Abstract:
Sample analyzers for analyzing a sample are described that include a pipette for suctioning the sample; a sample preparation unit for preparing a measured sample by diluting the sample supplied by the pipette with an acidic solution; a pipette washing unit for washing the pipette with the acidic solution; a detection unit for obtaining a detection signal from the measured sample prepared by the sample preparation unit; and a controller for calculating an analysis result from the detection signal obtained by the detection unit. Bacteria analyzers for analyzing bacteria and solutions for use in sample analyzers are also described.

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2002-310585, filed Oct. 25, 2002. 
     FIELD OF THE INVENTION 
     The present invention relates to sample analyzers provided with a pipette for suctioning samples, and to processing solutions for diluting and cleaning. 
     BACKGROUND 
     A urine analyzer provided with a washing means for washing a urine flow path is known, which includes a nozzle. After urine has been suctioned for examination from the nozzle and the urine has been completely titrated from the nozzle to a reagent pipette, the urine is examined based on the reaction in the reagent pipette. The urine analyzer is further provided with a concentration detection means for detecting the concentration of a specific component contained in the urine suctioned from the nozzle, and a washing capacity control means for varying the washing capacity of the washing means based on the detection result of the concentration detection means (for example, Japanese Laid-Open Patent Publication No. 2000-321270). 
     A washing device for a dispensation injection nozzle is known that is provided with an ultrasonic wave generating means for generating ultrasonic wave vibrations while optionally changing the position of the node on the dispensation injection nozzle without generating a node of the ultrasonic vibration in the dispensation injection nozzle that suctions and discharges a sample. The dispensation injection nozzle is vibrated to dislodge sample adhered to the inner surface and outer surface of the dispensation injection nozzle from the dispensation injection nozzle (for example, Japanese Laid-Open Patent Publication No. H5-1983). 
     A pipette washing device provided with a trough for accommodating water for washing is known provided with a brush arranged inside the trough, a magnetic body mounted on the bottom part of the brush, a rotating magnetic body having the same polarity as the magnetic body mounted on the bottom of the brush, and a drive means for rotating the rotating magnetic body (for example, Japanese Utility Model Publication No. H6-15772). 
     In sample analyzers which suction a sample from a nozzle (pipette) such as those described above, the nozzle must be washed before suctioning the next sample. Analysis of the next sample may be adversely affected if the nozzle is inadequately washed. 
     To solve this problem, in the urine analyzer disclosed in the above-mentioned Japanese Patent Publication No. 2000-321270, the number of washings or the amount of washing fluid used is changed in accordance with the detection result obtained by the concentration detection means. However, if the number of washings is increased, the processing capability of the device is markedly reduced. If the amount of washing fluid used is increased, the operating cost of the device is increased. Furthermore, this urine analyzer is provided with a concentration detection means for changing the washing capability, which also increases the size of the device. 
     The devices disclosed in Japanese Laid-Open Patent Publication No. H5-1983 and Japanese Utility Model Publication No. H6-15772 also result in larger devices similar to the device described in Japanese Patent Publication No. 2000-321270. 
     SUMMARY 
     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. 
     A sample analyzer embodying features of the present invention for analyzing a sample includes: a pipette for suctioning the sample; a sample preparation unit for preparing a measured sample by diluting the sample supplied by the pipette with an acidic solution; a pipette washing unit for washing the pipette with the acidic solution; a detection unit for obtaining a detection signal from the measured sample prepared by the sample preparation unit; and a controller for calculating an analysis result from the detection signal obtained by the detection unit. 
     A bacteria analyzer embodying features of the present invention for analyzing a bacterium in a sample includes: a pipette for suctioning the sample; a sample preparation unit for preparing a measured sample from the sample supplied by the pipette; a pipette washing unit for washing the pipette with an acidic solution; a detection unit for obtaining a detection signal from the measured sample prepared by the sample preparation unit; and a controller for calculating an analysis result from the detection signal obtained by the detection unit. 
     A solution embodying features of the present invention includes: a solvent; and an acidic buffering agent. The solution is acidic and the solution is used for diluting and cleaning in a sample analyzer that analyzes a predetermined component included in a sample. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a front view of a sample preparation device embodying features of the present invention. 
         FIG. 2  shows a top view of a portion of the device shown in  FIG. 1 . 
         FIG. 3  shows a longitudinal sectional view of the portion of the device shown in  FIG. 2   
         FIG. 4  shows a longitudinal sectional view of the portion of the device shown in  FIG. 2 . 
         FIG. 5  shows a longitudinal sectional view of the portion of the device shown in  FIG. 2 . 
         FIG. 6  shows a longitudinal sectional view of the portion of the device shown in  FIG. 2 . 
         FIG. 7  shows a side view showing the container holder unit removed from the device shown in  FIG. 1 . 
         FIG. 8  shows a top view showing the container holder unit removed from the device shown in  FIG. 1 . 
         FIG. 9  shows a top view of the container holder unit of the device shown in  FIG. 1 . 
         FIG. 10  shows a cross section view along the line A-A of  FIG. 9 . 
         FIG. 11  shows a cross section view along the line B-B of  FIG. 9 . 
         FIG. 12  shows a bottom view of the container holder unit of the device shown in  FIG. 1 . 
         FIG. 13  shows a side view of the catcher of the device shown in  FIG. 1 . 
         FIG. 14  shows a top view of the catcher of the device shown in  FIG. 1 . 
         FIG. 15  shows a side view of a disposable container used in the device shown in  FIG. 1 . 
         FIG. 16  illustrates parts of the optical system and fluid system of a sample analyzer embodying features of the present invention. 
         FIG. 17  shows a block diagram showing the control system of a sample analyzer embodying features of the present invention. 
         FIG. 18  illustrates the photointerrupter placement in an embodiment of the present invention. 
         FIG. 19  shows a flow chart for the initialization operation of the turntable of an embodiment of the present invention. 
         FIG. 20  shows a top view of a temperature control unit of an embodiment of the present invention. 
         FIG. 21  shows a cross-sectional view along the line E-E of  FIG. 20 . 
         FIG. 22  shows a cross-sectional view along the line F-F of  FIG. 20 . 
         FIG. 23  shows a cross-sectional view along the line G-G of  FIG. 20 . 
         FIG. 24  shows a longitudinal view of the pipette in an embodiment of the present invention. 
         FIG. 25  shows a longitudinal view of the washing chamber in an embodiment of the present invention. 
         FIG. 26  shows part of the fluid system of a sample analyzer embodying features of the present invention. 
         FIG. 27  shows part of the fluid system of a sample analyzer embodying features of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention provides a sample analyzer which improves washing capability without reducing the processing capability of the device, without increasing the amount of washing fluid used, and without increasing the size of the device. 
     An embodiment of the present invention is described hereinafter in reference to the drawings. The present invention is not limited to this representative description. This embodiment of the sample analyzer is a bacteria analyzer for counting the number of bacteria in a sample (urine). 
     The structure of various parts of the sample analyzer are described below. 
     Sample Preparation Device 
       FIG. 1  shows a front view of an embodiment of the sample preparation device of the present invention. 
     A slide rail  2  is provided horizontally to a main frame  1  as shown in the drawing, and a slide element  3  is supported by the slide rail  2  so as to be slidable in a horizontal direction. 
     The main frame  1  supports a drive pulley  5  driven by a stepping motor  4 , and supports a corresponding driven pulley  6  so as to be rotatable. A timing belt  7  is supported between the pulleys  5  and  6  so as to be parallel to the slide rail  2 . The slide element  3  is provided with a horizontally movable plate  8 , and the plate  8  is connected to the timing belt  7  via a connector  9 . When the stepping motor  4  rotates, the plate  8  is moved in the arrow X 1  direction or the arrow X 2  direction in accordance with the motor rotation direction. 
     Three slide rails  10 ,  11 , and  12  are provided in a perpendicular direction relative to the plate  8 , and the slide rails  10 ,  11 , and  12 , respectively, support slide elements  13 ,  14 , and  15  so as to be slidable in a perpendicular direction. 
     The plate  8  supports the drive pulleys  18  and  19 , which are respectively driven by the stepping motors  16  and  17 , and supports the corresponding driven pulleys  20  and  21  so as to be rotatable. Timing belts  22  and  23  are respectively supported between pulleys  18  and  20  and pulleys  19  and  21  in a perpendicular direction. 
     The slide elements  13  and  14  are provided with a first pipette  28  and a second pipette  29  through the respective support members  24  and  25 , and the slide element  15  is provided with a catcher  27  through the support member  26 . The first pipette  28  is provided with an external pipette heater  36 , which heats the suctioned fluid to 42° C. 
     The slide element  13  is connected to the timing belt  22  via a connector  30 , and the slide elements  14  and  15  are connected to the timing belt  23  via the connectors  31  and  32 , respectively. When the stepping motor  16  rotates, the first pipette  28  is moved in the arrow Y 1  direction or the arrow Y 2  direction in accordance with the motor rotation direction. When the stepping motor  17  rotates, the second pipette  29  and the catcher  27  are moved in the arrow Y 1  direction or the arrow Y 2  direction in accordance with the motor rotation direction. 
     The support frame  41  is provided with a turntable  42 , turntable rotation mechanism  43 , mixing container rotation mechanism  44 , stepping motor  45  as a rotation drive source, and container discard unit  46 . A third pipette  48  is fixedly attached to the support frame  47 , and a slide rail  49  is fixedly attached to the support frame  47  in a perpendicular direction. The slide rail  49  supports a slide element  50  so as to be slidable in a perpendicular direction. 
     The slide element  50  is provided with a washing unit  52  through the support member  51 . A stopper  53  is provided below the support frame  47 , to stop the slide element  50  at the position shown in  FIG. 1 , such that the slide element  50  does not move below the slide rail  49 . A table  33  is provided to the right of the support frame  41 , and a dilution solution container  34  is installed on top of the table  33 . A table  179  is provided to the right of the table  33 , and a washing chamber  180  is provided on top of the table  179 . 
       FIG. 2  shows a top view of the support frame  41 .  FIG. 3  shows a longitudinal section view of the turntable rotation mechanism  43 .  FIG. 4  shows a longitudinal section view of the mixing container rotation mechanism  44 . 
     As shown in  FIG. 4 , a pulley  53  is connected to the output shaft  40  of the stepping motor  45 . As shown in  FIG. 3 , a pulley  56  is connected via a one-way clutch  55  to the drive shaft  54  of the turntable  42 . 
     As shown in  FIG. 5 , a sample container rotation mechanism  57  is provided between the turntable  42  and the support frame  41 , and the rotation mechanism  57  has a pulley  58  supported by a shaft  59  on the support frame  41  so as to be rotatable. 
     As shown in  FIG. 2 , the pulleys  53 ,  56 , and  58  are connected by a single timing belt  60 . Accordingly, the rotational force of the stepping motor  45  is transmitted to the mixing container rotation mechanism  44  ( FIG. 4 ), and at the same time is also transmitted to the turntable rotation mechanism  43  ( FIG. 3 ) and sample container rotation mechanism  57  ( FIG. 5 ) through the timing belt  60  and the pulleys  53 ,  56 , and  58 . 
     The third pipette  48 , washing unit  52 , container discard unit  46 , pulley  53 , pulley  58 , and washing chamber  180  are arrayed in series on the straight line L shown in  FIG. 2 , and the first pipette  28 , second pipette  29 , and catcher  27  are provided so as to move on the line L via the drive of the stepping motor  4 . 
     The turntable  42  is constructed so that five sample containers Ts and five empty mixing containers Tm can be installed at equal intervals on concentric circular circumferences having different diameters, and so that one sample container Ts, and two empty mixing containers Tm on either side thereof can be aligned on the line L. 
     As shown in  FIGS. 2 ,  8 , and  18 , a photointerrupter  140  is provided on the support frame  1 , and a light shield  62   a  extends below the turntable  42  so as to block the light to the photointerrupter  140 . These elements are used to detect a reference position (initial position) of the turntable  42  in a manner described below. 
     Turntable 
       FIG. 6  shows a structural diagram showing a longitudinal section view of the turntable  42 . 
     As shown in the drawing, the turntable  42  includes a disk-like container holder  61  formed of resin, and a rotating plate  62  formed of a nonmagnetic material (stainless steel or aluminum) for holding the container holder  61  so as to allow its removal.  FIGS. 7 and 8  show, respectively, a side view and a top view of the turntable  42  with the container holder  61  removed from the rotating plate  62 . 
     As shown in these drawings, a guide block  63  is provided on the top surface of the rotating plate  62  to guide the installation of the container holder  61 . The guide block  63  is provided with a positioning pin  65  for centering the rotating plate  62 , and the positioning pin  65  is forced upward via a compression spring  64 . The guide block  63  is also provided with a protrusion  66  for stopping the container holder  61  at the edge position of the rotating plate  62 . 
       FIG. 9  shows a top view of the container holder  61  removed from the rotating plate  62 .  FIG. 10  shows a cross-sectional view along the line A-A in  FIG. 9 .  FIG. 11  shows a cross-sectional view along the line B-B in  FIG. 9 .  FIG. 12  shows a bottom view of the container holder  61 . As shown in  FIG. 9 , the container holder  61  is provided with five container holes  67  for accommodating the empty mixing containers Tm ( FIG. 2 ), and five first holders  68  for accommodating the sample containers Ts ( FIG. 2 ), which are provided at equal intervals on concentric circular circumferences having different diameters. 
     As shown in  FIGS. 10 and 11 , the container holder  61  is provided with a channel  70  which engages the guide block  63  when installed on the rotating plate  62  ( FIG. 7 ). The channel  70  has a positioning hole  69  for accepting the positioning pin  65  at the center of the container holder  61 . Furthermore, the top surface of the container holder  61  is provided with a handle  71  used when installing and removing the container holder  61  on the rotating plate  62 . 
     In the sample preparation device of the present embodiment, the disposable container (hereinafter referred to as “tube”) T shown in  FIG. 15  is used as the sample container Ts for holding a sample collected from a person being tested, and as a mixing container Tm for preparing an analysis sample by mixing the sample and a predetermined fluid. 
     The tube T is a cylindrical container formed of styrol (transparent) resin preferably with a height dimension H=39.85±0.1 mm, external diameter DT=7.6±8.2 mm, and capacity of approximately 0.7 mL. The tube is provided with a flange F (external diameter DF=10 mm) at the top edge so as to prevent the tube T from falling from the catcher  27  when held by the catcher  27  in a manner described below. 
     As shown in  FIG. 10 , the first holder  68  is inserted from the bottom of each of the five cylindrical concavities provided in the container holder  61  and is supported by a bottom plate  73  formed of a nonmagnetic material (e.g., stainless steel or aluminum). 
     The top of the first holder  68  is provided with a hole  74  for accepting the sample container Ts, and is supported by the outer wall of the concavity  72  so as to be rotatable about an axis. The first holder  68  is also provided with a magnetic rod  75  passing through the bottom of the first holder  68  in a direction intersecting the axis, such that the first holder  68  is rotated about the axis when a rotating magnetic field is introduced from below the bottom plate  73 . 
     Turntable Rotation Mechanism 
     As shown in  FIG. 3 , the base end of the drive shaft  54  of the turntable  42  is fixedly attached to the center of the back surface of the rotating plate  62  via a boss  78 . The support frame  41  supports a bearing holder  76 , and the drive shaft  54  is supported so as to be rotatable by the support frame  41  via a bearing  77  held on the bearing holder  76 . The drive shaft  54  is mounted on the bearing holder  76  through a one-way clutch  79 . 
     The one-way clutch  55  is disposed between the pulley  56  and the drive shaft  54  and linked with both as described above. A super gear  80  provided on the tip of the drive shaft  54  engages a super gear  82  provided on the rotating shaft of a damper  81 . The damper  81  normally acts on the drive shaft  54  to suppress a flywheel effect through the inertia of the turntable  42 , and operates so as to reduce over-rotation particularly when the turntable  42  is stopped. 
     The operation of the clutches  55  and  79  are described below. 
     Viewed from the output shaft side, when the stepping motor  45  ( FIG. 2 ) rotates in a clockwise direction causing the pulley  56 , viewed from above, to rotate in the clockwise direction, the one-way clutch  55  is ON (operating), and the one-way clutch  79  is OFF (open), such that the turntable  42  receives the action of the damper  81  and rotates in a clockwise direction when viewed from above. 
     Conversely, when the stepping motor  45  rotates in a counter clockwise direction, the one-way clutch  55  is OFF and the one-way clutch  79  is ON, such that the drive shaft  54  prevents rotation and is locked on the bearing holder  76 , and the pulley  56  idles. That is, the turntable  42  can rotate in a clockwise direction only when the stepping motor  45  rotates in a clockwise direction. 
     Mixing Container Rotation Mechanism 
     In the mixing container rotation mechanism shown in  FIG. 4 , a cylindrical holding member  85  is attached to a mounting plate  84  provided above the support frame  41 . A through-hole is provided in the holding member  85  to allow the second holder  86  to be received from above, and a film heater  87  is wrapped around the outer surface. 
     The second holder  86  has a hole  88  for receiving and holding the mixing container Tm from above. The holding member  85  is provided with a thin cylindrical oilless bushing inserted into the through hole, such that the inner surface of the oilless bushing  89  and the outer surface of the second holder  86  are in slidable contact so as to allow the second holder  86  to smoothly rotate about an axis. 
     A coupling  83  is attached to the top of the pulley  53 , and the coupling  83  is provided with two pins  90 , which extend upward. The bottom surface of the second holder  86  is provided with two holes, which accommodate the two pins  90 . In this way, the second holder  86  is mechanically linked with the pulley  53  so as to be removable. When the stepping motor  45  rotates in either a clockwise direction or a counter clockwise direction, the second holder  86  smoothly rotates in the same direction as the stepping motor  45  about the axis via the oilless bushing  89 . 
     Sample Container Rotation Mechanism 
     In the sample container rotation mechanism  57  shown in  FIG. 5 , a cylindrical magnet coupling  91  is attached to the top of the pulley  58 , and a pair of rod magnets  92  and  93  are embedded perpendicularly on the magnet coupling  91  disposed about the center of the shaft  59  of the pulley  58 . The rod magnet  92  has an N-pole confronting the turntable  42 , and the rod magnet  93  has an S-pole confronting the turntable  42 . 
     Since the bottom plate  73  and the rotating plate  62  are formed of nonmagnetic material as described above, when the first holder  68 , which is housed in the turntable  42 , confronts the magnet coupling  91 , the N-pole of the rod magnet  92  is magnetically attracted to the S-pole of the rod magnet  75 , and the S-pole of the rod magnet  93  is magnetically attracted to the N-pole of the rod magnet  75 . That is, the first holder  68  is magnetically coupled with the pulley  58  through the magnet coupling  91 . Accordingly, in this state, when the pulley  58  is rotated in either a clockwise direction or a counter clockwise direction by the stepping motor  45 , the first holder  68  is rotated in the same direction as the stepping motor  45  about the center axis of the sample container Ts in accordance with the rotation of the pulley  58 . 
     Catcher 
       FIGS. 13 and 14  are a side view and a top view, respectively, of the catcher  27 . As shown in these drawings, the catcher  27  is provided with a body  98 , and two fingers  94  and  95 , and the two fingers  94  and  95  are supported by the body  98  so as to be openable in the arrow C direction and arrow D direction via pins  96  and  97 . The fingers  94  and  95  are held in the state shown in  FIG. 14  via a force exerted in the closed direction by a tension spring  99 . 
     When the catcher  27  approaches the stationary mixing container Tm in the arrow M direction shown in  FIG. 13 , the fingers  94  and  95  grip the side surfaces of the mixing container Tm and are stopped by the flange F. With the mixing container Tm in a stationary state, when the catcher  27  moves in the arrow N direction shown in  FIG. 13 , the catcher  27  separates from the mixing container Tm. 
     Washing Chamber 
       FIG. 25  shows a cross-sectional view of the washing chamber  180  shown in  FIG. 1 . The washing chamber  180  is provided with a receptacle  184  for receiving sheath fluid and dilution fluid. The receptacle  184  is open to the atmosphere, and has a nipple  181  for supplying sheath fluid, and a nipple  182  for discharging sheath fluid, each having the same height, and a nipple  183  is provided on the bottom part for discharging sheath fluid and dilution fluid. 
     Optical System and Fluid System 
       FIG. 16  illustrates parts of the optical system and fluid system of a sample analyzer using the sample preparation device shown in  FIG. 1 .  FIG. 17  shows a block diagram of the control system of the sample analyzer. 
     As shown in  FIG. 16 , a sheath flow cell  107  is provided with a nozzle  113  for discharging an analysis sample upward toward an orifice  111 , sheath fluid supply port  110 , and drainage port  114 . Near the sheath flow cell  107  are provided a laser light source  117 , condenser lens  118 , beam stopper  119 , collector lens  120 , light shield  130  with a pinhole  121 , dichroic mirror  122 , filter  123 , photomultiplier tube  124 , and photodiode  125 . Thus, a flow cytometer is shown in part of  FIG. 16 . 
     A sheath fluid container  109  under positive pressure is connected to the sheath fluid supply port  110  through a temperature control unit  115  and a valve  105 . The drainage port  114  is connected to a discard chamber (not shown). The third pipette  48  of the sample preparation device ( FIG. 1 ) is connected to the nozzle  113  through a valve  101 . A negative pressure source is connected through the flow path  139  and a valve  102 . A syringe pump  133  is connected on the valve  102  side of the flow path  139 . The temperature control unit  115  is connected to a discard chamber (not shown) through a valve  106 , so as to appropriately remove air bubbles accumulating inside. 
     The second pipette  29  of the sample preparation device ( FIG. 1 ) is connected to the syringe pump  132  through a valve  103 . The syringe pump  132  is connected to a stain container  112  through a valve  104 . 
     As shown in  FIG. 26 , the washing chamber  180  is connected to a syringe pump  196  through a valve  192 . The valve  192  is connected to the sheath container  109  through a valve  191 . The washing chamber  180  is connected to a drainage chamber  195  for accommodating used sheath fluid, dilution solution, and the like through a valve  194  and valve  193 . 
     As shown in  FIG. 27 , the first pipette  28  is connected to a syringe pump  131 , and is further connected to a syringe pump  197  through a valve  199 . The valve  199  is connected to the sheath fluid container  109  through a valve  198 . 
     Temperature Control Unit 
       FIG. 20  shows a top view of the temperature control unit  115 .  FIG. 21  shows a cross-sectional view along the line E-E in  FIG. 20 .  FIG. 22  shows a cross-sectional view along the line F-F in  FIG. 20 .  FIG. 23  shows a cross-sectional view along the line G-G in  FIG. 22 . 
     As shown in  FIG. 21 , a metal heat accumulator block  149  (formed of brass) is provided at the center of the temperature control unit  115 , and disk-like heat insulator blocks  150  and  1051  (formed of polyacetal resin) are respectively fitted on the top and bottom surfaces of the metal block  149 . An air bubble elimination flow path  152  (internal diameter 3.2 mm) is formed in a perpendicular direction from the heat insulator blocks  150  to  151  at the center of the metal block  149 . 
     The interiors of the heat insulator blocks  150  and  151  are provided, respectively, with first and second drainage paths  153  and  154  (internal diameter 1 mm) in a horizontal direction. One end of the first drainage path  153  is connected to the top end of the air bubble elimination path  152 , and the other end is connected to a an external tube connector nipple  155  (internal diameter 1.5 mm, formed of stainless steel) protruding in a horizontal direction from the heat insulating block  150 . 
     One end of the second drainage path  154  is connected to the bottom end of the air bubble elimination path  152 , and the other end is connected to an external tube connector nipple  156  (internal diameter 1.5 mm, formed of stainless steel) protruding in a horizontal direction from the heat insulating block  151 . 
     Furthermore, the heat insulating block  150  is provided with a supply path horizontally connected between the top end and bottom end of the air bubble elimination path  152 , and a nipple  157  (internal diameter 0.9 mm) is inserted into the supply path. 
     A pipe  159  (stainless steel) is installed in the interior wall of the air bubble elimination path  152 . The top end of this pipe  159  is press-fitted into the heat insulating block  150 , and the bottom end is inserted into the heat insulating block  151  through an O-ring  158  so as to be watertight. In this way, the fluid flowing through the air bubble elimination path  152  is prevented from contacting the metal block  149 . 
     As shown in  FIGS. 22 and 23 , the metal block  149  is provided with a total of eight through-holes  160  provided in parallel rows of four so as to be symmetrical on the bilateral sides of the air bubble elimination path  152 . One supply tube  161  (internal diameter 0.8 mm, formed of FEP) passes through sequentially from the bottom through-hole  160  to the top through-hole  160 , so as to spiral around the air bubble elimination path  152 . 
     As shown in  FIG. 21 , the bottom end  161   a  of the supply tube  161  extends downward from the heat insulating block  151 , and the top end  161   b  is connected to the nipple  157 . As shown in  FIG. 23 , a concavity  162  is formed in the metal block  149  at the bilateral ends of the through-hole  160 , and the bent part of the supply tube  161  extending in a spiral shape is accommodated within the concavity  162 . 
     A plate-like sheath fluid heater  148  is provided so as to cover the side surface of the metal block  149 . As shown in  FIGS. 21 and 22 , a heat shield  163  (formed of foamed polyethylene) is provided between the heat insulating blocks  150  and  151  so as to cover the sheath fluid heater  148 . 
     Furthermore, a heat shield  164  (formed of foamed polyethylene) is provided so as to cover the heat shield  163  and the side surfaces of the insulating blocks  150  and  151 . A temperature sensor (thermistor)  146  and thermal protector (switching element)  147  are provided on the metal block  149 , as shown in  FIG. 22 . In this construction, when sheath fluid is supplied from the bottom end  161   a  of the supply tube  161  and the nipples  155  and  156  are open, as shown in  FIG. 21 , the sheath fluid is heated within the supply tube  161  and flows from the nipples  155  and  156 . 
     When the nipple  155  is closed, the heated sheath fluid not only flows from the nipple  156 , but also the air bubbles in the sheath fluid gradually rise up inside the air bubble elimination path  152  and accumulate at the top end. That is, since there is a rapid decrease in the flow rate of the sheath fluid flowing from the nipple  156  to the air bubble elimination path  152 , the air bubbles rise and are eliminated upward when the fluid in the air bubble elimination path  152  falls. 
     By closing the nipple  156  and opening the nipple  155  and supplying sheath fluid from the supply tube  165  as necessary, the air bubbles accumulated near the top end of the air bubble elimination path  152  are eliminated together with the sheath fluid draining from the nipple  155 . 
     The temperature of the metal block  149  is detected by the temperature sensor  146 , and the sheath fluid heater  148  heats the metal block  149  so as to maintain a temperature of 42° C. When the metal block  149  becomes overheated, the thermal protector  147  operates so as to block the current to the sheath fluid heater  148 . 
     First Pipette 
       FIG. 24  shows a longitudinal sectional view of the first pipette  28 . As shown in the drawing, the first pipette  28  is formed of stainless steel and has a slender and hollow barrel shape extending from the tip  165  to the base  166 . The first pipette  28  has, sequentially, from the tip  165  to the base  166 , a suction part  167  with a length L 0  and an internal diameter D 0 , a sample part  168  with a length L 1  and an internal diameter D 1 , and a reagent part  169  with a length L 2  and an internal diameter D 2 . 
     D 0 , D 1 , and D 2  are related as D 0 &lt;D 1 &lt;D 2 . In the present embodiment, D 0 =0.6 mm, D 1 =1.5 mm, and D 2 =2.1 mm; and L 0 =3 mm, L 1 =45 mm, and L 2 =150 mm. Accordingly, the volumes of the sample part  168  and the reagent part  169  are 79.5μ and 520μ, respectively. 
     The suction part  167  is narrow to suction sample and reagent without excess or deficiency. Sample and reagent are accommodated in the sample part  168 . Reagent alone is accommodated in the reagent part  169 , and no sample is accommodated therein. 
     The suction part  169  and sample part  168 , and the sample part  168  and reagent part  169  are connected, respectively, by connectors  170  and  171 , which have tapered orifices. The reagent part  169  is provided with a heat accumulator pipe  172  formed of copper on its outer wall, and the outer wall of the heat accumulator pipe  172  is provided with a pipette heater  36 . 
     The pipette heater  36  is formed of covered Nichrome wire, and is coiled around the outer wall of the heat accumulator pipe  172 . A temperature sensor (thermistor)  144  is provided on part of the outer wall of the heat accumulator pipe  172 . The reagent part  169  is provided with a protective cover  173  formed of stainless steel for covering the pipette heater  36  and the temperature sensor  144 . 
     Control System 
     As shown in  FIG. 17 , a controller  134  is provided with a calculator  134   a  and a memory  134   b . The controller receives the output from an input unit  135 , photomultiplier tube  124 , and photodiode  125 , and outputs analysis conditions and analysis results to an output unit  138 . A microcomputer, personal computer or the like including a CPU, ROM, RAM and the like may be used as the controller  134 . 
     The photointerrupter  140  detects the initial position of the turntable  42  as described above, and the position sensors  141  through  143  detect horizontal position of the horizontally movable plate  8 , and the vertical positions of the first pipette  28 , second pipette  29 , and the catcher  27 . 
     The temperature sensors  144  through  146  are sensors (thermistors) which respectively detect the temperature of the first pipette  28 , second holder  86 , and the temperature control unit  115 . The thermal protector  147  is a switching element which prevents overheating of the temperature control unit  115  as described above. 
     The controller  134  receives the output from the photointerrupter  140 , position sensors  141  through  143 , temperature sensors  144  through  146 , and thermal protector  147 , and controls the drive circuit unit  137 . In this instance, the controller  134  is a microcomputer, and the input unit  135  and the output unit  138  are integratedly formed touch panel type LCDs. 
     The drive circuit unit  137  is provided with a stepping motor drive circuit, syringe pump drive circuit, valve drive circuit, heater drive circuit, and laser drive circuit. The drive circuit  137  receives the output from the controller  134 , and drives the stepping motors  4 ,  16 ,  17 , and  45  shown in  FIG. 1 , syringe pumps  131  through  133  shown in  FIG. 16 , and syringe pumps  196  and  197 , valves  101  through  106 ,  191  through  194 ,  198  and  199 , heaters  36 ,  87 ,  148 , and laser light source  117 , as shown in  FIG. 16 . 
     Dilution Solution Composition 
     The composition of the dilution solution accommodated in the dilution solution container  34  is described below. 
     
       
         
               
               
               
               
             
               
               
               
             
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Citric acid 
                 100 
                 mmol 
               
               
                   
                 Sodium sulfate 
                 90 
                 mmol 
               
               
                   
                 Amidosulfuric acid 
                 100 
                 mmol 
               
             
          
           
               
                   
                 NaOH 
                 Amount to obtain a solution 
               
               
                   
                   
                 pH of 2.5 
               
             
          
           
               
                   
                 Tetradecyltrimethylammonium 
                 1 
                 g 
               
               
                   
                 salt 
               
               
                   
                 Purified water 
                 1 
                 liter 
               
               
                   
                   
               
             
          
         
       
     
     This dilution solution has a pH of 2.5. Since the dilution solution is acidic, the cell membrane and cell walls of the bacteria in the urine are damaged. Accordingly, the bacteria in the samples can be reliably stained with staining solution, and can be reliably detected by the flow cytometer shown in  FIG. 16 . When this dilution solution is used as a washing solution, since it is acidic, it damages the cellular membrane and cellular walls of the bacteria in the urine so as to weaken the adhesion of the bacteria to the pipette and provides highly effective washing. Polymethylene colorant may be used as a staining solution. A representative staining solution is described in detail in United States Patent Application Publication No. 2002/0076743. 
     Sheath Fluid Composition 
     The composition of the sheath fluid used in the sample analyzer of the present embodiment is described below. 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Sodium chloride 
                 53.0 
                 g 
               
               
                   
                 Maleic acid 
                 0.5 
                 g 
               
               
                   
                 Tris(hydroxymethyl)amino 
                 1.51 
                 g 
               
               
                   
                 methane 
               
               
                   
                 EDTA-2K 
                 0.2 
                 g 
               
               
                   
                 Purified water 
                 1.0 
                 liter 
               
               
                   
                   
               
             
          
         
       
     
     This sheath fluid has a pH of 7.8. 
     Analysis Sample Preparation Operation 
     The analysis sample preparation operation is described below. 
     (A) Turntable Initialization 
     First, the initialization operation is described wherein a required drive pulse number Nb is determined for the stepping motor  45  to rotate the sample container Ts only one pitch on the turntable  42  based on the flow chart of  FIG. 19 . 
     When the power source of the control system shown in  FIG. 17  is turned ON, a drive pulse is supplied to the stepping motor  45 , and the turntable  42  is rotated in the clockwise direction (S 1 ). Then, the light shield  62   a  shields the photointerrupter  140  (hereinafter referred to as “sensor ON”) (S 2 ), the count of the drive pulse applied to the stepping motor  45  starts (S 3 ), and the motor actuation continues (S 4 ). When the sensor is turned ON (S 5 ), the application of the drive pulse to the stepping motor  45  is stopped, the count ends for the drive pulse number N required for one rotation of the turntable  42 , and the stepping motor  45  stops (S 6 ). 
     The number of drive pulses required to rotate the turntable  42  one pitch is calculated as Na=N/5 (S 7 ). Na is a value which ignores over rotation due to inertia. 
     Next, Na individual drive pulses are repeatedly applied to the stepping motor  45 , and the turntable  42  is repeatedly rotated and stopped (S 8 , S 9 , and S 10 ). 
     This time, since the turntable  42  rotates with an accumulation of over rotations due to inertia each time the turntable stops, the sensor is turned ON while the fifth Na individual drive pulses are being applied insofar as the Na individual drive pulses have not all been applied (S 11 ), and the number of drive pulses remaining is only ΔN. Then, the remaining number of pulses ΔN is calculated as the accumulated amount of over rotation (S 12 ). 
     The Na calculated in S 7  is corrected as Nb=(N−ΔN)/5 in consideration of the amount of over rotation (S 13 ), and stored in the memory  134   b  ( FIG. 17 ) as the correct drive pulse number to rotate the turntable  42  one pitch (S 14 ). 
     A predetermined number of drive pulses are applied to the stepping motor  45  after the sensor is turned on in S 11 , and when the turntable  42  reaches a position that is most convenient for a user to remove the container holder  61  from the rotating plate  62 , that is, a position at which the guide block  63  crosses the straight line L at a right angle in  FIG. 2 , the stepping motor stops, and the turntable initialization operation ends (S 15 , S 16 , and S 17 ). 
     (B) Specimen Container and Mixing Container Placements 
     Next, the handle  71  shown in  FIG. 6  is grasped and pulled toward the front so as to slide the container holder  61  to the front on the rotating plate  62 , and the container holder  61  is then removed from the rotating plate  62 . A user then loads sample containers Ts containing different 300 μL samples (e.g., urine) into the five holes  74  of the first holders  68  of the container holder  61  shown in  FIG. 9 , and loads the empty mixing containers Tm into the five empty container holes  67 . 
     Then, the user grasps the handle  71  and installs the container holder  61  on the rotating plate  62  as shown in  FIG. 8 . At this time, the container holder  61  slides onto the rotating plate  62  so as to insert the guide block  63  shown in  FIG. 8  into the channel  70  shown in  FIG. 11 , and the positioning pin  65  is inserted into the positioning hole  69  via the force exerted by the compression spring  64  as shown in  FIG. 6 . Accordingly, the container holder  61  is stopped by the protrusion  66  so as to position the container holder  61  on the same axis as the rotating plate  62 . 
     (C) Automated Preparation Operation 
     The processes (1) through (26) are automatedly executed by the control system shown in  FIG. 17 . 
     (1) When a user places the container holder  61  on the rotating plate  62  as described above and a start command is input to the input unit  135  ( FIG. 17 ), the stepping motor  45  rotates in a clockwise direction so as to cause the turntable  42  to be rotated in conjunction therewith, and when the sensor is turned ON, the turntable  42  is stopped at the initial position shown in  FIG. 2 . This time, the first sample container Ts and the two mixing containers Tm on both sides of the sample container Ts are aligned on the straight line L. At the same time, the first holder  68 , which accommodates the first sample container Ts, confronts the magnet coupling  91  as shown in  FIG. 5 . 
     (2) Then, the stepping motors  4  and  17  shown in  FIG. 1  are operated, the mixing container Tm on the right side, among the two mixing containers Tm on the straight line L shown in  FIG. 2 , is held by the catcher  27  and inserted into the second holder  86  of the mixing container rotation mechanism  44 . At this time, a current is already flowing to the film heater  87  ( FIG. 4 ) of the mixing container rotation mechanism  44  and the temperature of the second holder  86  is maintained at 42° C. 
     (3) Next, the stepping motors  4  and  17  are operated, and the empty mixing container Tm remains in the second holder  86 , and the catcher  27  is pulled from the second holder  86 . 
     (4) Then, the valve  198  ( FIG. 27 ) is opened, and after the syringe pump  197  performs a suctioning operation, the valve  198  is closed and the valve  199  is opened and the syringe pump  197  performs a discharge operation so as to fill the sample part  168  of the first pipette  28  and the reagent part  169  ( FIG. 24 ) and the flow path connecting the two with sheath fluid. 
     (5) Thereafter, the stepping motors  4  and  16  are actuated, and the first pipette  28  is inserted into the dilution solution container  34  and 340 μL of the dilution solution is suctioned to the reagent part  169  ( FIG. 24 ), and heated to 42° C. by the pipette heater  36 . 
     (6) Next, the stepping motor  16  is actuated and the first pipette  28  is withdrawn from the dilution solution container  34 , and 20 μL of air is suctioned into the sample part  168 . In this way an air gap having a 20 μL volume is formed. 
     (7) Then, the stepping motors  4  and  16  are actuated, and the first pipette  28  is inserted into the sample container Ts located on the straight line L in  FIG. 2 . At this time, the first pipette  28  is held at a position which is eccentric from the axis of the sample container Ts. 
     (8) Next, the stepping motor  45  rotates in a counter clockwise direction for a predetermined time. In this way the pulley  58  is rotated in a counter clockwise direction, and the sample container Ts on the straight line L is also rotated in a counter clockwise direction. During the rotation of the sample container Ts, the first pipette  28  suctions the sample (40 μL) within the sample container Ts and discharges the sample into the sample part  168  ( FIG. 24 ). Then, the suctioning and discharging operations are repeated. The sample is thoroughly mixed by the rotation of the sample container Ts relative to the eccentrically positioned first pipette  28 , and the suctioning and discharging operation performed by the first pipette  28 . 
     (9) After the first pipette  28  has discharged all of the sample of the sample part  168 , 50 μL of the sample is suctioned from the sample container Ts. In the sample part  168 , an air gap having a 20 μL volume is formed between the suctioned sample and the dilution solution via the previously described process (6), and the sample and the dilution solution are not mixed. 
     (10) Next, the stepping motors  4  and  16  are actuated, and the first pipette  28  is withdrawn from the sample container Ts and inserted into the empty mixing container Tm held in the second holder  86  as described in process (2). At this time, the first pipette  28  is held at a position which is eccentric to the axis of the held mixing container Tm. 
     (11) Then, the first pipette  28  discharges the 340 μL of solution, which has been heated to 42° C., and the suctioned 50 μL of sample into the mixing container Tm. At the same time, the stepping motor  45  rotates counterclockwise for a predetermined time. Accordingly, the mixing container Tm containing the dilution solution and the sample is rotated about its axis. 
     During the rotation of the mixing container Tm, the first pipette  28  repeats the suctioning and discharging operation to a maximum volume of approximately 70 μL so that the fluid does not invade the reagent part  169 . 
     A sample uniformly diluted 8 times is prepared by the rotation of the mixing container Tm relative to the eccentrically positioned first pipette  28 , and the suctioning and discharging operation performed by the first pipette  28 . 
     (12) Thereafter, the stepping motors  4  and  16  are actuated, and the first pipette  28  is withdrawn from the mixing container Tm. 
     (13) Then, the stepping motors  4  and  16  are actuated, and the first pipette  28  is inserted into the receptacle  184  of the washing chamber  180 . 
     (14) Next, the valve  199  ( FIG. 27 ) is opened and, via the discharge operation of the syringe pump  197 , approximately 2 ml of the sheath fluid filling the first pipette  28  is discharged into the receptacle  184  by the previously described process (4). In this way the inside of the first pipette  28  is washed. 
     (15) Then, the valve  193  ( FIG. 26 ) is opened, and the sheath fluid discharged into the receptacle  184  is drained into the drainage chamber  195 . The valve  193  is then closed. 
     (16) In parallel with processes (14) and (15), valve  191  is opened, and the syringe pump  196  performs a suctioning operation. The valve  191  is then closed. 
     (17) Next, the stepping motor  16  is actuated, and the tip of the first pipette  28  is raised to a position approximately 2 cm lower than the nipple  181  and the nipple  182  ( FIG. 25 ). 
     (18) Then, the valves  192  and  194  ( FIG. 26 ) are opened, and the syringe pump  196  performs a discharge operation. In this way the sheath fluid is injected from the nipple  181  ( FIG. 25 ) into the receptacle  184  and discharged from the nipple  182 , and the outside of the first pipette  28  is washed by the flow of the sheath fluid generated at this time. The valves  192  and  194  are then closed. 
     (19) Next, the valve  193  is opened, and the sheath fluid inside the receptacle  184  is drained into the drainage chamber  195 . The valve  193  is then closed. 
     (20) Then, the stepping motors  4  and  17  are actuated, and the second pipette  29  is inserted into the mixing container Tm. At this time the second pipette  29  is held at a position which is eccentric to the axis of the mixing container Tm. 
     (21) Then, the second pipette  29  discharges 10 μL of a staining solution supplied from the stain container  112  shown in  FIG. 16  into the mixing container Tm. At the same time, the stepping motor  45  rotates in a counter clockwise direction for a predetermined time. Accordingly, the mixing container Tm is rotated about its axis. During the rotation of the mixing container Tm, the second pipette  29  repeats the suctioning and discharging operations. The staining fluid is uniformly mixed with the dilute sample by the rotation of the mixing container Tm relative to the eccentrically positioned second pipette  29 , and the suctioning and discharging operation performed by the second pipette  29  so as to prepare an analysis sample. The prepared analysis sample is held at 42° C. by the film heater  87  of the mixing container rotation mechanism  44 . 
     (22) Thereafter, the stepping motors  4  and  17  are actuated, and the second pipette  29  is withdrawn from the mixing container Tm. 
     (23) Then, the stepping motors  4  and  17  are actuated, the second holder  86  is withdrawn from the mixing container Tm by the catcher  27 , and transported to the third pipette  48 , whereupon the third pipette  48  is inserted into the mixing container Tm. Then, the third pipette  48  suctions analysis sample from the mixing container Tm. 
     (24) Next, the stepping motors  4  and  17  are actuated, and the catcher inserts the empty mixing container Tm into a discard hole  35  of the container discard unit  46  where it is discarded. 
     (25) Then, the stepping motors  4  and  17  are actuated, and the catcher grips and lifts the top part of the washing unit  52 , and inserts the third pipette  48  into the washing unit  52 . In this way the third pipette  48  is washed. 
     (26) Then, the stepping motors  4 ,  16 , and  17  are actuated, and the washing unit  52  is returned to the position shown in  FIG. 1 , and the first pipette  28 , second pipette  29 , catcher  27 , and the horizontally movable plate  8  are returned to the positions shown in  FIG. 1 . 
     Next, when Nb individual drive pulses are applied to the stepping motor  45  and the turntable  42  is rotated in a clockwise direction, the next sample container Ts and empty mixing containers Tm are aligned on the straight line L of  FIG. 2  so as to prepare the next analysis sample. 
     Sample Analysis Operation 
     In the structure shown in  FIGS. 16 and 17 , when the valves  101  and  102  are opened during a prescribed time, the analysis sample prepared by the sample preparation unit shown in  FIG. 1  and maintained at a temperature of 42 C flows into the flow path  139  between the valves  101  and  102  through the third pipette  48  via the negative pressure. Thereafter, the valves  101  and  102  are closed. 
     Next, the sample is discharged from the nozzle  113  to the sheath flow cell  107  when the syringe pump  133  pushes a fixed amount of the sample in the flow path  139  to the nozzle  113 . 
     At the same time, sheath fluid heated to 42° C. by the temperature control unit  115  is supplied to the sheath flow cell  107  by opening the valve  105 . 
     In this way the sample is encapsulated in sheath fluid, and a sheath flow is formed which is narrowed by the orifice  111 . The one side of the orifice  111  has a rectangular slot measuring 100 to 300 μm and formed of optical glass. 
     Particles or tangible components included in the sample can flow one by one in a row through the orifice  111  by forming the sheath flow in this way. The sample and sheath fluid which have passed through the orifice  111  are discharged from the discharge port  114 . 
     Then, laser light emitted from a laser light source  117  is condensed to an oval by a condenser lens  118  and directed at the sample flow  126  flowing through the orifice  111 . The size of this oval is approximately the same as the diameter of analysis particles in the direction of the sample flow, for example, about 10 μm, and is sufficiently larger than the analysis particle diameters in a direction perpendicular to the sample flow direction, for example, approximately 100 to 400 μm. 
     The laser light which has passed through the flow cell  107  without impinging the particles contained in the sample is blocked by the beam stopper  119 . Forward scattered light and forward fluorescent light from the particles irradiated by the laser light are collected by the collector lens  120 , pass through the pinhole  121  of the light shield  130 , and reach the dichroic mirror  122 . 
     The long wavelength scattered fluorescent light directly passes through the dichroic mirror  122  and is detected by a photomultiplier tube  124  after scattered light is eliminated by the filter  123 , and is then output as a fluorescent signal  127  (pulse-like analog signal). 
     The scattered light is reflected by the dichroic mirror  122 , received by the photodiode  125 , and output as a scattered light signal  128  (pulse-like analog signal). Then, the fluorescent light signal  127  and the scattered light signal  128  are input to the controller  134  shown in  FIG. 17 . 
     The calculator  134   a  calculates the scattered light pulse width Fscw and the scattered light intensity Fsc from the maximum value and pulse width of the scattered light signals  128 . 
     The calculator  134   a  similarly calculates the fluorescent light pulse Flw and fluorescent light intensity Fl from the pulse-like fluorescent light signal  127 . 
     The controller  134  creates distribution maps (histogram and scattergram) based on the obtained Fscw, Fsc, Flw, and Fl, and classifies leukocytes and bacteria. Then, the classified particles are counted and converted to a number per 1 μL of sample. The result is output to the output unit  138  together with each type of distribution map. This completes the analysis operation of a single analysis sample. The samples of the four remaining sample containers Ts are similarly subjected to the sequential rotation of the turntable  42 , analysis sample preparation, and analysis operation. 
     Washing Operation 
     When the particle count result indicates the presence of a bacteria population of 10 7  per 1 μL of sample or greater, the washing operation performed in the automated preparation process (14) and the like does not produce adequate washing of the first pipette  28  (particularly the inside of the first pipette  28 ), and this may adversely affect the measurement result of the subsequent analysis sample. Therefore, in this instance, the washing operation described below is performed. A threshold setting unit (not shown) may be provided in the controller  134  so as to enable the user of the apparatus to set a value (threshold) of 10 7 . 
     (1) The stepping motors  4  and  16  are actuated, and the first pipette  28  is inserted in the dilution solution container  34 , and 340 μL of dilution solution is suctioned to the reagent part  169  ( FIG. 24 ). 
     (2) Next, the stepping motors  4  and  16  are actuated, and the first pipette  28  is inserted in the receptacle  184  ( FIG. 25 ) of the washing chamber  180 . In this process, the dilution solution is kept in the first pipette  28  for approximately 3 seconds. 
     (3) Then, the syringe pump  131  ( FIG. 27 ) performs a discharge operation and the dilution solution in the reagent part  169  is discharged to the receptacle  184 . The syringe pump  131  then performs a suctioning operation and the dilution solution discharged to the receptacle  184  is suctioned into the reagent part  169 . 
     (4) Process (3) is repeated 5 times. Thereafter, the syringe pump  131  performs a discharge operation and the dilution solution in the reagent part  169  is discharged to the receptacle  184 . In this way the inside of the first pipette  28  is effectively washed. As mentioned above, the dilution solution is highly effective for washing because it is acidic (pH=2.5) and contains a type of surface-active agent, tetradecyltrimethyl ammonium salt. 
     (5) Next, the valve  193  ( FIG. 26 ) is opened, and the dilution solution discharged to the receptacle  184  is drained to the drainage chamber  195 . The valve  193  is then closed. 
     (6) In parallel with process (5), the valve  191  is opened, and the syringe pump  196  performs a suctioning operation. The valve  191  is then closed. 
     (7) Then, the stepping motor  16  is actuated and the tip of the first pipette  28  is raised to a position approximately 2 cm lower than the nipple  181  and the nipple  182  ( FIG. 25 ). 
     (8) Then, the valves  192  and  194  are opened and the syringe pump  196  performs a discharge operation. In this way the sheath fluid is injected from the nipple  181  ( FIG. 25 ) into the receptacle  184  ( FIG. 25 ) and discharged from the nipple  182 , and the outside of the first pipette  28  is washed by the flow of the sheath fluid generated at this time. The valves  192  and  194  are then closed. 
     (9) Next, the valve  193  is opened and the sheath fluid inside the receptacle  184  is drained into the drainage chamber  195 . The valve  193  is then closed. 
     The syringe pump  132  and valves  103  and  104  shown in  FIG. 16  operate during the above-described analysis sample preparation process (21). That is, the valve  104  is opened, and a staining solution is once suctioned from the stain container  112  by the syringe pump  132 , the valve  104  is then closed and the valve  103  is opened, and a predetermined amount of the suctioned staining solution is discharged from the second pipette  29  by the syringe pump  132 . Furthermore, the valve  103  is then closed, and the syringe pump  132  operates reciprocally so as to perform the suction and discharge operations to the second pipette  29 . 
     This sample analyzer improves the washing capability without reducing the processing capability of the apparatus, without increasing the amount of washing solution used, and without enlarging the apparatus. 
     Although the embodiment described above is constructed so that a sample suctioned from a sample container held by a first holder  68  is discharged into a mixing container held by a second holder  86 , the present invention is not limited to this arrangement, inasmuch as various structures may be used, such as suctioning a sample from a sample container positioned at another location and discharging this sample to a mixing container held by the first holder  68  and the like. 
     Sample suctioned from the pipette of the sample analyzer of the present embodiment may be fluids such as urine, peritoneal fluid, pleural fluid, bone marrow fluid, bile, blood, and the like from lactating animals including humans, and also beverages, organic and inorganic foods, and the like. 
     In addition to the optical detection units such as a flow cytometer and the like, electrical property detection units such as electrical resistance sensors and the like used for erythrocyte sensors in hematocytometers also may be used as the detection unit. 
     It is desirable that the dilution solution used in the sample analyzer of the present invention has a pH less than about 5.0. A pH of between about 2 and about 3 is particularly desirable. 
     Furthermore, the dilution solution used in the sample analyzer of the present invention may include an acidic buffering agent. 
     The acidic buffering agent is not specifically limited, and suitable examples include but are not limited to citric acid, phthalic acid, glycine, succinic acid, lactic acid, β-alanine, ε-aminocapronic acid, and fumaric acid, and the like, and combinations thereof. 
     The dilution solution used in the sample analyzer of the present invention may include a surface-active agent. 
     Examples of useful surface-active agents include but are not limited to cationic surface-active agents, anionic surface-active agents, ampholytic surface-active agents, nonionic surface-active agents, and the like, and combinations thereof. 
     Although cationic surface-active agents are not specifically limited, quaternary ammonium salts having the structural formula shown below are desirable: 
     
       
                 
         
             
             
         
      
     
     In the formula, R14 represents an alkyl group having 6 to 18 carbon atoms or (C 6 H 5 )—CH 2 —; R11, R12 and R13 represent the same or different alkyl groups or benzyl groups having 1 to 3 carbon atoms; and Y represents a halogen ion. 
     Examples of useful alkyl groups with 1 to 3 carbon atoms include methyl, ethyl, propyl, and the like. Examples of useful alkyl groups with 6 to 18 carbon atoms include but are not limited to hexyl, heptyl, octyl, decyl, dodecyl, tetradecyl, and the like. Examples of useful halogens include flourine, bromine, iodine, chlorine, and the like. Specifically, suitable materials are hexyltrimethyl ammonium salt, octyltrimethyl ammonium salt, decyltrimethyl ammonium salt, dodecyltrimethyl ammonium salt, tetradecyltrimethyl ammonium salt, hexadecyltrimethyl ammonium salt, octadecyltrimethyl ammonium salt, and benzyltrimethyl ammonium salt. 
     Another example of a cationic surface-active agents are pyridinium salts:
 
[(C5H5)N + —(CH2) n -CH3]Y − .
 
     In the formula, n represents 7 to 17; and Y represents a halogen ion. Specifically, suitable materials include octyl pyridinium salt, decyl pyridinium salt, dodecyltrimethyl pyridinium salt, tetradecyltrimethyl pyridinium salt, hexadecyltrimethyl pyridinium salt, and the like. The concentration of the cationic surface-active agent is in a range of about 10 to about 50,000 mg/ml, and is desirably in a range of about 100 to about 3,000 mg/ml. 
     The anionic surface-active agent is not limited, and suitable useful examples include but are not limited to lauroylsarcosine acid salt as a N-acylaminoacetic acid salt, cocoylsarcosine acid salt, myristoylsarcosine acid salt, oleoylsarcosine acid salt, and the like. Although not limited, the concentration of the anionic surface-active agent may be, for example, in a range of about 0.1 to about 10 mg/ml, and is desirably in a range of about 0.5 to about 5 mg/ml. 
     The amphoteric surface active agent is not limited, and a useful example is the betaine acetate shown below: 
     
       
                 
         
             
             
         
      
     
     In the formula, R14 represents an alkyl group having 8 to 20 carbon atoms; R15 and R16 represent the same or different alkyl group having 1 to 3 carbon atoms, alkenyl groups or alkynyl groups having 2 to 3 carbons atoms. 
     The alkyl group with 1 to 3 carbon atoms may be the same as above. Examples of useful alkenyl groups with 2 to 3 carbons atoms include vinyl, allyl, and the like. Examples of useful alkynyl groups with 2 to 3 carbon atoms include acetylenyl, propynyl, and the like. Examples of useful alkyl groups with 8 to 20 carbon atoms include but are not limited to octyl, decyl, dodecyl, tetradecyl, and the like. Representative examples include but are not limited to docecyldimethyl ammonium-betaine acetate, hexadecyldimethyl ammonium-betaine acetate, decyldimethyl ammonium-betaine acetate, and the like. The concentration of the amphoteric surface-active agent may be about 1 to about 100 mg/ml, and a concentration of about 5 to about 20 mg/ml is desirable. 
     Nonionic surface-active agents are not limited, and suitable examples of polyoxyethylene(n)alkyl ethers have an alkyl group with 10 to 20 carbon atoms, where n represents 10 to 20. Suitable polyoxyethylene(n)alkylphenyl ethers have an alkyl group with 8 to 10 carbon atoms, where n represents 2 to 20, for example, POE (10)octylphenyl ethers, and the like. 
     Examples of useful surface-active agents other than those described above include but are not limited to triton X-100 (polyethylene-glycol-mono[p-(1,1,3,3-tetramethylbutyl)phenyl]ether), CHAPS (3-[(3-chloroamidepropyl)diethylammonio]propane-sulfonic acid), CHAPSO (3-[(3-chloroamidepropyl)dimethylammonio]-2-hydroxypropane-sulfonic acid), BIGCHAP (N,N-bis(3-D-gluconamidepropyl)chloramide), dioxy-BIGCHAP (N,N-bis(3-D-gluconamidepropyl)dioxychloramide), sucrose monocaprate, sucrose monocholate, n-octyl-α-D-glucopyranoside, n-heptyl-α-D-thioglucopyranoside, n-octyl-α-D-thioglupyranoside, n-dodecyl-α-D-maltopyranoside, n-nonyl-α-D-thiomaltopyranoside, and the like. 
     Although a sheath fluid and dilution solution are used as the washing solution in the above described embodiment, purified water may be used instead of the sheath fluid. 
     Water such as purified water, and solvent mixtures such as water and alcohols such as ethanol, methanol, and the like may also be used as the solvent. 
     The foregoing detailed description and accompanying drawings have been provided by way of explanation and illustration, and are not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be obvious to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.