the analyte ion loss that typically results from transporting analyte ions in an atmospheric environment into a vacuum system. 
     EXAMPLE 1 
     An analysis of a tablet of Benadryl, a commercial antihistamine was performed using a device substantially as shown in  FIG. 1 . The active chemical ingredient in Benadryl is diphenhydramine. A heated inlet tube was attached to a standard Z-Spray interface to an orthogonal TOF mass spectrometer (Waters, Mass.). The inlet was heated to 90° C. and raised to a potential of 65V. A stainless steel capillary tube was used as an outlet. A Benadryl tablet was placed in the sampling region and exposed to a jet of Joule-Thomson cooling CO2. The arrival time spectrum shown in  FIG. 6  shows the signal corresponding to diphenhydramine obtained at m/z 256.17, together with the adjacent C13 isotope peak. 
     EXAMPLE 2 
     An analysis of a tablet of Benadryl was performed using a device substantially as shown in  FIG. 2 . A heated inlet tube was attached to a standard Z-Spray interface to an orthogonal TOF mass spectrometer (Waters, Mass.). The inlet was heated to 90° C. and raised to a potential of 65V. A stainless steel capillary tube was used as an outlet. The discharge member was raised to a potential of 4000V. A Benadryl tablet was placed in the sampling region and exposed to a jet of Joule-Thomson cooling CO2. The arrival time spectrum shown in  FIG. 7  shows the signal corresponding to diphenhydramine obtained at m/z 256.17, together with the adjacent C13 isotope peak. Signal strength was found to be 30-50 times greater than when using the device described in Example 1. 
     EXAMPLE 3 
     An analysis of a tablet of Benadryl was performed using a device substantially as shown in  FIG. 2 . A heated inlet tube was attached to a standard Z-Spray interface to an orthogonal TOF mass spectrometer (Waters, Mass.). The inlet was heated to 90° C. and raised to a potential of 65V. A stainless steel capillary tube was used as an outlet. The area impacted by the CO2 jet was blanketed with an aerosol formed from an eluent comprising methanol with 0.1% acetic acid. The eluent flowed into the aerosol source at 6 μL/min and was nebulized with nitrogen gas. A Benadryl tablet was placed in the sampling region and exposed to a jet of Joule-Thomson cooling CO2.