Abstract:
An ionization chamber  100  is provided between a liquid chromatograph unit  60  and a mass spectrometer  50 , and is formed of: an atomization means  15 ; and an ion introducing pipe  19  of which the entrance portion is created within the ionization chamber  100  in the horizontal direction that is perpendicular to the Z direction and of which the exit portion is created within the mass spectrometer unit  50 . A liquid sample that has been fed from the liquid chromatograph unit  60  is sprayed in the Z direction by the atomization means  15  while being ionized within the ionization chamber  100 , wherein the entrance portion has an opening in such a form that corresponds to the spread in the XY plane of the liquid sample sprayed in the Z direction. The sprayed liquid sample is then fed into the mass spectrometer unit  50  while being desolvated, which effectively contributes to analysis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority to Japanese Patent Application No. 2014-132302 filed Jun. 27, 2014, the subject matter of which is incorporated herein by reference in entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ionization chamber, and in particular to a liquid chromatograph mass spectrometer having an ionization chamber for ionizing a liquid sample fed from a liquid chromatograph unit and a mass spectrometer unit into which ions are introduced from the ionization chamber. 
     2. Description of Related Art 
     Liquid chromatograph mass spectrometers (LC/MS) are formed of a liquid chromatograph unit (LC unit) for eluting a liquid sample so that the liquid sample is separated into respective components, an ionization chamber (interface unit) for ionizing the sample components that have been eluted from the LC unit and a mass spectrometer unit (MS unit) for detecting the ions that have been introduced from the ionization chamber. In such ionization chambers, various ionization techniques are used in order to ionize a liquid sample, and atmospheric pressure ionization methods such as atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) are widely used. 
     In accordance with APCI specifically, the end of a nozzle connected to the terminal of the column in the LC unit is directed toward the inside of the ionization chamber, and at the same time a needle electrode is provided in front of the end of the nozzle. Thus, droplets of the sample that has been atomized through the application of heat in the nozzle are ionized through a chemical reaction with carrier gas ions (buffer ions) that have been generated by means of corona discharge from the needle electrode. In accordance with ESI, the end of a nozzle connected to the terminal of the column in the LC unit is directed toward the inside of the ionization chamber, and at the same time a high voltage of approximately 5 kV is applied to the end portion of the nozzle so that an intense non-uniform electric field is generated. Thus, the liquid sample undergoes charge separation in the electric field so as to be torn off for atomization by means of coulomb attraction. As a result, the solvent in the droplets of the sample evaporates after coming into contact with the surrounding air so that gas ions are generated. 
     As described above, a liquid sample is ionized in such a state that the sample is placed under pressure that is close to atmospheric pressure in accordance with APCI or ESI. Therefore, a structure is adopted such that middle chambers or the like are provided between the ionization chamber in a high pressure state (that is to say, a state that is close to atmospheric pressure) and the MS unit in a very low pressure state (that is to say a highly vacuumed state) so that the degree of vacuum is increased incrementally in order to secure the difference in the pressure between the ionization chamber and the MS unit (see Patent Document 1). 
       FIG. 7  is a schematic diagram showing the structure of an example of a liquid chromatograph mass spectrometer in accordance with an ESI method. Here, a certain direction that is horizontal relative to the ground is the X direction, the direction that is horizontal relative to the ground and perpendicular to the X direction is the Y direction, and the direction that is perpendicular to the X direction and the Y direction is the Z direction. 
     A liquid chromatograph mass spectrometer  101  is provided with a liquid chromatograph unit (LC unit)  60 , an ionization chamber  200  and a mass spectrometer unit  50 . In addition, a first middle chamber  12  that is adjacent to the ionization chamber  200 , a second middle chamber  13  that is adjacent to the first middle chamber  12  and a mass spectrometer chamber (MS unit)  14  that is adjacent to the second middle chamber  13  are provided sequentially, with partitions in between them, in the mass spectrometer unit  50 . 
     The liquid sample that has been separated into the respective components in the LC unit  60  is supplied through a flow path  155 . In addition, a nebulizer gas (nitrogen gas) is supplied through a flow path  156 . As a result, the liquid sample and the nebulizer gas are introduced into a spray  15  for atomization. 
       FIGS. 8A and 8B  are side diagrams showing the spray.  FIG. 8B  is a cross-section diagram showing an enlargement of A in  FIG. 8A . The spray (atomization means)  15  has a probe main body  151  and a nozzle  152  for atomizing a liquid sample. 
     The nozzle  152  has a double-pipe structure that is formed so as to protrude downward from the bottom of the probe main body  151 . The liquid sample that is supplied through the flow path  155  is ejected from the inside of the internal circular pipe (having an outer diameter of 0.27 mm, for example)  152   b . Meanwhile, the nitrogen gas supplied through the flow path  156  is ejected between the internal circular pipe  152   b  and the external circular pipe (having an inner diameter of 0.37 mm, for example)  152   a . As a result, the ejected liquid sample is sprayed in an atomized state due to the effects of impact with the nebulizer gas that is ejected from the space surrounding the internal circular pipe  152   b . In addition, wires (not shown) are connected to the end of the external circular pipe  152   a  so that a high voltage of approximately 5 kV is applied from the power supply (not shown) in order to achieve ionization. 
     In addition, the nozzle  152  can move approximately parallel to the probe main body  151  within a predetermined range in the XY plane perpendicular to the Z direction by means of a position-adjusting knob (not shown), and thus the position of nozzle  152  can be fixed using a position-fixing knob after the position has been adjusted appropriately. Furthermore, the nozzle  152  can be inserted and extracted in the Z direction relative to the probe main body  151  (adjustment of the extent of protrusion) and the position of the nozzle  152  can be fixed by means of a nut or the like after the position has been adjusted appropriately. 
     While in  FIGS. 8A and 8B  the spray  15  is for ESI, in general the spray  15  is removable from the ionization chamber  200 . In the case where an APCI method is used, the spray  15  is removed and instead a spray for APCI, where the needle electrode for charging forms a unit, is attached to the ionization chamber  200 . 
     The ionization chamber  200  is provided with a sub-chamber  210  in a rectangular parallelepiped form of 13 cm×13 cm×12 cm. The sub-chamber  210  has an upper surface, a front surface, a right-side surface, a rear surface (partition  26 ), a left-side surface and a lower surface. Thus, an internal space surrounded by six surfaces—upper, lower, left, right, front and rear—is formed in the ionization chamber  200 . 
     In addition, a circular opening (not shown) that runs through in the upward and downward directions (Z direction) is created in the upper surface so that a spray  15  can be attached to the opening from the top. Furthermore, a drain  211  is formed on the lower surface so that the unnecessary liquid sample can be discharged to the outside through the drain  211 . 
     Moreover, the partition  26  is provided so as to separate the inside of the sub-chamber  210  from the inside of the first middle chamber  12 . A heater block  20  in a rectangular parallelepiped form into which a temperature adjusting mechanism (not shown) is incorporated is fixed in the center portion of the partition  26 .  FIG. 9  is a diagram showing the structure of the heater block  20  that is provided on the partition  26  in the ionization chamber  200  in  FIG. 7 . 
     One desolvation pipe (ion introducing pipe)  119  of which the entrance is provided inside the sub-chamber  210  and of which the exit is provided inside the first middle chamber  12  is formed in the heater block  20 . The desolvation pipe  119  is in a circular pipe form having the center axis in the X direction (having an outer diameter of 1.6 mm and an inner diameter of 0.5 mm, for example). As a result, the entrance of the desolvation pipe  119  is pointed in a direction (X direction) that forms approximately a right angle relative to the direction in which the sample is sprayed from the nozzle  152  (Z direction), and a gigantic droplet of the sample that has been sprayed is thus prevented from directly flying into the desolvation pipe  119 . 
     In addition, six dry gas pipes  218  of which the exits are provided inside the sub-chamber  210  are formed in the heater block  20 . Each dry gas pipe  218  is in a circular pipe form (having a diameter of 0.5 mm, for example) of which the center axis is in the X direction. The six dry gas pipes  218  are arranged at equal intervals in a circle with the desolvation pipe  119  at the center. 
     Thus, the partition  26  of the sub-chamber  210  accelerates desolvation and ionization through the effects of the application of heat and of impact when ions and microscopic droplets of the sample that have been sprayed from the nozzle  152  pass through the inside of the desolvation pipe  119 . 
     A first ion lens  21  is provided inside the first middle chamber  12  and an exhaust vent  31  for discharging air by an oil-sealed rotary pump (RP) so as to create a vacuum of approximately 10 2  Pa is provided in the lower surface of the first middle chamber  12 . A skimmer  22  having an orifice is formed in the partition between the first middle chamber  12  and the second middle chamber  13 , and the inside of the first middle chamber  12  and the inside of the second middle chamber  13  are connected through this orifice. 
     An octapole  23  and a focus lens  24  are provided inside the second middle chamber  13 , and an exhaust vent  32  for discharging air by means of a turbo molecular pump (TMP) so as to create a vacuum of approximately 10 −1  Pa to 10 −2  Pa is provided in the lower surface of the second middle chamber  13 . An entrance lens  25  having an orifice is provided in the partition between the second middle chamber  13  and the mass spectrometer chamber  14 , and the inside of the second middle chamber  13  and the inside of the mass spectrometer chamber  14  are connected through this orifice. 
     A first quadrupole  16 , a second quadrupole  17  and a detector  18  are provided inside the mass spectrometer chamber  14 , and an exhaust vent  33  for discharging air by means of a turbo molecular pump (TMP) so as to create a vacuum of approximately 10 −3  Pa to 10 −4  Pa is provided in the lower surface of the mass spectrometer chamber  14 . 
     In the thus formed liquid chromatograph mass spectrometer  101 , the ions that have been generated in the ionization chamber  200  pass through the desolvation pipe  119 , the first ion lens  21  located within the first middle chamber  12 , the skimmer  22 , the octapole  23  and the focus lens  24  located within the second middle chamber  13  and the entrance lens  25  in this order so as to be fed into the mass spectrometer chamber  14 . In this chamber  14  unnecessary ions are discharged by means of the quadrupoles  16  and  17  and only the specific ions that have reached the detector  18  can be detected. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Unexamined Patent Publication 2001-343363 
     SUMMARY OF THE INVENTION 
     1. Problem to be Solved by the Invention 
     In the above described liquid chromatograph mass spectrometer  101 , however, the desolvation pipe  119  is a single unit, and only part of the liquid sample that has been sprayed from the nozzle  152  passes through the inside of the desolvation pipe  119 . Most of the liquid sample is discharged from the drain  211  without passing through the pipe. Therefore, the liquid sample is not effectively used and only part of the liquid sample contributes to the analysis, which is why the detection sensitivity cannot be increased. 
     In the liquid chromatograph mass spectrometer  101  the appropriate positional relationship between the nozzle  152  that sprays the liquid sample and the entrance of the desolvation pipe  119  defers depending on the measurement conditions such as the type of the liquid sample to be measured and the amount of the flow of the nebulizer gas. Therefore, the positional relationship between the nozzle  152  and the entrance of the desolvation pipe  119  is adjusted appropriately before analysis. However, most of the liquid sample is discharged from the drain  211  without passing through the pipe 
     2. Means for Solving Problem 
     In order to solve the above described problem, the present inventors carried out research to find a method for desolvating the liquid sample that has been sprayed from the nozzle  152  while feeding the desolvated liquid sample to the mass spectrometer unit so that the liquid sample effectively contributes to the analysis. 
     The flow of the atomized liquid sample that has been sprayed from the nozzle  152  with an inner diameter of 0.5 mm spreads as it proceeds in a circular form in the Z direction and ultimately increases in size to a diameter of approximately +/−2 mm to 4 mm.  FIG. 10A  is a side diagram showing the flow of the atomized liquid sample that has been sprayed from the nozzle  152 .  FIG. 10B  is a cross section diagram showing the XY plane in  FIG. 10A .  FIG. 11  is a diagram illustrating the spread of the flow of the atomized liquid sample that has been sprayed from the nozzle  152 . 
     The ionized liquid sample (charged droplets) is sprayed into the inside of the sub-chamber  210  under atmospheric pressure and is drawn into the desolvation pipe  119  due to the difference in the pressure vis-à-vis the inside of the first middle chamber  12  where the pressure is maintained at approximately 10 2  Pa. Thus the charged droplets are ejected with great force in the direction perpendicular to the desolvation pipe  119  (Z direction) and it was found that the charged droplets that pass through a part of the sub-chamber  210  that is far from the desolvation pipe  119  are not taken into the desolvation pipe  119  but are discharged through the drain  211 . 
     Thus, it is possible to increase the inner diameter d of the desolvation pipe  119  in order to increase the total amount of ions (charged droplets) that are taken into the desolvation pipe  119 . Here the general state of the flow within the pipe can be determined by the numeric value of the Reynolds number Re that is defined in Formula (1) in the following.
 
Re=ρ Ud/μ   (1)
 
     Here, μ is the viscosity coefficient (Pa·s) of the liquid, ρ is the density (kg/m 3 ) of the liquid, U is the rate of flow (m/s) and d is the inner diameter (m) of the pipe. 
     In the case where the Reynolds number Re exceeds  2000  the flow of the gas within the pipe becomes a turbulent flow as shown in the graph of the Reynolds number Re in  FIG. 12 . When the flow is turbulent the efficiency of the introduction of ions is lowered. That is to say, when the inner diameter d of the desolvation pipe  119  is increased, the flow field within the desolvation pipe  119  is disturbed and the efficiency of the introduction of ions decreases. 
     It was found that the inner diameter of the desolvation pipe (ion introducing pipe) can be determined taking the Reynolds number Re into consideration, and in addition the ion introducing pipe can be placed for better coordination with the form of the sprayed flow, so that the liquid sample that has been sprayed from the nozzle can be taken into the ion introducing pipe without being wasted. 
     That is to say, the ionization chamber according to the present invention is an ionization chamber that is provided between a liquid chromatograph unit and a mass spectrometer with: an atomization means for spraying a liquid sample that has been fed from the above described liquid chromatograph unit in the Z direction in the above described ionization chamber while ionizing the liquid sample; and an ion introducing pipe of which an entrance portion is created within the above described ionization chamber in the horizontal direction that is perpendicular to the Z direction and of which an exit portion is created so as to introduce ions into the above described mass spectrometer unit, wherein an opening in the above described entrance portion has such a form as to correspond to the spread in the XY plane of the liquid sample sprayed in the Z direction. 
     Here, the “Z direction” is the direction in which the liquid sample is sprayed from the atomization means and any one direction, for example the downward direction, that is predetermined by the designer of the system or somebody else. 
     3. Effects of the Invention 
     As described above, in the ionization chamber according to the present invention, the ion introducing pipe is placed for better coordination with the form of the sprayed flow, and thus the charged droplets that have been discharged without being introduced into the mass spectrometer unit due to the large distance between them and the entrance of the ion introducing pipe according to the prior art can be drawn into the ion introducing pipe, and as a result the detection sensitivity can be increased. 
     4. Other Means for Solving Problem 
     In addition, in the ionization chamber according to the present invention, the opening of the above described entrance portion may have such a shape that is longer in the horizontal direction than in the Z direction. 
     Here, the length of the “opening of the entrance portion” in the horizontal direction is the length of the entrance (opening) in the horizontal direction in the case where the entrance portion has one opening. In the case where the entrance portion has a number of openings, the length of the “opening of the entrance portion” is the total length in the horizontal direction when the number of entrances (openings) are viewed in the Z direction. Likewise, the length of the “entrance of the entrance portion” in the Z direction is the length of the entrance (opening) in the Z direction when the entrance portion has one opening. In the case where the entrance portion has a number of openings, the length of the “entrance of the entrance portion” is the total length of the number of entrances (openings) in the Z direction when the entrances are viewed in the horizontal direction. 
     Furthermore, in the ionization chamber according to the present invention, the above described entrance portion may have a number of entrances, and the number of entrances may be provided in the same XY plane. 
     In the ionization chamber according to the present invention, a number of ion introducing pipes may be provided in parallel so that the total area of the cross section of the inner diameters of the ion introducing pipes can be increased and thus ions can be efficiently introduced into the mass spectrometer unit while increasing the total amount of ions to be introduced without disturbing the flow through the inside of each pipe. As a result, the detection sensitivity can be increased. 
     Moreover, in the ionization chamber according to the present invention, the number of entrances may all be placed so as to face in the X direction. 
     Alternatively, in the ionization chamber according to the present invention, the number of entrances may be placed so as to face in directions different from each other. 
     In addition, in the ionization chamber according to the present invention the above described entrance portion may have an entrance of which the shape may be longer in the horizontal direction than in the Z direction. 
     Furthermore, in the ionization chamber according to the present invention, the inside of the above described ionization chamber is under atmospheric pressure, and the inside of the above described mass spectrometer unit may be a vacuum. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing the structure of an example of the liquid chromatograph mass spectrometer using an ESI method according to one embodiment of the present invention; 
         FIG. 2  is a diagram showing the structure of the heater block provided on the partition of the ionization chamber in  FIG. 1 ; 
         FIGS. 3A and 3B  are diagrams showing the flow of the atomized liquid sample that has been sprayed from the nozzle; 
         FIGS. 4A and 4B  are diagrams showing the ionization chamber in the liquid chromatograph mass spectrometer using an ESI method according to the second embodiment; 
         FIGS. 5A and 5B  are diagrams showing the ionization chamber according to the third embodiment in the same manner as in  FIG. 4 ; 
         FIGS. 6A and 6B  are diagrams showing the ionization chamber according to the fourth embodiment in the same manner as in  FIG. 4 ; 
         FIG. 7  is a schematic diagram showing the structure of an example of a liquid chromatograph mass spectrometer using an ESI method; 
         FIGS. 8A and 8B  are diagrams showing a spray; 
         FIG. 9  is a diagram showing the structure of the heater block provided on the partition of the ionization chamber in  FIG. 7 ; 
         FIGS. 10A and 10B  are diagrams showing the flow of the atomized liquid sample that has been sprayed from the nozzle; 
         FIG. 11  is a diagram illustrating the spread of the flow of the atomized liquid sample that has been sprayed from the nozzle; and 
         FIG. 12  is a graph showing the Reynolds numbers. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In the following, the embodiments of the present invention are described in reference to the drawings. Here, the present invention is not limited to the below described embodiments but of course includes various types of modification as long as the gist of the present invention is not deviated from. 
     First Embodiment 
       FIG. 1  is a schematic diagram showing the structure of an example of the liquid chromatograph mass spectrometer using an ESI method according to one embodiment of the present invention.  FIG. 2  is a diagram showing the structure of the heater block provided on the partition  26  of the ionization chamber  100  in  FIG. 1 . FIG.  3 A is a side diagram showing the flow of the atomized liquid sample that has been sprayed from the nozzle  152 .  FIG. 3B  is a cross section diagram showing the XY plane in  FIG. 3A . Here, the same symbols are attached to the same components as in the above described conventional liquid chromatograph mass spectrometer  101 . 
     A liquid chromatograph mass spectrometer  1  is provided with a liquid chromatograph unit (LC unit)  60 , an ionization chamber  100  and amass spectrometer unit  50 . In addition, a first middle chamber  12  that is located adjacent to the ionization chamber  100 , a second middle chamber  13  that is located adjacent to the first middle chamber  12  and a mass spectrometer chamber (MS unit)  14  that is adjacent to the second middle chamber  13  are provided sequentially with partitions in between them in the mass spectrometer unit  50 . 
     The ionization chamber  100  is provided with a sub-chamber  110  in a rectangular parallelepiped form of 13 cm×13 cm×12 cm. The sub-chamber  110  has an upper surface, a front surface, a right-side surface, a rear surface (partition  26 ), a left-side surface and a lower surface. Thus, an internal space surrounded by six surfaces—upper, lower, left, right, front and rear—is formed in the ionization chamber  100 . 
     In addition, a circular opening (not shown) that runs through in the upward and downward directions (Z direction) is created in the upper surface so that a spray  15  can be attached to the opening from the top. Furthermore, a drain  111  is formed on the lower surface so that the unnecessary liquid sample can be discharged to the outside through the drain  111 . 
     Moreover, the partition  26  is provided so as to separate the inside of the sub-chamber  110  from the inside of the first middle chamber  12 . A heater block  20  in a rectangular parallelepiped form into which a temperature adjusting mechanism (not shown) is incorporated is fixed in the center portion of the partition  26 . 
     A first desolvation pipe  19   a , a second desolvation pipe  19   b  and a third desolvation pipe  19   c , which are ion introducing pipes of which the entrance is placed inside the sub-chamber  110  and of which the exit is placed inside the first middle chamber  12  are formed in the heater block  20 . Each desolvation pipe  19   a  to  19   c  is in a circular pipe form having the center axis in the X direction (having an outer diameter of 1.6 mm and an inner diameter of 0.5 mm, for example). As shown in  FIG. 2 , the first desolvation pipe  19   a , the second desolvation pipe  19   b  and the third desolvation pipe  19   c  are aligned in this order side by side in the Y direction in the same XY plane. 
     As in  FIGS. 3A and 3B , the entrance of the first desolvation pipe  19   a , the entrance of the second desolvation pipe  19   b  and the entrance of the third desolation pipe  19   c  are provided in the same ZY plane. However, the flow of the atomized liquid sample that has been sprayed from the nozzle  152  is in a circular form in the XY plane, and therefore the entrance of the first desolvation pipe  19   a  and the entrance of the third desolvation pipe  19   c  may be located so as to protrude from the entrance of the second desolvation pipe  19   b  in the −X direction. 
     In addition, four dry gas pipes  118  of which the exits are provided inside the sub-chamber  110  are formed in the heater block  20 . Each dry gas pipe  118  is in a circular pipe form having the center axis in the X direction (having a diameter of 0.5 mm, for example). Two dry gas pipes  118  are aligned side by side in the Y direction above the desolvation pipes  19   a  to  19   c  and at the same time two dry gas pipes  118  are aligned side by side in the Y direction beneath the desolvation pipes  19   a  to  19   c.    
     The partition  26  of the thus formed sub-chamber  110  allows the flow of the atomized liquid sample that has been sprayed from the nozzle  152  having an inner diameter of 0.5 mm to spread as the flow progresses in the Z direction and ultimately increase in size to a diameter of approximately +/−2 mm to 4 mm. The ions that pass through the left end portion of the flow of the atomized liquid sample (−Y side) are drawn into the first desolvation pipe  19   a  having an inner diameter of 0.5 mm. The ions that pass through the center portion of the flow of the atomized liquid sample are drawn into the second desolvation pipe  19   b  having an inner diameter of 0.5 mm. The ions that pass through the right end portion of the flow of the atomized liquid sample (Y side) are drawn into the third desolvation pipe  19   c  having an inner diameter of 0.5 mm. 
     As described above, in the liquid chromatograph mass spectrometer  1  according to the present invention, three desolvation pipes (ion introducing pipes)  19   a  to  19   c  are placed for better coordination with the form of the sprayed flow, so that almost all of the charged droplets can be brought into the three desolvation pipes  19   a  to  19   c . As a result, the detection sensitivity can be increased. In addition, the three desolvation pipes (ion introducing pipes)  19   a  to  19   c  are aligned in parallel so that the total area of cross-section of the inside of the desolvation pipes  19   a  to  19   c  can be increased. Thus, the total amount of ions that can be introduced into the first middle chamber  12  can be increased and at the same time ions can be efficiently introduced without disturbing the flow through the inside of each desolvation pipe  19   a  to  19   c . As a result the detection sensitivity can be increased. 
     Second Embodiment 
       FIGS. 4A and 4B  are diagrams showing the ionization chamber of the liquid chromatograph mass spectrometer using an ESI method according to the second embodiment.  FIG. 4A  is a side diagram showing the flow of the atomized liquid sample that has been sprayed from the nozzle  152  and  FIG. 4B  is a cross section diagram showing the XY plane in  FIG. 4A . Here, the same symbols are attached to the same components in the above described conventional liquid chromatograph mass spectrometer  1 . 
     An ionization chamber  100  is provided with a sub-chamber  110  in a rectangular parallelepiped form of 13 cm×13 cm×12 cm. The sub-chamber  110  has an upper surface, a front surface, a right-side surface, a rear surface (partition  26 ), a left-side surface and a lower surface. 
     The partition  26  is provided so as to separate the inside of the sub-chamber  110  from the inside of the first middle chamber  12 . A heater block  20  in a rectangular parallelepiped form into which a temperature adjusting mechanism (not shown) is incorporated is fixed in the center portion of the partition  26 . 
     One desolvation pipe (ion introducing pipe)  219  of which the entrance is placed inside the sub-chamber  110  and of which the exit is placed inside the first middle chamber  12  are formed in the heater block  20 . The desolvation pipe  219  is a rectangular pipe having its center axis in the X direction (having long sides of 1.6 mm and short sides of 0.5 mm) and is provided so that the long sides are directed in the Y direction. 
     The partition  26  of the thus formed sub-chamber  110  allows the flow of the atomized liquid sample that has been sprayed from the nozzle  152  having an inner diameter of 0.5 mm to spread as the flow progresses in the Z direction and ultimately increase in size to a diameter of approximately +/−2 mm to 4 mm. The ions that pass through the left end portion of the flow of the atomized liquid sample are drawn into the left end portion of the desolvation pipe  219 . The ions that pass through the center portion of the flow of the atomized liquid sample are drawn into the center portion of the desolvation pipe  219 . The ions that pass through the right end portion of the flow of the atomized liquid sample are drawn into the right end portion of the desolvation pipe  219 . 
     Third Embodiment 
       FIGS. 5A and 5B  are diagrams showing the ionization chamber of the liquid chromatograph mass spectrometer using an ESI method according to the third embodiment.  FIG. 5A  is a side diagram showing the flow of the atomized liquid sample that has been sprayed from the nozzle  152  and  FIG. 5B  is a cross section diagram showing the XY plane in  FIG. 5A . Here, the same symbols are attached to the same components in the above described conventional liquid chromatograph mass spectrometer  1 . 
     An ionization chamber  100  is provided with a sub-chamber  110  in a rectangular parallelepiped form of 13 cm×13 cm×12 cm. The sub-chamber  110  has an upper surface, a front surface, a right-side surface, a rear surface (partition  26 ), a left-side surface and a lower surface. 
     The partition  26  is provided so as to separate the inside of the sub-chamber  110  from the inside of the first middle chamber  12 . A heater block  20  in a rectangular parallelepiped form into which a temperature adjusting mechanism (not shown) is incorporated is fixed in the center portion of the partition  26 . 
     A first desolvation pipe  319   a  to a sixth desolvation pipe  319   f , which are ion introducing pipes of which the entrance is placed inside the sub-chamber  110  and of which the exit is placed inside the first middle chamber  12  are formed in the heater block  20 . Each desolvation pipe  319   a  to  319   f  is in a circular pipe form having the center axis in the X direction (having an outer diameter of 1.6 mm and an inner diameter of 0.5 mm, for example). The first desolvation pipe  319   a  to the third desolvation pipe  319   c  are aligned in this order side by side in the Y direction in a first XY plane, and the fourth desolvation pipe  319   d  to the sixth desolvation pipe  319   f  are aligned in this order side by side in the Y direction in a second XY plane that is located beneath the first XY plane. 
     The flow of the atomized liquid sample that has been sprayed from the nozzle  152  is in a conical form having the nozzle  152  as its apex, therefore the entrances of the first desolvation pipe  319   a  to the third desolvation pipe  319   c  are placed so as to protrude from the entrances of the fourth desolvation pipe  319   d  to the sixth desolvation pipe  319   f  in the −X direction. 
     The partition  26  of the thus formed sub-chamber  110  allows the flow of the atomized liquid sample that has been sprayed from the nozzle  152  having an inner diameter of 0.5 mm to spread as the flow progresses in the Z direction and ultimately increase in size to a diameter of approximately +/−2 mm to 4 mm. First, in the first XY plane, the ions that pass through the left end portion of the flow of the atomized liquid sample are drawn into the first desolvation pipe  319   a  having an inner diameter of 0.5 mm, the ions that pass through the center portion of the flow of the atomized liquid sample are drawn into the second desolvation pipe  319   b  having an inner diameter of 0.5 mm, and the ions that pass through the right end portion of the flow of the atomized liquid sample are drawn into the third desolvation pipe  319   c  having an inner diameter of 0.5 mm. Next, in the second XY plane, the ions that pass through the left end portion of the flow of the atomized liquid sample are drawn into the fourth desolvation pipe  319   d  having an inner diameter of 0.5 mm, the ions that pass through the center portion of the flow of the atomized liquid sample are drawn into the fifth desolvation pipe  319   e  having an inner diameter of 0.5 mm, and the ions that pass through the right end portion of the flow of the atomized liquid sample are drawn into the sixth desolvation pipe  319   f  having an inner diameter of 0.5 mm. 
     Fourth Embodiment 
       FIGS. 6A and 6B  are diagrams showing the ionization chamber of the liquid chromatograph mass spectrometer using an ESI method according to the fourth embodiment.  FIG. 6A  is a side diagram showing the flow of the atomized liquid sample that has been sprayed from the nozzle  152  and  FIG. 6B  is a cross section diagram showing the XY plane in  FIG. 6A . Here, the same symbols are attached to the same components in the above described conventional liquid chromatograph mass spectrometer  1 . 
     An ionization chamber  100  is provided with a sub-chamber  110  in a rectangular parallelepiped form of 13 cm×13 cm×12 cm. The sub-chamber  110  has an upper surface, a front surface, a right-side surface, a rear surface (partition  26 ), a left-side surface and a lower surface. 
     The partition  26  is provided so as to separate the inside of the sub-chamber  110  from the inside of the first middle chamber  12 . A heater block  20  in a rectangular parallelepiped form into which a temperature adjusting mechanism (not shown) is incorporated is fixed in the center portion of the partition  26 . 
     A first desolvation pipe  419   a  to a seventh desolvation pipe  419   g , which are ion introducing pipes of which the entrance is placed inside the sub-chamber  110  and of which the exit is placed inside the first middle chamber  12  are formed in the heater block  20 . Each desolvation pipe  419   a  to  419   g  has a circular pipe form (having an outer diameter of 1.6 mm and an inner diameter of 0.5 mm, for example). The first desolvation pipe  419   a  to the third desolvation pipe  419   c  are provided in a first XY plane, the fourth desolvation pipe  419   d  and the fifth desolvation pipe  419   e  are provided in a second XY plane that is located beneath the first XY plane, and the sixth desolvation pipe  419   f  and the seventh desolvation pipe  419   g  are provided in a third XY plane that is located beneath the second XY plane. 
     In addition, the first desolvation pipe  419   a , the second desolvation pipe  419   b  and the third desolvation pipe  419   c  are in a circular pipe form having its center axis in the X direction (having an outer diameter of 1.6 mm and an inner diameter of 0.5 mm, for example), and are aligned in this order side by side in the Y direction in the first XY plane. That is to say, the entrance of the first desolvation pipe  419   a , the entrance of the second desolvation pipe  419   b  and the entrance of the third desolvation pipe  419   c  are directed so as to face the X direction in the first XY plane. In addition, the entrance of the fourth desolvation pipe  419   d  is directed so as to face the Y direction and at the same time the entrance of the fifth desolvation pipe  419   e  is directed to face the −Y direction in the second XY plane. Furthermore, the entrance of the sixth desolvation pipe  419   f  is directed so as to face the −X direction and at the same time the entrance of the seventh desolvation pipe  419   g  is directed to face the −X direction in the third XY plane. 
     The partition  26  of the thus formed sub-chamber  110  allows the flow of the atomized liquid sample that has been sprayed from the nozzle  152  having an inner diameter of 0.5 mm to spread as the flow progresses in the Z direction and ultimately increase in size to a diameter of approximately +/−2 mm to 4 mm. First, in the first XY plane, the ions that pass through the left end portion of the flow of the atomized liquid sample are drawn into the first desolvation pipe  419   a  having an inner diameter of 0.5 mm, the ions that pass through the center portion of the flow of the atomized liquid sample are drawn into the second desolvation pipe  419   b  having an inner diameter of 0.5 mm, and the ions that pass through the right end portion of the flow of the atomized liquid sample are drawn into the third desolvation pipe  419   c  having an inner diameter of 0.5 mm. Next, in the second XY plane, the ions that pass through the center left portion of the flow of the atomized liquid sample are drawn into the fourth desolvation pipe  419   d  having an inner diameter of 0.5 mm, and the ions that pass through the center right portion of the flow of the atomized liquid sample are drawn into the fifth desolvation pipe  419   e  having an inner diameter of 0.5 mm. Finally, in the third XY plane, the ions that pass through the rear left portion of the flow of the atomized liquid sample are drawn into the sixth desolvation pipe  419   f  having an inner diameter of 0.5 mm, and the ions that pass through the rear right portion of the flow of the atomized liquid sample are drawn into the seventh desolvation pipe  419   g  having an inner diameter of 0.5 mm. 
     Other Embodiments 
     While the liquid chromatograph mass spectrometer  1  has such a configuration that an ESI method is used as described above, an APCI method or other ionization techniques may be used in the configuration. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to a mass spectrometer and the like having an ionization chamber. 
     Explanation of Symbols 
     
         
         
           
               15  spray (atomization means) 
               19  desolvation pipe (ion introducing pipe) 
               50  mass spectrometer unit 
               60  liquid chromatograph unit (LC unit) 
               100  ionization chamber