Abstract:
Analyzers are disclosed that comprises an assay cartridge comprising a mixture measuring chamber for receiving a mixture of a sample and a dilution fluid, and a detector for detecting a signal from the mixture supplied from the mixture measuring chamber, the mixture measuring chamber having a predetermined capacity, and an amount of the mixture supplied to the detector being substantially equal to the capacity of the mixture measuring chamber; and an analyzing unit comprising a controller for analyzing the signal detected by the detector; wherein the assay cartridge is detachably mountable to the analyzing unit. An assay cartridges and analyzing method are also described.

Description:
[0001]     This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application Nos. 2003-400059 and 2003-400087 both filed Nov. 28, 2003, the entire contents of which are hereby incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to an analyzer for analyzing fluid samples by loading the removable assay cartridge provided with a detector, an assay cartridge loadable into the analyzer, and analyzing method for analyzing fluid samples using the assay cartridge.  
       BACKGROUND  
       [0003]     Analyzers for analyzing fluid samples often use an assay device provided with a maintenance-free detector which is installed in a replaceable cartridge.  
         [0004]     For example, United States Laid-Open Patent Publication No. 2002-172617 discloses an assay unit provided with a rotating valve for preparing analysate by measuring a fixed quantity of sample and mixing the sample and a reagent, and an electrical resistance measuring part for detecting a signal from a prepared analysate. This assay unit is removably installed in the assay device.  
         [0005]     In the assay unit disclosed in United States Laid-Open Patent Publication No. 2002-172617, a predetermined quantity of analysate is passed through a small hole in the electrical resistance measuring part by means of the suction operation perforemd [sic performed] for a specific time by a syringe pump provided in the assay device. Then, the number of white blood cells contained in the analysate that has passed through the small hole is counted. That is, in the assay unit, the quantity of analysate is measured by the suction time of the syringe pump.  
         [0006]     Before the suction operation of the syringe pump in this assay unit, however, the flow path is filled with air rather than fluid from the syringe pump to the electrical resistance measuring part. This air is greatly expanded compared to the fluid when the suction force is applied. Accordingly, a problem arises inasmuch as the quantity of analysate actually transferred and which passes through the small hole is not stable since an amount of expanded air is included even when the syringe pump operates a predetermined length of time. Therefore, in conventional assay units the quantity of analysate used for signal detection is unstable, and errors may occur in the analysis result.  
       SUMMARY  
       [0007]     The scope of the present invention is defined solely by the appended claims, and is not affected to any degree by the statements within this summary.  
         [0008]     An object of one embodiment of the present invention is to improve an accuracy of a result of analysis.  
         [0009]     The first aspect of the present invention relates to an analyzer comprising an assay cartridge comprising a mixture measuring chamber for receiving a mixture of a sample and a dilution fluid, and a detector for detecting a signal from the mixture supplied from the mixture measuring chamber, the mixture measuring chamber having a predetermined capacity, and an amount of the mixture supplied to the detector being substantially equal to the capacity of the mixture measuring chamber; and an analyzing unit comprising a controller for analyzing the signal detected by the detector; wherein the assay cartridge is detachably mountable to the analyzing unit.  
         [0010]     The second aspect of the present invention relates to a cartridge comprising a mixture measuring chamber for receiving a mixture of a sample and a dilution fluid, the mixture measuring chamber having a predetermined capacity; and a detector for detecting a signal from the mixture supplied from the mixture measuring chamber, an amount of the mixture supplied to the detector being substantially equal to the capacity of the mixture measuring chamber.  
         [0011]     The third aspect of the present invention relates to analyzing method embodying comprising a step of mounting an assay cartridge, which comprises a mixture measuring chamber having a predetermined capacity and a detector for detecting a signal from a mixture of a sample and a reagent, in an analyzer which comprises a controller for analyzing the signal detected by the detector; a step of introducing the mixture to the mixture measuring chamber; a step of supplying the mixture from the mixture measuring chamber to the detector; a step of detecting a signal from the mixture by the detector; and a step of analyzing the signals by the controller, wherein an amount of the mixture supplied to the detector is substantially equal to the capacity of the mixture measuring chamber.  
         [0012]     The fourth aspect of the present invention relates to an analyzer comprising an assay unit, which comprises an assay cartridge, which comprises a mixture receptacle having an opening on the inner wall near the base and capable of accommodating a mixture of sample and reagent; a projection provided on the base of the mixture receptacle and extending upward from the base; and a detector for detecting a signal from the mixture supplied through the opening; and an analyzing unit, which comprises a controller for analyzing the signal detected by the detector; wherein the assay cartridge is detachably mountable to the analyzing unit.  
         [0013]     The fifth aspect of the present invention relates to a cartridge comprising a mixture receptacle capable of accommodating a mixture of a sample and reagent, and comprising an opening on the inner wall near the base; a projection provided on the base of the mixture receptacle and extending upward from the base; and a detector for detecting a signal from the mixture supplied through the opening. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a perspective view of an embodiment of the assay cartridge of the present invention;  
         [0015]      FIG. 2  is a front view of an embodiment of the assay cartridge of the present invention;  
         [0016]      FIG. 3  is a back view of an embodiment of the assay cartridge of the present invention;  
         [0017]      FIG. 4  is a top view of an embodiment of the assay cartridge of the present invention;  
         [0018]      FIG. 5  is a bottom view of an embodiment of the assay cartridge of the present invention;  
         [0019]      FIG. 6  is a front view of an embodiment of the rotating valve of the present invention;  
         [0020]      FIG. 7  is a top view of an embodiment of the rotating valve of the present invention;  
         [0021]      FIG. 8  is a cross section view on the A-A arrow;  
         [0022]      FIG. 9  illustrates the operation of an embodiment of the rotating valve of the present invention;  
         [0023]      FIG. 10  is a cross section view on the B-B arrow of  FIG. 2 ;  
         [0024]      FIG. 11  is a cross section view on the C-C arrow of  FIG. 10 ;  
         [0025]      FIG. 12  is a cross section view on the D-D arrow of  FIG. 2 ;  
         [0026]      FIG. 13  is a perspective view of an embodiment of the analyzing unit of the present invention;  
         [0027]      FIG. 14  is a block diagram showing the structure of an embodiment of the analyzer of the present invention in which an assay cartridge is loaded in the analyzing unit;  
         [0028]      FIGS. 15 and 16  are flow charts showing the operation of an embodiment of the analyzer of the present invention; and  
         [0029]      FIGS. 17 through 27  illustrate the conditions of an embodiment of the assay cartridge of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0030]     The preferred embodiments of the present invention are described hereinafter.  
         [0031]     1. Structure of the Assay Cartridge Body  
         [0032]     As shown in  FIG. 1 , an assay cartridge  1  is provided with a first component  2  and a second component  3 . The first and second components are formed of transparent resin, for example, acrylic resin and polycarbonate resin mixed with antistatic agent, and the components are mutually adhered one to another with an air-tight seal via high-frequency welding.  
         [0033]     As shown in  FIGS. 2 and 3 , the assay cartridge  1  is internally provided with a long and slender sample receptacle  5  having a capacity of 200 μL and extending downward in a vertical direction and further having an opening  4  at the top, reagent compartment  6 , mixture measuring chamber  7 , mixture compartment (hemoglobin detector)  8 , detector  9 , overflow receptacle  10 , excess sample collector  11 , and rotating valve  12 . The bottom end of the sample receptacle  5  is connected to the rotating valve  12  through a flow path  15 . One of the ends of the U-shaped excess sample collector  11  is connected to the rotating valve  12  through a flow path  14 , and the other end is connected to the pump connector  23 .  
         [0034]     The base of the reagent compartment  6  is connected to the rotating valve  12  through a flow path  16 , and the base of the mixture compartment  8  is connected to the rotating valve  12  through a flow path  17 . Furthermore, the base of the mixture measuring chamber  7  is connected to the mixture compartment  8  by parallel flow paths  18  and  19 . A pellet (gate element)  20  is inserted between the flow paths  18  and  19 , and electrodes  21  and  22  are respectively exposed in the flow paths  18  and  19 . The detector  9  is formed by the flow paths  18  and  19 , electrodes  21  and  22 , and the pellet  20 . The top end of the mixture measuring chamber  7  is connected to the top of the overflow receptacle  10  through a flow path  13 . The top of each of the overflow receptacle  10 , reagent compartment  6 , and mixture compartment  8  respectively connected to the pump connectors  24 ,  25 , and  26  on the back side ( FIG. 3 ).  
         [0035]     A reagent injection port  27  which passes through the top of the reagent compartment  6  is provided in the front surface of the assay cartridge  1  ( FIG. 2 ), and a cap  28  is installed in the injection port  27 . Furthermore, the electrodes  21  and  22 , which are respectively exposed in the flow paths  18  and  19 , are pole electrodes formed of stainless steel and protrude from the back side of the assay cartridge  1 , as shown in  FIGS. 3 through 5 .  
         [0036]     When the assay cartridge  1  of the aforesaid construction is loaded in an analyzing unit described later, the sample within the sample receptacle  5  is measured by the rotating valve  12 . The measured sample is mixed with a reagent supplied from the reagent compartment  6  to prepare the analysate.  
         [0037]     After the hemoglobin concentration of the prepared analysate is measured in the mixture compartment  8 , the prepared analysate is measured in the mixture measuring chamber  7 . The measured analysate is subjected to the detector  9  and the number and size of the included white blood cells are measured.  
         [0038]     2. Rotating Valve Structure and Operation  
         [0039]     As shown in  FIGS. 6 through 8 , the rotating valve  12  is provided with a cylinder  29 , conical projection  30  extending upward from the cylinder  29 , and a disk-shaped base  31  supporting the bottom end of the cylinder  29 . Narrow channel-like first and second concavities  32  and  33  are formed in the axial direction of the cylinder  29  on the outer wall of the cylinder  29 , and a channel  49  is formed in a direcxtion [sic direction] intersecting the axis on the bottom surface of the base. A drive source for rotating the rotating valve is connected to the channel  49  in a manner described later.  
         [0040]      FIG. 9  illustrates the measuring operation and the operation of the rotating valve  12 . As shown in the drawing, the rotating valve  12  is inserted into a valve receiving hole formed on the bottom of the assay cartridge  1 .  
         [0041]      FIG. 9 ( a ) shows the condition when the two flow paths L 1  and L 2 , which are formed within the assay cartridge  1 , are blocked by the rotating valve  12 .  
         [0042]     When the rotating valve  12  is rotated to the position shown in  FIG. 9 ( b ), the flow paths L 1  and L 2  are connected through the first concavity  32  or second concavity  33 , such that fluid is able to flow from the flow path L 1  to the flow path L 2 . When the rotating valve  12  is rotated to the position shown in  FIG. 9 ( c ), the fluid flowing from the flow path L 1  to the flow path L 2  is cut off by the first concavity  32  or second concavity  33 , that is, fluid is measured in a quantity matching the capacity of the first concavity  32  or second concavity  33 .  
         [0043]     When the rotating valve  12  is rotated to the position shown in  FIG. 9 ( d ), the first concavity  32  or second concavity  33  holding the fluid flow cut off in  FIG. 9 ( c ) is connected to separate flow paths L 3  and L 4 , such that the measured fluid is mixed with the fluid flowing from the flow path L 3  to the flow path L 4 . In this way the rotating valve  12  opens and closes the flow paths, and measures the fluid flow. The capacities of the first concavity  32  and second concavity  33  of the rotating valve  12  in the present embodiment, is 2 □L in both cases.  
         [0044]     3. Structure of the Mixture Measuring Compartment  
         [0045]      FIG. 10  is a cross section view on the B-B arrow of  FIG. 2 , and  FIG. 11  is a cross section view of the essential part on the C-C arrow of  FIG. 10 . As shown in these drawings, the mixture measuring chamber  7  is shaped as a long and narrow hollow cylinder in a vertical direction and is tapered toward the top end and has a predetermined capacity; the top end is connected to the flow path  13 , and the conical projection  30  of the rotating valve  12  extends from the bottom surface so as to seal the bottom surface of the mixture measuring chamber  7 .  
         [0046]     The mixture measuring chamber  7  has an opening on the inner wall near the base, and a flow path  18  is connected to this opening; the center axis of the mixture measuring chamber  7  and the flow path  18  mutually intersect at right angles. Furthermore, this opening is provided below the apex of the conical projection  30 , such that the cross sectional area of the flow path  18  increases in conjunction with the separation from the opening.  
         [0047]     A hole through the flow path  13  is for discharging excess fluid from the mixture measuring chamber  7 , and a hole through the flow path  18  is for introducing fluid into the mixture measuring chamber  7 .  
         [0048]     When fluid (in the present embodiment, the fluid (analysate) is a mixture of blood and reagent) is measured in the mixture measuring chamber  7 , the analysate is supplied to the mixture measuring chamber  7  through the flow path  18 , the fluid level rises and the supply of the fluid is stopped when some of the fluid overflows into the overflow receptacle  10  through the flow path  13 . In this way the analysate fills the mixture measuring chamber  7  and predetermined quantity of the analysate is measured. The predetermined quantity of the analysate has quantity matching the capacity of the mixture measuring chamber  7 .  
         [0049]     Then, the measured analysate is discharged to the flow path  18 . The rotating valve  12  is provided at the bottom of the mixture measuring chamber  7 , and at this time the center of the opening of the flow path  18  of the mixture measuring chamber  7  is lower than the apex of the conical projection  30  of the rotating valve  12 , as shown in  FIG. 11 , the mixture measuring chamber  7  discharges the measured fluid without any remaining residue.  
         [0050]     4. Structure of the Detector  
         [0051]     As shown in  FIG. 11 , the detector  9  is provided with flow paths  18  and  19  connected in parallel to the same axis through the pellet (gate element)  20 . The pellet  20  is formed by injection molding using a resin, and is formed as a disk with an annular projection on its exterior circumference and a small hole (through hole) 100 □m in diameter at its center. The pellet  20  is inserted into the flow path  19 , and is fixed in place by an annular pellet fixing element  50 . The small hole of the pellet  20  has the same axis as the flow paths  18  and  19 .  
         [0052]     As shall be described later, when the analysate flows from the mixture measuring chamber  7  to the mixture compartment  8 , the detector  9  measures the change in electrical resistance of the analysate passing through the small hole of the pellet  20  by means of the electrodes  21  and  22 . In this case, when the assay cartridge  1  is installed so as to have a predetermined angle θ relative to the gravity direction of the center axis of the small hole of the pellet  20  and flow paths  18  and  19 , air bubbles contained in the analysate accumulate at the top (empty space formed by the pellet  20  and flow path  18 ) of the flow path  18  forward of the pellet  20 , and do not adhere to the small hole of the pellet  20 . Accordingly, the values measured by the electrodes  21  and  22  are not influenced by noise caused by the air bubbles. The angle  04  may be within the range of 15°≦θ≦90°; whereas the range of 45°≦θ≦90° is desirable, and the value θ=90° (horizontal) is ideal.  
         [0053]     5. Structure of the Reagent Compartment  
         [0054]     As shown in  FIG. 10 , the reagent compartment  6  is provided with a first compartment  6   a , and disposed below the first compartment  6   a  is a second compartment  6   b  which has a smaller transverse cross section area than the first compartment  6   a ; the first compartment  6   a  communicates with the second compartment  6   b , and the first compartment  6   a  has a decreasing transverse cross section as it approaches the second compartment  6   b . Furthermore, a reagent supply port to the flow path  16  is provided at a distance S above the bottom end of the second compartment  6   b , and the axis of the reagent supply port faces a horizontal direction, that is a direction intersecting the sequence direction of the first compartment  6   a  and second compartment  6   b . Before using the assay cartridge 1,1000 μL of diluting fluid (in the present embodiment, the reagent is a mixture of diluting fluid and hemolytic agent in a 2:1 ratio) is injected as a reagent through the reagent supply port into the reagent compartment  6 .  
         [0055]     Directly after the injection, the cap  28  is placed on the reagent injection port  27 , and a tape seal is adhered to the pump connector  25  to prevent leakage of the dilution fluid. When the dilution fluid is injected into the reagent compartment  6 , the air in the reagent compartment  6  is replaced by the dilution fluid, but the air in the flow path  16  remains and is not replaced by the dilution fluid since the reagent compartment  6  has the structure described above. Accordingly, an air gap is created between the outer wall of the rotating valve  12  and the dilution fluid within the reagent compartment  6 , such that the dilution fluid does not leak to the outside through the outer wall of the rotating valve  12  even when the dilution fluid is stored for a long period in the reagent compartment  6 .  
         [0056]     6. Structure of the Mixture Compartment  
         [0057]      FIG. 12  is a cross section view on the D-D arrow of  FIG. 2 .  
         [0058]     When the assay cartridge  1  is loaded into the analyzing unit  36  as described later, the mixture compartment  8  is interposed between a photoemitter  34  and a photoreceptor  35  of the analyzing unit  36 , such that the transmitted light (transmitted light intensity) of the fluid accommodated in the mixture compartment  8  can be measured.  
         [0059]     7. Structure of the Analyzing Unit  
         [0060]      FIG. 13  is a perspective view of the exterior of the analyzing unit  36 , which is provided with a liquid crystal display  37 , keyboard  38 , and door  39  on its front panel. To use the assay cartridge  1 , the door  39  is opened and the assay cartridge  1  is loaded into the analyzing unit  36 , then the door  39  is closed; this operation connects the electrodes  21  and  22  of the assay cartridge  1  to the analyzing unit  36 , and connects the pump connectors  23 ,  24 ,  25 , and  26 , and arranges the photoemitter  34  and photoreceptor  35  as shown in  FIG. 12 . In this case, the center axes of the pellet  20  and flow paths  18  and  19  of the assay cartridge  1  are horizontal (at right angles to the gravity direction).  
         [0061]      FIG. 14  is a block diagram of the analyzer produced by loading the assay cartridge  1  into the analyzing unit  36 . In the drawing, the assay cartridge  1  is shown expanded in a planar view to facilitate understanding of the structure.  
         [0062]     As shown in the drawing, a direct current constant-current power supply  40  provided in the analyzing unit  36  is connected to the electrodes  21  and  22  of the assay cartridge  1 , and a syringe pump  41  is connected to the pump connectors  23  through  26  of the assay cartridge  1  through a valve unit  42 . The output shaft of a stepping motor  48  is coupled to the channel  49  of the rotating valve  12  through a coupling not shown in the drawing.  
         [0063]     The valve unit  42  is provided with two-way electromagnetic valves SV 1  through SV 6 , and a pressure sensor  43  for detecting the pressure of the syringe pump  41  is connected to the outlet of the syringe pump  41 . Valves SV 3 , SV 4 , and SV 5  are respectively provided with air release openings  44 . A controller  45  is provided with a microcomputer which includes a CPU, ROM, RAM and the like, and stores programs for calculating analysis results and driving the valves and motor.  
         [0064]     The controller  45  receives the output from the keyboard  38  and the pressure sensor  43 , and drives the syringe pump  41 , the stepping motor  48 , valves SV 1  through SV 6 , and photoemitter  34 .  
         [0065]     The controller  45  counts the white blood cells based on the signals obtained from the electrodes  21  and  22 , calculates the particle size and creates a particle size distribution, and further calculates the amount of hemoglobin based on the signals obtained from the photoreceptor  35 . These results are displayed on the liquid crystal display  37 .  
         [0066]     8. Assay Operation  
         [0067]     The operation of the analyzer shown in  FIG. 14  is described below using the flow charts of  FIGS. 15 and 16  and the condition illustrations of  FIGS. 17 through 27 .  
         [0068]     First, in step S 1  of  FIG. 15 , when initialization settings are specified to the analyzing unit  36  through the keyboard  38 , the syringe pump  41 , stepping motor  48  and valves SV 1  through SV 6  are set to the initial states.  
         [0069]     At this time the valves SV 1  through SV 6  are all turned OFF, that is, set to the condition shown in  FIG. 14 .  
         [0070]     Then, using an injection device or pipette, a user injects 10 to 150 μL of whole blood as a sample (specimen) into the sample receptacle  5  of the assay cartridge  1  accommodated beforehand in the reagent compartment  6 . Alternatively, a capillary blood collection tube filled with suctioned whole blood may be inserted into the sample receptacle  5 .  
         [0071]     Next, a user removes the tape seal adhered to the pump connector  25  on the back side of the assay cartridge  1 , opens the door  39  on the front panel of the analyzing unit  36 , loads the assay cartridge  1  therein, and closes the door  39  (step S 2 ).  
         [0072]     At this time the rotating valve  12  of the assay cartridge  1  is connected to the sample receptacle  5  and the excess sample collector  11  through the first concavity  32 , as shown in  FIG. 17 .  
         [0073]     Then, the user specifies the [start] operation from the keyboard  38  (step S 3 ).  
         [0074]     In this way, when the syringe pump  41  has suctioned for a time T 1  (steps S 4  through S 6 ), the sample migrates from the sample receptacle  5  through the first concavity  32  to the excess sample collector  11 , as shown in  FIG. 18 .  
         [0075]     Then, the rotating valve  12  is rotated through a predetermined angle, 2 μL of sample is cut off and measured by the first concavity  32 , as shown in  FIG. 19 .  
         [0076]     The rotating valve  12  simultaneously connects the sample compartment  6  and mixture compartment  8  through the second concavity  33  (step S 7 ).  
         [0077]     Then, the valves SV 1  and SV 2  are turned ON, and the valves SV 3  through SV 6  are turned OFF (step S 8 ), and when the syringe pump  41  has suctioned for a predetermined time T 2  (steps S 9  through S 11 ), dilution fluid migrates from the reagent compartment  6  through the second concavity  33  to the mixture compartment  8 , as shown in  FIG. 20 . Here, the photoemitter is lighted, and a hemoglobin concentration blank value is measured by the photoreceptor  35  (step S 12 ).  
         [0078]     Subsequently, when the rotating value  12  is rotated through a predetermined angle, the rotating valve  12  connects the reagent compartment  6  and the mixture compartment  8  through the first concavity  32  (step S 13 ).  
         [0079]     Then, the valves SV 1 , SV 3 , and SV 4  are turned ON, and valves SV 2 , SV 5  and SV 6  are turned OFF (step S 14 ), and when the syringe pump  41  has suctioned for a predetermined time T 3  (step S 15  through S 117 ), the sample accommodated in the first concavity  32  migrates to the mixture compartment  8  and the reagent compartment  6 , as shown in  FIG. 22 .  
         [0080]     Thereafter, the valves SV 1  and SV 2  are turned ON, and valves SV 3  through SV 6  are turned OFF, and when the syringe pump  41  suctions for a predetermined time T 4  (steps S 19  through S 21 ), the sample and dilution fluid again migrate to the mixture compartment  8 , as shown in  FIG. 23 , and the sample is thoroughly diluted by the dilution fluid. That is, the analysate prepared by diluting the sample with the dilution fluid is stored in the mixture compartment  8 . Then, the photoemitter  34  is again lighted and the hemoglobin concentration is again measured by the photoreceptor  35  (step S 22 ).  
         [0081]     When the rotating valve  12  is rotated through a predetermined angle, the rotating valve  12  completely blocks the flow path between the sample receptacle  5  and the excess sample collector  11 , and the flow path between the reagent compartment  6  and the mixture compartment  8  (step S 23 ).  
         [0082]     Then, the valves SV 3  and SV 6  are turned ON, and valves SV 1 , SV 2 , SV 4 , and SV 5  are turned OFF (step S 24 ), the syringe pump  41  suctions for a predetermined time T 5  (steps S 25  through S 27 ), and the analysate in the mixture compartment  8  migrates to the mixture measuring chamber  7  through the pellet  20 , as shown in  FIG. 25 , and after the mixture measuring chamber  7  is filled, some analysate overflows to the overflow collector  10 . In this way analysate is measured in a quantity matching the capacity of the mixture measuring chamber  7 .  
         [0083]     Thereafter, the valves SV 1 , SV 2 , SV 5 , and SV 6  are turned ON, and valves SV 3  and SV 4  are turned OFF, and when the syringe pump  41  applies suction, the analysate in the mixture measuring chamber  7  starts to migrate to the mixture compartment  8  through the pellet  20 , as shown in  FIG. 26  (steps S 28  and S 29 ).  
         [0084]     At this time the change in the electrical resistance of the analysate passing through the pellet  20  is detected by the electrodes  21  and  22  simultaneously with the start of suction by the syringe pump  41 , and when all the analysate measured by the mixture measuring chamber  7  has passed through the pellet  20 , the suction pressure of the syringe pump  41  quickly changes. This change in pressure is detected by the pressure sensor  43 , and the suction of the syringe pump  41  is stopped (steps S 30  and S 31 ). That is, in this way the number and size of all the white blood cells are measured in the analysate quantity matching the capacity of the mixture measuring chamber  7 .  
         [0085]     When the rotating valve  12  is rotated through a predetermined angle, the rotating valve  12  connects the sample receptacle  5  and the excess sample collector  11  through the second concavity  33  while blocking the flow path between the reagent compartment  6  and the mixture compartment  8 , as shown in  FIG. 27  (step S 32 ).  
         [0086]     All the valves SV 1  through SV 6  are turned OFF (initial setting), and when the syringe pump  41  is suctioned for a predetermined time T 6 , all the sample stored in the sample receptacle  5  migrates to the excess sample collector  11  (steps S 33  through S 36 ).  
         [0087]     The user then removes the assay cartridge  1  from the analyzing unit  36  and discards the cartridge in this state (step S 37 ).  
         [0088]     11. [sic 9.] White Blood Cell and Hemoglobin Measurements  
         [0089]     As shown in  FIG. 14 , when a constant current is supplied from the direct current constant current power supply  40  through the electrodes  21  and  22  to the analysate cut off by the pellet  20  which is provided with a small hole, the resistance between the electrodes  21  and  22  is dependent on the inherent resistance of the liquid component of the analysate.  
         [0090]     When white blood cells pass through the small hole, there is a change in the electrical resistance between the electrodes  21  and  22  since the liquid component is eliminated by the volume of the white blood cells, and this change can be detected as a pulse voltage generated between the electrodes  21  and  22 . Accordingly, the controller  45  counts the number of white blood cells from the number of pulses. Since the height of the pulse is proportional to the volume of the particle, the controller  45  detects the height of the pulse, calculates the spherical equivalent of the white blood cell, and creates a particle size distribution. The controller  45  determines the transmission light intensity (blank value) of the dilution fluid obtained by the photoreceptor  35 , and the light absorption of the analysate from the transmission light intensity of the analysate using well known methods, and calculates the amount of hemoglobin in the sample from the determined light absorption.  
         [0091]     Although the present embodiment has been described in terms of an analyzer including an analyzing unit  36  and an assay cartridge  1  removably loaded in the analyzing unit  36 , the present invention is not limited to this arrangement inasmuch as a hemocytometer provided with a non-user-detachable detector may include a conical projection  30  and mixture measuring chamber  7 . The present invention is also applicable to urine analyzers for analyzing tangible components in urine. Furthermore, the present invention is applicable to industrial analyzers for analyzing organic powders such as powdered food, and inorganic powers such as toner and pigment.  
         [0092]     Although blood and a fluid mixture of reagent including dilution fluid and hemolytic agent are used as the analysate in the present embodiment, the present invention is not limited to this arrangement inasmuch as blood diluted with dilution fluid, blood subjected to hemolysis with hemolytic agent, and suspension fluid formed by powder particles suspended in a suitable fluid also may be used.  
         [0093]     Although the conical projection  30  is integratedly formed with the rotating valve  12  in the present embodiment, the present invention is not limited to this arrangement inasmuch as the conical projection may also be integratedly formed with the mixture measuring chamber  7 .  
         [0094]     A flow cell and optical elements for detecting an optical signal from the analysate flowing in the flow cell may also be used as the detector. The optical signal detected by such a detector may be a scattered light signal, fluorescent light signal or the like.