Abstract:
An analyzing device includes a splitting part for causing fluid containing a sample component to flow separately in a first flow passage and a second flow passage; an analyzing column provided on the first flow passage for separating the sample component from the fluid; a first back pressure regulating valve corresponding to a first pressure controlling unit for controlling a pressure in the first flow passage; and a second back pressure regulating valve corresponding to a second pressure controlling unit for controlling a pressure in the second flow passage, wherein flow rate of the fluid in the first flow passage and flow rate of the fluid in the second flow passage are controlled based on a ratio of the pressure in the first flow passage to the pressure in the second flow passage.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an analyzing device that separates a plurality of components contained in a sample into the individual components, and specifically, relates to a chromatograph using supercritical fluid. 
       BACKGROUND ART 
       [0002]    Supercritical fluid can be realized by holding fluid that is gas at normal temperature and normal pressure (for example, carbon dioxide) at higher temperature and pressure than those at the critical point of the fluid (in the case of carbon dioxide, the critical temperature is 31° C. and the critical pressure is 7.4 MPa). The supercritical fluid exhibits excellent ability as solvent to many substances, and is often used for supercritical fluid extraction (hereinafter referred to as SFE) and supercritical fluid chromatography (hereinafter referred to as SFC). 
         [0003]    Patent Literature 1 discloses an extraction and separation/analyzing device using supercritical fluid which can perform any of SFE and SFC by switching between a flow system for SFE and a flow system for SFC with a switching valve. With separate SFE and SFC flow systems, a component extracted from a sample by SFE is first trapped in a trap column, and then, is eluted with a solvent. Therefore, in order to measure the SFE-extracted substances by the chromatograph, human intervention is needed for adjusting the concentration of the extracted substance and placing it in a sample introducing unit of the chromatograph. As such, with an off-line configuration in which extracted substances are not directly introduced into a column, a series of operations from extraction to analysis cannot be automatically performed. 
         [0004]    Patent Literature 2 discloses an analyzing device using supercritical fluid which has an on-line configuration in which SFE and SFC are integrated into one flow system, and is capable of automatically performing a series of operations from extraction to analysis. An example of such an analyzing device with the on-line configuration is shown in  FIG. 3 . 
         [0005]    The analyzing device  30  of  FIG. 3  is configured of a cylinder  300 , a pressurizing pump  301 , a solvent container  302 , a modifier pump  303 , a first flow passage switching valve  304 , a sample storing container  305 , a temperature adjusting device  306 , a needle  307 , a second flow passage switching valve  308 , an analyzing column  309 , an ultraviolet detector (UV)  310 , a back pressure regulating valve  311  and a mass spectrometer (MS)  312 . 
         [0006]    Carbon dioxide that is drawn out of the cylinder  300  by the pressurizing pump  301  and pressurized (to supercritical fluid) is sent, via the first flow passage switching valve  304  along with a modifier agent drawn out of the solvent container  302 , to the sample storing container  305  which is temperature controllable by the temperature adjusting device  306 . By the pressurizing pump  301  and the later-mentioned back pressure regulating valve  311 , the pressure of the flow passage between them is set to a pressure exceeding the critical pressure, and the temperature of the sample storing container  305  is set to a temperature exceeding the critical temperature by the temperature adjusting device  306 . Thereby, carbon dioxide is put into supercritical state inside the sample storing container  305 , and the supercritical carbon dioxide, with its excellent capability as solvent, extract components from a sample in the sample storing container  305  (SFE). 
         [0007]    The supercritical fluid containing the SFE-extracted components flows into the analyzing column  309  from the needle  307  attached to the sample storing container  305  via the second flow passage switching valve  308 . The supercritical fluid containing the SFE-extracted components is separated to individual components by the analyzing column  309 , and then, flows through the ultraviolet detector (UV)  310 , the back pressure regulating valve  311  and the mass spectrometer (MS)  312 , where the individual components are analyzed (SFC). 
       CITATION LIST 
     Patent Literature 
       [0008]    [Patent Literature 1] JP 4-332863 A 
         [0009]    [Patent Literature 2] JP 60-8747 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    When an agricultural product is analyzed as a sample by a chromatograph to measure the amount of pesticide residues in the agricultural product using the conventional analyzing device  30 , a large amount of substances that constitute noise to the analysis of the pesticide, such as pigments, lipids and saccharides in the agricultural product itself, are extracted in addition to the target component in the SFE-extracted components. With the configuration of the conventional analyzing device  30 , when such a sample is analyzed, the entirety of the SFE-extracted components is introduced into the analyzing column  309 . Consequently, the analyzing column  309  tends to deteriorate due to the large amount of unwanted constituents, and saturation of the ultraviolet detector (UV)  310  and contamination of the mass spectrometer (MS)  312  tend to arise. As such, for some samples, the analyzing device  30  may be burdened or correct measurement may be difficult, which narrows the range of analyzable samples of the analyzing device  30  and lessens its versatility. 
         [0011]    A problem to be solved by the present invention is to provide a highly versatile analyzing device that widens the range of analyzable samples. 
       Solution to Problem 
       [0012]    An analyzing device according to the present invention devised to solve the aforementioned problem includes: 
         [0013]    a) a splitting part for causing fluid containing a sample component to flow separately in a first flow passage and a second flow passage; 
         [0014]    b) a column provided on the first flow passage for separating the sample component from the fluid; 
         [0015]    c) a first pressure controlling unit for controlling a pressure in the first flow passage; and 
         [0016]    d) a second pressure controlling unit for controlling a pressure in the second flow passage, wherein 
         [0017]    flow rate of the fluid in the first flow passage and flow rate of the fluid in the second flow passage are controlled based on a ratio of the pressure in the first flow passage to the pressure in the second flow passage. 
         [0018]    Moreover, an analyzing method according to the present invention devised to solve the aforementioned problem includes the steps of: 
         [0019]    a) controlling a pressure in a first flow passage by a first pressure controlling unit; 
         [0020]    b) controlling a pressure in a second flow passage by a second pressure controlling unit; 
         [0021]    c) controlling flow rate of fluid containing a sample component in the first flow passage and flow rate of fluid containing a sample component in the second flow passage based on a ratio of the pressure in the first flow passage to the pressure in the second flow passage; 
         [0022]    d) splitting the fluid to flow separately in the first flow passage and the second flow passage by means of a splitting part; and 
         [0023]    e) separating the sample component from the fluid using a column provided on the first flow passage. 
         [0024]    The “fluid” is preferably supercritical fluid, but it is not limited to this, and it may be gas or liquid. When the fluid is supercritical fluid, the pressure in the first flow passage and the pressure in the second flow passage are set such that a sum of values of these pressures is a value of a pressure exceeding a critical pressure of the fluid. 
         [0025]    Both of the first pressure controlling unit and the second pressure controlling unit may have pressure controlling valves, and the pressure controlling valves may be provided on the first flow passage and the second flow passage respectively. 
         [0026]    Upstream of the splitting part, an extracting unit (SFE Unit) for performing extraction using supercritical fluid (SFE) may be connected, or a sample injecting unit (auto-sampler) may be connected. In other words, there may be applied an on-line configuration in which SFE and SFC are integrated into one flow system or a configuration in which only chromatography using supercritical fluid (SFC) can be performed. 
       Advantageous Effects of Invention 
       [0027]    According to the analyzing device and the analyzing method according to the present invention having the aforementioned configurations, by changing the ratio of the pressure in the first flow passage to the pressure in the second flow passage using the first pressure controlling unit and the second pressure controlling unit, the flow rate of the fluid in the first flow passage and flow rate of the fluid in the second flow passage after split at the splitting part can be controlled. When a large amount of unwanted constituents for analysis are contained in the fluid containing the sample components, the flow rate of the fluid in the column provided on the first flow passage is reduced such that the entirety of the unwanted constituents is not introduced into the column. This can suppress deterioration of the column and can reduce burden on the analyzing device. In this way, a highly versatile analyzing device that can widen the range of analyzable samples can be provided. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0028]      FIG. 1  is a schematic configuration diagram of an analyzing device according to a first embodiment of the present invention. 
           [0029]      FIG. 2  is a schematic configuration diagram of an analyzing device according to a second embodiment of the present invention. 
           [0030]      FIG. 3  is a schematic configuration diagram of a conventional analyzing device. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0031]    Hereafter, modes for implementing the present invention are described with reference to embodiments. 
       First Embodiment 
       [0032]      FIG. 1  is a schematic configuration diagram of an analyzing device of a first embodiment. The analyzing device  10  of this embodiment is configured of a cylinder  100 , a pressurizing pump  101 , a solvent container  102 , a modifier pump  103 , an extracting unit  114 , an analyzing column  109 , a splitting part  110 , a first back pressure regulating valve  111 , a second back pressure regulating valve  112 , a mass spectrometer (MS)  113  and a recovering container  115 . The extracting unit  114  is configured of a first flow passage switching valve  104 , a sample storing container  105 , a temperature adjusting device  106 , a needle  107 , a second flow passage switching valve  108 , and pipes connecting these. 
         [0033]    The analyzing device  10  of this embodiment has a feature of including the splitting part  110 , the first back pressure regulating valve  111  and the second back pressure regulating valve  112 . Fluid containing sample components flows in pipes separately in two flow passages of a first flow passage and a second flow passage by means of the splitting part  110 . This embodiment has an on-line configuration in which the extracting unit  114  is directly connected upstream of the splitting part  110 , and the analyzing column  109  is directly connected to the first flow passage downstream thereof Hereafter, description will be made to a case where the extracting unit  114  extracts pesticide residues contained in a sample (agricultural product) by SFE using carbon dioxide as supercritical fluid, and the analyzing column  109  separates components in the pesticide residues. The first back pressure regulating valve  111  and the second back pressure regulating valve  112  that are pressure controlling valves correspond to a first pressure controlling unit and a second pressure controlling unit, respectively. The analyzing device  10  operates as follows to separate a plurality of components contained in extracted substances by the extracting unit  114  into the individual components using the analyzing column  109 , thereby to identify the individual components by the mass spectrometer  113 . 
         [0034]    First, an agricultural product as a sample is put in the sample storing container  105 , to one end of which the needle  107  is attached. These operations may be performed by a user or may be performed by a not-shown controlling device. In this way, the individual parts are connected as in  FIG. 1 . One or plurality of sample storing container s 105  may be prepared as in  FIG. 1 , and a configuration may be adopted in which extraction for a plurality of samples can be performed. 
         [0035]    Next, carbon dioxide (supercritical fluid) is drawn out of the cylinder  100  under pressurization by the pressurizing pump  101 . Also, a modifier agent that is a polar solvent (methanol, ethanol or the like) is drawn out of the solvent container  102  by the modifier pump  103 . These are sent, via the first flow passage switching valve  104 , to the sample storing container  105  which is temperature controllable by the temperature adjusting device  106  such as a heater. When the pressure in a flow passage between the pressurizing pump  101  and the splitting part  110  is set to be a pressure exceeding the critical pressure (7.4 MPa) of carbon dioxide by the pressurizing pump  101  and the later-mentioned first back pressure regulating valve  111  and second back pressure regulating valve  112 , and the sample storing container  105  is set to have a temperature exceeding the critical temperature (31° C.) of carbon dioxide by the temperature adjusting device  106 , carbon dioxide is in the supercritical state (supercritical fluid) inside the sample storing container  105 . Since carbon dioxide in the supercritical state exhibits excellent ability as solvent, it dissolves the sample (agricultural product) in the sample storing container  105 . Thereby, in addition to pesticide residues that are the target components in the sample, a large amount of substances that constitute noise to analysis of the pesticide residues, such as pigments, lipids and saccharides, are extracted (SFE). 
         [0036]    The supercritical fluid containing the SFE-extracted components reaches the splitting part  110  from the needle  107  via the second flow passage switching valve  108 , and splits thereat into the first flow passage and the second flow passage. The analyzing column  109  heated at a temperature exceeding the critical temperature by a not-shown column oven is provided on the first flow passage, and thus the supercritical fluid containing the SFE-extracted components and flowing in the first flow passage is in the supercritical state inside the analyzing column  109 . After the components are separated thereat into individual components, the supercritical fluid flows in the first back pressure regulating valve  111  and the mass spectrometer (MS)  113 , where the individual components are analyzed (SFC). In this configuration, a detector (ultraviolet detector (UV)  310  or the like) (not shown) may be provided between the analyzing column  109  and the first back pressure regulating valve  111 , and the mass spectrometer  113  is not essential. After the supercritical fluid containing the SFE-extracted components and flowing in the second flow passage is released from the supercritical state by flowing in the second back pressure regulating valve  112 , it is recovered by the recovering container  115 . 
         [0037]    Description will now be made to a case where structures (sectional shapes and sizes of sectional areas) and materials of the pipes constituting the first flow passage and the second flow passage are substantially the same and no difference occurs in resistances of the fluid due to them. In the case where the pipes constituting the first flow passage and the second flow passage have substantially the same structure, and the resistance of the analyzing column  109  is eliminated, flow rate of fluid in the first flow passage and flow rate of fluid in the second flow passage are determined by a split ratio depending on the ratio of the pressures in these flow passages. 
         [0038]    Assume that the pressure in the first flow passage controlled by the first back pressure regulating valve  111  is P 1 , the pressure in the second flow passage controlled by the second back pressure regulating valve  112  is P 2 , and the resistance of the analyzing column  109  is eliminated for convenience of description. When the flow rate upstream of the splitting part  110  is, for example, 10 mL/min, the split ratio of the first flow passage to the second flow passage can be set to be 1:99, that is, P 1 =99P 2 , and most of the fluid flows in the second flow passage at low pressure, and the flow rate of the fluid in the analyzing column  109  reaches 0.1 mL/min. In reality, although the resistance of the analyzing column  109  cannot be ignored, the values of the pressures P 1  and P 2  which realize a desired split ratio can be grasped by investigating relation between the ratio of the pressures P 1  to P 2  and the flow rate in advance thorough a preliminary experiment. When using supercritical fluid, the sum of the values of the pressure P 1  in the first flow passage and the pressure P 2  in the second flow passage should be set to be the value of a pressure exceeding the critical pressure of the fluid. 
         [0039]    By changing the ratio of the pressure P 1  in the first flow passage to the pressure P 2  in the second flow passage using the first back pressure regulating valve  111  and the second back pressure regulating valve  112  as above, the flow rate of the fluid in the first flow passage and the flow rate of the fluid in the second flow passage after split at the splitting part  110  can be controlled. When a large amount of substances that constitute noise to analysis are contained in the fluid containing the sample components, the flow rate of the fluid in the analyzing column  109  provided on the first constitute noise to the is reduced as in the aforementioned example of the split ratio 1:99 in order to prevent the entirety of the fluid from being introduced into the analysing column  109 . This supresses, deterioration of the analyzing column  109  and reduces burden on the analyzing device  10 . In this way, even a sample from which a large amount of substances that are unwanted constituents can be an analysis target, which can enhance versatility of the analyzing device. 
         [0040]    In the conventional on-line configuration shown in  FIG. 3  in which SFE and SFC are integrated into one flow system, while it is desired for SFE to increase the flow rate in the sample storing container  305  for prioritizing the speed for extraction, it is desired for SFC to reduce the flow rate in the analyzing column  309  for prioritizing separation using the analyzing column  309 . In other words, since SFE and SFC have a trade-off relationship for the flow rates, extraction time has had to be sacrificed to prioritize precision of separation by SFC, or the precision of separation has had to be sacrificed to prioritize the speed of extraction by SFE, or an intermediate flow rate has had to be set such that both of the extraction time and the precision of separation were sacrificed in some extent. Therefore, there has been conventionally a case where since the flow rate of the fluid containing the sample components and flowing in the analyzing column  309  is larger than that suitable for SFC, the fluid has passed through the analyzing column  309  without sufficient separation of the sample components, which causes peak broadening (causes broad peaks). When using supercritical fluid, its excellent ability as solvent sometimes exceed the trapping ability of the analyzing column  309 , which further causes broad peaks. Such broad peaks lead to insufficient separation of the components, which interrupts accurate analysis. 
         [0041]    On the contrary, in the configuration of this embodiment, the flow rate of the fluid in the analyzing column  109  can be changed by changing the ratio of the pressure P 1  in the first flow passage to the pressure P 2  in the second flow passage. Therefore, in the case of employing the configuration in which the extracting unit  114  for performing extraction using supercritical fluid (SFE) is provided upstream of the splitting part  110 , the flow rate in the analyzing column  109  provided on the first flow passage can be reduced while the flow rate in the sample storing container  105  in the extracting unit  114  is increased, which can realize the flow rates respectively suitable for SFE and SFC. Thereby, in an on-line configuration in which SFE and SFC are integrated into one flow system, accurate analysis in which the sample components are sufficiently separated in the analyzing column  109  and broad peaks are reduced is possible. 
         [0042]    Moreover, because a portion of the fluid containing SFE-extracted components is recovered into the recovering container  115  in an on-line configuration, the portion can be subjected to subsequent analysis using another analyzing device as in the case of an off-line configuration. 
         [0043]    In this embodiment, although the example is described in which the first back pressure regulating valve  111  and the second back pressure regulating valve  112  correspond to the first pressure controlling unit and the second pressure controlling unit, respectively, and have the same piping structures, it is not limited to this, and a mechanism in which structures (sectional shapes and sizes of sectional areas) of pipes constituting the first flow passage and the second flow passage are different from each other may be used for the first pressure controlling unit and the second pressure controlling unit. 
       Second Embodiment 
       [0044]      FIG. 2  is a schematic configuration diagram of an analyzing device of a second embodiment. The analyzing device  20  of this embodiment includes a third flow passage switching valve  21  and an autosampler  22  in addition to the similar configuration to that of the analyzing device  10  of the first embodiment including the cylinder  100 , the pressurizing pump  101 , the solvent container  102 , the modifier pump  103 , the extracting unit  114 , the analyzing column  109 , the splitting part  110 , the first back pressure regulating valve  111 , the second back pressure regulating valve  112 , the mass spectrometer (MS)  113  and the recovering container  115 . 
         [0045]    In this embodiment, the third flow passage switching valve  21  is connected upstream of the splitting part  110 , and the splitting part  110  is connected to the extracting unit  114  or the autosampler  22  by changing connections between ports in the valve  21  as shown in dotted lines or solid lines. The autosampler  22  corresponds to a sample injecting unit. A configuration in which the splitting part  110  is connected to is the same with that in the first embodiment, and hereafter, description will be made to a configuration in which the splitting part  110  is connected to the autosampler  22  and only chromatography (SFC) using supercritical fluid can be performed. 
         [0046]    Under pressurization by the pressurizing pump  101 , carbon dioxide (supercritical fluid) is drawn out of the cylinder  100 . Also, a modifier agent that is a polar solvent (methanol, ethanol or the like) is drawn out of the solvent container  102  by the modifier pump  103 . They are sent to the autosampler  22  as a mobile phase (fluid) through the third flow passage switching valve  21  provided between the pressurizing pump  101  and the modifier pump  103 , and the first flow passage switching valve  104 , and a sample is injected in the autosampler  22 . The sample injected by the autosampler  22  reaches the splitting part  110  again via the third flow passage switching valve  21  on a flow of the mobile phase. In other words, in place of fluid containing SFE-extracted components using the extracting unit  114 , the mobile phase containing the sample is supplied to the splitting part  110 . Then, after the components are separated into individual components in the analyzing column  109  similarly to the first embodiment, the mobile phase flows in the first back pressure regulating valve  111  and the mass spectrometer (MS)  113 , where the individual components are analyzed (SFC). Also in this embodiment, a detector (ultraviolet detector (UV)  310  or the like) (not shown) may be provided between the analyzing column  109  and the first back pressure regulating valve  111 , and the mass spectrometer  113  is not an essential configuration. 
         [0047]    In this way, in the analyzing device  20  of this embodiment, a user can freely select and use the on-line configuration in which SFE and SFC are integrated into one flow system or the configuration in which only chromatography (SFC) using supercritical fluid can be performed by changing the connections between the ports in the third flow passage switching valve  21 . Therefore, a sample is not limited to one in the state before performing SFE, which can widen the range of analysable samples more than conventional and can enhance versatility of an analyzing device. 
         [0048]    The aforementioned embodiments are merely examples of the present invention, and it is apparent that proper variations, modification and additions within the spirit of the present invention are included in the scope of the appended claims of the present application. In any of the aforementioned embodiments, while description has been made to the case where fluid containing sample components flows separately in two flow passages of the first flow passage and the second flow passage at the splitting part  110 , a configuration of an analyzing device according to the present invention is not limited to this, but it may be configured such that it flows separately in two or more plural flow passages at the splitting part. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10 ,  20 ,  30  . . . Analyzing Device 
           21  . . . Third Flow Passage Switching Valve 
           22  . . . Autosampler 
           100 ,  300  . . . Cylinder 
           101 ,  301  . . . Pressurizing Pump 
           102 ,  302  . . . Solvent Container 
           103 ,  303  . . . Modifier Pump 
           104 ,  304  . . . First Flow Passage Switching Valve 
           105 ,  305  . . . Sample Storing Container 
           106 ,  306  . . . Temperature Adjusting Device 
           107 ,  307  . . . Needle 
           108 ,  308  . . . Second Flow Passage Switching Valve 
           109 ,  309  . . . Analyzing Column 
           110  . . . Splitting Part 
           111  . . . First Back Pressure Regulating Valve 
           112  . . . Second Back Pressure Regulating Valve 
           113  . . . Mass Spectrometer 
           114  . . . Extracting Unit 
           115  . . . Recovering Container 
           310  . . . Ultraviolet Detector 
           311  . . . Back Pressure Regulating Valve