Automatic sampler apparatus
United States Patent Pecsar et al.  
 [451 Apr. 15, 1975 AUTOMATIC SAMPLER APPARATUS Inventors: Raymond Ernest Pecsar, Walnut Creek; Brent Earl Wadsworth, Concord, both of Calif.  
 Assignee: Varian Associates, Palo Alto, Calif.  
 Filed: Mar. 5, 1973 Appl. No.: 337,799  
 U.S. Cl. 73/425.6; 23/230; 23/259; 134/22 C; 134/34 Int. Cl. r. B08b 9/02; GOln l/OO Field of Search 7-3/422 GC, 423 A, 425.6; 23/253 R, 259 R; 134/22 R, 22 C, 34, 37  
 References Cited UNITED STATES PATENTS 11/1969 Mutter et al. 73/423 A 8/1973 Harris, Sr. et al. 73/423 A Primary ExaminerS. Clement Swisher Attorney, Agent, or FirmGerald M. Fisher; Stanley Z. Cole [57] ABSTRACT A system for injecting sample fluids into an analyzer and processing the analysis data is disclosed. The system comprises a fluid sample analyzer, a sample storage module for a number of fluid samples, an injection module by which samples are injected into the analyzer, a data recording or processing device, and a control module for governing and sequencing the operation of the system.  
 The storage module houses a plurality of sample containing trays which can be loaded with samples remote from the system. A gas operated purging system is employed for minimizing the quantity of residual material injected into the analyzer with successive samples.  
 2 Claims, 9 Drawing Figures PATENTEUAPR 1 51975 sum 3 or 5 suznunrg;  
  N3 Sq EOE PATENTEDAPR I 51915 3.877, 3 1 0 sum 5 1 5 FIG.9  
 AUTOMATIC SAMPLER APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the analysis of sample fluids and more particularly relates to systems for controlling the introduction of sample fluids into an analyzer.  
 2. Prior Art Systems for supplying fluid samples for analysis by equipment, such as chromatographic analyzers, have been proposed by the prior art. Some prior art systems have employed a syringe for introducing a predetermined quantity of sample fluid into the analyzer equipment. Sample fluids to be analyzed were disposed in separate closed sample containers and successive individual fluid samples were removed from their containers, supplied to the syringe, and injected into the equipment.  
  It is imperative in most sample analyses that the sample fluid being analyzed be as free as possible from any type of foreign substance. Accordingly, the injection syringe was required to be thoroughly purged of one sample fluid and/or any residual cleansing solvent before a succeeding sample was placed in the syringe. The syringes employed for sample fluid injection were quite delicate because of the extremely small quantities of sample fluid they handled, e.g. quantities of from 5 50 microliters, this made manual operation and purging of the syringes both tedious and time consuming. Furthermore, when large numbers of samples were being successively analyzed, a skilled operator was required to attend the equipment and perform the tedious and repetitive task for purging and filling the syringe.  
  In order to increase the speed and efficiency of the analysis of multiple fluid samples, mechanized syringe handling systems were proposed. The purpose of such systems was to reduce the amount of operator time required in connection with the analysis procedures and to reduce equipment failures, e.g. the syringe breakage and damage which inevitably resulted from frequent handling. 5  
  The mechanized systems generally consisted of a supporting tray for sample containers and an injection syringe manipulating mechanism which functioned to enable removal of sample fluid from individual containers, injection of the fluid into the analyzer and purging of the syringe. The sample container trays were usually actuatable to index successive sample containers to a location from which fluid was transferred to the syringe.  
  While the prior art mechanized systems were effective in reducing the amount of operator time required to analyze fluid samples, several problems relating to syringe manipulation and purging remained unsolved and errors in sample identification due to handling by the operators were encountered.  
  In some proposals the mechanized syringe purging left undesirably large quantities of foreign materials in the samples which were injected into the analyzers. In one type of system, for example, the syringe plunger was mechanically reciprocated during purging to draw in the expel successive charges of solvent and/or sample fluid prior to injection of that sample fluid into the analyzer.  
  In another type of system, a side arm syringe was employed and purging was accomplished by retracting the syringe plunger beyond the syringe side arm port after which solvent and/or sample fluid was pumped through the syringe barrel for a predetermined period of time.  
  Both of these purging procedures, while preferable to manual purging, left undesirably large quantities of foreign material in the sample fluid injected into the analyzers. ln particular it was discovered that volatile fluids created pump cavitation which resulted in the formation of gas bubbles in the purge fluid. This reduced the purging effectiveness.  
  In still other proposals, sample liquids were subjected to a predetermined differential gas pressure for a predetermined period of time so that the sample liquid was forced through the injection syringe and associated conduits to effect purging. Because sample fluid viscosity varied widely, these systems were subject to expending to much sample fluid during the purging process when low viscosity fluids were employed, and did not expend adequate quantities of fluid for complete purging of highly viscous samples. In circumstances where highly volatile fluid samples were analyzed the partial pressure of the fluid vapor tended to substantially increase the applied pressure differential and the purge volume was thus difficult to accurately control.  
 SUMMARY OF THE INVENTION The present invention provides a new and improved sample analysis method and system wherein fluid samples to be analyzed need not be loaded by the operator of the analysis system and confusion as to the identify of fluid sample analysis results is minimized; sample fluid injection equipment and associated sample flow conduits are purged by a controlled volume of purging fluid so that samples of fluid injected in the apparatus are nearly uniformly pure regardless of differences in sample fluid viscosity and/or volatility; the volume of sample fluid injected into the analyzer is accurately governed by adjustable dosage controls; damage to syringe-like elements of the system resulting from misalignment of sample containers or other fluid receivers and the styringe-like elements is avoided; and numerous different sample fluids can be analyzed automatically without requiring full time attendance of a skilled operator.  
  In a preferred and illustrated embodiment of the invention a system is provided which comprises a sample analyzer, a sample injection module by which a sample of fluid to be analyzed is injected into the analyzer, a sample storage module which houses a number of discrete samples of fluid to be analyzed and which supplies sample fluid to the injection module, a sample analysis computer which may be programmed to partially govern operation of the system, and an electronic control module which governs operation of the components of the system.  
  The sample storage module receives a plurality of separate sample storage trays, or racks, in which a number of sample containers may be placed. The trays or racks are detachably connected to the storage module and as such can be loaded with samples remote from the analysis system. The trays or racks can be loaded with containers in laboratories and forwarded to the analysis system. The operator of the system thus does not have to load or unload trays and is not required to account for the identify and location of any given fluid sample.  
  The sample storage module is detachably connected to the injection module and sample fluid which is withdrawn from an individual container in the storage module is conducted into the injection module via a sample conduit. The injection module includes a syringe connected to the conduit which injects a predetermined dose of the fluid into the analyzer. Prior to the injection of a sample, the sample conduit and the injection syringe in the module are purged to remove residual fluid from a previous cycle of the system.  
  In the preferred and illustrated embodiment of the invention, purging fluid (either sample fluid or a solvent) is located in a container which is closed by a septum. A syringe-like dipper tube assembly is advanced into the container through the septum. The dipper tube assemblies comprises a first tube which communicates with the injection syringe through the sample conduit and a second tube which is connected with a purging system.  
  When the dipper tube assembly is advanced into the container, the purging system is then operated to expose the fluid in the container to a predetermined volume of gas at a predetermined pressure, preferably by discharging an accumulator into the container via the second dipper tube conduit. This creates a pressure differential across the sample extracting dipper tube, the conduit and the injection syringe so that a predetermined quantity of the fluid is directed through the-injection module. The pressure differential across the purging fluid diminishes as fluid flows from the container and when the pressure differential has decayed to about zero, a predetermined quantity of the fluid has beer flowed through a conduit and injection syringe. It has been found tht the use of a purging volume approximately times the volume of the sample conduit and injection syringe consistently reduces the quantities of residual material in the system extremely low extremelylow levels.  
  Another important feature of the invention resides in the positioning of the injection syringe plunger during the purging process. In the preferred and illustrated embodiment of the invention the injection syringe is a side arm syringe and the projecting end of the syringe plunger is at least partially aligned with the side arm port in the syringe barrel so that purging fluid directed through the syringe impinges directly on the end of the plunger. This has the effect of scouring the plunger end to dislodge any remaining material from previous injection or purging cycle and to remove that material from the syringe.  
  While the system is being purged, the injection syringe directs the purging fluid into a drain system which retains the fluid and minimizes the amount of fluid vapor in the atmosphere around the injection module. When purging has been completed the injection syringe is operated to move the plunger of the syringe to a position at which a controlled dose of the sample liquid is disposed in the syringe after which the syringe is removed from the drain and inserted into the analyzer inlet. The predetermined dose of the sample is then injected into the inlet for analysis.  
  Another feature of the inention is the provision of a sample analysis system wherein a control module governs operation of sample storage and injection modules and is capable of interrelating these operations with a computer. The system is constructed and arranged so that the entire analysis of multiple samples can be controlled by a programmed computer while at the same time permitting system operation by an operator.  
  Other features and advantages of the invention will be apparent from the following detailed description of a preferred embodiment made with reference to the accompanying drawings which form a part of the specification.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of an injection module;  
  FIG. 2 is a cross sectional view seen approximately from the plane indicated by the line 22 of FIG. 1;  
  FIG. 3 is a cross sectional view seen approximately from the plane indicated by the line 33 of FIG. 1;  
  FIG. 4 is a cross sectional view seen approximately from the plane indicated by the line 4-4 of FIG. 3;  
  FIG. 5 is a cross sectional view seen approximately from the plane indicated by the line 5-5 of FIG. 3;  
  FIG. 6 is a plan view of a sample storage container module;  
  FIG. 7 is a cross sectional view seen approximately from the line 77 in FIG. 6;  
  FIG. 8 is a cross sectional view of part of a dipper tube assembly; and  
  FIG. &#39;9 is a schematic diagram of a fluid pressure system contained within the injection and storage modules.  
 DESCRIPTION OF A PREFERRED EMBODIMENT An automatic sample system embodying the present invention is illustrated in FIG. 8 as comprising a sample analyzer 12a, which may be, for example, an apparatus for analyzing a fluid sample by liquid or gas chromotography; a sample injection module 14 by which a sample of fluid to be analyzed is injected into the analyzer 12a; a sample storage module 16 which houses a number of discrete samples of fluid to be analyzed and which supplies sample fluid to the injection module.  
  In brief, the system 10 operates in the following manner: The injection module and sample storage module are connected to each other in a desired orientation and are detachably connected to the analyzer 12a, which may be of any suitable or conventional type or construction, and a number of containers of sample fluid are disposed in the storage module. Automatic operation of the system is then initiated by the operator which results in a predetermined quantity of sample fluid from one container inthe storage module 16 being extracted and delivered to the injection module 14 from which a predetermined quantity of the sample is injected into the analyzer l2a.The analyzer 12a processes the sample fluid and data resulting from the analyzer process is fed to a computer and/or a recorder.  
  Prior to the injection of each fluid sample into the analyzer, the flow passageways through which the sample passes from the storage module into the analyzer are purged to remove substantially all traces of the preceding sample fluid from the passages prior to the introduction of the next succeeding sample to the analyzer. Purging/ls conducted using the next succeeding sample fluid itself or using a suitable solvent and then the next succeeding sample fluid so that the possibility of contaminating any given fluid sample by the preceding sample or the solvent is minimized. The purging solvent is contained by the storage module like the samples and is introduced into the passages to be purged.  
  The sequence of operation of the system is governed by a control module.  
  It should be appreciated that the brief description of the operation of the system has been simplified and generalized in order to provide an overall understanding of the functions and interrelationships of the various modules and components of the system. The various modules and components of the system are described separately below.  
 The Injection Module 14 The injection module 14 comprises a support frame 30 which supports a syringe carriage assembly 32, a carriage actuator 34 and a waste receiving system 36. The syringe carriage assembly 32 includes a sample injecting syringe, described in detail presently, which is movable by operation of the carriage actuator 34 to inject a predetermined quantity of sample fluid into the analyzer 12a as well as to inject purging fluid into the waste receiving system 36. The injection module 14 is illustrated in FIGS. 1-5 of the drawings.  
  Referring particularly to FIGS. 1 and 3, the frame 30 is illustrated as including side panels 40, 42, opposite end walls 44, 46 extending between the side panels, and a base section 48 extending from the end wall 46 between the side panels 40, 42. A pair of cylindrical guide rods, or ways, 50 extend between the end walls 44, 46 parallel to the side panels. The end wall 44 mounts along the face of the analyzer 12a by interconnection of the end wall 44 to the analyzer by suitable connectors (not shown). The end wall 44 defines an opening 52 which is aligned with an analyzer sample inlet which is shown in part in FIG. 3 at 12a. The sample inlet 12a is provided with an inlet port through which the needle or canulla, of the injection syringe extends when a sample is being injected into the analyzer. The inlet sample port is covered by a septum as is conventional, so that in order to inject a sample of fluid into the analyzer the syringe needle must pierce the septum covering the analyzer inlet port.  
  The side panels 40, 42 extend away from the analyzer 12 and each defines an access port 56 and connector openings 58. Fluid and/or electric conduits extend through one or the other of the ports 56 from the storage module 16 depending upon which of the side panels 40 or 42 is engaged with the storage module. The connector openings 58 function to enable detachable connection of the storage module to the injection module by screws or other suitable fasteners which extend between the modules.  
  Slot 60 enables repositioning of the storage module from one side panel of the frame 30 to the other side panel without requiring disconnection of the conduits extending between the modules during the repositioning. That is to say, the conduits can be guided from one access opening through the associated slot 60, and to the other access opening through its associated slot 60 without disconnecting the conduits from the injection module. Repositioning of the storage module with respect to the injection module might be occasioned where the storage and injection modules are utilized in connection with various analyzers having different physical configurations.  
  Removable cover panels 62, 64 are connected to the frame 30 to shield the internal components of the injection module 14 when in use, and are removed to enable access to these components for servicing and maintenance. One or both cover panels are also removed when the injection module is repositioned with respect to the storage module to enable manipulation of the interconnecting conduits from one access opening to the other as described above.  
  The syringe carriage assembly 32 is supported on the ways 50 and is reciprocally movable towards and away from the end wall 44 to accomplish the functions of injecting a sample fluid into the analyzer as well as to direct purging fluid into the waste system. The assembly 32 comprises a carriage support body which is slidably mounted upon the ways 50, a syringe assembly 72 carried by the body 70, and a syringe actuating assembly 74 also carried by the body 70.  
  The body 70 comprises a base 76 which extends parallel to the frame base section 48 between the side panel 40, 42. The base 76 carries projecting transverse flange-like portions 78, 80 through which the ways 50 slidably extend. The projecting flange-like portions are spaced apart along the body 76 to assure rectilinear motion of the carriage assembly.  
  The actuator 34 is preferably a single acting pneumatic ram type actuator comprising a cylinder 84 which is connected to the frame base 48 by a suitable pillow block connection and which has a piston rod 86 connected to the carriage flange 78. When the actuator 34 is supplied with operating fluid pressure the piston rod 86 moves the carriage assembly towards the left, as seen in FIGS. 3, to advance the syringe assembly 72 toward the frame wall 44. The actuator 34 is provided with an internal return spring which functions, when the cylinder 84 is vented, to move the carriage assembly towards the right as seen in FIG. 3 to the position which is illustrated in FIG. 5. At this position the syringe assembly 72 is retracted away from the end wall 44 to the limit of its travel.  
  The syringe assembly 72 comprises a tubular syringe barrel 90 within which a solid plunger 92 is slidably disposed. The barrel 90 and plunger 92 cooperate to define a variable volume chamber 93 within the syringe barrel. The end of the syringe barrel remote from the plunger supports a hollow needle, or canulla, 94 which communicates with the chamber 93 and projects from the syringe barrel towards the frame end wall 44. The syringe barrel 90 is preferably of the type known as a side arm syringe and defines a side wall port 96 through which fluid can be directed into the chamber 93 between the plunger and the needle 94.  
  The syringe barrel 90 is mounted on the support body 70 by a barrel support member 100 and a barrel sup porting bracket 102. The syringe barrel itself is formed from glass and is graduated appropriately. The barrel is removably connected to the barrel support member 100 and the support bracket 102 for easy replacement.  
  A syringe needle guiding and supporting member 104 is associated with the barrel support member 100 and functions to both guide and support the needle 94 as it is thrust through a septum. The member 104 is a generally U-shaped member having legs 106, 108, which extend parallel to the needle 94 along the support member 100, and a bight portion 11.0 which extends transverse to the needle. A guiding bore 1 12 is formed in the bight portion through which the needle 94 extends. The bore 112 is of a diameter which is just slightly larger than that of the needle so that the needle is guided through the bore and supported by the bight portion 110. The tip of the needle 94 extends just beyond the bight portion 110 when the carriage assembly is in the position illustrated in FIGS. 1 and 3. The leg 106 extends through an opening in the support member 100 and carries a flange-like collar 106a which is engaged by a compression spring 114 which reacts between the collar 106a and a spring abutment element 115 fixed to the body 70. The leg 106 slidably extends through an opening in the spring abutment element 115 and is aligned with an opening formed in the bracket 102 so that the member 104 may reciprocate relative to the needle 94 against the force of the spring 114.  
  The member 104 provides point of entry support for the needle 94 as the needle is advanced through a septum. For example, referring to the analyzer inlet 12a, as the carriage assembly is advanced towards the analyzer inlet 12a the bight portion 110 of the member 104 engages the analyzer inlet at about the same time that the tip of the needle 94 engages the inlet septum. As the carriage continues to advance, the needle is thrust through the septum while the member 104 engages the analyzer inlet and is prevented from moving further towards the analyzer with the needle. The member 104 thus is moved relative to the barrel support member 100 against the bias of the spring 1 14 and the bight portion 110 of the member remains adjacent that portion of the needle which is currently passing through the septum. Hence, the bight portion of the U-shaped member continually supports the needle adjacent the point of entry of the needle into the septum thus tends to minimize the possibility of bending the needle as it is being advanced through a septum.  
  The chamber 93 and the plunger 92 are preferably cylindrical and have relatively small diameters since desirable sample quantities of fluid being injected into the analyzer are normally quite small, e.g. from to 50 microliters. Accordingly, the plunger has an extremely small diameter as compared to its overall length. The plunger is supported for reciprocal movement relative to the barrel by guides which prevent the plunger from buckling under compressive loads. As seen in FIGS. 1 and 3, the plunger projects out of the syringe barrel away from the analyzer 12 and through a guide tube 92&#39; formed in a projecting leg 122 of the bracket 102. The guide tube 92&#39; closely surrounds the plunger 92 to maintain the plunger accurately aligned with the syringe barrel. The plunger projects beyond the leg 122 and terminates in a radially projecting flange-like end portion 92a.  
  The syringe actuating assembly 74 functions to reciproate the plunger 92 in the syringe barrel 90 so that a predetermined quantity, or dose, or sample fluid can be injected into the analyzer 12 and to enable purging of the chamber 93 and the needle 94. The syringe actuating assembly 74 includes a plunger drive mechanism 130, an actuator 132 for the plunger drive mechanism, and adjustable dosage stops 134, 136 which individually function to control the position of the plunger within the syringe barrel prior to the injection of a sample of fluid into the analyzer, and hence determine rather precisely the dosage of the fluid which is injected.  
  The plunger drive mechanism 130 comprises a cross bar 140 which is slidably disposed on the ways 50 and plunger engaging elements carried by the cross bar which cooperate to cushion compressive shock loadings which might otherwise be applied to the plunger, as well as to withdraw the plunger from the syringe barrel. The plunger engaging elements include a plunger guide member 142, a plunger engaging leaf spring 144 and a spring backup member 146 all of which project from the cross bar towards the plunger end portion 92a. The plunger guide 142 defines a bore through which the plunger 92 extends and the flange 92a at the projecting end of the plunger is interposed between the guide member 142 and the leaf spring 144.  
  The actuator 132 is operative to shift the cross bar and its related elements along the ways 50 relative to the carriage to reciprocate the plunger 92 with respect to the plunger barrel. When the plunger 92 is withdrawn from the syringe barrel and moved towards the right, as viewed in FIG. 3, to the position illustrated, the guide 142 engages the plunger flange 92a to transmit plunger retracting force from the actuator 132 to the plunger.  
  As the actuator 132 is operated to shift the cross bar and associated elements towards the left as seen in FIG. 3, the plunger 92 is thrust into the syringe barrel and the force from the actuator is transmitted to the plunger 92 through the leaf spring 144. When the actuator is initially operated to advance the plunger 92 into the syringe it has a spring constant so that the leaf spring 144 deflects only very slightly. The backup member 146 is positioned beyond the leaf spring so that undue deflection of the spring will not occur.  
  The actuator 132 is preferably a double acting pneumatically operated ram which provides for positive positioning of the syringe plunger 92 in the barrel. The actuator comprises a cylinder 150 ported at both ends and fixed to the carriage body 70, and an internal piston supporting a piston rod 152 connected to the cross bar 140. The piston rod 152 reciprocates the cross bar 140 relative to the carriage body.  
  The piston rod can be prevented from moving relative to the cylinder by fluid pressure forces applied to both sides of the piston when desired. This positively maintains the cross bar 140 at a predetermined location and prevents the plunger from moving relative to the syringe barrel.  
  The carriage body 70 is provided with a slot 156 (see FIG. 1) which enables the guide 142, leaf spring 144 and backup member 146 to be shifted along the direction of movement of the plunger 92 without interferring with the carriage body.  
  The dosage stops 134, 136 are identical and accordingly only the stop 136 is described in detail. The stop 136 is preferably formed by a solenoid 160 which is slidably disposed in an elongated slot 162 formed in the carriage body 70 (see FIG. 1). A clamp mechanism 164 is associated with the solenoid 160 to enable the solenoid to be clamped and maintained at any desired position along the slot 162.  
  The solenoid 160 includes an armature 168 in the form of a pin, or stop element, which, when the solenoid is actuated, projects from the solenoid 136 into the path of movement of the cross bar 140 to prevent the plunger 92 from being advanced further into the syringe barrel. The pin 168, in its extended position, is illustrated in FIG. 3. When the solenoid 160 is deenergized, the pin 168 is retracted by operation of a return spring (not illustrated) and the cross bar 140 is movable to further advance the plunger 92 into the syringe barrel.  
  When the plunger drive mechanism is in its position illustrated in FIG. 3, the cross bar is at the limit of its travel towards the frame end 46 and the plunger 92 is retracted from the syringe barrel to its limit of travel. As illustrated in FIG. 5, at the limit of plunger travel in the retracted direction, the projecting tip of the plunger 92 is adjacent the side arm port 96 of the syringe barrel so that fluid can be directed through the side arm 96 into the chamber 93 and though the needle 94. This is the manner by which the syringe barrel is purged. It should be noted that the tip of the plunger 92 is impinged on by the fluid passing through the side arm port 96 and the turbulent fluid flow at the tip of the plunger produces a scouring action on the plunger tip which aids in removing any residual materials which may otherwise cling to the plunger tip.  
  After purging is accomplished, one or the other of the dosage stops 134, 136 is energized and the actuator 132 is operated to advance the plunger 132 into the syringe barrel until the cross bar 140 abuts the projecting pin 168 of the energized dosage stop. This prevents further movement of the plunger 92 into the syringe and provides a predetermined quantity of sample fluid in the chamber 93 and needle 94 which can be then objected into the analyzer 12. The piston of the actuator 132 is then locked in position by the application of substantially equal fluid pressure on both sides of the piston and the dosage stop solenoid is deenergized to retract the pin 168. The application of fluid pressure to both sides of the actuator piston relieves any shearing force exerted by the cross bar on the pin 168 so that the pin is freely retracted.  
  The carriage body 70 is then advanced to thrust the needle 94 into the analyzer inlet after which the actuator 132 is again energized to advance the plunger 92 into the syringe barrel from the dosage stop location of the plunger to the limit of the plunger travel towards the analyzer. A predetermined dose of fluid is thus injected into the analyzer. The limit of plunger travel, in the preferred and illustrated embodiment, occurs when the cross bar 140 encounters the mounting nut for the actuator 142; however, any other suitable abutment can be provided if desired. The individual operation of the dosage stops allows two different sample dosages to be preset without requiring readjustment of the dosage stop positions.  
  As described previously with reference to FIGS. 1, 3 and 5 the syringe barrel and needle are purged by flowing fluid through the side arm 96, the chamber 93 and the needle 94 prior to the injection of a predetermined dose of the sample fluid into the analyzer 12. The purging operation is necessary to assure that the sample fluid injected into the analyzer is as pure as practical. During the purging operation, the purging fluid, whether it be a solvent or sample fluid, is expelled from the needle 94 into the waste system 36.  
  The waste system 36 is particularly adapted to receive purging fluid which is relatively volatile at room temperature and atmospheric pressure and to prevent the vapor of such fluid from escaping in quantity from the injection module. Such vapor, depending upon the nature of the fluid, can be flammable and/or toxic. The waste system 36 comprises a waste receiver 200 which communicates with a removable waste storage tank 202 through a flexible conduit 204.  
  The waste receiver 200 is generally tubular member having an end opening 206 which is covered by a septum 208. The waste receiver 200 is connected to a movable support arm 210 which normally supports the receiver 200 at a position where it is interposed between the needle 94 and the analyzer inlet 12a. The needle 94 is advanced through the septum 208 by movement of the carriage body after which purging of the syringe barrel is accomplished with the purging fluid being directed into the receiver 200 to the tank 202 via the conduit 204.  
  The support arm is pivoted to a bracket 212 and is movable with respect to the bracket to pivot the receiver 200 from its normal waste receiving position to a retracted position at which the receiver does not interfere with the movement of the needle 94 into the analyzer inlet. The receiver 200 is pivoted to its retracted position by operation of a solenoid 214 which, when energized, moved the receiver to its retracted position. When the solenoid 214 is deenergized a return spring, not illustrated, operates to return the receiver 200 to its waste receiving position.  
  The support arm 210 carries a stop member 216 which projects from the support arm towards the end wall 44 of the frame 30 and towards the carriage body 70. When the waste receiver 200 is positioned away from its retracted position, i.e. when it is interposed between the needle 94 and the analyzer inlet 12a, and the carriage 70 is advanced, the stop 216 is engaged between the carriage 70 and the end wall 44 of the frame 30 so that the actuator 34 cannot advance the needle 94 into the far end of the waste receiver 200. This prevents breakage of the syringe needle which would otherwise occur. When the waste receiver 200 is in its retracted position the stop 216 is aligned with a slot 218 formed in the carriage flange 78. Hence, when the needle 94 is advanced into the analyzer inlet 12a the stop 216 passes through the slot 218 in the carriage flange and does not impede movement of the carriage towards the analyzer.  
  In the preferred embodiment of the invention the electrical conduits for the various solenoids, the pressure conduits for the carriage body and plunger actuators and a sample fluid supply conduit to the syringe side arm port 96 are all channeled into the injection module through one of the access openings 56 from the storage module. The storage module 16 houses fluid control valves and associated parts for the various conduits.  
 The storage Module The storage module 14 supports a plurality of separate containers 240 for fluid samples and purging solvents and defines an extraction station 250 at which a fluid sample or purging solvent is extracted from a respective container and is directed to the injection module 14. The individual containers 240 are supported by a plurality of the sample supporting tray members, or racks, indicated by the reference characters 252-255 (see FIG. 6). The trays, or racks, are individually removable from the storage module 16 with their associated sample containers. An actuator assembly 258, forming a part of the module 16, moves the container supporting trays in carrousel fashion so that individual containers are successively moved to the extraction station 250 from which the contents of the container at the extraction station can be removed and directed to the injection module.  
  Referring now to FIG. 7, the storage module 16 comprises a support frame 260 which is defined by a peripherally extending skirt 262 and a circular base plate 264 connected to the skirt. Side panels 266, 268 extend perpendicularly with the respect to each other and generally tangentially with respect to the support base portion 264 and skirt 262 to define a projecting corner of the storage module. The extraction station 250 is located at the projecting corner of the module and the trays 252-255 are circularly arranged over the support base 264.  
  The sample supporting tray members 252-255 are, in most respects the same, and only the tray 253 is described in detail to the extent that the trays are identical. The tray 253 is shaped to approximate a frustum of a 90 circular segment having a circularly curved outer wall 270, radially extending side edges 272, 274 and a radially inner edge 276 which extends between the side edges. A segmental radially inner tray body 280 extends between the edges 272, 274, 276 and terminates in a circular wall portion 282. The edges of the tray member are defined by lips which project from face to the body 280 and these lips, along with radially extending webs 284, rigidify the tray body portion 280. A pair of cylindrical bosses 285 extends from the body 280 beyond the webs 284. The bosses provide a detachable driving connection with the tray actuator assembly 258 as is described in greater detail presently.  
  A radially outer tray body portion 286 extends from the wall 282 and is recessed from the body 280. The outer tray body portion 286 terminates in the circumferential wall 270 and is rigidified by integral webs 292 which extend radially outwardly from the wall 282 flush with the inner tray body portion 280.  
  A circumferential series of sample container pockets 296 (preferably 15 pockets for accommodating 15 separate containers) is disposed circumferentially about the periphery of the outer tray body 186. The pockets 286 are defined by semicircular recesses 298 formed in the tray wall 270 and semicircular faces 300 formed on projecting lugs 302 at the radially outer ends of the webs 292. The recesses 298 and faces 300 are positioned with respect to each other so that the container in each individual pocket is maintained accurately positioned in the pocket and constrained against tipping, even if the tray shoulld be vertically oriented.  
  The container support actuator 258 comprises a turntable assembly 310 to which the individual trays 252-255 are detachably connected and a turntable drive mechanism 312 by which the assembly 310, and the attached trays, can be rotated with respect to the frame base 264. The assembly 310 comprises a support shaft 314 which extends through the frame base 264 and is supported for rotation about an axis 315 by a bearing unit 316 connected to the frame base. The projecting end of the support shaft 314 carries a circular tray support member 320 which is fixed to the shaft 314 for rotation about the axis 315 and which defines four pairs of circumferentially spaced locating holes 321. A drum-like member 322 is disposed between the tray support 320 and the frame base 264 and is fixed to the shaft 314 for rotation with it.  
  A tray locking assembly 324 is disposed beyond the tray support 320 from the drum 322 and functions to permit the individual sample supporting trays to be connected to and locked in place on the tray support member.  
  The locking assembly comprises a cylindrical body 330 which is fixed to the end of the shaft 314 for rotation about the axis 315. Four shouldered holes 332 are formed in the body 330 at locations spaced 90 apart about the axis 315, with the holes extending generally parallel to the axis. A circular retainer plate 334 is connected to the body 330 to close the holes 332. Each of the holes 332 supports a shouldered detent pin 336 and a helical compression spring 338 which reacts between the detent pin 36 and the retainer plate 334 so that the projecting end of the detent pin is urged from the body 330 towards the tray support 320.  
  Trays are inserted and locked in placed in the assembly 310 by cocking the tray slightly with respect to the support member 320 and inserting the inner edge 276 of the tray between the support member 320 and the body 330 of the locking assembly. The end of the detent pin 336 is rounded so that the detent pin is forced into its shouldered hole 322 against the force of the spring 338 as the tray is slid radially inwardly along the support member 320. When the locating bosses 285 are aligned with one pair of the locating holes 321 the tray is cocked downwardly so that the bosses 285 extend through the associated locating holes 321. At this juncture the webs 284 of the tray are engaged along the face of the support member 320 and the detent pin 336 is firmly engaged with the tray body portion 280 to maintain the tray member in contact with the support member 320. The bosses 285 cooperate with their respective locating holes to enable the transmission of drive from the rotatable support member 320 to the tray.  
  The drive mechanism 312 includes a reversible electric motor 340 having a gear reduction (not shown) connected to its rotor shaft. An output shaft of the gear reduction (not shown) extends through the frame base 264 and an output pulley 344 is connected to the projecting end of the gear reduction output shaft. A drive belt 346 is reeved about the pulley 344 and the drum 322 so that drive from the motor 340 is transmitted to the turntable assembly 310 and thence to the individual trays supported by the turntable assembly.  
  The containers 240 may be of any suitable construction but in the illustrated embodiment are glass vials which fit snuggly into the pockets 296. The containers 240 have a capacity of several milliliters of fluid and each container is closed by a septum 241 which is carried by a removable cap 348.  
  The turntable assembly 310 moves the trays to position successive container locations at the extraction station 250. Fluid in a container at the extraction station is removed by a syringe-like dipper tube assembly 352 and is directed to the injection module 14. The storage module 16 provides a container locating assembly which functions to precisely align the containers at the extraction station with the dipper tube assembly so that the dipper tube assembly is not damaged from being advanced into engagement with a misaligned container.  
  The storage module also houses a fluid container identifying system which functions to identify the container at the extraction station by tray and pocket number as well as by whether the container is a sample container or a solvent container. When a container has been appropriately located at the extraction station and identified, the dipper tube assembly 352 is operated to enter the container, extract fluid from it, and direct the fluid to the injection module 14.  
  The container identification system comprises a container identifying arrangement which ascertains the kind of fluid, i.e. sample fluid or solvent, at the extraction station. When a sample fluid container is located at the extraction station the system is enabled to perform a complete purging and/or analysis cycle utilizing the sample fluid. When a solvent container is located at the extraction station the system is automatically conditioned to perform only a purge cycle to avoid the injection of the solvent into the analyzer.  
 In the preferred embodiment of the invention, the  
 containers 240 each cooperate with SPDT micro switches 382, 384 when the containers are at the extraction station and the interaction between the containers and the switch depends on whether the containers are sample or solvent containers. Three different containers 240a, 240b, and 2406 are illustrated in FIG. 7. The containers 240a and 24011 are representative of containers for solvent and sample fluid, respectively. The container 24% carries a removable ring 380a disposed about its cap 348 and spaced from the projecting end of the cap. All of the fluid sample containers 24Gb are provided with a ring 380a of the character described, and in each case the ring is positioned remote from the projecting end of the container cap 348. The container 240a carries a removable ring 38% which is disposed about the cap 348 at its projecting end. All of the solvent containers 24% are provided with a similar ring 38Gb disposed at the projecting end of the container cap 348.  
  As is best seen in FIGS. 7, the dipper tube assembly 352 comprises an extraction syringe needle assembly 430, an associated pneumatic fluid purging system 432 (see FIG. 9) and an extraction syringe actuator assembly 434. The actuator assembly 434 comprises a syringe needle support plate 436 which is connected to a single acting pneumatic ram including a cylinder 440 connected to the frame by a supporting bracket 442 and a piston rod 444 extending between the cylinder 440 and the support plate 436. A radially inwardly projecting plate and 446 carries the needle assembly 430 for reciprocating motion towards and away from a container 240 at the extraction station. The plate 436 is connected to guide rods 450, 452 which extend through bores in the bracket 442 to guide the motion of the plate and the needle assembly as the plate is reciprocated by the ram 438. The guide rod 450 is surrounded by a helical compression spring 454 reacts against the syringe support plate 436 to urge the piston rod 44 towards its fully extended position. When the piston rod retracted the plate and needle assembly 430 move towards the container and the needle assembly is thrust into the container through its system.  
  FIG. 8 illustrates the needle assembly construction and the relationship between the needle assembly and the container when the needle assembly has been forced into the container. The needle assembly 430 comprises a central tubular needle 460 having a bulletnosed tip 462 for piercing the septum and a central flow passageway 464. The central passageway communicates with a sample fluid conduit 466 which extends from the needle 460 to the side arm port of the injection syringe in the injection module. The passageway 464 opens into the container adjacent the tip 462 via ports 468 defined by a cross bore extending transversely through the needle. The ports are spaced from the tip so that they cannot core the septum and become blocked. When the needle assembly 430 is properly positioned in the container, the ports 468 are well below the level of the liquid in the contaner.  
  The needle 460 is surrounded by a second tubular needle 470 having a tapered end portion 472 fixed and sealed to the needle 460 at a location spaced from the tip 462. The needle 470 defines a passageway 474 surrounding the needle 460 which communicates with the purging system 432 via a manifold 4&#39;76 and with the container via ports 478 formed by transverse holes extending through the wall of the needle 470. The needle 470 penetrates the container septum sufficiently that the ports 470 are located within the container. The ports 478 open transversely of the needle 470 to prevent coring of the septum.  
  The purging system functions to force fluid from the container and into the injection module by exposing the container to a controlled volume of gas at a predetermined pressure. The volume of gas at the predetermined pressure can be considered to possess a predetermined amount of purging energy proportional to the product of the pressure and the volume The PV energy of the purging gas thus accurately determines the quantity of fluid which is directed to the injection module. The waste system 36 is maintained at atmospheric pressure throughout each purge cycle. As fluid is forced from the container to the injection module. the pressure in the container decays until the purging gas has expanded to a pressure about equal to atmospheric pressure.  
  As shown schematically by FIG. 9 the purging system 432 compises a pressure regulating valve 54M), a pressure accumulator 56b2, an accumulator control valve 504 and a vent valve 506. The regulating valve 500 is connected to a source of pressurized gas by a supply conduit 538 and a pressure manifold Slltl disposed in the storage module 16. The pressure source can be of any suitable or available construction and preferably provides air at pressures around 60 psig to the manifold 510 through the conduit 508 which extends into the module 16.  
  The regulating valve drops the supply pressure to a predetermined lesser pressure, e.g. 25 psig. The valve 500 can preferably be adjusted so that the controlled pressure can be varied as desired by the operator. A gauge M2 is associated with the valve Silt) so that the magnitude of the controlled pressure can be monitored.  
  The accumulator 502 is communicated with the regulating valve 504) via the control valve 504 which is a three-way solenoid operated valve having a small internal volume. The solenoid operator 504a is illustrated schematically and is operated from the control module 22. The control valve 504 has a first operating position in which the accumulator is communicated to the regulating valve Silt) for charging the accumulator. This valve position is the normal&#34; valve position and the accumulator is nearly continuously maintained in its charged state.  
  The accumulator SQZ may be of any suitable or conventional construction and is not illustrated in detail. The accumulator preferably has a volume of about microliters and, when charged, the accumulated gas is at 25 psig. Because of the small accumulator volume it can be rapidly charged from the regulator valve 500 when the control valve 504 is in its normal position.  
  The control valve solenoid 504a is operated from the control module 22 to a second valve position wherein communication between the accumulator and the regulating valve 500 is cut off and the accumulator is communicated to the dipper tube needle 470 via a low internal volume conduit 520. This enables the accumulator to discharge into a fluid container via the needle 470 so that fluid can be forced from the container through the needle 460 to the injection module. The accumulator discharge is relatively rapid and accordingly the control valve 504 is only operated to its second, or accumulator discharging, position for about 4 seconds after which it returns to its normal position and the accumulator is recharged.  
  In the preferred and illustrated system, the injection syringe has an internal volume of about microliters and the sample conduit 466 has an internal volume of about 10 microliters. It has been found that purging such a system with a flow of fluid equal to about 10 times the combined syringe and conduit volumes reduces the quantity of residual material in the purged volume to consistently low levels, e.g. to less than 0.01% by volume. Accordingly, in the preferred system, the 100 microliter accumulator, charged to 25 psig, is effective to produce a purging volume of solvent and/or sample fluid of about 200 microliters.  
  Some sample fluids have high vapor pressures at room temperature and if the accumulator were discharged into a container of such a fluid, the partial pressure of the vapor combined with the PV energyof the purging gas could cause an excessive quantity of the fluid to be forced from the container. Accordingly, in the preferred embodiment of the invention, after the needle assembly has been inserted into a container, the vent valve 506 is opened to communicate the container to atmospheric pressure via the needle 470, the conduit 520 and the valve 506. The valve 506 is operated by a solenoid 506a which is energized and deenergized from the control module 22.  
  After the vent valve 506 is opened to vent the container, it is reclosed and the container volume is substantially at atmospheric pressure. The control valve 504 is then actuated to discharge the accumulator into the container so that a predetermined controlled pressure differential is applied across the sample fluid, the fluid conduit 466 and the injection syringe assembly 72. In the preferred embodiment of the invention the control module functions to allot a one minute period during which purging is accomplished. Purging is normally completed within the alloted time.  
  Referring further to P16. 9 the injection and storage modules 14, 16 are shown schematically by broken lines along with the various elements of the pneumatic system for operating the actuators in the modules.  
  As illustrated by FIG. 9 the injection syringe carriage actuator 34 is communicated to a. solenoid control valve 530 in the storage module by a conduit 543. The control valve 530 is in turn connected to the pressure manifold 510 by a conduit 534. The valve solenoid 530a is energized and deenergized from the control module 22 to control operation of the valve. When the actuator 34 is operated to advance the syringe carriage towards the analyzer inlet 12a or the waste receptacle, the valve 530 is operated to direct high pressure air to the actuator 34. The carriage is retracted by operating the valve 530 to vent the actuator 34 so that the actuator return spring retracts the carriage.  
  The double acting plunger actuator 132 is communicated to the manifold 510 at one end via a conduit 540, a control valve 542 and a conduit 544. The opposite end of the actuator 132 is communicated to the manifold via a conduit 546, a control valve 548 and a conduit 550. The valves 542 and 548 each are operated by solenoids 542a, 548a which are wired to the control module. The valves 542, 548 are constructed like the 5 valve 530 to either supply high pressure air to their respective ends of the actuator 132 or to vent the actuator, depending on energization of the solenoids. When both valves direct pressurized air to the actuator 132 the plunger is positively positioned by the actuator, as noted previously. This operation of the valves only occurs when the cross bar 140 engages one or the other of the dosage stops 134, 136, which are schematically illustrated in FIG. 16, to enable retraction of the dosage stop element.  
  The single acting dipper tube actuator 434 is communicable to the manifold 510 via a conduit 554, a control valve 556 and a conduit 558. The control valve 556 includes a solenoid 556a wired to the control module 22. The valve 556 is constructed and functions the same as the valve 530.  
  As is apparent from FIG. 9 the pressure conduits 532, 540 and 546, as well as the sample fluid conduit 466 all extend between the storage and injection modules. Additionally, as noted above, the electric conductors for the dosage stops 134, 136 and the waste system solenoid 214 also extend from the storage module to the injection module.  
  While a single embodiment of the present invention has been illustrated and described in considerable detail, the invention is not to be considered limited to the precise construction shown. Numerous adaptations, modifications and uses of the invention may occur to those skilled in the art to which the invention relates and it is the intention to cover all such adaptations, modifications and uses which fall within the scope or spirit of the appended claims.  
 We claim:  
  1. A method of purging material from a syringe comprising:  
 a. providing a syringe comprising a tubular barrel defining an internal passageway having an axial end opening and a side opening and a plunger supported in said passageway for axial movement relative to said barrel, the imaginary solid intersection of said internal passageway and an extension of the perimeter of said side opening defining a space within said internal passageway;  
 b. positioning said plunger in said barrel with a projecting plunger end portion disposed at least adjacent said side opening such that said plunger end portion intersects said space defined by said imaginary solid intersection;  
 c. directing a purging liquid fluid into said passageway through one of said openings and discharging said fluid from said passageway through the other of said openings to purge said passageway; and  
 d. impinging said fluid on said projecting plunger end portion prior to discharging the fluid from said pas- 60 sageway to scrub said material from said plunger while purging said passageway.  
  2. The method claimed in claim 1 further comprising placing said purging fluid in a container which is closed by a septum, providing a septum piercing dipper tube element comprising a first passageway having at least a first port for communicating purging fluid from said container to said chamber, and a second passageway separate from said first passageway having a second port for communicating said gas into said container, the container and spaced from said first passageway and further comprising piercing said septum with said dipper tube element so that said first port is disposed in said container within the volume occupied by said purging fluid and said second port is disposed within port whereby the purging fluid is forced from said container through said first passageway.