Abstract:
The present invention discloses a system for analyzing elements contained in a sample in very slight amounts, such as C, S, O, N, H and the like in materials, such as steel and ceramics. An element analyzer can gasify the sample elements in an appropriate gas, such as oxygen gas in a high-frequency heating furnace or an electric resistant furnace. Resulting gas can be introduced into a mass spectrometer to permit a quantitative analysis of the sample elements. A metal sample can be levitated and heated and melted with induction current for producing the resultant gas for introduction to a mass spectrometer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system for analyzing elements of C (carbon), S (sulfur), O (oxygen), N (nitrogen), H (hydrogen) and the like contained in slight amounts, respectively, in a material such as steel, and ceramics and more particularly, to a combustion furnace system that can burn a sample and analyze the gaseous ingredients in an improved manner. 
     2. Description of Related Art 
     A method obtained by combining a combustion of a sample in an oxygen gas stream with an infrared absorption scan has been generally used for analyzing quantitatively C, and S contained in steel in slight amounts, respectively. While a method obtained by combining a fusion extracting of a sample in an inert gas with an infrared absorption scan or a thermal conductivity test has also been commonly employed as a method for analyzing quantitatively O, N, and H contained in steel in slight amounts, respectively. 
     More specifically, the combustion method has a steel sample burned while feeding oxygen gas into a heating furnace and the resultant combustion gas, containing CO/CO2 and SO2 produced at that time, is analyzed by a nondispersive infrared analyzer (NDIR). The fusion extraction method has a graphite crucible containing a sample such as steel disposed in a heating furnace, the sample is heated and fused while feeding an inert gas to the combustion chamber, and the CO 2  produced at that time is analyzed by a NDIR, while N 2  and H 2  are analyzed by a thermal conductivity method. 
     In both of the method s described above, a lower limit of detection for an element in the sample is about 1 wt ppm (although 0.1 wt ppm is possible with respect to H). However, there is a demand for new materials such as metals and ceramics having a higher purity to be employed in recent years, so that the elements, as described above as impurities must exhibit a lower concentration level. 
     Under these circumstances, the sensitivity of the testing procedures have become insufficient in conventional analyzers as described above, and as a result, a precise determination cannot be effected. In addition, there is also a problem of a false or blank value due to possible contamination of a graphite crucible, so that an accurate determination in the region of very slight amounts of impurities becomes difficult. 
     Although there is known an ICP-MS method and the like as one type of analyzing method for analyzing steel and the like by the use of a mass spectrometer, it is difficult to realize a measurement with sufficiently high sensitivity, because a large amount of a major component (for example, Fe) of the sample material enters the mass spectrometer, so that the potential excellent resolving power and excellent sensitivity in the order of a ppb which could be derived from a mass spectrometer cannot be easily achieved. 
     Other examples of combustion furnaces for burning a sample to be analyzed can be found in U.S. Pat. No. 5,110,554, U.S. Pat. No. 3,936,587, U.S. Pat. No. 4,087,249. U.S. Pat. No. 4,234,541 and U.S. Pat. No. 5,236,353. 
     There is still a desire in the prior art to optimize the ability to measure very minute amounts of elements in a sample in an economical and efficient manner. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a system for analyzing elements contained in a sample (hereinafter referred to simply and optionally as an “element analyzer”) by which elements of C, S, O, N, H and the like which may be contained in very slight amounts, respectively, in a sample material such as steel, ceramics and the like can be quantitatively analyzed with high sensitivity. 
     In order to attain the above described object, the element analyzer according to a first embodiment is constituted so that a sample is burned up while feeding oxygen gas into a high-frequency heating furnace or an electric resistance furnace, and the gas produced at that occasion is introduced to a mass spectrometer, thereby to analyze quantitatively at least any one element of C, S, and N. 
     An element analyzer according to a second embodiment uses a graphite crucible containing a sample. The crucible is placed into an impulse furnace, and the sample is heated and fused while feeding an inert gas into the furnace. The resultant gas is extracted and introduced into a mass spectrometer, thereby to analyze quantitatively at least one element, such as O, N, and H that may be contained in the sample. 
     Furthermore, an element analyzer according to a third embodiment has the sample heated while feeding a hydrogen gas to an electric resistance furnace, and the gas produced at that occasion is introduced into a mass spectrometer, thereby to analyze quantitatively at least any one of C, S, and N. 
     In any of the above described element analyzers, the desired elements to be measured can be analyzed quantitatively with high sensitivity. The mass spectrometer can concentrate its excellent resolving power at specific components to be measured thereby to achieve a measurement with higher sensitivity, over that of the prior art, as a result of removal of oxidized dust by means of a dust filter, removal of water vapor (moisture) by means of a dehumidifier, and oxidation of CO into CO 2  by means of an oxidizing device. 
     In any of the above described element analyzers, it may be alternately arranged so that a gas initially produced in a furnace is again supplied to the furnace through a re-circulating passageway before the final combustion or extraction of the sample, and the above described gas is then supplied to the mass spectrometer after completing the combustion or extraction. According to such an arrangement, stable measured results can be obtained in a single procedure of testing. 
     An element analyzer according to a fourth embodiment is constituted in such a manner that a laser beam of an appropriate intensity is irradiated upon a metal sample, which is disposed in an irradiation cell, to which is selectively introduced oxygen gas or an inert gas, and a gas produced at that occasion is then introduced to a mass spectrometer to analyze quantitatively at least any one of carbon, sulfur, nitrogen, and hydrogen contained in the metal sample. 
     Moreover, an element analyzer according to a fifth embodiment has a laser beam irradiating a metal sample which has been disposed in an irradiation cell to which is introduced oxygen gas, and a gas produced at that occasion is introduced to a mass spectrometer, thereby to analyze quantitatively either of carbon, and sulfur contained in the metal sample. 
     Still further, an element analyzer according to a sixth embodiment is constituted so that a laser beam is irradiated upon a metal sample disposed in an irradiation cell to which is introduced an inert gas, and a gas produced at that occasion is introduced to a mass spectrometer, thereby to analyze quantitatively either of nitrogen and hydrogen contained in the metal sample. 
     Yet further, an element analyzer according to a seventh embodiment is constituted so that a laser beam is irradiated upon a metal sample disposed in an irradiation cell to which are introduced hydrogen gas and an inert gas at a predetermined ratio, and a resultant gas produced at that occasion is introduced to a mass spectrometer, thereby to analyze quantitatively at least any one of carbon, sulfur, and nitrogen contained in the metal sample. 
     In the above described element analyzers according to the fourth to the seventh embodiments, desired elements can be analyzed quantitatively with high sensitivity. The mass spectrometer can concentrate its excellent resolving power at components to be measured and thereby achieve measurement with higher sensitivity as a result of removal of oxidized dust by means of a dust filter, and removal of water vapor (moisture) by means of a dehumidifier. 
     An element analyzer according to an eighth embodiment is constituted so that either one of an inert gas and an oxygen gas can be supplied to an extracting cell around which has been wound a high-frequency coil. While the high-frequency coil is energized, the metal sample is maintained in position inside the extracting cell by means of high-frequency levitation, at the same time, the sample is heated and fused, and the gas produced at that occasion is conveyed and carried by the inert gas or the oxygen gas to the mass spectrometer, thereby to analyze quantitatively therein at least one of carbon, sulfur, nitrogen, and hydrogen contained in the metal sample. 
     Furthermore, the element analyzer according to a ninth embodiment is constituted so that oxygen gas is supplied to an extracting cell around which has been wound a high-frequency coil. When the high-frequency coil is energized, the metal sample is maintained at an elevated position inside the extracting cell by means of high-frequency levitation, at the same time, the sample is heated and fused, and the gas produced at that occasion is conveyed and fed to the mass spectrometer by means of the oxygen gas, thereby to analyze quantitatively therein at least one of carbon, sulfur, and nitrogen contained in the metal sample. 
     In addition, it may be arranged in the above described eighth and the ninth embodiments that the high-frequency coil is moved vertically along the longitudinal direction of the extracting cell. 
     In the above described element analyzers according to the eighth and the ninth embodiments, desired elements can be analyzed quantitatively with high sensitivity. The mass spectrometer can concentrate its excellent resolving power at components to be measured to achieve measurement with higher sensitivity as a result of removal of. oxidized dust by means of a dust filter and removal of water vapor (moisture) by means of a dehumidifier. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a view showing schematically an example of the system for analyzing elements according to a first embodiment; 
     FIG. 2 is a view showing an example of the mechanical features of a spectrometer used in the above described system for analyzing elements; 
     FIG. 3 is a graphical representation schematically showing an example of a mass spectrum of CO 2 +obtained in the above described system for analyzing elements; 
     FIG. 4 is a view showing another embodiment of the system for analyzing elements according to the first embodiment; 
     FIG. 5 is a graphical representation showing schematically an example of mass spectrum of CO 2 +obtained in the above described system for analyzing elements; 
     FIG. 6 is a view showing another embodiment of a heating furnace used in the above described system for analyzing elements; 
     FIG. 7 is a view schematically showing an example of the system for analyzing elements according to a second embodiment; 
     FIG. 8 is a graphical representation showing schematically a mass spectrum of N+obtained in the above described system for analyzing elements; 
     FIG. 9 is a view showing another embodiment of the system for analyzing elements according to the second embodiment; 
     FIG. 10 is a graphical representation showing schematically a mass spectrum of N+obtained in the above described system for analyzing elements; 
     FIG. 11 is a view showing schematically an example of the system for analyzing elements according to a third embodiment; 
     FIG. 12 is a graphical representation showing schematically an example of mass spectrum of CH4+obtained in the above described system for analyzing elements; 
     FIG. 13 is a view showing another embodiment of the system for analyzing elements according to the third embodiment; 
     FIG. 14 is a graphical representation showing schematically an example of mass spectrum of CH 4 +obtained in the above described system for analyzing elements; 
     FIG. 15 is a view showing schematically a constitution of the system for analyzing elements in a preferred embodiment according to a fourth embodiment; 
     FIG. 16 is a modified example of the above described system for analyzing elements being a preferred embodiment according to the fifth and the sixth embodiments; 
     FIG. 17 is a view showing schematically a constitution of the system for analyzing elements in a preferred embodiment according to the seventh embodiment; 
     FIG. 18 is a view showing schematically a constitution of the system for analyzing elements in a preferred embodiment according to the eighth embodiment; and 
     FIG. 19 is a view showing schematically a constitution of the system for analyzing elements in a preferred embodiment according to the ninth embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the general principles of the present invention have been defined herein specifically to provide an improved combustion furnace system for analyzing elements in a sample. 
     Preferred embodiments of the invention will be described hereinafter by referring to the accompanying drawings wherein FIGS. 1 through 3 indicate a first embodiment of the invention. FIG. 1 shows schematically an example of a system for analyzing elements wherein the system can analyze quantitatively at least any one element of C, S and N. In FIG. 1, reference numeral  1  designates a high-frequency heating oven as a heating source and  2  is a porcelain crucible to be set in the high-frequency heating oven  1 , in the interior of which is contained a sample  3  which has been weighed. Reference numeral  4  is an oxygen gas feed passage for feeding oxygen gas g 1  to the high-frequency heating oven  1 , and  5  is an oxygen gas cylinder, respectively. 
     A flow channel  6  provides a passageway through which a gas G 1  produced as a result of burning up the sample  3  in the high-frequency heating oven  1 , flows. The gas flow channel  6  is provided with a dust filter  7  for removing any oxidized dust such as iron oxide contained in the produced gas G 1 , a dehumidifier  8  for removing water vapor (moisture) contained in the produced gas G 1 , and an oxidizing device  9  for oxidizing CO contained in the produced gas G 1 , into CO 2 , a sampling section  10  is disposed on the downstream side of these stations. Furthermore, the sampling section  10  is coupled to an exhaust section (not shown), and joined to a mass spectrometer (for example, Q-MS)  12  through a flow channel  11 . 
     FIG. 2 is a view showing an example of the mass spectrometer  12  wherein an ionizing section  13  having a filament  16  is disposed on one side of a gas inlet  15  which is connected to the flow channel  11  in such a manner that the filament is opposed to an electron collecting electrode  18  for collecting electrons  17  produced at the time when the filament  16  is heated in a container  14  maintained at a high vacuum. An ion producing electrode  19 , and an ion extracting electrode  20  are further disposed. in the container  14 , thereby producing ions  21 . Reference numeral  22  denotes an exhaust pump for drawing a gas contained inside the container  14  at a high degree of vacuum, arid  23  denotes a pressure gage, respectively. An analyzing section  24  extends from the above described ionizing section  13 , and is encompassed with a magnet member  25  for generating a magnetic field. An ion collector  26  collects the ions  21  which have passed through the analyzing section  24 . 
     While the ionic current obtained by the ion collector  26  has not been illustrated in the drawing, it is input to a control unit (for example, computer)  27  through a pre-amplifier, a main amplifier, and an A/D converter, and the ionic current thus input is suitably processed therein. 
     Operation of a system for analyzing elements having the above constitution can be described by referring also to FIG. 1, wherein steel is used as a sample  3 . The sample  3  is weighed and contained in the porcelain crucible  2 , and the porcelain crucible  2  containing the sample  3  is set in the high-frequency heating oven  1 . The sample  3  is heated and burned while supplying oxygen gas g, to the high-frequency heating oven  1 . The gas G 1  produced as a result of the burning contains CO, CO 2 , SO 2 , NO 2 , and water vapor. 
     The produced gas G 1  is introduced into the flow channel  6  by means of the oxygen gas g 1 , as a carrier gas, and the produced gas flows towards the downstream side thereof. In mid course thereof, the produced gas is subjected to pretreatments such as removal of oxidized dust, such as iron oxide, by a dust filter  7 , removal of water vapor in the dehumidifier  8 , and further CO is oxidized into CO 2  in an oxidizing device  9 . Accordingly, the gas G 1 , in the former part of the sampling section  10  contains CO 2 , SO 2 , and NO 2  as components. 
     The produced gas G 1 , containing the above described CO 2 , SO 2 , and NO 2  is sampled at a constant interval and constant amounts in the sampling section  10 , and these samples are fed to the ionizing section  13  of the mass spectrometer  12 . In the ionizing section  13 , CO 2 , SO 2 , and NO 2  are ionized to CO 2 +(m/z=44), SO 2 +(m/z=64), and NO 2 +(m/z=48), respectively, and they are subjected to a mass spectrometric analysis in the analyzing section  24 . 
     FIG. 3 is a graphical representation showing schematically a graphic example of a mass spectrum of CO 2 +obtained by the system for analyzing elements having the above described constitution wherein the mass spectrum varies with time in response to a burning pattern of the sample  3 . Since a value of the mass spectrum integrated, is proportional to an amount of C contained in the sample  3 , the C in the sample  3  can be determined on the basis of the value integrated. 
     Furthermore, since the mass spectra are also obtained for SO 2 +and NO 2 +, as in the case of CO 2 +, C and N in the sample  3 , they can be determined, as a matter of course, by integrating these mass spectra in accordance with a similar manner as that described above. 
     Since the gas G 1 , produced in the high-frequency heating oven  1  is suitably pretreated, then the produced gas G 1  as supplied to the mass spectrometer  12  may contain elements such as C, S, and N which are merely slight amounts thereof (at a degree of ppm or less) yet they can be positively and precisely determined. 
     FIGS. 4 and 5 show another preferred embodiment of the above described invention. In a system for analyzing elements according to the present embodiment, a gas G 1 , produced in a high-frequency heating oven  1  is subjected to a prescribed treatment, and then the gas G 1  thus treated is supplied repeatedly to the high-frequency heating oven  1  as shown in FIG.  4 . Namely, reference numeral  28  in FIG. 4 designates a switch cock valve disposed in a feed passage  4  for feeding oxygen gas to the high-frequency heating oven  1 . Reference numeral  29  denotes a circulating passage for connecting the switch cock valve  28  to a sampling section  10 , and is provided with a suction pump  30 . 
     The gas G 1  produced in the high-frequency heating oven  1  is fed back to the high-frequency heating oven  1  by an action of the suction pump  30  provided in the circulating passage  29 , and the gas G 1 , output from the high-frequency heating oven  1  is circulated so as to return to the high-frequency heating oven  1  through a flow channel  6 , the sampling section  10 , the circulating passage  29  and the switch cock valve  28 , so that the produced gas G 1  further aids in burning up a sample  3  as a supplemental oxygen source. The above-mentioned circulation of the gas G 1  is conducted repeatedly until burning of the sample  3  is completed. After the completion of burning, the gas G 1 , is supplied to the mass spectrometer  12  through the sampling section  10 . 
     Since the gas G 1  produced in the high-frequency heating oven  1  is recycled and supplied repeatedly to the high-frequency heating oven  1  through the circulating passage  29  until burning of the sample  3  is completed. In the gas G 1 , which is fed to the mass spectrometer  12  after completing the burning of the sample  3 , a composition in the gas G 1 , which varies with time is averaged, so that C, S, and N can be determined by conducting a single mass spectrometric analysis. FIG. 5 shows an example of the mass spectrum of CO 2 +obtained in the system for analyzing elements arranged as described above. 
     While a heating oven of a high-frequency induction heating type has been used as the heating oven  1  in the above described embodiments, also an electric resistance heating type of oven, as shown in FIG. 6, may be employed. More specifically, a heating furnace  31  shown in FIG. 6 is an electric resistance furnace which is constituted such that a heater  33  is disposed around the outer circumference of a porcelain tube  32 , and inside there is placed a porcelain boat  34  (a porcelain crucible may also be used) containing a sample  3 . 
     In place of the above described mass spectrometer  12  of a so-called Q-MS type, a time of flight mass spectrometry (TOF-MS) type may be employed. A TOF-MS type ionizes the target sample and provides a fixed energy to the sample to accelerate it to a detector. The difference in velocity of flight generated from a difference in individual ionic masses enable a detection of the time of flight to obtain a mass spectrum. 
     In this case, since it is required to sample instantaneously a produced gas G 1 , it is preferred to arrange a pulse-formed electric field for the produced gas, for example, ionizing the same in the electric field, and only the gas that is ionized is introduced into the TOF-MS. 
     FIGS. 7 and 8 show a second embodiment of the invention wherein FIG. 7 shows schematically an example of a system for analyzing elements to perform quantitative analysis of at least one of the elements O, N, and H. It is to be noted that a component in FIG. 7 designated by the same reference numeral as that of FIG. 1 is the same component in FIG.  1 . 
     In FIG. 7, reference numeral  35  denotes an impulse furnace as a melting and extracting furnace,  36  a graphite crucible which is to be set in the impulse furnace  35 , respectively, and inside which is contained a sample  37  which has been weighed. Reference numeral  38  designates an inert gas feed passage for feeding an inert gas g 2  such as argon (Ar) gas, and helium (He) gas to the impulse furnace  35 , and  39  an inert gas cylinder, respectively. 
     Reference numeral  40  designates a flow channel for flowing a gas G 2  extracted by heating the sample  37  in the impulse furnace  35 , and a dust filter  41  for removing oxidized dust such as iron oxide contained in the gas G 2  is disposed downstream in the flow channel, and further downstream thereof is disposed a sampling section  10 . One of the portions, on the downstream side of the sampling section  10 , is connected to an exhaust section (not shown), while the other portion is connected to a mass spectrometer (for example, Q-MS)  12  through a flow channel  11 . 
     Operation of the element analyzer having the constitution as described above will be described by referring also to FIG. 8 wherein steel is employed as the sample  37 . The sample  37  is weighed and placed in the graphite crucible  36 , which is then set in the impulse furnace  35 . The graphite-crucible  36  is energized while supplying an inert gas (for example, Ar or He) g 2  to the impulse furnace  35  to heat the sample  37  at a predetermined temperature. As a result of this heating procedure, O contained in the sample  37  reacts with the graphite crucible  36  to produce CO, while N and H contained in the sample  37  are changed into N 2  and H 2 , respectively. The gas G 2  containing these gases CO, N 2 , and H 2  is introduced into the flow channel  40  by means of the inert gas g 2  as a carrier gas, and the gas G 2  flows towards the side of a downstream thereof. In mid course thereof, the produced gas is subjected to a pretreatment wherein oxidized dust such as iron oxide is removed by the dust filter  41 . Accordingly, the gas G 2  in the sampling section  10  contains CO, N 2 , and H 2  as its components. 
     The gas G 2  containing the above described CO, N 2 , and H 2  is sampled at a constant interval and a constant amount in the sampling section  10 , and these samples are fed to an ionizing section  13  of the mass spectrometer  12 . In the ionizing section  13 , CO, N 2 , and H 2  are ionized to CO +  (m/z=28), N +  (m/z=14), and H +  (m/z=1), respectively, and they are subjected to mass spectrometric analysis in an analyzing section  24 . 
     FIG. 8 is a graphical representation showing schematically an example of a mass spectrum of N+obtained by the element analyzer having the above described constitution wherein the mass spectrum varies with time in response to an extracting pattern of the sample  37 . Since a value of the mass spectrum integrated is proportional to an amount of N contained in the sample  37 , N in the sample  37  can be determined on the basis of the value integrated. 
     Furthermore, since mass spectra are also obtained as to CO+ and H+, as in the case of N+, O and H in the sample  37 , they can be determined, as a matter of course, by integrating these mass spectra in accordance with a similar manner as that above. As mentioned above, since the gas G 2  extracted in case of heating and melting of the sample  37  in the impulse furnace  35  is suitably pretreated, and then the gas G 2  is supplied to the mass spectrometer  12 , elements such as O, N, and H which are contained merely in slight amounts thereof (at a degree of ppm or less) can be positively and precisely determined. 
     Furthermore, it may also be arranged, that the gas G 2  extracted in the impulse furnace  35  is subjected to a prescribed treatment, and then the so treated gas is supplied repeatedly to the impulse furnace  35 . More specifically, FIG. 9 shows another preferred embodiment of the invention wherein reference numeral  42  is a switch cock valve disposed in a feed passage  38  for feeding an inert gas to the impulse furnace  35 . Reference numeral  43  denotes a circulating passage for connecting the switch cock valve  42  to a sampling section  10 , and is provided with a suction pump  44 . 
     Since operation of the element analyzer constituted as shown in FIG. 9 is basically the same as that shown in FIG. 7, the details thereof will be omitted. FIG. 10 shows an example of a mass spectrum of N +  obtained in the element analyzer having a constitution as described above. 
     It is to be noted that a TOF-MS may be employed also as the mass spectrometer  12 . In this case, since it is required to sample instantaneously the gas G 2 , it is preferred to arrange a pulse-formed electric field for ionizing the gas in the electric field, and only the gas ionized is introduced into the TOF-MS. 
     FIGS. 11 and 12 show a third embodiment of the invention, respectively, wherein FIG. 11 shows schematically an example of a system for analyzing elements quantitatively of at least any one element of C, S, and N. It is to be noted that a component in FIG. 11 designated by the same reference numeral as that of FIG. 1 is the same component in FIG.  1 . 
     In FIG. 11, reference numeral  45  designates an electric resistance furnace having the same constitution as that of the electric resistance furnace  31 , and  46  is a container such as a porcelain crucible which is to be set in the electric resistance furnace  45 , respectively, inside of which contains a sample  47  which has been weighed. Reference numeral  48  denotes a hydrogen gas feed passage for feeding hydrogen gas g 3  to the electric resistance furnace  45 , and  49  is a hydrogen gas cylinder, respectively. 
     Reference numeral  50  designates a flow channel through which a gas G 3  produced by heating the sample  47  in the electric resistance furnace  45 , flows to a dust filter  51  for removing foreign matters contained in the produced gas G 3 . The dust filter  51  is disposed in the flow channel  50 , and downstream thereof is disposed a sampling section  10 . One of the conduit portions on the downstream side of the sampling section  10  is connected to an exhaust section (not shown), while the other portion is connected to a mass spectrometer (for example, Q-MS)  12  through a flow channel  11 . 
     Operation of the element analyzer having the constitution as described above will be described by referring also to FIG. 12 wherein steel is employed as the sample  47 . The sample  47  is weighed and placed in the porcelain crucible  46 , which is set in the electric resistance furnace  45 . The porcelain crucible  46  is energized while supplying the hydrogen gas g 3  to the electric resistance furnace  45  to heat the sample  47  at a predetermined temperature. As a result of this heating procedure, C, S, and N contained in the sample  47  reacts with the hydrogen gas g 3  to produce gases of CH 4  (methane), H 2 S (hydrogen sulfide), and NH 3  (ammonia), respectively. The gas G 3  containing these gases CH 4 , H 2 S, and NH 3  is introduced into the flow channel  50  by means of hydrogen gas g 3  as a carrier gas, and the gas G 3  flows towards the downstream side. In mid course thereof, the gas G 3  is subjected to a pretreatment wherein foreign matters such as dust is removed by the dust filter  51 . Accordingly, the gas G 3  in the former part of the sampling section  10  contains CH 4 , H 2 S, and NH 3  as its components. 
     The gas G 3  containing the above described CH 4 , H 2 S, and NH 3  is sampled at a constant interval in constant amounts in the sampling section  10 , and these samples are fed to an ionizing section  13  of the mass spectrometer  12 . In the ionizing section  13 , CH 4 , H 2 S, and NH 3  are ionized to CH 4 +(m/z=16), H 2 S+(m/z=34), and NH 3  +(m/z=17), respectively, and they are subjected to mass spectrometric analysis in an analyzing section  24 . 
     FIG. 12 is a graphical representation showing schematically an example of a mass spectrum of CH 4 + obtained by the system for analyzing elements having the above described constitution wherein the mass spectrum varies with time in response to a heating and melting pattern of the sample  47 . Since a value of the mass spectrum integrated is proportional to an amount of C contained in the sample  47 , C in the sample  47  can be determined on the basis of the value integrated. 
     Furthermore, since mass spectra are also obtained as to H 2 S +  and NH 3   + , as in the case of the above described CH 4   + , S and N in the sample  47  can be determined by integrating these mass spectra in accordance with a similar manner as that described above. 
     As described above, since the gas G 3  produced in the case of heating and melting the sample  47  in the electric resistance furnace  45  is suitably pretreated and then, the gas G 3  is supplied to the mass spectrometer  12 , elements such as C, H, and N which are contained merely in slight amounts thereof (at a degree of ppm or less) can be positively and precisely determined. 
     Furthermore, it may also be arranged that the gas G 3  produced in the electric resistance furnace  45  is subjected to a prescribed treatment, and then the treated gas is supplied repeatedly to the electric resistance furnace  45 . More specifically, reference numeral  52  in FIG. 13 is a switch cock valve disposed in a feed passage  48  for feeding hydrogen gas to the electric resistance furnace  45 . Reference numeral  53  denotes a circulating passage for connecting the switch cock valve  52  to a sampling section  10 , and it is provided with a suction pump  54 . 
     Since operation of the element analyzer constituted as shown in FIG. 13 is the same as that shown in FIGS. 4 and 9, the details thereof will be omitted. FIG. 14 shows an example of a mass spectrum of CH 4   +  obtained in the element analyzer having the constitution as described above. 
     In place of the above described mass spectrometer  12  of a so-called Q-MS type, a mass spectrometer of time of flight (TOF-MS) type may be employed. In this case, since it is required to sample instantaneously the gas G 3 , it is preferred that a pulse-formed electric field is prepared for ionizing the gas in the electric field, and only the gas ionized is introduced into the TOF-MS. Furthermore, a porcelain boat may be employed in place of the porcelain crucible  46 . 
     FIG. 15 shows another embodiment according to the fourth embodiment, and FIG. 16 shows a preferred embodiment according to a fifth and sixth embodiment, respectively, wherein a system for analyzing elements can analyze quantitatively at least any one element of C, S, N, and H. 
     In FIG. 15, reference numeral  61  designates a block-shaped irradiation cell the inside of which is defined with a suitable space  62 . On the side of the top surface of the irradiation cell  61 , a sample resting portion  64  for resting a metal sample  63  such as steel thereon is formed. Reference numeral  65  denotes an annular packing as a sealing member made of, for example, an acid proof synthetic rubber which functions to hold stable the metal sample  63  on the sample resting portion  64 . Reference numeral  66  designates an annular packing as a sealing member disposed on the side of the bottom surface of the irradiation cell  61  and which is made from the same material as that of the above described packing  65 . Reference numeral  67  denotes a laser beam permeating window which is disposed so as to close the lower opening of the irradiation cell  61 . More specifically, when the space  62  in the irradiation cell  61  is closed by the metal sample  63  in the upper part, and by means of the permeating window  67  in the lower part, the space is shut off from the outside. It is to be noted that the irradiation cell  61  can be adjusted by means of a three-dimensional stage  68 . More specifically, the three-dimensional stage  68  is constituted so as to be movable along three-dimensional directions, for example, a traverse direction X on the drawing, a vertical direction Y on the drawing, and a Z-direction perpendicular to the direction Y, respectively. 
     A sample pressing member  69  presses the metal sample  63  and is suitably movable in a vertical direction. A laser oscillator  70  is constituted so that a laser beam  71  output therefrom is irradiated at a predetermined position on the bottom surface  63   a  of the metal sample  63  through a mirror  72 , a condenser lens  73 , and the permeating window  67 . 
     A gas jetting nozzle  74  is disposed in an end side of the irradiation cell  61  and functions to jet oxygen gas or an inert gas (such as helium, and argon) to a sample portion which is irradiated by the laser beam  71 . The metal sample  63  is placed so as to close the top portion of the cell space  62 , and the upstream side of the gas jetting nozzle  74  is joined to an oxygen gas cylinder  76  and an inert gas cylinder  77  through the gas feed passage  75 , respectively. Reference numerals  78  and  79  denote valves provided on the gas cylinders  76  and  77 , respectively. In other words, it is arranged that either of the oxygen gas and the inert gas may be selectively supplied to the internal space  62  of the irradiation cell  61 . 
     Reference numeral  80  denotes an outlet of a gas G produced in the cell space  2 , a gas flow channel  81  communicates with the gas outlet  80 . The gas flow channel  81  is provided with a dust filter  82  for removing oxidized dust such as iron oxide contained in the produced gas G, a three-way electromagnetic valve  83 , a dehumidifier  84  for removing water vapor (moisture) contained in the produced gas, another three-way electromagnetic valve  85 , and a sampling section  86 . A gas flow channel  87  connects the three-way electromagnetic valve  83  with the other three-way electromagnetic valve  85  in order to bypass the dehumidifier  84 . Either of portions on the downstream side of the sampling section  86  is connected to the above described mass spectrometer  12  through a flow channel  88 , while the other portion is connected to an exhaust section (not shown). 
     In this case, steel is used as a metal sample  63 . A steel material to be analyzed is cut out by means of a cutter into a block-shaped piece having a suitable dimension, the cut out surface thereof is ground sufficiently by the use of a sandpaper to prepare the metal sample  63 . The metal sample  63  thus prepared is set on the sample resting portion  64  of the irradiation cell  61  in such a manner that a plane  63   a  thus ground of the metal sample  63  faces the downward direction. 
     A case where an amount of C or S contained in the steel sample  63  (content) is determined will be described. Before conducting quantitative analysis of elements, purging of air and the like as well as preliminary irradiation of the laser beam are effected. More specifically, the valve  78  is opened to supply oxygen gas to the cell space  62  of the irradiation cell  61 , whereby a flow channel extending from the irradiation cell  61  to the mass spectrometer  12  is purged, so that air and the like remaining in the flow channel is exhausted. Thereafter, the laser oscillator  70  is operated to irradiate the laser beam  71  onto the bottom surface  63   a  of the steel sample  63  under a state where oxygen gas is supplied to the cell space  62 , whereby contamination produced at the time of cutting, grinding, or handling of the bottom surface  63   a  is removed. In the preliminary irradiation for cleaning a sample, it is preferred to irradiate the bottom surface  63   a  of the steel sample  63  over a wider range than that in case of analysis thereof accordingly the three-dimensional stage  68  is operated to transfer suitably the irradiation cell  61  together with the steel sample  63  in a two-dimensional direction, or to change an angle of the mirror  72 . 
     When the above described preliminary irradiation is completed, the steel sample  63  which has been cleaned is removed from the sample resting portion  64  the steel sample  63  thus removed is weighed, and then it is set on the sample resting portion  64 . Thereafter, air and the like in the flow channel is excluded by purging again with the use of oxygen gas. 
     A quantitative analysis for elements is then carried out. The laser beam  71  is irradiated to a predetermined site of the above described bottom surface  63   a  (a portion to be analyzed) while supplying oxygen gas into the cell space  62 , and more specifically, while jetting oxygen gas to the bottom surface  63   a  of the steel sample  63  from the extreme end of the gas jetting nozzle  74 . In this case, it is preferred that the laser beam  71  is irradiated so as to focus on a position which deviates from the bottom surface  63   a  of the steel sample  63  by several μm towards the inside of the cell space  62 , and that the bottom surface  63   a  is scanned along X-Y direction as a result of operating the three-dimensional stage  68 . 
     The portion to be analyzed of the steel sample  63  which has been irradiated by the laser beam  71  in the above described oxygen stream reaches a high temperature, so that C and S contained in the steel sample  63  are burned up by means of oxygen to produce CO gas, CO 2  gas, and SO 3  gas, respectively. A gas G containing these gases flows into a produced gas flow passage  81  through a gas outlet  80  with the aid of oxygen gas as a carrier gas. In this case, both the three-way electromagnetic valves  83  and  85  in the produced gas flow passage  81  are turned on, so that a bypass flow passage  87  is in a closed state. 
     Accordingly, the CO gas, the CO 2  gas, and the S 0   2  gas flow through the dust filter  82 , the three-way electromagnetic valve  83 , the dehumidifier  84 , and the three-way electromagnetic valve  85 , and finally the gases reach the sampling section  86 . In this occasion, oxidized dust such as iron oxide contained in the CO gas, the CO 2  gas, and the SO 2  gas is removed by the dust filter  82 , and water vapor is removed in the dehumidifier  84 . Accordingly, the gas G in the former part of the sampling section  86  contains CO, CO 2 , and SO 2  as its components. 
     The gas G containing the above described CO, CO 2 , and SO 2  is sampled at a constant interval and constant amount in the sampling section  86 , and these samples are fed to an ionizing section  13  of the mass spectrometer  12 . In the ionizing section  13 , CO, CO 2 , and SO 2  are ionized to CO +  (m/z=28), CO 2   +  (m/z=44), and SO 2   +  (m/z=64), respectively, and they are subjected to mass spectrometric analysis in an analyzing section  24 . Based on the results obtained, an amount of C and S can be obtained. 
     After conducting a mass spectrometric analysis through effecting a laser irradiation for a required period of time, a weight of the steel sample  63  is measured, and a difference between the present weight and the weight of the steel sample  63  obtained immediately after the above described preliminary irradiation is used as a weight of the sample. As a result, a content of C and S in the sample can be determined on the basis of the weight which was finally obtained and the above described amounts of C and S measured. 
     In order to measure each amount of N and H (content) contained in the steel sample  63 , an inert gas (for example, argon gas) is used in place of oxygen gas. Also in the case of measuring N and H, the flow channel extending from the irradiation cell  61  to the mass spectrometer  12  is purged by means of argon gas, and a similar preliminary irradiation is made upon the steel sample  63  to clean the steel sample  63  prior to analysis of these N and H as in the above described case of C and S. 
     After measuring a weight of the above described steel sample  63 , it is set on the sample resting portion  64 . Thereafter, air and the like in the flow channel is excluded by purging again with the use of argon gas. The laser beam  71  is irradiated to a predetermined site of the bottom surface  63   a  (a portion to be analyzed) of the steel sample  63  while supplying argon gas into the cell space  62 . The portion to be analyzed of the steel sample  63  which has been irradiated by the laser beam  71  in the argon gas stream as described above comes to be a high temperature, so that N and H contained in the steel sample  63  are changed to N 2  gas, and H 2  gas, respectively. A gas G containing these gases N 2  and H 2  flows into a gas flow passage  81  through a gas outlet  80  with aid of argon gas as a carrier gas. In this case, both the three-way electromagnetic valves  83  and  85  in the gas flow passage  81  are turned off, so that a bypass flow passage  87  is in an opened state. Accordingly, the above described gas G containing N 2  gas, and H 2  gas flows through the dust filter  82 , the three-way electromagnetic valve  83 , a bypass flow channel  87 , and the three-way electromagnetic valve  85 , and finally the gas G reaches the sampling section  86 . In this occasion, dust contained in the H 2  gas and the like is removed by the dust filter  82 . Accordingly, the gas G in the former part of the sampling section  86  contains N 2 , and H 2  as its components. 
     When the gas G is sampled at a constant interval in a constant amount in the sampling section  86  and these samples are fed to the mass spectrometer  12 , amounts of N and H can be measured. In this case also, when weights of the steel sample  63  before and after irradiating laser beam while jetting argon gas to a portion to be analyzed of the steel sample  63  are measured, contents of N and H in the steel sample  63  can be also determined. 
     As mentioned above, since the element analyzer is constituted so that the laser beam  71  is irradiated onto the metal sample  63  in an oxygen or inert gas stream to produce gases, and these gases are introduced to the mass spectrometer  12  together with the oxygen gas or the inert gas, unlike a conventional element analyzer wherein a weighed metal sample is placed in a graphite crucible, a problem of an erroneous or blank value due to contamination in case of employing a graphite crucible and the like is solved, so that even in the case where C, S, N, and H are merely contained in the metal sample  63  at a slight amount (ppm or less), respectively, these components can be quantitatively analyzed precisely and positively. 
     As is understood from the above description, the flow channel extending from the irradiation cell  61  to the mass spectrometer  12  is purged, and the metal sample  63  is cleaned over a wide range including a portion to be analyzed therein before conducting a quantitative analysis, so that a result of measurement with high precision can be obtained in the present preferred embodiment, although it is not required for consideration with respect to contamination in case of arranging or the handling of a sample. 
     Furthermore, in the aforementioned embodiment, a detecting section for detecting gas components is sufficient for only one mass spectrometer  12 , it is not required to provide a plurality of analyzing sections each having a different measuring principle unlike the arrangements in the prior art. Moreover, there is a remarkable advantage in that C and S/N and H can be analyzed by one analyzing section by means of switching a gas to be supplied to the irradiation cell  61  to the other. 
     In the above-mentioned preferred embodiment, although it has been constituted so that either oxygen gas or an inert gas may be selectively supplied with respect to the internal space  62  of the irradiation cell  61 , merely either of an oxygen gas cylinder or an inert gas cylinder  90  may be joined to the upstream of the gas feed passage  75  through valve  89  as shown in FIG. 16 instead of the above described arrangement. For instance, when the oxygen gas cylinder  90  is coupled upstream of the gas feed passage  75 , oxygen gas is fed to the internal space  62  of the irradiation cell  61 , so that at least either one of C and S contained in the metal sample  63  can be analyzed quantitatively. On the other hand, when the inert gas cylinder  90  is coupled the upstream of the gas feed passage  75 , at least either one of N and H contained in the metal sample  63  can be analyzed quantitatively. 
     While the mass spectrometer  12  has been employed as a detecting section in the aforementioned embodiment, another detecting mechanism may be utilized in place of the mass spectrometer  12 . More specifically, in case of feeding oxygen gas to the irradiation cell  61 , NDIR may be used, while when an inert gas is passed through the irradiation cell  61 , a thermal conductivity meter may be utilized. 
     FIG. 17 shows a preferred embodiment according to a seventh embodiment wherein an element analyzer of the present embodiment can analyze at least any one element of C, S, and N. In the system for analyzing elements shown in FIG. 17, a gas prepared by admixing hydrogen gas with a basic inert gas at a certain ratio (for example, hydrogen gas: inert gas=2:8) is supplied to an irradiation cell  61 . In FIG. 17, reference numerals  91 , and  92  designate a hydrogen gas cylinder, and an inert gas cylinder, respectively, and they are connected to a gas flow passage  75  through flow regulating valves  93  and  94  as well as flow meters  95  and  96 , respectively. Furthermore, reference numeral  97  denotes a dehydrator having a function for removing a dust filter and disposed on a produced gas flow passage  81 . It is to be noted that the constitutional components other than those described above are the same with that shown in FIG. 15, so that they are designated by the same reference numerals as that of FIG.  15 . 
     In the following, operation of the element analyzer having the above described constitution will be described and steel is used as a metal sample  63 . A steel material to be analyzed is cut out by means of a cutter into a block-shaped piece having a suitable dimension, the cut out surface thereof is ground sufficiently by the use of a sandpaper to prepare the metal sample  63 . The metal sample  63  thus prepared is set on a sample resting portion  64  of the irradiation cell  61  so that a plane  63   a  thus ground of the metal sample  63  is directed in a downward direction. 
     In this embodiment, purging of air and the like, and preliminary irradiation of laser beam are carried out before conducting quantitative analysis of elements. More specifically, the valves  93  and  94  are opened to supply a gas prepared by admixing oxygen gas with an inert gas (for example, argon gas) in a ratio of about 2:8 (hereinafter referred to simply as “mixed gas”) to the cell space  62  of the irradiation cell  61 , whereby a flow channel extending from the irradiation cell  61  to the mass spectrometer  12  is purged, so that air and the like remaining in the flow channel is exhausted. Thereafter, the laser oscillator  70  is operated to irradiate the laser beam  71  onto the bottom surface  63   a  of the steel sample  63  under a state where the mixed gas is supplied to the cell space  62 , whereby contamination produced at the time of cutting, grinding, or handling of the bottom surface  63   a  is removed. In the preliminary radiation for cleaning a sample, it is preferred to irradiate the bottom surface  63   a  of the steel sample  63  over a wider range than that in case of analysis thereof by such a manner that the three-dimensional stage  68  is operated to transfer suitably the irradiation cell  61  together with the steel sample  63  in two-dimensional directions, or to change an angle of the mirror  72 . 
     When the above described preliminary irradiation is completed, the steel sample  63  which has been cleaned is removed from the sample resting portion  64 , the steel sample  63  thus removed is weighed, and then it is set on the sample resting portion  64 . Thereafter, air and the like in the flow channel is excluded by purging again the same with the use of the mixed gas. 
     A quantitative analysis for elements is carried out in accordance with the manner as described hereinafter. The laser beam  71  is irradiated to a predetermined site of the above described bottom surface  63   a  (a portion to be analyzed) while supplying the mixed gas into the cell space  62 , and more specifically, while jetting the mixed gas to the bottom surface  63   a  of the steel sample  63  from the extreme end of the gas jetting nozzle  74 . In this case, it is preferred that the laser beam  71  is irradiated so as to focus on a position which deviates from the bottom surface  63   a  of the steel sample  63  by several μm towards the inside of the cell space  62 , and that the bottom surface  63   a  is scanned along X-Y directions as a result of operating the three-dimensional stage  68 . 
     The portion to be analyzed of the steel sample  63  which has been irradiated by the laser beam  71  in the above described mixed gas stream reaches a high enough temperature to be vaporized, so that C, S, and N contained in the steel sample  63  can react with the hydrogen gas contained in the mixed gas to produce CH 4 , H 2 S, and NH 3 , respectively. A gas G containing these gases flows into a gas flow passage  81  through a gas outlet  80  with aid of the mixed gas as a carrier gas. At a point halfway thereof, dust and/or moisture are removed by a dehydrator  97  having a function to act also as a dust filter. Accordingly, the gas G in the former part of the sampling section  86  contains CH 4 , H 2 S, and NH 3  as its only components. 
     The gas G containing the above described CH 4 , H 2 S, and NH 3  is sampled at a constant interval in constant amounts in the sampling section  86 , and these samples are fed to an ionizing section  13  of the mass spectrometer  12 . In the ionizing section  13 , CH 4 , H 2 S, and NH 3  are ionized to CH 4   +  (m/z=16), H 2 S+(m/z=34), and NH 3   +  (m/z=17), respectively, and they are subjected to a mass spectrometric analysis in an analyzing section  24 . Based on the results obtained, the amounts of C, S, and N can be obtained. 
     After conducting mass spectrometric analysis through effecting laser irradiation for a required period of time, the weight of the steel sample  63  is measure and a difference between the present weight and the weight of the steel sample  63  obtained after the above described preliminary irradiation is used as a weight of the sample. As a result, a content of C, S, and N in the sample can be determined on the basis of the weight which was finally obtained and the above described amounts of C, S, and N measured. 
     According to the element analyzer of the present preferred embodiments, the following advantages are obtained. Namely, since the element analyzer according to the present embodiment is constituted so that the laser beam  71  is irradiated onto the metal sample  63  in a mixed gas (a basic inert gas containing hydrogen gas) stream to produce CH 4 , H 2 S, NH 3  and the like gases, and these gases are introduced to the mass spectrometer  85  together with the above described mixed gas unlike a conventional system for analyzing elements wherein a weighed metal sample is placed in a graphite crucible. Accordingly, a problem of blank value readings due to contamination in the case of employing a graphite crucible and the like is solved, so that even in a case where C, S, and N are merely contained in the metal sample  63  at a slight amount (ppm or less), respectively, these components can be quantitatively analyzed precisely and positively. 
     As is understood from the above description, a flow channel extending from the irradiation cell  61  to the mass spectrometer  12  is purged, and the metal sample  63  is cleaned over a wide range including a portion to be analyzed therein before conducting a quantitative analysis, so that a measurement with high precision can be obtained in the present preferred embodiments, although contamination in the case of handling a sample is not considered. 
     Furthermore, in the aforementioned preferred embodiments according to the fourth to the seventh embodiments, only one mass spectrometer  12  is sufficient therefor as a detecting section for detecting gas components, so that it is not required to provide a plurality of analyzing sections each having a different measuring principle unlike arrangements in the prior art. 
     Moreover, in the above described preferred embodiments according to the fourth to the seventh embodiments, a mass spectrometer of time of flight (TOF-MS) type may be employed in place of the above described mass spectrometer  12  of a so-called Q-MS type. In this case, since it is required to sample instantaneously the gas G, it is preferred to arrange a pulse-formed electric field for the gas in case of, for example, ionizing the same in the electric field, so that only the gas which is ionized is introduced into the TOF-MS. 
     Besides, in the preferred embodiments, it may be arranged so that the gas G produced in the irradiation cell  61  is introduced to the mass spectrometer  12  without any processing (the gas is not passed through the filters  82  and  97 ), and in such a case, Fe (iron) can be detected in the mass spectrometer  12 . 
     FIG. 18 shows a preferred embodiment according to an eighth embodiment of the invention wherein the element analyzer in the present embodiment can analyze quantitatively at least any one element of C, S, N, and H. 
     In FIG. 18, reference numeral  101  designates a cylindrical extracting cell having, for example, 20 mm inner diameter and 130 mm length, and made of a quartz tube which is disposed vertically. Reference numeral  102  denotes a sample holder functioning also as a member for sealing a lower opening of the extracting cell  101 , and which is transferred in a vertical direction (indicated by arrows A and B) by means of a vertically moving mechanism  103 , thereby to seal or release the lower opening of the extracting cell  101 . Reference numeral  104  designates a high-frequency coil (referred to also as “levitation coil”) for levitating a metal sample  105  and heating to melt the same as it stands, The coil is transferred in a vertical direction along the longitudinal direction of the extracting cell  101  (in the direction along arrows A and B) by means of a vertically moving mechanism  106 , and is stopped at a desired position. To the high-frequency coil  104  is connected a high-frequency power source which is not shown. 
     Reference numeral  107  denotes agas jetting nozzle for introducing a gas into the extracting cell  101 , the end  107   a  of which is directed to a downward direction, and to the upstream side of which is joined a gas feed passage  108 . Further, an inert gas cylinder  111  and an oxygen gas cylinder  112  are coupled to the gas feed passage  108  through valves  109  and  110 , respectively. 
     Reference numeral  113  designates a gas exhaust pipe for taking out a gas produced in the extracting cell  101 , and to the downstream side of which is connected a gas flow passage  114 . Moreover, the gas flow passage  114  is provided with a dust filter  115  for removing oxidized dust such as iron oxide contained in the produced gas, a three-way electromagnetic valve  116 , a dehumidifier  117  for removing water vapor (moisture) contained in the produced gas, a three-way electromagnetic valve  118 , and a sampling section  119 , respectively. Further, reference numeral  120  denotes a gas flow passage disposed to communicate the three-way electromagnetic valve  116  with the three-way electromagnetic valve  118  so as to bypass the dehumidifier  117 . Either of portions on the downstream side of the-sampling section  119  is connected to the above described mass spectrometer  12  through a flow channel  121 , while the other portion is connected to an exhaust section (not shown). 
     In the following, operation of the element analyzer having the above described constitution will be described wherein steel is employed as the metal sample  105 . The steel being an object to be analyzed is cut out by means of a cuter to obtain a columnar or spherical piece having a suitable dimension (a weight of which is about 1.5 g). The metal sample  105  thus obtained is rested on a sample holder  102 . 
     Then, the sample holder  102  is raised along a direction indicated by the arrow A to position the metal sample  105  in the extracting cell  101 , and the lower opening of the extracting cell  101  is closed at the same time. The valve  109  is opened to feed an inert gas (for example, helium gas) from the gas jetting nozzle  107  into the extracting cell  101  while maintaining this situation. 
     The high-frequency coil  104  is lowered in a direction indicated by the arrow B to position the metal sample  105  inside the high-frequency coil  104  while keeping the above described situation. In this situation, when a high-frequency current is applied to the high-frequency coil  104 , an upward force (in a direction indicated by the arrow A) acts upon the metal sample  105  by means of an interaction between an induction current induced by the metal sample  105  and a magnetic field of the high-frequency coil  104 , whereby the metal sample  105  is levitated (high-frequency levitation) in the extracting cell  101  while maintaining a balance with the gravitational force. Thus, it is adjusted so that the high-frequency coil  104  is transferred upwardly to position the metal sample  105  levitated by high-frequency at a position where it is 10 to 20 mm downward from a nozzle hole  107   a  of the gas jetting nozzle  107  which is jetting helium gas. 
     On the other hand, an induction current flows through the metal sample  105  itself at the same time of the above described levitation to produce Joule heat, whereby the metal sample  105  is heated to a molten state. It is preferred to control heating of the metal sample  105  at a temperature of up to 1000° C. by adjusting a magnitude of a high-frequency current applied to the high-frequency coil  104 . As mentioned above, when the metal sample  105  is molten in a helium gas stream, H contained in the metal sample  105  is extracted in the form of H 2  gas. 
     The H 2  gas produced as mentioned above flows into a produced gas flow passage  114  through a gas taking-out pipe  113  with the aid of helium gas as a carrier gas. In this case, both the three-way electromagnetic valves  116  and  118  in the produced gas flow passage  114  are turned off, so that a bypass flow passage  120  is in an opened state. Accordingly, the above described H 2  gas and the like flow through the dust filter  115 , the three-way electromagnetic valve  116 , a bypass flow channel  120 , and the three-way electromagnetic valve  118 , and finally these gases reach the sampling section  119 . In this occasion, dust contained in the above described H 2  gas and the like is removed by the dust filter  115 . Accordingly, the gas in the former part of the sampling section  121  contains H 2  as its components. 
     The gas containing H 2  is sampled at a constant interval in constant amounts in the sampling section  119 , and these samples are fed to an ionizing section  13  of the mass spectrometer  12 . In the ionizing section  13 , H 2  is ionized to H 2   30   (m/z=2), and it is subjected to mass spectrometric analysis in an analyzing section  24 . Based on the results obtained, an amount of H can be obtained. 
     When the extraction of H 2  at a temperature of 1000° C. or less is finished, a gas to be fed to the extracting cell  101  is switched from helium gas to oxygen gas. In other words, the valve  109  is closed, while the valve  110  is opened. 
     Under the condition where oxygen gas is supplied to the above described extracting cell  101  through the gas jetting nozzle  107 , a magnitude of high-frequency current to be applied to the high-frequency coil  104  is increased to burn up the metal sample  105  at a temperature of 1000° C. or more. As mentioned above, when the metal sample  105  is burned up in oxygen gas stream, CO x (CO, CO 2 ), SO x (SO 2 , SO 3 ), and NO x (N 2 O, NO, NO 2 , . . . ) are produced. 
     The gases CO x , SO x , and NO x  produced as mentioned above flow into the produced gas flow passage  114  through the gas taking-out pipe  113  with the aid of oxygen gas as a carrier gas. In this case, both the three-way electromagnetic valves  116  and  118  in the produced gas flow passage  114  are turned on, so that the bypass flow passage  120  is in a closed state. Accordingly, the above described gases CO x , SO x , NO x  and the like flow through the dust filter  115 , the three-way electromagnetic valve  116 , a dehumidifier  117 , and the three-way electromagnetic valve  118 , and finally these gases reach the sampling section  119 . In this occasion, oxidized dust such as iron oxide contained in the above described CO x , SO x , NO x  and the like gases is removed by the dust filter  115 , while water vapor is removed by the dehumidifier  117 . Accordingly, the gas in the former part of the sampling section  121  contains CO x ,SO x  and NO x  as its components. 
     The above described gas containing CO x , SO x  and NO x  is sampled at a constant interval in constant amounts in the sampling section  119 , and these samples are fed to the ionizing section  13  of the mass spectrometer  12 . In the analyzing section  24 , they are subjected to mass spectrometric analysis. Based on the results obtained, each amount of C, S, and N can be obtained. 
     As mentioned above, the element analyzer according to the present preferred embodiments is constituted so that the metal sample  105  is subjected to levitating fusion in an inert gas or an oxygen gas stream, and the gas containing H 2  or CO x , SO x  and NO x  produced at that time is introduced to the mass spectrometer  12  together with the above described inert gas or oxygen gas unlike a conventional element analyzer wherein a weighed metal sample is placed in a graphite crucible, so that a problem of blank value due to contamination in case of employing a graphite crucible and the like is solved, and hence, even in the case where C, S, N, and H are merely contained in the metal sample  105  at a slight amount (ppm or less), respectively, these components can be analyzed quantitatively in a precise and positive manner. 
     Furthermore, in the aforementioned preferred embodiment, since one mass spectrometer  12  is sufficient as a detecting section for detecting gas components, it is not required to provide a plurality of analyzing sections each having a different measuring principle unlike an arrangement in the prior art. Moreover, there is a remarkable advantage in that elements C, S, N, and H can be analyzed in a single analyzing section by merely switching a gas to be supplied to the extracting cell  101  with another gas. 
     Since the above described embodiment is arranged so that the high-frequency coil  104  transfers vertically along the longitudinal direction of the extracting cell  101 , it is not required to separately provide a means for positioning the metal sample  105  at a predetermined site of the high-frequency coil  104 . Thus, the potential of contamination from a crucible is eliminated and an induction current will flow directly through the metal sample for heating and melting the metal sample. 
     In the aforementioned embodiment, although an inert gas or oxygen gas has been supplied to the extracting cell  101  by switching from one source to another source, either one of an inert gas and oxygen gas may be supplied to the extracting cell  101  instead of the former arrangement. 
     FIG. 19 shows a preferred embodiment according to a ninth embodiment of the invention, and more specifically, oxygen gas is supplied to an extracting cell  101 , that is, an oxygen gas cylinder  112  is coupled to a gas feed passage  108  joined to the extracting cell  101 . When the system is constituted as described above, quantitative analysis of C, S, and N contained in the metal sample  105  can be conducted as is understood from the above description, so that the constitution in the produced gas feed passage  114  becomes simple. 
     Furthermore, in the element analyzer shown in FIG. 19, when an inert gas cylinder is connected to the gas feed passage  108  in place of the oxygen gas cylinder  112  and further, the dehumidifier  117  removed, H in the metal sample  105  can be quantitatively analyzed. 
     The present invention is not limited to the above described embodiments, for example, the high-frequency coil  104  can be fixedly disposed instead of transferred in a vertical direction, and the sample holder  102  is transferred vertically in the extracting cell  101  so that the metal sample  105  may be positioned at a predetermined site of the high-frequency coil  104 . 
     In preferred embodiments, a mass spectrometer of a time of flight (TOF-MS) type may be employed in place of the above described mass spectrometer  12  of a so-called Q-MS type. In this case, since it is required to sample instantaneously the produced gas G, it is preferred to arrange a pulse-formed electric field to be prepared for the gas in case of, for example, ionizing the gas in the electric field, and only the gas ionized is introduced into the TOF-MS. 
     According to the present invention, elements such as C, S, O, N, H and the like, even in a slight amount, respectively, in a raw material such as steel, ceramics and the like, can be quantitatively analyzed positively at high sensitivity and order of weight ppm or less, for example, 0.1 to 0.01 ppm. 
     It will be appreciated by those of ordinary skill in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than the foregoing description, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.