Patent Publication Number: US-2006013729-A1

Title: Fluid handling apparatus for an automated analyzer

Description:
BACKGROUND OF THE INVENTION  
      The present invention is generally directed to an automated analyzer for conducting binding assays of various liquids, particular biological fluids for substances contained therein.  
      The present invention is particularly directed to a machine for performing automated immunoassay testing, in particular heterogeneous immunoassays in which paramagnetic particles are the solid phase reagent and the labeled reagent (tracer reagent) includes a chemiluminescent label. The system can accommodate both competitive and sandwich type assay configurations. A chemiluminescent flash is initiated and its intensity measured as an indication of the presence or absence of an analyte in the test fluid which is being assayed. The analyzer can be selectively run in batch-mode or random access sequence.  
      Over the last several years, automated instrumentation has been developed for routine testing the clinical laboratory. Limited automation has been applied to the area of immunoassay testing. Although some instruments have been developed for limited immunoassay testing, many of the procedures are still performed manually. Test results are very often delayed because of the time factor and labor intensity for many of the manual steps, and long incubation or reaction times. These delays can be critical in many clinical situations. In addition, the manual procedures cause variations in test results and are quite costly. The causes of such variations include nonuniform testing protocols, technician experience skills and the precision of the apparatus/analyzer. These and other difficulties experienced with the prior art analyzer and manual testing systems have been obviated by the present invention.  
      It is, therefore a principal object of the invention to provide an automated analyzer for diagnostic immunoassay testing which is particularly applicable to heterogeneous immunoassay testing.  
      Another object of this invention is the provision of an analyzer which has a high degree of versatility, capable of performing a wide range of binding assay protocols for a wide range of clinical and non-clinical analytes.  
      A further object of the present invention is the provision of an automatic analyzer which is capable of handling a plurality of test protocols simultaneously, continuously and sequentially.  
      It is another object of the present invention to provide an automated analyzer which is capable of high sample throughput.  
      A still further object of the invention is the provision of an automated analyzer which greatly reduces the amount of time per assay or sample test.  
      It is a further object of the invention to provide an automated analyzer which provides consistent and reliable assay readings.  
      It is a further object of the invention to provide an automated analyzer which is self-contained and requires a minimal amount of space for complete sample processing.  
      A further object of the invention is to provide a constant luminescent light source for automatic monitoring of the luminometer calibration of an assay apparatus.  
      It is still a further object of the invention to provide an automated analyzer which can be selectively run in a bath-mode or random access sequence.  
      With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.  
     SUMMARY OF THE INVENTION  
      In general, the automated analyzer of the present invention is a self-contained instrument which is adapted to be located on a suitable laboratory bench. It requires no external connections other than a standard power line and operates accurately within an ambient temperature range of 18° to 30° C. The functional units of the analyzer include a process track, a sample handling or transport system, a reagent handling or transport system, a separation and washing system, a detection system (luminometer) and data collection/processing system. The reagents and test samples are reacted in discreet, disposable cuvettes. The cuvettes are automatically and sequentially dispensed from a cuvette loader onto a ii near process tract which moves each cuvette one cuvette space every twenty seconds. The temperature of the test reaction is controlled by a thermal system which preheats the cuvettes and reagents and maintains an environmental temperature of 37° C., plus or minus one degree, throughout incubation. Test samples are dispensed into the cuvettes by an aspirating and dispensing probe and reagents are added at software-controlled intervals by means of three aspirating and dispensing reagent probes. The analyzer is particularly adapted for performing heterogeneous specific bind assays. The analyzer can be selectively run in batch-mode or random access sequence.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The character of the invention, however, may be best understood by referee to one of its structural forms, as illustrated by the accompanying drawings, in which:  
       FIG. 1  is a front perspective view of the analyzer of the present invention;  
       FIG. 2  is a diagrammatic plan view showing the general organization of the subunits of the analyzer;  
       FIG. 3  is a diagrammatic plan view of a sequential series of cuvettes which are disposed on the pre-heater section and event conveyor;  
       FIG. 4  is a front elevational view of a cuvette which is used with the automated analyzer of the present invention for holding sample and reagent;  
       FIG. 5  is a top plan view of the cuvette;  
       FIG. 6  is a bottom plan view of the cuvette;  
       FIG. 7  is a side elevational view of the cuvette;  
       FIG. 8  is a perspective view of the cuvette;  
       FIG. 9  is a side elevational view of a container for holding reagent, specifically labeled reagent (tracer reagent);  
       FIG. 10  is a top plan view of the container;  
       FIG. 11  is a bottom plan view of the container;  
       FIG. 12  is a perspective view of the container;  
       FIG. 13  is a vertical cross-sectional view of the container taken along the line  13 - 13  and looking in the direction of the arrows;  
       FIG. 14  is a bottom plan view of a cover for a container including the container which is shown in  FIG. 9 ;  
       FIG. 15  is a vertical cross-sectional view of the cover taken along the line  15 - 15  and looking in the direction of the arrows;  
       FIG. 16  is a side elevational view of a reagent container, specifically for solid phase reagent;  
       FIG. 17  is a top plan view of the solid phase reagent container.  
       FIG. 18  is a bottom plan view of the reagent container;  
       FIG. 19  is a vertical cross-sectional view of the reagent container, taken along the line  19 - 19  of  FIG. 17  and looking in the direction of the arrows:  
       FIG. 20  is a perspective view of the reagent container with portions broken away;  
       FIGS. 21A and 21B , when viewed together, is a front elevational view of the analyzer of the present invention, the sheets being joined along the line  21 A;  
       FIG. 22  is a top plan view of the analyzer, with portions broken away;  
       FIG. 23  is an end view of the analyzer;  
       FIG. 24  is an exploded perspective view of a system for feeding cuvettes from a storage hopper;  
       FIG. 25  is a perspective view of a cuvette storage hopper;  
       FIG. 26  is an exploded perspective view of the cuvette feed system and hopper;  
       FIG. 27  is a front elevational view of the cuvette feed system;  
       FIG. 28  is a rear elevational view of the cuvette feed system;  
       FIG. 29  is a right side elevational view of the cuvette feed system, with portions broken away;  
       FIG. 30  is a plan view of the hopper and feed system;  
       FIG. 31  is a fragmentary view of a feed chute which forms part of the cuvette feed system, with portions broken away;  
       FIGS. 32A, 32B  and  32 C, when taken together, form a front view of a conveyor system for feeding cuvettes from the hopper feed system through the vent areas of the machine, the sheets being joined along the lines  32 A and  32 B;  
       FIGS. 33A, 33B  and  33 C, when viewed together, form a top plan view of the cuvette conveyor system the sheets being joined along the lines  33 A and  33 B;  
       FIG. 34  is a vertical cross-sectional view showing magnetic means for attracting para magnetic particles from the test sample and reagent mixture in a cuvette taken along the line  34 A- 34 A of  FIG. 33C  and looking in the direction of the arrows;  
       FIG. 35  is a vertical cross-sectional view showing another aspect of the magnetic means for attracting the paramagnetic particles from the test sample and reagent mixture within a cuvette taken along the line  35 A- 35 A of  FIG. 33C  and looking in the direction of the arrows;  
       FIG. 36  is a front elevational view of a sample transport system;  
       FIG. 37  is a top plan view of the sample transport system;  
       FIG. 38  is a vertical cross-sectional view of the sample transport system taken along the line  38 A- 38 A of  FIG. 37 ;  
       FIG. 39  is an exploded perspective view of some of the elements of the sample transport system;  
       FIG. 40  is an exploded perspective view of one of the drive mechanisms for the sample transport system;  
       FIG. 41  is an exploded diagrammatic elevational view of the sample transport system;  
       FIG. 42  is a perspective view of one of the drive elements of the sample transport system;  
       FIG. 43  is a top plan view of a reagent transport system;  
       FIG. 44  is a front elevational view of a reagent transport system;  
       FIG. 45  is a vertical cross-sectional view of the reagent transport system;  
       FIG. 46  is an exploded perspective view of some of the elements of the reagent transport system;  
       FIG. 47  is an exploded perspective view of additional elements of the reagent transport system;  
       FIG. 48  is an exploded perspective view of one of the drive elements for the reagent transport system;  
       FIG. 49  is a diagrammatic elevational view of the reagent transport system;  
       FIG. 50  is a front elevational view of a sample probe transport system;  
       FIG. 51  is a diagrammatic right side elevational view of the sample probe transport system;  
       FIG. 52  is a right side elevational view of the sample probe transport system;  
       FIG. 53  is a plan view of the sample probe transport system;  
       FIG. 54  is an exploded perspective view of some of the elements of the sample probe transport system;  FIG. 55  is an exploded perspective view of the horizontal drive components of the sample probe transport system;  
       FIG. 56  is an exploded perspective view of a sample probe supporting carriage which forms part of the sample probe transport system;  
       FIG. 57  is an exploded elevational view of one of the drive components for the sample probe transport system;  
       FIG. 58  is an exploded perspective view of one of the horizontal drive components for the sample probe transport system;  
       FIG. 59  is an exploded perspective view of one of the vertical drive components for the sample probe transport system;  
       FIG. 60  is a top plan view of a reagent probe transport system;  
       FIG. 61  is a right side elevational view of the reagent probe transport system;  
       FIG. 62  is a front elevational view of the reagent probe transport system;  
       FIG. 63  is an exploded perspective view of some of the elements of the reagent probe transport system;  
       FIG. 64  is an exploded perspective view of the components of the left hand reagent probe;  
       FIG. 65  is an exploded perspective view of the central reagent probe components;  
       FIG. 66  is an exploded perspective view of the right reagent probe components;  
       FIG. 67  is an exploded perspective view of one of the horizontal drive elements of the reagent probe transport system;  
       FIG. 68  is an exploded perspective view of one of the drive components for moving the left probe vertically;  
       FIG. 69  is an exploded perspective view of the probe supporting elements for the central probe of the reagent probe transport system;  
       FIG. 70  is an elevational view of a post which forms part of the mechanism for rotating the left probe about a vertical axis;  
       FIG. 71  is an exploded perspective view of the probe supporting elements for the right probe of the reagent probe transport system;  
       FIG. 72  is an exploded perspective view of the probe supporting elements for the left probe of the reagent probe transport system;  
       FIG. 73  is an exploded perspective view of the syringe bank for the sample and reagent probes;  
       FIG. 74  is a cross-sectional view of a healing system for a tube which extends from one of the reagent probes to its corresponding syringe;  
       FIG. 75  is an exploded perspective view of an event conveyor system and all of the wash stations for the sample and reagent probes;  
       FIG. 76  is a perspective view of the right hand end of the analyzer which illustrates the aspirate resuspend area of the event track and the luminometer;  
       FIG. 77  is an exploded perspective view of the aspirate resuspend components;  
       FIG. 78  is a cross-sectional view of one of the aspirating probes;  
       FIG. 79  is a vertical cross-sectional view of a cuvette wash apparatus which forms part of the aspirate resuspend section of the event conveyor taken along the line  79 A- 79 A of  FIG. 33C ;  
       FIG. 80  is a vertical cross-sectional view of the acid resuspend mechanism taken along the line  80 A- 80 A of  FIG. 33C ;  
       FIG. 81  is a right hand elevational view of a luminometer and elevator mechanism which conveys cuvettes to the luminometer at the end of the event conveyor;  
       FIG. 82  is a top plan view of the luminometer;  
       FIG. 83  is a vertical cross-sectional view of the luminometer and cuvette elevator;  
       FIG. 84  is an exploded perspective view of some of the elements of the luminometer;  
       FIG. 85  is a perspective view of the luminometer;  
       FIG. 86  is a diagrammatic plan view showing the path of the cuvettes within the luminometer;  
       FIG. 87  is a schematic diagram of a preferred embodiment of a reference LED module;  
       FIG. 88  is a block diagram of the module;  
       FIG. 89  is a diagram of the preferred timing scheme of an electronically adjustable potentiometer in the reference LED module;  
       FIG. 90  is an exploded perspective view of the valve modules which are located at the left side of the analyzer;  
       FIG. 91  is a perspective view of the left side valve components and peristaltic pumps;  
       FIG. 92  is an exploded perspective view of the valve components at the right hand side of the analyzer;  
       FIGS. 93A and 93B  is a schematic view of all of the pneumatic and plumbing components for the analyzer;  
       FIGS. 94-102  are flow diagrams of the coordinated operation of the various subunits of the analyzer. 
    
    
      It is noted that the representations shown in the FIGS. may not indicate actual scales or ratios.  
     Glossary  
      The following terms as used in this specification and claims are defined as follows:  
      Acid Reagent:  
      0.1 N HNO 3  with 0.5% peroxide; added to the magnetic particles after the wash cycle. The peroxide attaches to the acridinium ester at a low pH (pH1).  
      This reaction readies the acridinium ester for light emission.  
      Acridinium Ester (AE):  
      The chemical ‘label’ responsible for the chemiluminescent flash when base reagent is added to the acidified magnetic particle/analyte/AE mixture in the cuvette. See U.S. Pat. Nos. 4,745,181, 4,918,192 and 4,946,958, which are incorporated by reference.  
      Analte:  
      A substance of unknown concentration present or suspected of being present in a test sample.  
      Antibody (Ab):  
      1) a protein produced by the body in response to the presence of a foreign substance; part of the body&#39;s resistance to disease  2 ) proteins or carbohydrates containing proteins having the ability to combine with a specific antigen.  
      Antigen (Ag):  
      1) a substance foreign to the body which when introduced into the body stimulates the production of antibodies  2 ) under analysis conditions; a protein or non-protein compound capable of reacting with a specific antibody.  
      Assay:  
      a diagnostic or analytical protocol for determining the presence and amount or absence of a substance in a test sample, said assay including immunoassays of various formats.  
      Base Reagent:  
      0.25 N NaOH, pH 13, and ARQUAD; added to the magnetic particles suspended in acid when the cuvette is in the luminometer. When injected, the pH shift and accompanying electron excitation causes light emission at a specific wavelength (a flash). See U.S. Pat. No. 4,927,769 which is incorporated by reference.  
      Buffer:  
      A solution used for pH maintenance; composed of a weak acid (or base) and its salt.  
      Calibrator:  
      A protein based solution (often human based) containing known concentrations of analytes providing a reference curve for converting measured signal into concentration.  
      Calibration Curve:  
      A pair of calibrators are run as samples and the calibrator data is normalized against the stored Master Curve data for the tested analyte, compensating for current running conditions and instrument variability.  
      Chemiluminescence:  
      A chemical reaction in the production of light  
      Competitive Assay:  
      An Ab/Ag reaction where the unknown Ag in a sample and a labeled Ag in reagent compete for a limited amount of reagent labeled Ab.  
      Control:  
      A protein based product containing specific analytes within a pre-determined concentration range; i.e., low, medium, high. Many controls are human serum based. Controls are used as a total system performance check  
      Counts:  
      The basic unit of measurement of PMT signal after processing by the PAD electronics.  
      Count Profile:  
      Counts vs time; information is stored in files in system and can be plotted  
      Dark Counts:  
      The electronic noise of the PMT in the absence of light.  
      Diluent (DIL):  
      A protein based solution; used to dilute a patient sample when the original result is beyond the curve range.  
      Flash:  
      A short-lived burst of light produced from the immunoassay when the pH is rapidly changed from acidic to basic (with the addition of the base reagent).  
      Hapten:  
      An incomplete antigen being incapable alone of causing the production of antibodies but capable of combining with specific antibodies  
      Immunoassay:  
      A chemical test involving an antibody/antigen reaction to determine the presence of and/or quantify a specific substance; the substance being assayed may be the antibody or antigen in the reaction.  
      Light Counts:  
      The electronic signal of the PMT in the presence of light, including dark counts.  
      Master Curve:  
      A ten point curve generated by Quality Control for each matched set of SP and Lite reagents, data is published in assay&#39;s package insert and programmed into instrument by operator; used by instrument as the master reference curve for converting measured signal into concentration.  
      NSB:  
      Non-specific binding—All tracer material which is present during the measurement phase but does not represent specific Ab binding. Tracer material may attach indiscriminately to cuvette wall or particles and does not wash away, resulting in signal that mimics an Ab/Ag reaction  
      PAD:  
      Electronics that amplify the PMT signal (pulse) and filter it for signal not generated by photons.  
      Photon:  
      A unit of light.  
      PMP:  
      Para-magnetic particles; used in Solid Phase reagent.  
      PMT:  
      Photomultiplier tube—a vacuum (or gas-filled) phototube with a cathode, usually nine dynodes, and an anode. The cathode is capable of emitting a stream of electrons when exposed to light. The dynode arrangement provides successive steps in amplification of the original signal from the cathode. The resulting signal produced is directly proportional to the amount of illumination.  
      Pre-Treatment Agent (TRX):  
      A solution mixed and incubated with sample to protect the analyte from releasing agent.  
      Releasing Agent (REL):  
      A solution mixed with sample for the purpose of separating the analyte from another molecule and rendering it available for immuno-reaction.  
      RLU:  
      Relative light units; used on the manual Magic® Lite analyzes. A unit of light measurement calibrated against a tritium source and unique for each instrument.  
      Sandwich Assay:  
      An Ab/Ag reaction where unknown Ag reacts with two forms of reagent labeled Ab; a solid phase or physical carrier reagent and a signal producing reagent, resulting in a Ab/Ag/Ab “sandwich” 
      Solid Phase Reagent (SP):  
      A physical carrier reagent coupled with antigen or antibody (as required by assay) in a buffer. See U.S. Pat. Nos. 4,554,088 and 4,672,040.  
      SYSTEM FLUID (System Water, System Diluent):  
      All system syringes are water backed with D.I. water from the on-board supply; used to follow sample and reagent dispense to cuvette, wash all probes, wash magnetic particles in cuvette at aspirate/resuspend position in track.  
      Test Sample:  
      A specimen for testing; including biological fluids, e.g. serum, urine, cellular products, controls, calibrators, etc., non biological fluids, e.g. chemical compounds, drugs, etc, and any other fluid of interest for which an assay protocol may be formatted.  
      Total Counts:  
      1) the area under the flash curve  2 ) counts per read interval.  
      Tracer Reagent (Lite Reagent (LR)):  
      Antibody or antigen (as required by assay) labeled with acridinium ester in a barbitol buffer (synonym—tracer).  
      Tritium:  
      A radioactive light source in a sealed scintillation-solution; it emits light and serves as a calibration reference for evaluating luminometer performance (Los Alamos Diagnostics product insert; PN 71×002 &amp; 61-006).  
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
      General Organization of Machine Subunits  
      The analyzer requires on-board supplies of cuvettes, deionized water, and the acid and base reagents. Sensors monitor volumes of liquid supplies and indicate necessary refilling before the assay run is initiated. Additional cuvettes may be loaded at any time, even while the instrument is operating. Waste liquid is collected in an on-board removable reservoir, and used cuvettes are collected in a waste bin, after aspiration of all liquid waste. The analyzer advises the operator when either of these waste collectors are in need of emptying.  
      Referring first to  FIGS. 1, 2  and  3 , the automated analyzer of the present invention and includes a housing  21  which contains or supports a plurality of subunits for performing the various steps for completion of a plurality of binding assays on fluid samples, e.g. blood serum. The analyzer is specifically adapted to perform heterogeneous immunoassays having various formats. The subunits include a cuvette hopper and feeder mechanism which is generally indicated by the reference numeral  22 , a cuvette conveying system  23 , a sample probe transport system  24 , a plurality of reagent probe transport systems R 1 , R 2  and R 3 , a sample transport system which is generally indicated by the reference numeral  26 , and a reagent transport system which is generally indicated by the reference numeral  27 . A detection device  29  is located at the end of and above the conveyor system  23 . The detection device of the preferred embodiment is a luminometer. Other devices, e.g. fluorimeter, isotope emitter counters, etc. are known in the arts. The uses of such other devices is determined by the type of label that is utilized in a test reaction. This system  20  also includes a syringe bank  32 , a central processing unit (CPU), not shown, which is operably connected to a cathode ray tube (CRT)  36  and keyboard  37 . The syringe bank  32  is operatively connected to the sample probe transport system  24  and reagent probe transport systems R 1 , R 2  and R 3 .  
      A wash station for the sample aspirating and dispensing probe is located behind the sample transport system and is generally indicated by the reference numeral  18 . Additional wash stations, generally indicated by the reference numerals  15 ,  16  and  17 , for the reagent aspirating and dispensing probes are located behind the reagent transport system  27 , see also  FIGS. 21A, 21B  and  22 .  
      Referring particularly to  FIG. 3 , the conveyor system  23  is divided into two sections, a cuvette preheater section which is generally indicated by the reference numeral  38  and a cuvette dispense and incubation section which is generally indicated by the reference numeral  39 . The cuvette  40  are stored in a random manner in a hopper  22  and conveyed to the end of the preheater section  38  in an upright orientation. A plunger  19  is fixed to the end of a lead screw  41  which is driven horizontally by an electric motor  25  along its central longitudinal axis and the axis of the preheater section  38 . The plunger  19  is moved from an outer retracted position to an extended position as shown in  FIG. 3  to push a cuvette which has just been deposited on the preheater section  38  one cuvette space towards the incubation section  39 . This advances all of the cuvettes  40  along the preheater section  38  so that the furthest cuvette is transferred onto the incubation section  39 . The plunger  41  is then moved back to the retracted position to engage the next cuvette which will drop into the starting position. The lead screw  41  does not rotate about its axis. Cuvette sensors, generally indicated by the reference numeral  43 , are positioned at the end of the preheat section  38  and at the beginning of the incubation section  39  to monitor the presence of cuvettes at these locations. The cuvettes  40  are conveyed along the incubation section  39  by conveyor means, described below, which is driven by a motor  42 . As each cuvette reaches a sample dispense point  44  along the incubation section  39 , a probe, described below, from the sample probe transport system  24  aspirates a predetermined amount of fluid to be analyzed from a container, described below, in the sample transport system  26  and deposits the sample in the cuvette at the sample dispense point  44 . When the cuvette reaches any one of three predetermined positions  45 ,  46  or  47  adjacent the reagent transport system  27 , a pair of reagents from the reagent transport system  27  is added to the fluid sample in the cuvette to initiate a test reaction for form a detectable product by one or more of the reagent probes from the reagent probe systems R 1 , R 2  or R 3 . The sequence of reagent addition into the cuvette is determined by the assay protocol selected for the test sample. Variation in reagent addition occurs for example when an incubation of test sample and one of the reagents is required. The reagents comprise a solid phase reagent and a labeled reagent (tracer reagent) which, in the preferred embodiment, is of a luminescent compound.  
      The solid phase reagent in the preferred embodiment is paramagnetic particles having a binding substance coupled thereto. Alternate solid phase materials are known in the arts as well as separation techniques for isolating the said solid phase materials. The detectable product that is formed in the preferred embodiment is a complex that includes the solid phase reagent, analyte that is being assayed and the labeled reagent. The complex will vary depending on the format of the assay. Examples of binding assay formats which generate a detectable product include competitive and sandwich type reactions, each of which may be performed by the analyzer of the present invention. Thereafter, the cuvette passes an aspirate/resuspended area which is generally indicated by the reference numeral  28 , which prepares the mixture for a ‘flash’ or light emitting reaction in the luminometer  29 . Referring particularly to  FIG. 3 , the aspirate resuspend area  28  of the preferred embodiment includes a magnetic apparatus  49 . An aspirate/wash probe is located at point  50 . An aspirate probe is located at point  51  and an acid resuspension probe is located at point  52 .  
      When the cuvette reaches the end of the incubation section  39 , it is lifted vertically by an elevator mechanism at point  53  to the luminometer  29 . When the cuvette which contains the acid resuspended detectable product has been properly positioned within the luminometer, a base solution is added which results in a chemiluminescent detection reaction (‘flash’). The ‘flash’ effects a photomultiplier tube which counts photons from the “flash” and produces an electrical signal. The signal is processed by the central processing unit and an appropriate value reading is recorded. Deionized water is used for a system backing fluid and for many of the washing steps for typical assay protocols which are stored in a removable reservoir  30 . A second removable reservoir  31  is located below the reservoir  30  for accepting all fluid waste. After each assay, the contents of the cuvette are aspirated from the cuvette and discharged into the fluid waste reservoir  31 . The empty cuvette is then discarded into a waste receptacle  35 . Acid reagent is stored in a reservoir  33  and base reagent is stored in a reservoir  34 . An example of an acid reagent which is suitable for use with the present system is: 0.1N. HNO 3 , pH 1.0 with 0.5% peroxide. An example of a base reagent which is suitable for use with the present system is 0.25N., NaOH, pH 13, and ARQUAD. Variations in the concentration of the acid and base reagents may be required depending on the chemiluminescent label. The chemiluminescent label in the preferred embodiment is an acridinium ester.  
      Cuvette and Reagent Containers  
      Referring to  FIGS. 4-8 , the cuvette which is used as part of the automated analyzer of the present invention is generally indicated by the reference numeral  40 . Cuvette  40  is generally rectangular in cross-section and consists of a bottom wall  55 , a pair of opposite broad side walls  56  and a pair of opposite narrow sidewalls  57 . The cuvette  40  has an interior chamber which is aced from a top opening  69 . A pair of flanges  58  extend outwardly from the broad sidewall  56  at the top of the cuvette. A pair of spaced teeth  59  extend outwardly from each broad sidewall  56  just below the flange  58 . The flanges  58  and teeth  59  are instrumental in enabling the cuvette to be conveyed and transported through the various subsystems of the machine  20 , as will be described hereafter. The cuvette can be made of polypropylene or polyethylene which have been found to produce a more even light distribution during the subsequent-flash in the luminometer than other polymers which have been tested such as polystyrene. However, polypropylene has been found to be the preferred material for obtaining reliable results.  
      Referring to  FIGS. 9-13 , one of the two type of reagent containers which arm utilized in the analyzer, is generally indicated by the reference numeral  60 . The container  60  is utilized for carrying a labeled reagent (tracer reagent) which is specific for certain test protocols and comprises a main body portion  64  which has an inner chamber  61 , a threaded neck portion  65  and a top opening  62  at the upper end of the neck portion  65  which opens into the chamber  61 . A skirt  63  extends outwardly from a point below the neck  65  and extends downwardly to a point just below the main body portion  64 . The skirt  63  is spaced from the main body portion  64  and consists of three flat sides and one rounded side. The skirt  63  enables the container  60  to be securely mounted on the reagent transport means, described below.  
       FIGS. 14 and 15  illustrate a cover for a container including the reagent container  60  which is generally indicated by the reference numeral  66  and includes a top wall  67  which has a plurality of slits  68  which cross at the center of the top wall  67 . The cover  66  is made of an elastomeric material such as natural or synthetic rubber which enables the cover to engage the top of the neck portion  65  of the container  60 . The cover  66  reduces evaporation of reagent from the container  60  and the slits  68  enable a reagent aspirating and dispensing probe to penetrate the top wall  67  to access the reagent fluid within the container. The slits  68  all intersect at the center of the top wall  67  to form a plurality of pie-shaped flaps which converge at the center of the cover and give way when pressure is applied to the center of the cover. The bottom of the cover  66  has an outer annular flange  70 .  
       FIGS. 16-20  illustrate a second reagent container which is used with the analyzer and which is generally indicated by the reference numeral  75  for holding a solid phase reagent. The container  75  has a generally cylindrical main body portion  76  which has an inner chamber  77  which extends to a top opening  78  above a threaded neck portion  79 . An annular skirt  80  extends outwardly from the main body portion  76  at a point just below the neck  79  and extends downwardly to a point below the main body portion  76 , as shown most clearly in  FIG. 19 . A pair of fins  81  extend inwardly into the chamber  77  from the inner chamber wall as shown most clearly in  FIGS. 17 and 20 . The fins  81  are utilized for agitating the solid phase reagent within the container in a manner described below in connection with the reagent transport system  27 . The top opening  78  is also sealed by the cover  66  by inverting the cover so that the top wall  67  extends below the top opening  78  and inside of the neck portion  79  so that the flange  70  of the cover rests on top of the neck portion  79 .  
      Cuvette Feed and Orientation Mechanism  
      Referring to  FIGS. 24-31 , the cuvette feed and orientation mechanism  22  comprises a hopper which is generally indicated by the reference numeral  87 , a feed conveyor which is generally indicated by the reference numeral  86 , and an orientation chute which is generally indicated by the reference numeral  131 . The hopper  87  is preferably made of an optically clear plastic material. This makes it easier for the operator to determine when the level of cuvettes in the hopper is low whereby the hopper requires additional cuvettes. In addition, the elements which are below the hopper, see  FIG. 30 .  
      Referring particularly to  FIGS. 25, 26  and  30 , the left side wall of the hopper has a vertical opening  88  and a pair of spaced outer flanges  89  which end outwardly from the left side wall of the hopper on opposite sides of the opening  88 , as shown most clearly in  FIG. 25 . An upper horizontal flange  83  extends outwardly from the left and rear side wall of the hopper. The forwardmost flange  89  has an; opening  84  just below the top flange  83 , as shown in  FIG. 25 . Referring also to  FIG. 24 , a pair of elongated reinforcing plates  82  are fastened to the outer surfaces of the outer flanges  89  by bolts  91 . The bolts  91  are also utilized to fasten the hopper  87  to a pair of chain guide plates  90  which are mounted to a hopper feeder support  92  which is, in turn, mounted on a base plate  93  by means of bolts  95 . The chain guide plates  90  are separated by a plurality of tubular spacers  97  through which the bolts  91  extend. A support bracket  94  is also mounted on the base plate  93  and is fastened to the side of the hopper feeder support  92  as shown in  FIG. 24 . A support bar  96  is also mounted to the outside of the rear most plate  90  by the bolts  91 . A ball slide assembly  110  is mounted to the support bar  96 . A mixing bar mounting plate  111  is mounted to the ball slide assembly  110 . An endless conveyor chain  98  is located at the vertical side opening  88  and extends around a lower idler sprocket  101  and an upper drive sprocket  100 . The sockets  100  and  101  are mounted on bushings  102  and are rotatively mounted on the hopper feeder support  92 . The upper drive sprocket  100  is driven by a stepper motor  103  which is mounted on the support  92 . One section of the conveyor chain  98  is guided along grooves in the outer longitudinal edges of the guide plate  90  and is located between the inner surfaces of the flanges  89  which define the opening  88 . A plurality of spaced bars  99  are located on the outside of the conveyor chain  98  and slant downwardly and forwardly toward the event conveyor. The chain  98  travels upwardly from the bottom of the hopper  87  at an angle from the vertical. An idler sprocket shaft  112  extends through the bushing  102  and rotates with the idler sprocket  101 , see  FIGS. 26 and 27 . The forward end of the shaft  112  is fixed to a cam wheel  113  so that the cam wheel  113  rotates with the idler sprocket  101  by of a clamp  114 . A lever arm  115  is pivotally mounted on a shaft  116  which is mounted in an adjusting fixture  117  which is located at a notch  118  in the left hand edge of the hopper feed support  92 . The pivoted end of the lever arm  115  has a flanged bearing  122  which enables the lever to pivot freely on the shaft  116 . The opposite end of the lever arm  115  has a slot  121  which receives a pin  120  of a slider block  109 . The slider block  109  is fixed to the mixing block mounting plate  111  and has an upper surface  123  which slants downwardly from back to front at the same angle as the bars  99 . The mixing block  109  is parallel with the section of the conveyor  98  which travels upwardly along the vertical opening  88  of the hopper and is located adjacent the bars  99 . A ball bearing follower  119  is rotatively mounted on the lever arm  115  and rides in a cam slot, not shown, on the rear side of the cam wheel  113 . As the cam wheel  113  rotates with the idler sprocket  101 , the lever arm  115  oscillates about the shaft  116 . The right hand end of the lever arm  115  as viewed in  FIG. 24 , moves up and down and in turn causes the mixing block  109  to move up and down. The timing of the upper movement of the block  109  is such that the block moves upwardly at the same rate as the upward movement of the conveyor chain  98 . The cuvettes are stored in the hopper  87  in a random manner. The mixing block  109  serves two functions. The first function is to agitate the cuvettes within the hopper  87 , and the second function is to assist in guiding the cuvettes onto the bars  99 , one cuvette per bar. As the cuvettes are carried upwardly by the bars  99 , the ends of the cuvettes are guided by the inner surfaces of the flanges  89  to maintain the cuvettes in position on the bars  99 . As each cuvette reaches the opening  84 , it slides forwardly along its respective bar  99  through the opening  84 , see  FIGS. 25 and 27 , in the forwardmost flange  89  and falls into the orientation chute  131 .  
      The orientation chute  131 , as viewed in  FIGS. 24, 27  and  30 , consists of a left hand plate  129  and a right hand plate  132  which are connected together by screws  139  and held in a spaced parallel relationship by a pair of spacer blocks  133 . Each plate  132  and  129  has an upper slide surface  134  which define, therebetween, a slot  135  toward the event conveyor. The slide surfaces  134  extend at a downward angle from back to front and at a downward angle toward the slot  135 . As each cuvette  40  falls through the opening  84  from the conveyor chain  98  to the orientation chute  131 , the bottom end of the cuvette falls into the slot  135  and the flanges  58  are supported on the slide surfaces  134 . This enables the cuvette  40  to slide down the surfaces  134  in a nearly upright orientation. The chute  131  is mounted to die hopper feeder support  92  by a chute support bracket  130 . A chute end plate  136  is attached to the front edges of the plates  129  and  132  by screws  137 . The plate  136  stops the downward slide of the cuvettes  40 . The end plate  136  has a hole  147  for receiving a position sensor  148  which is mounted on a PC board  138 . The PC board  138  is mounted on the plate  136  by fasteners  149 . The forward end of each slide surface  134  has a flat upper surface  127  for receiving a flat spring  128  which helps to insure that the cuvette remains in the slot  135  when the cuvette strikes the end plate  136 . The forward end of the slot  135  has a widened portion or access opening  141  which is slightly greater in width than the distance between the outer edges of flanges  58 , see  FIG. 30 . The access opening  141  between the plates  129  and  132  enables the cuvette to fall between the plates into the orientation tube  140 . The cuvette falls between a pair of opposed guide surface  142  and  143  along the inwardly facing surfaces of the plates  129  and  132 , respectively. The guide surface  143  has an upwardly facing jutting surface  144 . The guide surface  142  has a recessed portion  145  which forms a downwardly facing undercut surface  146 . The undercut surface  146  is opposed to the jutting surface  144  of the plate  132 . The orientation tube  140  has a top opening  150  and a bottom opening  151  and extends from the bottom of the orientation chute  131  to the top of the preheater section  38 . When the cuvette falls into the access op  141  at the end of the orientation chute, one of the flanges  58  of the cuvette strikes the jutting surface  144 . This deflects the cuvette laterally toward the recessed portion  145  of the left hand plate  129 . As the cuvette shifts laterally, the opposite flange of the cuvette strikes the recessed portion  145  just below the downwardly facing undercut surface  146 . This traps the flange of the cuvette below the undercut portion  146  and prevents the cuvette from accidentally flipping upside down when it reaches the end of the chute  131 . The cuvette, thereafter, falls in an upright orientation along the guide surface  142  and  143  into the orientation tube  140  through the top opening  150  and through the bottom opening  151  into the preheater section  38 . The orientation tube  140  has a helical twist which causes the cuvette to rotate approximately 90° about its vertical axis so that when the cuvette falls into the preheater section  38 , the broad sides  56  of the cuvette are forward and back as well as the flanges  58 .  
      Referring to  FIG. 29 , the preheater section  38  comprises a pair of spaced horizontal bars  158  and  159  which define therebetween a vertical slot  160 . Each of the bars  158  and  159  has a top edge  161 . When a cuvette falls from the bottom of the orientation tube  140 , the body of the cuvette falls into the slot  160  and the flanges  58  rest on the top edges  161 . Plunger  19  is moved to its extended position into the slot  160  by the motor  25  from left to right as viewed in  FIGS. 3, 32  and  33 . The plunger  19  is moved from left to right a distance which is approximately or slightly more than a cuvette width which pushes all of the cuvettes in the preheater section toward the cuvette dispense and incubation section  39 . The plunger  19  is then retracted by the motor  25  to allow a subsequent cuvette to fall from the orientation tube  140  into the preheater section  38 . The motor  25  is activated to reciprocate the plunger  19  once every twenty seconds or when, a test is requested. The cuvettes are deposited into the orientation tube  140  at a faster rate than they are pushed along the preheater section  38  so that the tube  140  becomes full of cuvettes as generally shown in dotted lines in  FIG. 29 . The sensor  148  is a reflective object sensor which indicates the presence of a stationary cuvette when the tube is full. The sensor  148  forms part of the overall analyzer control system and is effective to stop the motor  103  when the sensor senses a stationary cuvette at the top of the orientation tube. The software which is used to control the instrument keeps track of the cuvettes as they are subsequently used out of the orientation tube and controls when the stepper motor  103  is reactivated. The preheater section  38  contains a thermistor for controlling a pair of solid state DC driven thermoelectric modules (TEMs which maintain the temperature of the preheater section at a set temperature of 37° C. TEMs are also known as thermoelectric cooling couples which are used to maintain a predetermined temperature by transferring heat from one mass to another. The transfer of heat is reversed by reversing the direction of current flow. The machine framework provides a heat sink for the pre-heater section  38 . When the temperature of the pre-heater section is below the set temperature, heat is transferred from the machine framework to the pre-heater section  38 . When the set temperature of the pre-heater section is above the set temperature, as detected by the thermistor, the current through the TEMs is reversed and heat is transferred from the pre-heater section  38  to the machine framework. The cuvette dispense and incubation section  39  is also provided with a thermistor at two spaced strategic locations. Each thermistor controls a pair of thermoelectric modules (also strategically placed) for maintaining the cuvette temperature at 37° C. throughout the chemistry event line. In the particular embodiment shown, the preheater section  38  holds seventeen cuvettes and the cuvette dispense and incubation section  39  holds forty-five cuvettes.  
      Referring particularly to  FIGS. 32 and 33 , the track section  23  is shown in greater detail. The entire track section, including the preheater section  38  and the dispense and incubation section  39 , is covered by a top plate  162  which has a plurality of access openings at the dispense points  44 ,  45 ,  46  and  47 . The plate  162  has an opening  186  at the sample dispense point  44  as shown in  FIG. 33A . The plate  162  has openings  187  and  188  for the reagent dispense points  45  and  46 , respectively, as shown in  FIG. 33B  and an opening  189  for the reagent dispense point  47  as shown in  FIG. 33C .  
      Referring particularly to  FIG. 32A , the plunger  19  (not shown) has a tab  154  which extends horizontally toward the motor  25 . When the plunger is in the outer or retracted position, it extends between a pair of spaced components of an interruption sensor  155 . The sensor  155  has a photo transmitting portion which directs a beam toward a photo receiving portion. When the beam is interrupted by the tab  154 , a signal is transmitted to the CPU to indicate that the plunger is at the ‘home’ position (After a predetermined time period or when another test is requested), the stepper motor  25  is actuated for a predetermined number of steps to move the plunger  19  a predetermined distance out to the extended position. The motor is then reversed to bring the plunger back until the sensor  155  is interrupted by the tab  154  at the “home” position. All of the ‘interrupter’ sensors described hereinafter are connected to the CPU through the machine controller board and operate in the same manner as the sensor  155 . The cuvettes are pushed along the preheater section  38  and into the cuvette dispense and incubation section  39 , at which point they are positively conveyed by a pair of conveyor belts  167  and  168 . Each of the conveyor belts  167  and  168  has a plurality of teeth  164  on one side of the belt for engaging the teeth  59  of the cuvettes. A stepper motor  42  has a drive shaft  184  which is rotated in a clockwise direction when viewed from the front. The belt  168  is driven by the motor  42  through the toothed drive pulley  170  which is located between and below a pair of idler pulleys  171  and  179 . The belt  168  extends over the pulley  179  to and around an idler pulley  178  at the beginning of the incubation section  39 . The belt  168  then travels along the front edge of the incubation section  39  to an idler pulley  172  at the end of the section  39  and then back over the idler pulley  171  to the drive pulley  170 . The teeth  164  of the belt  168  face upwardly as the belt  168  extends around the drive pulley  170  and the idler pulleys  171  and  179  so that the teeth  164  of the belt engage the teeth of the drive pulley  170 . As the belt travels to the pulley  178 , it gradually assumes a vertical orientation so that the teeth  164  face forwardly. As the belt extends around the pulley  178  and travels along the front edge of the dispense and incubation section  39 , the teeth  164  face rearwardly and, thereby, engage the flanges  58  of the cuvettes. The belt  168  continues in a vertical orientation around the idler pulley  172  and gradually reassumes its horizontal orientation as it reaches the idler pulley  171 . The pulleys  170  and  171  are rotatably mounted on horizontal shafts  182  and  183 , respectively. The pulleys  178  and  172  are rotatably mounted on vertical shafts  180  and  184 , respectively. The drive belt  167  is located on the rear side of the dispense and incubation section  39  and is driven longitudinally by a drive pulley  175  which is fed to the drive shaft  181 . The drive pulley  175  has external teeth  191  and is located between and below idler pulleys  174  and  176 . The belt  167  extends over the idler pulley  176  which is rotatively mounted on the horizontal shaft  182  and around an idler pulley  177  which is rotatively mounted on a vertical shaft  190 . The belt  167  then extends along the back side of the cuvette dispense and incubation section  39  to and around an idler pulley  173  which is rotatively mounted on a vertical shaft  185 . The belt  167  then extends over the idler pulley  174  which is rotatively mounted on the horizontal shaft  183  and back to the drive pulley  175 . The belt  167  has a plurality of teeth  193  on one side of the belt. The teeth  164  on the belt  167  face upwardly as the belt  167  extends over the idler pulley  174  and under the drive pulley  175  and back up around the idler pulley  176 . The teeth  193  of the belt  167  are in drive engagement with the teeth  191  of the drive pulley  175 . When the belt  167  travels between the pulley  176  and the pulley  177  it gradually assumes a vertical orientation so that the teeth  193  face forwardly as the belt travels along the aspiration and incubation section  39  to the idler pulley  173 . As the inner sections of the belts  167  and  168  travel from left to right as viewed in  FIGS. 32 and 33 , the rearwardly facing teeth of the belt  168  and the forwardly facing teeth of the belt  167  engage the flanges  58  of the cuvettes  40  to advance the cuvettes along the event track or dispense and incubation section  39  for a predetermined time period during the twenty second system cycle.  
      Sample Transport System  
      The sample transport system consists of a sixty position sample tray for receiving sample containers containing test samples, calibrators, controls, and diluents; a laser bar code reader; and a digital diluter. The sample tray consists of two concentric rings, each capable of holding a mixed population of various tubes and sample containers. The outer ring can accommodate thirty-four sample containers, the inner ring twenty-six sample containers. Each position has a spring clip so that different sizes of sample containers can be accommodated. The bar code reader recognizes six versions of bar code language, and recognizes the identity of each bar coded sample and the identity of the bar coded tray. The operator may program the analyzer to automatically repeat any sample whose initial test result exceeds a selected range. Also, for most assays, the system will automatically dilute and re-assay any sample above the range of the standard curve, if desired. Various dilution ratios are selectable, based upon sample size. The sample aspirating and dispensing probe is specially coated and has capacitance level sensing in order to recognize the surface of the sample. This insures that liquid is present in a sample container before aspirating, as well as minimizing immersion into the test sample. After each aspiration and dispensing cycle, the inner and outer surfaces of the probe are thoroughly washed with deionized water at a wash station to minimize sample carryover.  
      The sample transport system  26  is shown in  FIGS. 36-42 . Referring first to  FIGS. 38, 39  and  41 , the transport system  26  includes a fixed base which is generally indicated by the reference numeral  211  and which is mounted in a fixed position on the machine framework in front of the cuvette dispense and incubation section  39 . The fixed base  211  includes an upper horizontal plate  212  and three descending legs  213 , each with a horizontally and outwardly extending foot portion  214 . Each foot portion  214  supports a roller  247  which is rotatively mounted on a horizontal shaft  215  for rotation about a horizontal axis. Each foot  214  also supports a roller  218  which is rotatively mounted on a vertical shaft  217  for rotation about a vertical axis. An electric stepper motor  219  is fixed to the bottom of the upper plate  212  and has a drive shaft  220  which extends through a hole  216  in the upper plate  212 . A friction drive wheel  221  is fixed to the outer end of the shaft  220  for rotation therewith. An inner tray, generally indicated by the reference numeral  222 , and an outer tray, generally indicated by the reference numeral  223 , are rotatively mounted on the base  211  for rotation independently of one another about a vertical axis  209 .  
      The inner tray  222  includes an inner hub portion  225  which is rotatively mounted on a vertical shaft  224  which is fixed to the upper plate  212  and which extends along the vertical axis  209 , see  FIG. 38 . The inner hub portion  225  has a downwardly extending annular flange  226  which is in frictional engagement with the drive wheel  221 . When the motor  219  is actuated, the drive wheel  221  is rotated by the shaft  220  which, in turn, rotates the inner hub portion  225  about the axis  209  due to the frictional engagement of the roller  221  against the inner surface of the annular flange  226 . The inner hub  225  has an outwardly extending circular flange  208  at the bottom of the hub. The flange  208  is rotatably supported on the rollers  297 . The inner tray  222  also includes an outer hub  227  which has an outer annular flange  228  which supports a plurality of receptacles  229  for supporting a plurality of sample containers, see  FIG. 37 . The receptacles  229  are arranged in a circle which is concentric with the axis  209 . Each receptacle  229  has an outwardly facing opening  195 .  
      The outer tray  223  includes a drive ring  230  which has an outer downwardly extending annular flange  231 . The annular flange  231  has an inwardly facing annular groove  232  for receiving the rollers  218  which support the drive ring  230  for rotation about the axis  209 . The drive ring  230  supports an outer ring  233  which contains a plurality of upwardly extending receptacles  234  for supporting a plurality of sample containers. The receptacles  234  are arranged in a circle which is concentric with the axis  209  and is located outside of the circle of receptacles  229  as shown in  FIG. 37 . Each receptacle  234  has an outwardly facing opening  260 . Each of the receptacles  229  and  234  is at least partially lined with a metal plate  270  which has a plurality of inwardly protruding resilient fingers  271 . The fingers provide a snug fit for a test tube or sample container and enable test tubes of different diameters to be used and held securely. The plates  270  and fingers  271  also provide a ground connection to the metallic machine framework to provide one component of a capacitance level sensing system to be described in a later section entitled: ‘SAMPLE PROBE TRANSPORT SYSTEM’. The outer tray  223  is rotated independently of the inner tray  222  by means of a sty motor  235  which is fixed to a mounting plate  236  which is, in turn, supported on the framework of the machine. The stepper motor  235  has a drive shaft  237  which is fixed to a drive pulley  238 . A pulley  239  is fixed to a vertical shaft  241  which is mounted for rotation on the plate  236 . The pulley  239  is driven from the pulley  238  by a timing belt  240 . A drive wheel  242  is fixed to the pulley  239  and is in frictional engagement with the outer surface of the flange  231 . When the motor  235  is activated, the roller  242  is rotated about the axis of the shaft  241  which, through its frictional engagement with the outer surface of the flange  231 , causes the drive ring  230  to rotate about the axis  209 . This rotation is totally independent of the rotation of the inner tray  222  by the stepper motor  219 .  
      Referring to  FIGS. 40 and 42 , a PC board  245  is mounted to the machine base adjacent the sample transport system  26 . The PC board  245  supports a plurality of interrupt sensors for the inner and outer trays. The sensors are arranged in two groups, an outer group for the outer ring, and an inner group for the inner ring. The outer group includes a pair of spaced outer sensors  246  and an inner home sensor  266 . The inner group includes a pair of inner sensors  244  and an inner home sensor  267 . The outer ring  230  has a single downwardly descending home tab  253  which interrupts the beam of the home-sensor  266  to determine a starting position for the outer ring at the beginning of a test or a series of tests. A plurality of tabs  268  extend downwardly from the drive ring  230  of the outer tray  223  outside of the home tab  253  and extend in a circle about the axis  209 . As the outer ring rotates about the axis  209 , the tabs  268  pass through both sets of sensors  246 . There is a tab  268  for each sample position of the ring  230  so that each time that the ring is rotated one position, the beam in each of the sensors  246  is interrupted to provide a signal to the CPU to indicate that the outer tray  223  has moved one position. The distance between the two sensors  246  differs from the spacing between two adjacent tabs  268  so that the sensors are not interrupted simultaneously. This enables the control electronics to determine the direction of rotation of the ring  230 . To position a particular bottle or sample container about the axis  209 , a command is given to the stepper motor  235  to move a number of steps in a certain direction and acceleration. The optical interrupt sensors  246  count the number of positions moved by the drive ring  230  to determine the final desired position of the ring. When the correct number of transitions have occurred, the stepper motor  235  will move a calibrated number of steps past the transition point and stop. This will be the final container positioning point. The CPU is programmed to move the ring  230  and outer tray  223  in whichever direction will result in the smallest amount of rotation of the ring for each new sample container position. A single ‘home’ tab  259  extends downwardly from the inner tray  222  for interrupting the beam of the home sensor  267  to determine the starting or “home” position of the inner tray. A plurality of tabs  243  extend downwardly from the tray  222  outside of the “home” tab  269  and extend in a circle which concentric with the axis  209 . The tabs  243  interact with the interrupt sensors  244  for controlling the stepper motor  219  and selectively positioning the inner tray  222  in the same manner as the tabs  268  and sensors  246  are utilized to selectively position the outer tray  223 . The inner and outer trays are moved selectively and independently to position a specified predetermined sample container to a predetermined pickup position for aspiration by the sample aspirating and dispensing probe  24 . Referring to  FIG. 22 , the pickup position for the outer tray is located at the opening  255  in the outer cover  257 . The pickup position for the inner tray is located at the opening  256  in the outer cover  257 . A bar code label is affixed to the outer wall of each sample container. The label has a specific bar code which identifies the test sample within the container. All of the information relating to the sample, such as the name of the patient and the tests which are to be performed with the sample, are stored within the memory of the central processing unit. Referring to  FIG. 22 , a bar code reader  258  is located adjacent the sample transport system  26  and has two lines of sight which are indicated by the dotted lines  259  and  272 . Prior to a run of tests, the receptacles in the inner and outer trays are charged with sample containers each containing its own specific bar code which can be viewed through the openings  260  in the outer parts of the receptacles  234  and the clear plastic cover  257 . The outer tray  223  is rotated about the axis  209  so that each sample container passes through the lines of sight  272  and  259  relative to the bar code reader  258  so that the bar code on each sample container can be read by the bar code reader. The energy beam from the transmitting portion of the bar code reader  258  passes along the line of sight  272  and the beam is reflected hack from the bar code label on the sample container along the line of sight  259  to the beam receiving portion of the barcode reader. The vertical openings  260  and the transparency of the outer cover  257  enable the bar codes on the samples to be ‘seen’ by the bar code reader. This enables the identity of each sample container to be correlated with the position of the outer tray relative to a home position. After all of the sample containers have been read by the bar code reader, the outer tray  223  is positioned so that a gap  261  in the circle of receptacles  234  is aligned with the lines of sight  259  and  272 . This enables the bar codes on the sample containers in the inner tray  222  to be exposed through openings  195  in the outer portions of the receptacles  229  to the bar code reader  258 . The inner tray  222  is rotated so that each sample container in the inner tray passes through the lines of sight  259  and  272  so that the specific bar code of each sample in the inner tray  222  is read by the bar code reader. This information is utilized by the central processing unit to correlate the position of each sample container in the inner tray  222  relative to the home position of the inner tray.  
      Referring particularly to  FIGS. 39 and 41 , a contact ring  250  is fastened to the drive ring  230  by a screw  262  which also mounts a positioning key  263  to the drive ring  230 . A contact ring  252  is fastened to the upper wall of the hub  225  by a screw  264 . Positioning key  265  is fixed to the hub  225  at the base of the flange  226 . The metal grounding wire  248  is connected to the contact ring  252  and connected to the keys  265  and  263  by a connecting wire  249 . These elements form part of the grounding system for grounding the fingers  271  to the machine framework.  
      The bar code-labeled sample containers may be loaded in any order in the sample tray. The analyzer will read all bar codes automatically, and identify the sample and its position in the tray. If bar code labels are not used, a worklist printout is utilized, which directs placement of samples in specific sample tray positions.  
      Reagent Transport System  
      The reagent transport system or tray provides a carrier for twenty-six reagent bottles or containers, sufficient for up to thirteen different assays. The inner portion is made to specifically accept the solid-phase reagent containers, and periodically agitates these containers to maintain homogeneity of the solid phase reagent. This mixing action is aided by the design of the reagent bottles, which have agitator fins molded into their inner walls. The tracer or labeled reagent bottles are also specially shaped to automatically orient the identifying bar code label affixed to the container, and are loaded into the outer positions on the reagent tray. Reagents are bar code labeled. A reagent laser bar code reader records the loaded position of each specific reagent, including identity and tot number, making random loading permissible. Reagents may be loaded directly from refrigerated storage, since they are warmed to 37° C. before dispensing. The three reagent aspiring and dispensing probes have capacitance level sensing and may be programmed to make an initial reagent level check before sating an assay run to insure that adequate reagent volumes have been loaded to complete the scheduled worklist stored in the CPU. Reagent volumes used range from 50-450 uL, depending on the assay, and specific reagents may be added to the sample in the cuvette at each of the three reagent probes, with incubation times of 2.5 to 7.5 minutes, depending on optimal condition for specific assays. Reagent probes, like the sample probes, are thoroughly washed with deionized water between dispensings.  
      Referring to  FIGS. 43-49 , the reagent transport system is generally indicated by the reference numeral  27 . The reagent transport system  27  comprises a fixed supporting base  286  which is fixed to the machine framework  283  and an electric stepper motor  287  which is fixed to the supporting base  286  by fasteners  282  and connecting rods  285 . The stepper motor  287  has a drive shaft  290  which is fixed to a motor hub  291  by a trantorque clamp  280 . The drive shaft  290  is rotated about a vertical drive axis  293 . The base of the motor hub  291  consists of a ring of upwardly facing gear teeth  292 . The circular spill tray  288  has a central circular opening  289  and is fixed to the supporting base  286  by a plurality of fasteners  279  so that the stepper motor  287  extends upwardly through the opening  289 . Referring to  FIGS. 45 and 46 , a support ring  294  is located concentrically of the central vertical axis  293  and has a central circular opening  295  and a plurality of smaller openings  308  which are arranged in a circle which is concentric with the axis  293 . A reagent tray  296  is mounted on the support ring  294  and contains a ring of inner pockets  297  and a ring of outer pockets  299 . The pockets  297  and  299  are arranged in concentric cycles about the axis  293 . Each outer pocket  299  contains a tubular outer bottle or reagent container holder  298  which is fixed to the pocket by a Ding disc  301 . The connector  301  extends through an aperture  302  at the base of the pocket to the support ring  294  for fastening the reagent tray  296  to the ring  294 . When a container  60  of labeled or tracer reagent is placed in the pocket  299 , the tubular holder  298  extends between the skirt  63  and the main body portion  64  as shown in  FIG. 45 .  
      Each inner pocket  297  contains an inner container holder  300 . A fastening disc  303  bears against the bottom wall of the holder  300  and has a vertical shaft  304  which extends through an opening in the bottom wall of the holder. The fastening discs  301  and  303  are metallic and are grounded to the machine framework. The discs  301  and  303  provide one component of a capacitance level sensing system which is described in a following section entitled ‘REAGENT PROBE TRANSPORT SYSTEM’. A gear  306  is fastened to the bottom of the holder  300  by a pair of screws  305  which also effectively clamp the fastening disc  303  and the gear  306  against the bottom wall of the holder  300 . The bottom of the shaft  304  extends below the gear  306  and into a pair of flanged bearings  307  which are mounted in one of the apertures  308  of the support ring  294 . This enables each holder  300  and its respective gear  306  to rotate about its own central longitudinal secondary axis  278 . The gears  306  extend about a ring gear  309  and are in driving engagement with the outer teeth of the ring gear, see  FIG. 46 . The ring gear  309  has a large central opening  277 . A pair of pins  310  are fixed to the gear  309  and extend below the gear into driving engagement with the teeth of the ring gear  292 , see  FIG. 45 . Actuation of the stepper motor  287  causes the hub  291  in the ring gear  292  to rotate about the axis  293 . This causes rotation of the ring gear  309  through the drive pins  310 . The ring gear  309 , in turn, drives all of the satellite gears  306  for rotating each bottle holder  300  about its respective secondary axis  278 . The ring gear  309  is fully supported by the satellite gears  306 . A plurality of retainers  311  are fixed to the ring gear  309  and extend below the gear  309  for straddling the inner edge of the support ring  294 . The bottle holder  300  holds a solid phase bottle or reagent container  75 . The side walls of the holder  300  has a plurality of vertical slots  276  which form a plurality of resilient fingers  274  which extend between the main body  76  and the skirt  80  of the reagent bottle or reagent container  75  for holding the reagent container  75  in a friction fit. The stepper motor  287  is reversible and controlled by the central processing unit to oscillate the drive shaft  290  at predetermined intervals. Each of the bottle holders  300  is adapted to receive a solid phase reagent container  75 . The oscillations of the holder  300  provide the necessary motion to the reagent container  75  for enabling the fins  81  to agitate the solid phase reagent solution within the bottle  75  and, thereby, maintain a uniform concentration of the solid phase elements within the solution. Each of the bottle holders  298  is adapted to receive a labeled reagent container  60  which does not require agitation. Referring particularly to  FIGS. 45 and 47 , a ring gear  312  encircles the spill tray  288  and is mounted for rotation on supporting base  286  about the axis  293 . The lower part of ring gear  312  has an inwardly facing V-shaped bead  275  which engages a plurality of V-guide wheels  323  which support the ring  312  for rotation about the axis  293 . Each wheel  323  is rotatively mounted on a vertical shaft  324  which is fixed to the base  286 . The ring gear  312  supports the support ring  294  and the reagent tray  296 . Referring also to  FIGS. 48 and 49 , part of the ring gear  312  has an annular flange which is opposite the V-shaped beads  275  and contains a ring of outwardly facing gear teeth  329  which are in driving engagement with an idler gear  319  which is keyed to a vertical shaft  320 . The shaft  320  is rotatively mounted in flanged bearings  321  which are supported on flanges  322  of a motor mount  314 . The motor mount  314  has a circular bore  316  which contains a drive gear  318  which is fixed to the drive shaft  317  of a stepper motor  315 . The stepper motor  315  is fixed to the motor mount  314 . The wall of the bore  316  of the motor mount  314  has a lateral opening which enables the drive gear  318  to engage the idler gear  319 . Actuation of the motor  315  causes the drive gear  318  to drive the ring gear  312  through the idler gear  318  about the vertical axis  293 . The inner and outer pockets  297  and  299 , respectively, are enclosed within a clear stationary plastic covers  327 . The cover  327  has a plurality of openings  328 ,  338 ,  339 ,  340 ,  341 , and  342  which provide access to the bottles within the pockets  297  and  299  by reagent aspirating and dispensing probes to be described in a later section, see  FIG. 22 .  
      Referring to  FIG. 47 , a PC board  330  contains a pair of interrupter sensors  331  and  336  and a photo reflector sensor, not shown; which is located beneath the sensors  331  and  336 . The optical reflector sensor has a beam transmitting portion and beam receiving portion. If a beam from the transmitting portion of strikes a reflective surface, the beam is reflected back to the receiving portion of the sensor. When the beam is not reflected back, the sensor generates a signal to the CPU. The PC board  330  is mounted to the base plate  286  so that the sensor optical reflector faces outwardly toward the ring  312 . The beam from the transmitting portion of the beam reflector sensor strikes the ring  312  and is reflected back to the beam receiving portion of the sensor. The ring  312  has an aperture  326 , see  FIG. 49 , which is at the same level as the beam from the photo reflector sensor. At the beginning of a testing sequence, the ring  312  is rotated about the axis  293  until the beam of the photo reflector sensor is aligned with the aperture  326 . When this occurs, the beam passes through the aperture and is not reflected back to the sensor. The absence of the reflected beam initiates a signal to the CPU to indicate the ‘home’ or starting position of the reagent tray at the beginning of a series of tests. Referring to  FIG. 47 , the ring  312  has a plurality of tabs  334  which extend inwardly from the ring  312  and which pass between the two spaced elements of each interrupter sensor  331  and  336  for interrupting a beam from each optical sensor which provides feedback to the control electronics for reagent bottle positioning. There is a tab for each reagent bottle position in the tray  296  so that each time that the ring is rotated one position, the beam in each of the sensors  331  and  336  is interrupted to provide a signal to the CPU to indicate that the tray has moved one position. The distance between the two sensors is less than the spacing between two adjacent tabs  334  so that the sensors  331  and  336  are not interrupted simultaneously. This enables the CPU to determine the direction of rotation of the reagent tray. To position a particular bottle or container to a reagent probe pickup or aspiration position, a command is given to the stepper motor  315  to move a fixed number of steps in a certain direction. This causes the reagent tray  296  to rotate along with the tabs at the bottom of the drive ring  312 . The sensors  331  and  336  counts the number of tab transitions an determines the position of the reagent tray  296 . When the correct number of transitions have occurred, the stepper motor  315  will move a calibrated number of steps past the transition point and stop. The bottle containing the designated reagent will thereby be positioned at the predetermined pickup point for one of the reagent probes  
      A photo reflective sensor  337  is mounted on the plate  286  and directs a light beam upwardly. The motor hub  291  has a bottom reflective surface which has a plurality of spaced apertures. As the hub  291  oscillates, the beam from the sensor  337  is alternately reflected back to the sensor by the bottom reflective surface of the hub and absorbed by the apertures in the bottom surface. This provides appropriate signals to the CPU to indicate that the hub is being oscillated at predetermined intervals.  
      Each reagent container has a bar code label affixed to its outer skirt portion. The label contains a specific bar code which identifies the reagent within the container. The information relating to all of the reagents in the bar codes associated with the reagents are stored within the memory of the central pressing unit. Referring to  FIGS. 43 and 22 , a bar code reader  332  is located, adjacent the reagent transport system  27 . The bar code reader  332  transmits an energy beam along a line of sight which is indicated by the dotted line  333 . The beam is reflected back go the bar code reader  332  from the bar code label along a line of sight which is indicated by the dotted line  344 . The return beam along the line of sight  344  is received by the beam receiving portion of the bar code reader. The bar code in the preferred embodiment is printed on the label for each reagent bottle in a vertical direction. The inner pockets  297  and outer pockets  299  are staggered with respect to each other. As the reagent tray  27  is rotated about the axis  293  by the stepper motor  315 , the inner and outer pockets alternately pass through the lines of sight  333  and  334  of the bar code reader  332 . The stepper motor  287  is also utilized during the initial reading of reagent container bar codes prior to a run of tests. Referring to  FIGS. 43 and 46 , there is a relatively large space between each outer pocket  299 . Each inner pocket  297  is horizontally aligned with the space between two adjacent pockets  299 . A vertical wall  335  which separates the inner and outer pockets  297  and  299 , respectively, has a relatively large opening  328  at each space between outer pockets  299  so that each reagent container is exposed to the line of sight of the bar code reader when the container is rotated about the axis  293  by the stepper motor  315 . As the reagent tray  27  is rotated about the axis  293 , each reagent container or bottle in the ring of inner pockets  297  is given one and one-half revolutions per pass of a reagent container  75  through the lines of sight  333  and  334  to insure that the bar code is exposed to the reader. The bar codes on the bottles in the inner and outer pockets can be read by the bar code reader  332  through the clear plastic cover  327 .  
      The operator loads required assay reagents, in original bar code-labeled bottles, into the reagent tray in any order, solid-phase reagents on the inner bottle holders  300 , labeled or tracer reagents on the outer bottle holders  298 . Due to the design of the reagent bottles, it is not possible to mis-load reagents. The analyzer will read all bar codes before initiating a run, identifying each reagent, its position, its lot number and expiration date. If greater than 50 tests of a specific assay has been requested in the worklist, multiple bottles of the necessary reagents may be loaded on the reagent tray and the analyzer will access them sequentially, as needed.  
      Sample Probe Transport System  
      Referring to  FIGS. 50-59  and first to  FIGS. 54 and 55 , the sample probe transport system  24  comprises a fixed upper horizontal support plate  357 , and a sample probe supporting carriage, generally indicated by the reference numeral  363 , which is mounted for horizontal back and forth movement relative to the supporting plate  357 . The support plate  357  has an opening  366 . A PC board  358  is fixed to the upper surface of the plate  357  by screws  359 . The under surface of the PC board has a plurality of electrical junctions J 1 , J 2 , J 3 , J 4  and J 5  which extend into the opening  366 . A vertical bracket  364  is fixed to the underside of the plate  357  at the rear end of the plate. An electrical stepper motor  365  is fixed to the forward side of the bracket  364  and has a drive shaft  369  which is rotatable about a horizontal axis. A lead screw  371  is fixed to the drive shaft  369  through a drive coupling  370  and extends through a roll nut  409  which is fixed within a bore  408  of a block  372  (See also  FIG. 58 .) The block  372  is mounted in a yoke  373  between a pair of upper and lower dowel pins  374 . The dowel pins  374  enable the block  372  to pivot about a vertical axis to compensate for slight misalignments between the block  372  and the lead screw  371 . The block  372  has a laterally extending horizontal shaft  375  which is mounted to the carriage  363  in a manner described herein below.  
      A guide bracket  360  is fixed to the underside of the plate  357  by the screws  359  and has a downwardly facing horizontal groove  361 . A carriage supporting bar  362  is slidably mounted in the groove  361 . The carriage  363  is fixed to the sliding bar  362  by a screw  391  and an anti pivot rod  387  which has a threaded upper end. The carriage  363  includes a forwardly facing vertical wall  376 , a top horizontal wall  377  and a lower horizontal wall  378 . The top wall  377  has an aperture  389  and the bottom wall  378  has an aperture  388 . The anti pivot rod  387  extends freely through the apertures  388  and  389  and is threaded into the block  362 . Referring also to FIG.  56 , the wall  376  has a horizontal bore  379  which has a bearing  380  at each end of the bore. The shaft  375  of the yoke  373  extends through the bore  379  within the bearings  380 . A vertical lead screw  385  is rotatably mounted in upper and lower bearings  383  and  384 , respectively, in the upper and lower walls  377  and  378 , respectively. The lower end of the lead screw  385  extends below the bottom wall  378  and is fixed to a pulley  386 . An electrical stepper motor  394  is fixed to the underside of a rearwardly extending horizontal flange  393  of the carriage  363 . The stepper motor  394  has a vertical drive shaft  395  which is fixed to a pulley  396 , see also  FIG. 57 . The pulley  396  is drivingly connect to the pulley  386  through a timing belt  397 . The inner surface of the timing belt  397  has a plurality of teeth for engaging corresponding teeth on the drive pulleys  396  and  386 , (teeth not shown). A lead screw follower  401  is positioned between the walls  377  and  378  and has a vertical bore  403  and a vertical bore  404  which contains a roll nut  405  (see also  FIG. 59 ). The anti pivot rod  387  extends freely through the bore  403  and the lead screw  385  extends through the roll nut  405 . The roll nut  405  is fixed relative to the follower  401  so that as the lead screw  385  is rotated about its vertical axis, the follower  401  moves along the central longitudinal axis of the lead screw  385  relative to the walls  377  and  378 . A probe holding arm  402  is fixed to the forward end of the follower  401  and carries an aspirating and dispensing sample probe  407 .  
      A PC board  398  is fixed to the carriage  363  and has an electrical connector  399  which is connected to the electrical junction J 2 . The stepper motor  394  has a connector  400  which is connected to the electrical junction J 4 . The stepper motor  365  has a connector  368  which is connected to the junction J 5 . The probe supporting arm  402  has a PC board  406  which is connected to a connector  411  through a flexible ribbon  421 . The connector is connected to junction  420  of the PC board  398   
      The stepper motor  365  is reversible. When the lead screw  371  is rotated in one direction, the carriage  363  moves rearwardly along the central longitudinal axis of the lead screw  371  toward the flat bracket  364 . This causes the carriage  363  and the sample probe  407  to move from a forward position to a rearward position relative to the sample tray. When the stepper motor  365  is reversed, the lead screw  371  is rotated in the opposite direction. This causes the carriage  363  to move forwardly and, thereby, move the sample probe  407  from its rearward position to one of two forward pickup positions above the sample tray. The sample probe  407  can also be positioned in intermediate positions between rearward and forward positions, as for example, above the wash station  18 . The motor  394  is also reversible. Rotation of the lead screw  385  in one direction causes the follower  401  and the arm  402  to move upwardly. Rotation of the lead screw  385  in the opposite direction, causes the follower  401  and the arm  402  to move downwardly. The sample aspirating and dispensing probe  407  is moved forwardly when it is in the upper position until it reaches one of the sample pickup or aspiration positions above the sample tray and is then moved downwardly to pick up a volume of a sample. The probe  407  is then moved to the upper position and returned to a point above the wash station, whereupon it is moved downwardly again for a wash cycle, or to its rearward position above one of the cuvettes, whereupon it is lowered into the cuvette for depositing the sample volume into the cuvette. The stepper motors  394  and  365  are capable of making very precise step-by-step motions for very precise, horizontal and vertical positioning of the sample probe  407 .  
      Referring to  FIGS. 54 and 56 , a plurality of spaced tabs  410  extend upwardly from the carriage  363  from front to back on one side of the carriage. A single ‘home’ tab  415  extends upwardly from the carriage  363  on the opposite side of the carriage. When the carriage  363  reaches its rearward ‘home’ position, the tab  415  passes between the elements of an interrupt sensor  413  which extends downwardly from the support plate  357 . The tab  415  interrupts a light beam between the two elements of the sensor  413  which initiates a signal to the CPU that the carriage has reached its ‘home’ position and the sample probe  407  is directly above a cuvette at the sample dispense point  44 . The upper portion of the probe carrying arm  401  is determined by an interrupt sensor  416  which is fixed to the PC board  398 . The PC board is fixed to the carriage  363  so that it extends horizontally toward the probe carrying arm  401 , see  FIGS. 50 and 56 . The follower  401  has a tab  355  which extends toward the sensor  416 . The tab  355  cannot be seen in  FIGS. 54 and 56  since it is located on the hidden side of the follower  401 , but is indicated by dotted lines in  FIG. 53 . When the follower  401  reaches the upper position, the tab  355  passes between the two elements of the sensor  416  and interrupts a light beam. The interruption of the light beam provides a signal to the CPU to indicate that the follower  401  and the probe  407  have reached the upper position. This insures that the carriage  363  can be safely moved to a new horizontal position at a predetermined point of time in the operating cycle, whereupon the motor  365  is given pulses for a predetermined number of half steps. At the appropriate time, the motor  394  is activated to move the arm  401  and the probe  407  downwardly. For each sample pickup cycle, the motor  365  is actuated for a predetermined number of half steps to move the carriage forwardly with the probe  407  in the upper position from the home position until the probe  407  is above the wash station  18 . The motor  394  is actuated for a predetermined number of half steps to lower the probe  407  into the wash station  18  for a wash cycle. The probe  407  is then raised by reversing the stepper motor  394  for a predetermined number of half steps. The motor  365  is actuated for a predetermined number of half steps to move the carriage  363  forwardly until the probe  407  is above the opening  255  or the opening  256  in the outer cover  257  of the sample transport system. The motor  394  is actuated to move the follower  401  together with the arm  402  downwardly to lower the probe  407  into the sample container which is located beneath whichever of the openings  256  or  255  which is vertically aligned with the probe  407 . The lower position of the sample probe  407  is determined by a capacitance fluid sensing system. The capacitance fluid sensing is a function of a signal change occurring through two conductive materials such as the metal probe  407  and ground fluid and one non-conductive material such as air or plastic/glass sample container. When the probe is in the upper position, the probe&#39;s reference current is measured, as the probe moves downwardly seeking fluid, an increase in signal indicates the presence of fluid. When fluid is detected, the motor  394  is actuated for a predetermined number of half steps to move the probe  407  a predetermined distance below the meniscus of the fluid. This distance is determined by the amount of fluid to be aspirated, a large volume requiring a deeper penetration of the probe than a smaller volume. After aspiration of a volume of sample by the probe  407 , the probe is raised to its upper position, whereupon the motor  365  is actuated for a predetermined number of half steps to move the carriage  363  rearwardly to its “home” position so that the probe  407  is directly above the sample dispense point  44 . The motor  394  is actuated for a predetermined number of half steps to lower the probe  407  in the cuvette which is located beneath the dispense point  44 . The quantity of sample is then dispensed by the probe  407  into the cuvette. The probe  407  is raised to its upper position to begin another cycle. As the carriage moves between the ‘home’ and forward positions, the tabs  410  pass between the elements of an interrupt sensor  412 . The tabs  410  are positioned so that when the carriage stops at a forward position for a sample pickup or a wash cycle, none of the tabs  410  will interrupt the light beam which passes from one element of the sensor  412  to the other. The light beam will pass through one of the spaces between the tabs  410  or outside of the outer edge of one of the tabs when the probe is properly positioned. If the probe is not properly positioned, due to a malfunction in the system, one of the tabs  410  will interrupt the light beam and a signal will be sent to the CPU to stop the machine. This will prevent the lowering of an improperly positioned probe and subsequent breaking of the probe.  
      For most test protocols, the sample probe will make one forward step after the wash cycle to pick up a volume of sample from either the outer tray or the inner tray. In some cases, the sample probe stops at both of the openings  255  and  256  to pick up a volume of diluent as well as a volume of sample. The diluent is generally a protein based solution which is used to dilute a patient sample when an original test result is beyond a test curve range. The type of diluent used should correspond to the type of assay being performed by the analyzer. Diluent solutions are normally placed in the inner tray. The sample probe picks up the diluent before picking up the test sample as to avoid contaminating the diluent with sample. Other treatment liquid materials which are sometimes picked up with a sample solution are pretreatment agents and releasing agents. A releasing agent is sometimes mixed with the sample for the purpose of separating the analyte from another molecule and rendering it available for reaction. A pretreatment agent is a solution which is mixed and incubated with the test sample to protect the analyte from a releasing agent  
      Reagent Probe Transport System  
      The reagent probe transport system is shown in  FIGS. 60-72 . Referring first to  FIGS. 60-63 , the reagent probe transport system is generally indicated by the reference numeral  440  and includes the reagent probe transport systems R 1 , R 2  and R 3 . The system  440  comprises an upper horizontal support plate  441  which has openings  442 ,  443 ,  444  and  445 . A PC board  446  is fixed to the upper surface of the plate  441  and has a plurality of interrupter sensors on the undersurface of the PC board which extend into the openings  442 ,  443 ,  444  and  445 . Interrupter sensors  448 ,  449 ,  450  and  451  end into the opening  442 . Interrupter sensor  452  extends into the opening  443 . Interrupter sensor  453  extends into the opening  444  and interrupter sensors  454  and  453  extend into the opening  445 . A plurality of electrical junctions are also mounted on the other side of the PC board  446  and are accruable through the opening  442 ,  443 ,  444  and  445 . Junctions J 11  and J 12  are accessible through the opening  442 . The junctions J 13 , J 14  and J 15  are accessible through the opening  443 . Junctions J 16 , J 17 , J 18  and J 19  are accessible through the opening  444 . Junctions J 20 , J 21  and J 22  are accessible through the opening  445 . Three horizontal guide brackets  455 ,  457  and  459  are fixed to the underside of the support plate  441 . The guide brackets  455 ,  457  and  459  have elongated horizontal grooves  456 ,  458  and  460 , respectively. Elongated carriage supporting guide bars  461 ,  462  and  463  are slidably mounted in the grooves  456 ,  458  and  460 , respectively. The guide bar  461  is fixed to a reagent probe supporting carriage which is generally indicated by the reference numeral  464  and which forms part of the reagent probe transport system R 1 . The carriage supporting slide bar  462  is fixed to a reagent probe supporting carriage which is generally indicated by the reference numeral  465  and which forms part of the reagent probe transport system R 2 . The carriage supporting slide bar  463  is fixed to a reagent probe supporting carriage which is generally indicated by the reference numeral  466  and which forms part of the reagent probe transport system R 3 . Slide bars  461 ,  462  and  463  enable the carriages  464 ,  465  and  466  to move forwardly and rearwardly relative to the support plate  441 .  
      A flat vertical rear bracket  467  is fixed to the back end of the support plate  441  and extends downwardly from the under surface of the support plate. A plurality of stepper motors  468 ,  469 ,  470  and  471  are fixed to the front side of the plate  467 . The stepper motors  468 ,  469 ,  470  and  471  have forwardly extending and horizontal drive shafts  472 ,  473 ,  474  and  475 , respectively. The motors  468 ,  469 ,  470  and  471  have electrical connectors  476 ,  477 ,  478  and  479 , respectively, which are connoted to the electrical junctions J 10 , J 12 , J 20  and J 18 , respectively, on the PC board  446 . A bracket  480  is connected to the right side of the support plate  441  as viewed in  FIG. 63  and fixedly supports a horizontal slide bar  481  which is slidably mounted in the horizontal groove  482  of a guide bracket  483 . The guide bracket  483  is fixed to a guide rail  487  which is fixed to the framework of the machine. A horizontally extending slide bar  484  is fixed to the left side of the support plate  441  as viewed in  FIG. 63  and is slidably mounted in a horizontal groove  485  in a guide bracket  486 . The guide bracket  486  is fixed to an upwardly extending arm of a U-shaped bracket  488  which is fixed to a guide rail  489 . The guide rail  489  is, in turn, fixed to the machine framework. Brackets  483  and  486  are fixed relative to the machine frame and the slide bars  484  and  481  are fixed to the support plate  441 . The support plate  441  is able to move forwardly and rearwardly between the guide brackets  486  and  483 , along with the carriages  464 ,  465  and  466  which are supported from the underside of the support plate  441 .  
      The forward and backward motion of the support plate  441  is provided by the stepper motor  469 . The drive shaft  473  of the motor  469  is fixed to a horizontally extending lead screw  490  through a coupling  491  (See also  FIG. 67 ). The lead screw  490  extends through a roll nut  497  which is located in a bore  492  of a block  493 . The block  493  is pivotally mounted between the parallel arms of a yoke  494  by means of a pair of upper and lower dowel pins  495  which extend into a bore  435  of the block  493 . The roll nut  497  is fixed to the block  493  so that as the lead screw  490  is rotated, the block  493  moves along the central longitudinal axis of the lead screw. The pivoting motion of the block  493  along the longitudinal axis of the bore  435  within the yoke  494  compensates for any possible misalignments between the block  493  and the lead screw  490 . The yoke  494  has a shaft  496  which extends upwardly through a tubular follower guide  437  which is located in an aperture  439  in a bottom wall  438  of the U-shaped bracket  488 , see  FIG. 63 . The shaft  496  rides in a pair of bearings  436  at opposite ends of the follower guide  437 . When the lead screw  490  is rotated upon actuation of the motor  469 , there is relative motion between the block  493  and the lead screw  490  along the longitudinal axis of the lead screw. Since the block  493  is fixed relative to the machine framework, this motion causes the lead screw  490  and the motor to move relative to the machine framework which, in turn, causes the support plate  441  to move forwardly or backwardly, depending upon the rotation of the lead screw  490 .  
      The forward position of the plate  441  is the normal operating position for the reagent probe transport systems R 1 , R 2  and R 3  which are carried by the plate  441 . In this normal operating position, the reagent aspirating and dispensing probes for each of the Systems R 1 , R 2  and R 3  move forwardly and rearwardly between a rearward ‘home’ position in which the probe is above a corresponding reagent dispense point and a forward aspirating position in which the probe is above a corresponding opening in the cover  327  of the reagent transport system. The plate  441  is moved to the rearward position between test runs in order to position the guard which extends in front of the reagent probe transport systems in back to the cover  327  of the reagent trays to enable the cover to be removed for replacement of the reagent containers. The forward and rearward positions of the plate  441  are determined by the sensors  448  and  450  and a tab  431  which extends upwardly from the bracket  488 . When the plate  441  reaches its rearward position, the tab  431  passes between the elements of the sensor  450  to interrupt a light beam and provide a signal to the CPU that the plate  441  is properly positioned at the rearward position of the plate. When the plate  441  is in its forward position, the tab  431  is located between the elements, of the sensor  449  so that the beam which passes from one element to the other is interrupted to provide an electrical signal to the CPU that the plate is properly positioned in its forward position.  
      Referring particularly to  FIGS. 63 and 64 , the carriage  464  of the reagent probe transport system R 1  includes a rear vertical wall  508  which has a horizontal bore  511 , a top wall  509 , which has a vertical bore  514  and a bottom wall  510  which has a vertical bore  515 . A being  517  is located tin the bore  515  and a bearing  521  is located in the vertical bore  514 . A mounting guide  518  is fixed to the wall  508  and has a cylindrical portion  516  which extends into the bore  511 . A horizontal bore  513  extends through the mounting guide  518  and there is a pair of bearings  427  at each end of the bore  513 . A lead screw  499  is fixed to the drive shaft  472  of the motor  468  by a coupling  500 . The lead screw  499  extends through a roll nut  501  in a bore  502  of a block  503 . The block  503  is pivotally mounted between a pair of parallel arms of a yoke  506  in the identical manner as the mounting of the block  493  in the yoke  494  as shown in  FIG. 67 . The yoke  506  has a laterally extending shaft  507  which is supported within the bearings  4279  and extends through the bore  513  of the follower guide  518 . Since the roll nut  501  is fixed to the block  503 , rotation of the lead screw  499  upon the actuation of the motor  468 , causes the block  503  to move axially along the lead screw  499 . This causes the carriage  44  to move forwardly or rearwardly relative to the support plate  441 , depending on the direction of rotation of the lead screw  499 .  
      Referring also to  FIG. 72 , a probe holding arm  519  is mounted to a follower guide  505 . The follower guide  505  has a horizontal bore  520  which contain a roll nut  521  which is located between and in axial alignment with the bearings  521  and  517  in the upper and lower walls  509  and  510 , respectively, see  FIG. 64 . The lead screw follower  505  has a tab  433  which is slidably mounted in a vertical groove  432  of a vertical post  522 , see  FIGS. 64 and 70 . The post  522  has a lower horizontal flange  512  which is located below the bottom wall  510 . The flange  512  has a bore  523  which is vertically aligned with the bore  515 . The upper end of the post  522  is fixed to a gear segment  524  which has a bore  525 . The gear segment  524  has gear teeth  526  which extend radially about the center of the bore  525 . The gear segment  524  is located above the top wall  509  so that the bore  525  is in axial alignment with the bore  514 . The teeth of the gear segment  524  are in driving engagement with the teeth  631  of a horizontal plate  629  which is fixed to the plate  444  as shown in  FIG. 60 . When the carriage  464  is in its rear position, the probe holding arm  519  faces to the left as viewed in  FIG. 60 . As the carriage  464  moves forwardly, the gear segment  524  rotates about the vertical axis of the lead screw  527 . This causes the probe supporting arm  519  to rotate approximately 90 from the leftwardly facing position as shown in  FIGS. 60 and 62  to a forwardly facing position. Referring to  FIG. 22 , this causes the probe  535  to move along a curved path which is indicated by the dot and dash line  428 . The line  428  intersects the vertical axes of the dispensing point  45 , wash station  15  and the openings  329  and  338  in the clear plastic cover  327  of the reagent tray as shown in  FIG. 22 .  
      A stepper motor  528  is fixed to a rearwardly extending horizontal flange  529  of the carriage  464 . The motor  528  has 3 downwardly extending drive shaft  530  which is fixed to a pulley  531 . A vertical lead screw  527  is rotatably mounted within the bearings  521  and  517  and is drivingly engaged with the bushing  521  of the follower  505 . The lead screw  527  extends through the bores  523  and below the flange  512 . The lower end of the lead screw  527  is fixed to a pulley  533 , which is drivingly connected to the pulley  531  through a timing belt  532 . The inner surface of the timing belt  532  has a plurality of teeth which engage corresponding teeth on the pulleys  533  and  531  to provide a precise predetermined degree of rotation of the pulley  533  for each driving step of the stepper motor  528  (teeth not shown). When the stepper motor  528  is actuated for rotating the lead screw  527  in one direction, the probe holding arm  519  is moved upwardly. When the lead screw  527  is rotated in the opposite direction, the probe holding arm  519  is moved downwardly relative to the upper and lower walls  509  and  510  and the post  522 .  
      An interrupt sensor  571  is located at the top of the groove  432 . When the probe holding arm  519  is moved to its upper position, a beam in the sensor  571  is interrupted to provide an electrical signal to the CPU that the probe  535  is property positioned in its upper position. The sensor  571  is mounted on a PC board  537  which is attached to the post  522 , see  FIG. 64 . A connector  540  connects the PC board  537  to the junction J 15  of the PC board  537 .  
      Referring to  FIG. 72 , a PC board  534  is fixed to the probe holding arm  519 . The arm  519  also supports a first reagent probe  535 , see  FIG. 62 . Referring to  FIG. 64 , a bracket  538  is fixed to the upper wall  509  of the carriage  464  and has a plurality of upwardly extending tabs  536  for interacting with interrupt sensors  451  and  449  on PC board  446 . The sensor  451  is a ‘home’ sensor which provides a signal to the CPU when the rearmost tab  536  interrupts a beam between the two elements of the sensor when the carriage is in its ‘home’ or ard position. When the carriage is in the “home” position the probe  535  is directly over a cuvette at the reagent dispense point  45 . The tabs  536  also interact with the interrupt sensor  449  to insure that the probe  535  is located precisely at each of its forward positions. If the probe  535  is properly positioned, at any of the forward positions, the beam of the sensor  449  will be aligned with a space between two adjacent tabs or to the outside of one of the tabs. If the probe is not properly positioned, the beam will be interrupted by one of the tabs and a signal will be sent to the CPU to stop the machine.  
      The forward positions of the probe  535  include the wash station  15  and the openings  328  and  338  of the outer cover  327  of the reagent tray  27 . For each reagent pickup cycle, the motor  468  is actuated for a predetermined number of half steps to move the carriage  464  forwardly with the probe  535  in the upper position from the home position until the probe  535  is above the wash station  15 . The motor  528  is actuated for a predetermined number of half steps to lower the probe  535  into the wash station  18  for a wash cycle. The probe  535  is then raised by reversing the stepper motor  528  for a predetermined number of half steps. The motor  468  is actuated for a predetermined number of half steps to move the carriage  464  forwardly until the probe  535  is above the opening  328  or the opening  338  in the outer cover  327 . If the test protocol requires that the tracer or labeled reagent and the solid phase reagent are to be picked up by the probe  535 , the probe is moved to each of the openings  328  and  338  in succession. At each position  328  or  338 , the probe  535  is lowered by the motor  528 . The lower position of the probe  535  is determined by a capacitance fluid sensing electronics as described for the aspirating step for the sample probe  407 . After aspiration of a volume of reagent, the probe  535  is raised to its upper position, whereupon the motor  528  is actuated for a predetermined number of half steps to move the carriage  464  so that the probe  535  is above the other reagent opening or moved rearwardly so that the probe  535  is above the reagent dispense point  15 . The reagent aspirating and dispensing probe is then lowered into a cuvette which is beneath the point  15 . The volume of reagent is then dispensed into the sample solution in the cuvette. The probe  535  is then raised to its upper position and moved to the wash station  15  for a wash cycle which is described in detail in following section of the description. After washing of the probe, the probe is ready to begin another aspirating and dispensing cycle. The speed of the motor  564  is controlled by the CPU in accordance with the operating program. The probe  535  is lowered to a point just above the surface of the sample in the cuvette and then raised at a predetermined rate while reagent is dispensed into the cuvette. The probe  535  is raised at a rate which maintains the tip of the probe just above the rising surface of fluid in the cuvette. This provides maximum uniform mixing of the sample and reagent and minimizes splashing of fluids. This procedure also minimizes the introduction of air bubbles into the reaction mixture. This procedure is followed for the reagent probe systems R 2  and R 3  which are described hereinafter. A connector  572  is connected to the PC board  534  of the arm  519  through a flexible lead  578  and is connected to the PC board  537 . The metallic probe  535  is electrically connected to the connector  572  and forms part of the capacitance level sensing system.  
      Referring more specifically to  FIGS. 63, 65  and  69 , the carriage  465  of the reagent probe system R 2  includes a vertical forwardly facing wall  541 , a top horizontal wall  542  and a bottom horizontal wall  543 . The wall  541  has a horizontal bore  549  with a bearing  544  at each end of the bore. The top wall  542  has a bearing  557  which is located in a vertical bore  556 . The bottom wall  543  has a bearing  558  which is located in a vertical bore  559 . The bores  556  and  559  are vertically aliened. The wall  542  also has a vertical bore  545  which is vertically aligned with a vertical bore  546  in the bottom wall  543 . An anti pivot rod  547  is located in the bores  546  and  545  and has an upper threaded end  548  which is threaded into the carnage supporting slide bar  462 . A lead screw  550  is connected to the stepper motor  471  through a coupling  551  and extends through a roll nut  552  in a block  553 . The block  553  is mounted in a yoke  554  in the same manner as the mounting of the yoke  493  in the yoke  494  as shown in FIG;  67 . Since the roll nut  552  is fixed within the block  553 , rotation of the lead screw  550  upon actuation of the stepper motor  471  causes the block  553  to move along the longitudinal axis of the lead screw  550 . The yoke  554  has a shaft  555  which is mounted within the bearings  554  and extends through the horizontal bore  549 . As the block moves forwardly and rearwardly along the longitudinal axis of the lead screw  550 , it causes the entire carriage  465  to move forwardly and rearwardly relative to the support plate  441 , depending on the direction of rotation of the lead screw  550  by the reversible stepper motor  471 . A follower guide  561  is located between the upper and lower walls  542  and  543 , respectively, and has a vertical bore  560  through which the anti pivot rod  547  extends. Referring to  FIG. 69 , the follower guide  561  also has a vertical bore  574  which contains a roll nut  563 . The follower  561  is feed to a probe carrying arm  562  which carries a reagent probe  576 , see  FIG. 62 . A PC board  575  is connected to the arm  562 , see  FIG. 69 . A vertical lead screw  573  is located within the roll nut  563  and is rotatably mounted within the bearings  557  and  55 &amp;. The bottom end of the lead screw  573  extends below the bottom wall  543  and is fixed to a pulley  568 . An electric reversible stepper motor  564  is fixed to a lower and rearwardly extending horizontal bracket  565  of the carriage  465  and has a downwardly extending drive shaft  566 . A pulley  567  is fixed to the shaft  566  and is drivingly engaged with the pulley  568  through a timing belt  569 . The interior surface of the timing belt  569  has teeth which engage corresponding teeth on the pulleys  567  and  568 , (teeth not shown). When the lead screw  573  is rotated in one direction by the stepper motor  564 , the follower guide  561  moves upwardly relative to the support plate  441  along with the reagent probe  576 . The reagent probe  576  is moved downwardly with the follower guide  561  when the motor  564  is reversed to rotate the lead screw  573  in the opposite direction. An electrical connector  570  extends from the stepper motor  564  and is connected to the junction J 13  on the PC board  446 . A bracket  582  is fixed to the top wall  542  and has a plurality of upwardly extending tabs  581  which interacts with the interrupter sensor  452  for insuring that the probe  576  is properly positioned at the several forward positions. If one of the tabs  581  interrupts a beam in the sensor  452  as any one of the forward positions of the probe  576 , a signal is transmitted to the CPU that the probe is improperly positioned. A ‘home’ tab  634  extends upwardly from the carriage  465  and interacts with the interrupt sensor  453 . When the carriage  465  reaches its rearward ‘home’ position, the tab  634  interrupts the beam of the sensor  453  which transmits a signal to the CPU that the carriage is properly positioned at the “home” position in which the probe  576  is positioned over the reagent dispensing point  46 .  
      The stepper motors  471  and  564  are selectively controlled by the CPU to move the carriage vertically and horizontally to position the probe  576  in the same aspirating and dispensing sequence as described for the probe  535  except that the probe  576  is moved in a straight forward to back line  426 , see  FIG. 22 , which interests the vertical axes of the reagent dispensing point  46 , the wash station  16 , and the holes  339  and  340  in the cover  327  of the reagent transport system  27 . Depending on the test protocol, the probe  576  will be moved forwardly to pick up or aspirate a labeled or tracer reagent at the opening  339  or a solid phase reagent at the opening  346 . The test protocol may also require that a labeled reagent and a solid phase reagent are to picked up by the probe  576 . The probe  576  is lowered by the motor  564  at each position  339  and  340 . The lower position of the probe  576  is determined by a capacitance fluid sensing electronics as described for the sample probe  407 . After aspiration a volume of reagent, the probe  576  is moved to its upper position, whereupon the motor  471  is actuated for a predetermined number of half steps to move the probe above the other reagent opening or rearwardly so that the probe  576  is above the reagent dispense point  16 . The probe is then lowered into a cuvette which is beneath the point  16 . The aspirated reagent is then dispensed into the sample solution in the cuvette. The probe  576  is then raised to its upper position and moved to the wash station  16  for a wash cycle, whereupon it will be ready to begin another aspirating and dispensing cycle.  
      Referring to  FIGS. 22, 63 ,  66  and  71 , the carriage  466  of the reagent probe system R 3  includes a rearwardly extending vertical wall  594 , a top horizontal wall  592  and a bottom horizontal wall  593 . The vertical wall  594  has a bore  595  which contains the cylindrical portion  580  of a guide  608  which has a bore  579 . A bearing  607  is located at each end of the bore  579 . The top horizontal wall  592  has a bearing  590  which is located in a bore  591 . The bottom wall  593  has a bearing  584  which is located in a bore  589 . A lead screw  583  is rotatably mounted in the bearings  590  and  584  and extends from the top wall  592  to the bottom wall  593 . The bottom of the lead screw  583  extends below the bottom wall  593  and is fixed to a pulley  600 . A reversible stepper motor  596  is fixed to a lower horizontally and rearwardly extending bracket  597 . The motor  596  has a downwardly extending drive shaft  598  which is fixed to a pulley  599 . The pulley  600  is drivingly connected to the pulley  599  through a timing belt  601 . The inner surface of the belt  601  has teeth which engage corresponding teeth on the drive pulleys  599  and  600  (teeth not shown). A reagent probe carrying arm  617  has a tab  627  which extends into a vertical slot in the rear side of the post  609  is fixed to a lead screw follower  615  which has a roll nut  625  within a bore  616 . The lead screw  583  is drivingly engaged with the roll nut  625  for moving the probe carrying arm  617  vertically up or down depending on the direction of rotation of the lead screw by the stepper motor  596 . A vertical post  609  is located between the upper wall  592  and the lower wall  593 , and has a lower rearwardly extending horizontal flange  610 . The flange  610  extends below the lower wall  593  and has a bore  611  which is vertically aligned with the bore  589  so that the post is mounted on the bearing  584  for rotation about the central longitudinal axis of the lead screw  583 . The rear side of the post  609  has a vertical slot which is identical to the slot  432  of the post  522 . The reagent probe carrying arm  617  has a tab  627  which extends horizontally into the vertical slot of the post  609 . This enables the post  609  to rotate with the gear segment  612  about the longitudinal axis of the lead screw  583  for changing the angular position of the third reagent probe  633  relative to the carriage  466 . A PC board  618  is fixed to the post  609  and has an interrupter sensor  624 . An electrical connector  622  extends from the PC board  618  and is connected to the Junction J 16  of the PC board  446 . When the probe carrying arm  617  reaches its upper position, the tab  627  interrupts a beam on the sensor  624  which initiates a signal to the CPU which indicates that the probe is properly positioned in its upper position. The back and forth motion of the carriage  466  is provided by the stepper motor  470  which has a drive shaft  474 . The shaft  474  is fixed to a lead screw  602  by a coupling  628 . The lead screw  602  is engaged with a roll nut  603  in a block  604 . The block  604  is mounted in a yoke  605  in the same manner as block  493  which is mounted in the yoke  494  as shown in  FIG. 67 . The yoke  605  has a shaft  606  which is mounted in the bearing  607  and extends through the bore  579  of the follower guide  608 . Rotation of the lead screw  602  causes the block  604  to move along the central longitudinal axis of the lead screw. When the stepper motor  596  is rotated in one direction, the carriage  466  moves forwardly relative to the plate  441 . When the stepper motor  596  is reversed, the carriage  466  is moved rearwardly relative to the plate  441 . A bracket  620  is fixed to the upper wall  592  of the carriage  466  and has a plurality of upwardly extending tabs  621  which interact with the interrupt sensors  453  and  454 . The sensor  454  is a home sensor. When the carriage  466  is in its award position so that the probe  633  is located above the reagent dispensing point  17 , the rearmost tab  621  interrupts a beam in the sensor  454  which initiates a signal to the CPU that the probe is in its ‘home’ position. The tabs  621  interrupt a beam in the sensor  453  when the probe  633  is improperly positioned in any one of its forward aspirating or wash positions as described for the reagent probe systems R 1  and R 2 . A PC board  618  is fixed to the post  609  and has an electrical connector  622  which is connected to the electrical junction J 16  of the PC board  446 . Referring to  FIG. 71 , a PC board  626  is fixed to the probe supporting arm  617  and is connected to the PC board  618  by an electrical connector  619 .  
      The upper end of the post  609  is fixed to a gear segment  612  which has a bore  613 . The gear segment  612  has gear teeth  614  which extend radially about the center of the bore  613 . The gear segment  612  is located above the top wall  592  so that the bore  613  is in axial alignment with the bore  613 . The teeth of the gear segment  612  are in driving engagement with the teeth  631  of a horizontal plate  630  as shown in  FIG. 60 . When the carriage  466  is in its rear position, the probe holding arm  617  faces to the right as viewed in  FIG. 60 . As the carriage  466  moves forwardly, the gear segment  612  rotates about the vertical axis of the lead screw  583 . This causes the probe supporting arm to rotate approximately 90 from the rightwardly facing position as shown in  FIGS. 60 and 62  to a forwardly facing position. This causes the probe  633  to move along a curved path which is indicated by the dotted dot and dash line  429  as shown in  FIG. 22 . The line  429  intersects the vertical axes of the dispensing point  46 , wash station  17 , and the openings  341  and  342  in the cover  327  of the reagent tray  27  as shown in  FIG. 22 .  
      Depending on the test protocol, the reagent aspirating and dispensing probe  633  will be moved forwardly to pick up or aspirate a labeled or tracer reagent at the opening  341  or a solid phase reagent at the opening  342 , see  FIG. 22 . Although the probe  633  is capable of picking up labeled and solid phase reagent, the probe  633  is normally used for picking up a single reagent. The probe  633  is utilized for picking up a reagent which compliments the single reagent which was picked up and dispensed into a cuvette by a preceding probe in accordance with a particular test protocol. At each position  341  and  342 , the probe  633  is lowered by the motor  596 . The lower position of the probe  633  is determined by a capacitance fluid sensing electronics as described for the sample probe  407 . After aspiration of a volume of reagent, the probe  633  is moved to its upper position, whereupon the motor  470  is actuated for a predetermined number of half steps to move the probe above the other reagent opening or rearwardly so that the probe  633  is above the reagent dispense point  17 . The probe is then lowered into a cuvette which is beneath the point  17 . The aspirated reagent is then dispensed into the sample solution in the cuvette. The probe  633  is then id to its upper position and moved to the wash station  17  for a wash cycle, whereupon it will be ready to begin another aspirating and dispensing cycle.  
      The lower position of each reagent probe is determined by a capacitance fluid sensing system as described for the reagent probe systems R 1  and R 2 .  
      In the preferred embodiment, the solid phase reagent and the labeled reagent are arranged in two separate concentric circles which maximizes the number of reagent pairs that can be used with the analyzer. This means that each of the reagent probes must have two reagent aspirating positions in order to pick up either of the reagents. It is possible to place the labeled reagent in the same type of container as the solid phase reagent and to place the container on the inner circle of holders with the solid phase reagents. If a test protocol calls for both reagents of a pair to be picked up by a probe, the probe would be raised after aspirating one of the reagents. This would allow the reagent tray to position the second reagent of the pair beneath the probe. The second reagent would then be picked up by the probe.  
      Fluid Aspirating and Dispensing Apparatus  
      Referring to  FIG. 73 , the means for aspirating and dispensing fluid through the sample reagent probes includes the syringe bank  32  which includes a housing  650  and a plurality of stepper motors  655 ,  656 ,  657 , and  658  which are mounted to the back of the housing  650 . A plurality of syringes  651 ,  652 ,  653 , and  654  are mounted to the front of the housing and are actuated by the stepper motors  655 ,  656 ,  657 , and  658 , respectively, the drive mechanism between each stepper motor and its respective syringe is a frictional rack and pinion drive which is shown and described in U.S. Pat. No. 4,539,854 to Bradshaw et al. and incorporated herein by reference. Each syringe can be controlled to aspirate or dispense a small amount of fluid by controlling the signals to the corresponding stepper motor from the CPU in accordance with the machine control program. The syringe  651  is operatively connected to the sample aspirating and dispensing probe  407  through a tube  659 . The syringe  652  is operatively connected to the reagent aspirating and dispensing probe  531  of the reagent probe system R 1  through a tube  660 . The syringe  653  is operatively connected to the reagent aspirating and dispensing probe  576  of the reagent probe system R 2  by means of a tube  661 . The syringe  654  is operatively connected to the reagent aspirating and dispensing probe  633  of the of the reagent probe system R 3  by a tube  662 . Each tube which connects a reagent probe to its corresponding syringe passes through a heated fluid bath  648 . Each reagent probe aspirates a predetermined volume of reagent and after the probe has been raised out of contact with the reagent solution the corresponding syringe is operated for a predetermined draw of air which also draws the aspirated reagent into the fluid bath  648 . The fluid bath  648  maintains the reagent at a predetermined operational temperature, preferably 37° C. A portion of the tube which is in the fluid bath is coiled so that the entire quantity of reagent solution is equilibrated to the operational temperature before the reagent is dispensed into the appropriate cuvette. The air which has been drawn in behind the reagent is dispensed until the reagent reaches the tip of the probe prior to dispensing of the reagent into the cuvette.  
      Referring to  FIG. 75 , wash stations  15 ,  16 ,  17 , and  18  are shown mounted in front of the cuvette dispense and incubation section  39 . Station  18  comprises a tubular housing  666  which is mounted to the machine framework by a clamp  672 . The housing  666  has a top opening  667 , a bottom outlet nipple  668  and a side port  669  which is located near the bottom opening  668 . A tube  670  is connected to the nipple  668  and a tube  671  is connected to the side port  669 . The wash station  15  comprises a tubular housing  672  which is mounted to the machine framework by a post  688 . The housing  672  has a top opening  673 , a bottom outlet nipple  674  and a side port  676  which is located near the bottom opening  674 . A tube  675  is connected to the nipple  674 . A tube  677  is connected to the side port  676 . The wash station  16  comprises a tubular housing  678  which is mounted to the machine framework by a clamp  665 . The housing  678  has a top opening  679 , a bottom opening  680 , and a side port  682  which is located near the bottom outlet nipple  680 . A tube  681  is connected to the nipple  680  and a tube  683  is connected to the side port  682 . The wash station  17  comprises a tubular housing  684  which is fixed to a post  691  which is fixed to the supporting base of the machine framework. The housing  684  has a top opening  685 , a bottom outlet nipple  686 , and a side port  687 . A tube  690  is connected to the bottom opening  686  and a tube  689  is concerned to the side port  687 .  
      Water supply to the wash stations from the reservoir  30  will be described below.  
      The wash stations function to wash the various probes of the present invention between aspiration and dispense cycles. Deionized water is utilized as the wash solution in the preferred embodiment. Wash solution is discarded in waste container  31  after the wash cycle, as will be described below.  
      Separation/Wash/Resuspend System  
      The reaction kinetics of the assays performed by the analyzer of the pre invention are maximized by the elevated temperature and the very efficient binding afforded by the large surface area of the paramagnetic solid-phase particles. Each assay ample undergoes the same total incubation time of seven and one half minutes. When a cuvette reaches the end of this total incubation time, it enters a section of the process track or incubation section where separation and washing is accomplished. Powerful permanent magnets of neodymium-boron are mounted on the process track at this point, and the paramagnetic particles are rapidly pulled to the back wall of the cuvette. Liquid is aspirated from the cuvette by a vacuum probe which consistently seeks the bottom of the cuvette, the liquid being held in a waste reservoir for later disposal. Washing of the cuvette and particles is accomplished by forceful (ing of deionized water, followed by rapid magnetic separation and aspiration. One or two washes may be performed, based upon the specific assay, yielding non-specific binding of less than 01%. After completion of the wash cycle, the particles are resuspended in an acid containing 0.5% hydrogen peroxide in a weak nitric acid, added from a fixed port above the cuvette.  
      Referring to  FIGS. 76-80 , the aspirate resuspend area  28  includes a block  694  which is mounted above the cuvettes and the aspirate resuspend area at the downstream end of the cuvette dispense and incubation section  39 . A pair of spaced plumbing fixtures  695  and  700  are mounted in the block  694 . The fixture  695  has a bore  696  which extends completely through the block  694  to the cuvette and two tubes  697  and  698 , which communicate with the bore  696  and a nozzle  699  which extends through the fixture  695  in a fixed angular position. The nozzle  699  is connected to a tube  692  which is operatively connected to the reservoir  30  of deionized water. The nozzle  699  is positioned to direct a stream of deionized water against the front wall of the cuvette as shown in  FIG. 79 . The fixture  700  has a bore  701  which extends completely through the block  694  to the cuvettes and two tubes  702  and  703  which communicate with the bore  701 . An acid dispense fixture  704  is mounted to the block  694  downstream of the fixture  700 . As shown in  FIG. 80 , a nozzle  706  is mounted in an angular fixed position in the fixture  704  so that the end of the nozzle  706  is located just above the top opening of the cuvette which is positioned just beneath the fixture  704 . As shown in  FIG. 79 , the nozzle  706  is connected to a tube  707  which is operatively connected to the acid reservoir  33 , see  FIG. 21B . The probe  699  is positioned at an angle to the vertical so that the stream of acid which is dispensed from the end of the nozzle is directed against the back wall of the cuvette  40  for a purpose to be described.  
      Referring to  FIG. 77 , an aspirating unit which is generally indicated by the reference numeral  708  is mounted on the fixed position behind the block  694 . The aspirating unit  708  comprises a fixed horizontal supporting plate  709 . As motor  710  and a bracket  727  which are mounted on the plate  709 . The bracket  727  has an upper horizontal flange  714 . A lead screw  717  is rotatably moue in bearings  715  and  716  in the flange  714  and the base  709 , respectively. The lead screw  717  extends through a roll nut  718  which is fixed within a bore  706  of a follower  719 . The lower end of the lead screw  717  extends below the base  709  and is fixed to a pulley  712 . The drive shaft of the stepper motor  710  extends below the base  709  and is fixed to a pulley  711 . The pulley  712  is driven from the pulley  711  through a timing belt  713  which engages corresponding teeth on the pulleys  711  and  712 , (teeth not shown). A forwardly extending arm  720  is fixed to the follower  719  and has a pair of laterally extending arms  721  and  722 . Referring also to  FIG. 78 , a probe  725  extends freely through the arm  721  and a housing  723  which is fixed to the arm  721  and  725  has a protuberance  730  within the housing  723  which limits the upward movement of the probe relative to the housing  73 . The probe  725  is biased in the downward position by a spring  731 . A probe  726  extends freely through the arm  722  and a housing  724  which is identical to the housing  723  to limit the upward movement of the probe  726  relative to the arms  722  and the housing  724  and to bias the probe  726  downwardly. The probes  725  and  726  are vertically aligned with the bore  696  and  701  respectively. Actuation of the motor  710  causes the lead screw  717  to rotate about its vertical longitudinal axis which causes the follower  719  to move upwardly or downwardly depending on the direction of rotation of the drive shaft of the stepper motor  710 . The vertical motion of the follower  719  causes the probe  725  and  726  to move from an upper position in which the probes are above the top openings of the cuvette and a lower position in which the bottom tips of the probe extend down to the bottom of the cuvettes. The arm  720  is moved downwardly a distance which is slightly more than that which is required to enable the probes  725  and  726  to reach the bottom of the cuvettes. When the probes  725  and  726  strike the bottoms of their respective cuvettes, the additional slight movement of the arm  720  causes the probes to move upwardly relative to the arms  721  and  722 , respectively, against the bias of the springs  731 . This guarantees that the bottom ends of the probes  725  and  726  will always be at the bottom of each cuvette for complete aspiration of the fluid in the cuvette. The follower  719  has a laterally extending horizontal tab  744  which rides in a vertical slot  745  in the post  727 . This prevents rotation of the follower about the longitudinal axis of the lead screw  717 . Au interrupter sensor  746  is located at the top of the slot  745 . When the follower  719  reaches its upper position, the tab  744  interrupts a light beam between the two elements of the sensor  746  which initiates an electrical signal to the CPU to indicate that the probes  725  and  726  have reached their upper predetermined positions. At a designed time in the machine operation sequence, the motor  710  is energized for a predetermined number of half steps to lower the probes  725  and  726  to their lower positions.  
      Referring to  FIG. 74 , there is shown a cross-section of a heated tube configuration which is generally indicated by the reference numeral  733 . This configuration forms a portion of the tubing which connects each reagent probe to its corresponding syringe that extends between the probe and the heated fluid bath  648 . The heated tube configuration  733  comprises a teflon tube  734  through which the reagent flows, an insulated heater wire  735  which is spirally wound around the tube  734  and a thermistor  736 . The tube  734 , the heater wire  735  and the thermistor  736  are all enclosed within a shrink-wrap tube  737 . The heater wire  735  is a nickel-chromium wire which has a return lead  738  outside of the shrink-wrap tube  737 . The shrink-wrap tube  737  and the ret lead  738  are, in turn, enclosed in a polyvinyl chloride tubing  739 . The function of the heated tube  733  is to maintain the temperature of the reagent at 37° C. after it is transferred from the heated fluid bath  648  to the reagent aspirating and dispensing probe. The CPU controls energization of the heater coil  735  in accordance with electrical signals which are received from the thermistor  736  which functions to maintain the temperature of the tube  734  at 37° C., plus or minus one degree. Although the heated fluid bath  648  is effective in heating the reagent to the desired predetermined temperature, i.e., 37° C., experience has shown that the temperature of the reagent drops below the predetermined set temperature as it passes back from the heated fluid bath  648  to the reagent probe. The reason that this occurs is that the section of tubing between the reagent probe and the heated fluid bath is chilled by the reagent as it is aspirated from its container, particularly if the reagent is colder than room temperature, which sometimes occurs at the beginning of the initial set-up of a run of tests. The pre-chilling of this section of the tube causes the tube to act as a heat-sink and absorb heat from the reagent when it passes back from the heated fluid bath  648 . The heated tube configuration  733  maintains the tube at the set temperature and prevents this chilling effect. This insures that the temperature of the reagent remains the same as it was in the heated fluid bath  648 . The entire structure of the heated tube configuration  733  is flexible to compensate for the vertical movement of the reagent probe. The wall thickness of the teflon tube  734  is very important for the satisfactory operation of the heated tube configuration  733 . Ile wall thickness of the teflon tube  734  is between and including 0.006 and 0.010 inches. If the wall thickness is below the lower value, the breakage frequency of the tube is considered unacceptable. If the thickness is greater than 0.010 inches, the efficiency of heat transfer from the heater wire  735  to the reagent fluid as it passes through the tube  734 , is significantly reduced, thereby making it difficult to maintain the reagent at the set temperature.  
      The tube  734  is made of a fluoroplastic material, specifically PTFE (polytetrafluorethylene). PTFE has exceptional residence to chemicals and heat and is used for coating and to impregnate porous structures. The relative stiffness or rigidity of PTFE renders it generally unsuitable for fluid tubes. However, for the optimum thickness range of the tube  734 , PTFE is sufficiently flexible and yet provides superior heat transfer and chemical resistant qualities to the tube.  
      Referring also to  FIGS. 34 and 35 , the aspirate/resuspend area  28  also includes three magnets  740 ,  741  and  742  which are located beneath the cuvette conveyor along the back wall of a channel  743  through which the cuvettes pass as they are carried by the drive belts  167  and  168 . Each of the magnets  740  and  741  is elongated and extend horizontally, see also  FIG. 21B . The magnet  741  extends from the end of the 740 on the downstream side and is located at a slightly lower level than the magnet  740  as shown in  FIGS. 34 and 35 . Each magnet  740  and  741  creates a magnetic field having a vertical north-south polarity. The magnet  742  is located on the front wall of the channel  743  and extends downstream from the end of the magnet  741 . The magnet  742  creates a magnetic field having a north-south polarity which is below the magnetic field of the magnet  741 . As a cuvette enters the aspirate/resuspend area  28 , the paramagnetic particles from the solid phase reagent are attracted toward the magnet  740  and migrate to the back wall of the cuvette. As the cuvette continues to travel along the magnet  740 , the paramagnetic particles begin to concentrate more towards the center of the magnet  740 . As the cuvette passes beneath the bore  696 , the liquid in the cuvette is aspirated by the probe  725  and delivered to the waste fluid reservoir  311  while deionized water from the reservoir  30  is introduced into the cuvette through the nozzle  699 . The aspiration of the liquid from the cuvette effectively removes all of the unbound labeled reagent and unbound test sample from the sample reagent mixture. This process isolates the detectable product that is formed by the test reaction, i.e. the complex including the paramagnetic particles. The deionized water from the nozzle  699  is directed against the front wall of the cuvette to minimize any disturbance of the paramagnetic particles against the back wall of the cuvette. As the cuvette advances from the position beneath the bore  696  to the position beneath the bore  701 , the paramagnetic particles continue to concentrate into a progressively tightening mass or “pellet” against the back wall of the cuvette. The magnet  741  is located in this area and since it is lower than the magnet  740 , the paramagnetic particles tend to congregate at a lower point in the cuvette. This locates the concentrated mass of particles in an area which is below the level of the acid solution which is added in a subsequent step. When the cuvette stops at the point beneath the bore  701 , the probe  726  descends to the bottom of the cuvette and aspirates the wash solution of deionized water which is delivered to the fluid waste reservoir  31 . When the cuvette is next positioned beneath the bore  705  of the fixture  704 , the nozzle  706  dispenses a volume of an acid solution such as hydrogen peroxide from the acid reservoir  33 . Because of the angle of the probe  706 , the acid is delivered against the back wall of the cuvette just above the concentration of paramagnetic particles. This effectively washes the particles away from the back wall and resuspends them in the acid solution. As the cuvette moves away from the bore  705 , it passes along the front magnetic  742  which helps to pull some of the paramagnetic particles away from the rear part of the cuvette toward the front. This helps to distribute the particles evenly within the acid solution. Since the probes  725  and  726  are linked into the same actuating mechanism, they are lowered into the bore  696  and  701 , respectively, simultaneously. While the probe  725  aspirates a sample reagent solution from a cuvette beneath the bore  696 , the probe  726  aspirates a wash solution from a cuvette which is located beneath the bore  701 . At the same time, the probe  706  dispenses a volume of acid solution to a cuvette which is located downstream of the cuvette which is located beneath the bore  701 . The cuvette which is beneath the acid probe  706  is then advanced toward the elevator mechanism to the luminometer which is described in the next section.  
      Luminometer System  
      The luminometer includes a rotary housing with six wells A detector includes a photomultiplier tube (PMT) which is mounted in front of the housing. A cuvette enters one of the wells in the housing from the entrance opening and is moved in increments to the exit opening. At the third position from the entrance opening, the cuvette is aligned with the PMT. This design effectively eliminates ambient light from the measuring chamber prior to initiating the chemiluminescent reaction. With the cuvette positioned in front of the PMT, a base solution, containing dilute sodium hydroxide, is injected into the cuvette. For one particular assay, for example, this causes the oxidation of an acridinium ester label and results in the emission of light photons of 430 nm wavelength. This emission is a sharp spike within one second and has a duration of 34 seconds. The intensity of the emission is measured over as second interval by the PMT, which operates in the photon-counting mode. “Dark counts” are measured before the light emission, and are subtracted automatically.  
      The luminometer system is shown in  FIGS. 76 and 81 - 86  and comprises a luminometer assembly which is generally indicated by the reference numeral  760  which is mounted on top of an elevator assembly which is generally indicated by the reference numeral  761 . The luminometer assembly  760  comprises a housing  762  which has a vertical bore  763  which extends from a chamber  764  at the end of the event conveyor to the luminometer assembly. Referring particularly to  FIG. 83 , the elevator assembly  761  also includes a top plate  765  and a lower plate  766 . A lead screw  767  is rotatably mounted in bearings  768  in the lower and upper plates  766  and  765 , respectively A follower  769  is mounted on the lead screw  767  for movement along the central longitudinal axis of the lead screw upwardly or downwardly depending upon the direction of rotation of the lead screw. Plunger  771  is located below the chamber  764  and is fixedly connected to the follower  769  by a horizontal arm  770 . A vertical anti-pivot rod  772  is fixed to the bottom plate  766  and the upper plate  765  and extends freely through an aperture  780  in the arm  770 . The lower end of the lead screw  767  extends below the bottom plate  766  and is fixed to a sprocket  776 . A stepper motor  773  is mounted to the lower end of the elevator assembly  761  and has a downwardly extending drive shaft  774  which is fixed to a sprocket  775 . The sprocket  776  is driven from the sprocket  775  through a drive chain  777 , see  FIG. 81 . The motor  773  is reversible. When the lead screw  767  is rotated in one direction the follower  769  is moved from the lower position shown in full lines to the upper position shown in dotted lines in  FIG. 83 . This causes the plunger  771  to move from the lower full line position to the upper dotted line position as shown in  FIG. 83 . When the lead screw  767  is rotated in the opposite direction, the follower  769  and the plunger  771  move downwardly from the dotted line position to the full line position. The cuvettes  40  are conveyed along the event conveyor at twenty second intervals. Every twenty seconds a cuvette  40  is deposited into the camber  764  from the event conveyor while the plunger  771  is in the lower full line position. The motor  773  is actuated for rotating the lead screw  767  so that the plunger  771  moves to the upper position carrying the cuvette  40  which is in the chamber  764  to the luminometer assembly  760 . The follower  769  has a horizontally ending tab which interacts with upper and lower interrupter sensors  758  and  759 . When the follower is at the lower position shown in full lines in  FIG. 83 , the tab  778  interrupts a light beam between the two elements of the sensor  759  which initiates a signal to the CPU that the plunger  771  is properly positioned at the lower position. At a predetermined time in the overall machine sequence, a cuvette  40  is delivered by the event conveyor to a point above the plunger  771  as shown in full lines in  FIG. 83  and the motor  773  is energized for a predetermined number of half steps to raise the plunger  771  to the dotted line position which delivers the cuvette  40  to a song position within the luminometer assembly  760 . When the follower  769  reaches its upper position, the tab  778  interrupts a light beam between the two elements of the sensor  758  which initiates a signal to the CPU that the plunger  771  is property positioned at its upper position. The motor  773  is then reversed for a predetermined number of half steps to return the plunger  771  to its lower position.  
      Referring particularly to  FIGS. 83 and 84 , the luminometer assembly  760  comprises a bottom support plate  789  which is supported on the top plate  765  of the elevator assembly. A luminometer housing  790  includes a cylindrical vertical wall  788 , a bottom wall  792  and a top wall  793 . The housing  790  has a large circular chamber  791  which contains a carrousel  800 . The luminometer housing  790  is supported on the bottom support plate  789 . The bottom plate  792  has a central uplifted portion  794  which has an aperture  795  which contains a bearing  796 . The top wall  793  has an aperture  799  which contains a bearing  798 . A vertical shaft  797  is rotatably mounted in the bearings  796  and  798  and is fixed to a hub  787  of the carrousel  800 . The upper end of the shaft  797  extends above the top wall  793  and is fixed to a gear  801 . A stepper motor  804  is mounted on the top  793  and has a downwardly descending drive shaft  803  which is fixed to a gear  802 . The gear  802  is in driving engagement with the gear  801  for rotating the shaft  797  which causes the carousel  800  to rotate about the central longitudinal axis of the shaft  697 . An encoder wheel  805  is fixed to the top end of the shaft  797  above the gear  801 . A luminometer sensor board assembly  806  is fixed to the top wall  793 . The encoder wheel  805  has a plurality of spaced upwardly extending tabs  784  which interacts with an interrupt sensor  783  which extends downwardly from the PC board  806 . In the embodiment shown in  FIG. 84 , there are six tabs  784  which correspond to six external cavities or wells  814  in the outer wall of the carousel  800 . The carousel  800  is indexed to a new position every twenty seconds by the stepper motor  804  through the gears  801  and  802 . The stepper motor  804  is given an input signal from the CPU which causes the carousel  800  and the encoder wheel to rotate about the axis of the shaft  797 . The carousel continues to rotate until the edge of one of the tabs  784  interrupts a light beam between the elements of the interrupt sensor  783 . When this occurs, the motor  804  is de-energized for a predetermined time period, whereupon the motor will be energized to move the carousel  800  to the next position. A side opening  807  is located in the cylindrical vertical wall  788  and opens into a tunnel  810  of a connector arm  809  which connects the luminometer housing  790  to a photo multiplier tube  808 . The bottom wall  792  has an entrance opening  811  and an exit opening  812 . The entrance opening  811  is vertically aligned with the vertical bore  763  of the elevator assembly  761 . The exit opening  812  is vertically aligned with a waste receptacle  35  for the cuvettes, see  FIG. 21B . The six cavities  814  in the outer surface of the carousel  800  are sequentially vertically aligned with the openings  811  and  812  as the carrousel  800  is rotated about the axis of the shaft  797 . Each cavity  814  has an outer opening which is closed by the cylindrical wall  788  of the hub  780  and a bottom opening which is closed by the bottom wall  792 . The upper wall of each cavity has a small access opening  852  which leads to the cavity. The access openings  852  are covered by the top wall  793  except when they are vertically aligned with a pair of holes  836  and  851  in the top wall  793  for a purpose to be described. Referring to  FIG. 86 , as the carousel rotates about the central vertical axis of the shaft  797 , relative to the housing  790 , each cavity  814  is maintained light tight from light from the outside except where the cavity is aligned with one of the openings  812  and  811 . Each cuvette is delivered by the elevator  761  into a cavity  814  which is aligned with the opening  812 . The carousel is rotated  60  every twenty seconds. The cuvette is carried in a circle about the axis of the shaft  797  until it reaches the opening  811  and falls into the waste receptacle  35 . Every twenty seconds, a new cuvette is delivered into a cavity  814  and a processed cuvette is dropped through the opening  811 . The central uplifted portion  794  forms a downwardly facing cavity  785 . The uplifted portion  794  has an aperture  786  which faces the side opening  807 . A reference LED (light emitting diode)  830  is mounted on a PC board  829 . The PC board  829  is fixed to the bottom wall  792  so that the reference LED  830  extends into the cavity  785 . The LED  830  is periodically energized to emit a beam of light and is positioned so that the beam of light passes through the aperture  786  to the photomultiplier tube  808 . The bottom opening of the cavity  785  is closed by a cover  831  so that light cannot enter the cavity from the outside. The amount of light from the LED is substantially greater than the light from a test flash and is beyond the normal operating range of the photomultiplier tube  808 . A light filtering means, not shown, is positioned between the LED and the photomultiplier tube  808  to alter or reduce the amount of light which reaches the PMT from the LED.  
      Referring particularly to  FIGS. 84 and 85 , a wash/waste tower assembly  816  is fixed to the tops of a plurality of vertical posts  815  which are in turn fixed to the bottom support plate  889 . The assembly  816  comprises a support plate  817  which is fixed to the posts  815 , a stepper motor  818  and a post  819  which is fixed to the top of the plate  817 . The post  819  has a laterally extending upper arm  820 . A vertical lead screw  823  is rotatably mounted in bearings  821  in the arm  820  and the plate  817 . A follower  824  is mounted on the lead screw  823  for movement along the central longitudinal axis of the lead screw. The lead screw is drivingly engaged with a roll nut  813  which is mounted within the follower  824 . The stepper motor  818  has a downwardly extending drive shaft which is fixed to a pulley  826 . The lower end of the lead screw  823  extends below the plate  817  and is fixed to a pulley  825 . The pulley  825  is driven from the pulley  826  through a timing belt  827 . The inner surface of the timer belt  827  has teeth which engage corresponding teeth on the pulleys  825  and  826  (teeth not shown). Rotation of the stepper motor  818  in one direction causes the follower  824  to move upwardly along the lead screw  823  while rotation of the stepper motor in the opposite direction causes the follower  824  to move downwardly along the lead screw  823 . A probe retainer arm  828  is fixed to the follower  824  and extends forwardly and horizontally therefrom. The forward end of the arm  828  has a bore  833  which holds a probe assembly  832 . The probe assembly  832  includes a housing  835  which is fixed to the arm  828  with the bore  833  and an aspirating probe  834 . The probe  834  is mounted in the housing  835  for limited vertical movement and is biased in the downward position in the same manner as the probes  725  and  726  as illustrated in  FIG. 78 . The upper end of the probe  834  is fixed to a tube  836  which is operatively connected to the waste fluid reservoir  31 . The follower  824  has a laterally extending arm  782  which rides in a vertical groove  781  in the post  819  as the follower  824  moves vertically relative to the lead screw  823 . The tab  782  prevents the follower  824  from rotating about the central longitudinal axis of the lead screw. A plumbing fixture  837  is mounted to the top wall  793  above the hole  836 . The fixture  837  has a nozzle  838  which extends into the hole  836  and is connected to a tube  839  which is operatively connected to the base solution reservoir  34 . A plumbing fixture  840  is fixed to the top wall  793  just above the hole  851  and has a bore  841  which extends down to the hole  851 . The probe  834  is vertically aligned with the bore  841  so that when the probe is moved to its lower position, it enters the bore  841  and extends through the hole  851  and through the access opening  852  of one of the cavities  814  which is vertically aligned with the hole  851 . The fixture  840  also has a pair of tubes  844  and  845  which are operatively connected to the bore  841 . The tube  844  is operatively connected to the deionized water reservoir  30  and the tube  845  is operatively connected to the waste fluid reservoir  31 . The upper end of the probe  834  is located in a housing  835  which is identical to the housing  723  which is shown in  FIG. 78 . The probe  834  is programmed to be lowered to the bottom of a cuvette which is located beneath the bore  841  and slightly beyond. When the probe  834  reaches the bottom wall of the cuvette, it is forced upwardly relative to the housing  835  against the bias of the spring within the housing. This insures that the probe will always reach the bottom of the cuvette for complete aspiration of fluid within the cuvette.  
       FIG. 86  is a diagrammatic representation of the bottom wall  792  and the photomultiplier tube  808 . The cuvette  40  is delivered by the elevator  761  through the opening  812  in the bottom wall  792  to one of the cavities  814  which is aligned with the opening  812  and which is identified in  FIG. 86  as position  846 . The cuvette is moved every twenty seconds in 60′ increments in a circle about the axis of the shaft  797 . The cuvette is moved from position  846  to position  847  and then to position  848  in front of the opening  807 . In this position, the nozzle  838  delivers a predetermined volume of a basic solution 0.25 N. NaOH to the acid solution, eg. 0.1 N. HNO 3  with 0.5% H 2 O 2 , which is already in the cuvette. This causes the generation of a chemiluminescent signal. The signal is detected over a five second interval by the PMT which operates in a photon-counting mode. A chemiluminescent signal or flash produces a flash profile which is compared to a stored standard curve to determine the analyte concentration in the sample. A master dose-response curve is generated for each lot of reagents. This information is put into the analyzer by keyboard or bar code. The information is calibrated by measuring two standards, whose values are used to adjust the stored master-curve. The recommended date of reduction methods are selected from a spline fit, or four or five parameter logistic curve fits, and are preprogrammed for each assay. The cuvette is next moved to position  849  which is beneath the bore  841 . The probe  834  is lowered to the bore  841 , the opening  851  and into the cuvette, which is beneath this position, through the access opening  852 . All of the fluid contents in the cuvette are aspirated by the probe  834  whereupon the probe  834  is raised to its upper position the cuvette is moved to position  850  and then moved toward position  851 . When the cuvette reaches the opening  811 , it falls through the opening and into the cuvette waste receptacle  35 .  
      Corrected counts are used to calculate analyte concentration in the sample using a stored master curve. At the time of manufacture of each lot of reagents, a master dose-response curve is generated using multiple assay runs on multiple instruments. This lot-specific dose-response curve data is supplied with the reagents and input into the CPU memory using an integral bar code-reading wand, or through the keyboard. The stored master curve is recalibrated by assaying two calibrators, whose values are predetermined and provided to the software. Multi-analyte calibrators are provided for this purpose, and weekly recalibrations are recommended for most assays.  
      Reference LED Module for Chemiluminescence Assay  
       FIG. 87 , schematically illustrates the analyzer&#39;s LED module. The reference LED utilizes optical feedback to provide a constant light output which can be presented to the PMT.  
      The light output level may be set by adjusting an electronically adjustable potentiometer (EEPOT). This EEPOT is used to adjust the light output for manufacturing and component variances. The EEPOT may be set with a specific sequence of control signals, and is not designed for field adjustment.  
      Advantageous features of the reference LED board are: 
          Compact packaging fits under the luminometer     Optical feedback yields constant 470 nm. calibration for the photomultiplier tube signal     Compensated voltage reference for added stability     Electronically adjustable light output allows mV factory calibration     May be powered on/off from machine controller board        

      The power requirements of the preferred embodiments are: 
          for the Logic +5.00 V+/−5% (75 mA max.);     for the Analog +12.0 V+1-0.10% (300 mA max.).        

      The unit is preferably configured as a 2.1 diameter two-sided board, with a ground plane on bottom side. The following connectors should be provided: 
          a 5 pin pigtail connector to mate with the machine controller and power source,     connection to luminometer home sensor board, and     a 4 pin header to facilitate programming of the EEPOT.        

      The Power Connector pigtail, J 1 , shown as in  FIG. 87  has the following pin assignments:  
                                   Pin   Name                  1   LEDCTL (from machine controller, O = off, 1 = on)       2   SB3 (from machine controller, not used)       3    +5 V       4   +12 V       5   GND                  
 
      The EEPOT header Connector. J 2  shown as in FIG. A, has the following pin assignments:  
                                   Pin   Name                                            1   /INC   EEPOT wiper increment line       2   UP/DOWN♯   EEPOT direction select line       3   /CS   EEPOT chip select       4   GND                  
 
      The preferred embodiment of the reference LED circuitry is further detailed in  FIG. 87 . Because stray light from the LED could affect the photomultiplier tube, reading during sample analysis, the reference LED can be turned off via a control line on the luminometer machine controller board. Q 1  and R 1  form the power control logic. (A in  FIG. 87 ) Bringing LED CTL low (0 volts) turns off all op-amps and the LED; returning LED CTL high turns the LED power on.  
      The closed loop that drives the LED uses a voltage as a command input (see  FIG. 88 ). VR 1 , U 1 , U 3 A and R 2 , R 3 , and R 7  comprise an adjustable voltage reference. (B in  FIG. 87 ) VR 1  provides a temperature-compensated zener reference of 6.9V+/−5%. The heater to VR 1  is on at all times to allow faster responses after instrument warm-up. R 3 , the EEPOT wiper resistance ( 10 K), and R 7  form a voltage divider. With the nominal values of these components, the EEPOT wiper has a voltage range of 0.5-2.5V. Op-amp U 3 A buffers the reference voltage to provide a low-impedance source for the control loop.  
      An optical feedback loop is used to control the LED&#39;s light output. CR 1  (blue LED, 470 nm wavelength) is a diffused bezel LED mounted in a housing such that its light is incident upon the surface of CR 2 , a blue-sensitive photodiode CR 2  faces CR 1  and is preferably positioned at 45′ off CR 1 &#39;s optical axis. The positioning of CR 1  and CR 2  is controlled by the LED mounting block. (Alternately a beam splitter may be provided to bring a portion of the LED output to CR 2 ). CR 2  is used in current mode (v short circuit across its terminals) to eliminate dark noise in the reference.  
      Q 2  and R 6  are used to drive current through the LED; this current is limited to 50 mA by the values of the circuit components and the upper voltage rail of U 2 . U 2  alone cannot drive the LED at 50 mA.  
      FET-input op-amp U 2  can tolerate inputs down to ground and can swing its output from ground to about 3 volts off the positive rail. This ground output capability is important for operating the LED at low light levels. The FET-input capability was chosen to minimize effects of input current (Iin&lt;30 pA) on the summing junction.  
      U 2  works to maintain 0 volts between its input pins. This will force the voltage across the series combination of R 5  and R 8  to be virtually equal to the reference voltage applied by U 3 A. The reference voltage across R 5 +R 8  yields a reference current of 2.5-12.5 nA. In steady state, CR 2 &#39;s current will equal the reference current; if CR 2 &#39;s current is constant, the light from CR 1  causing that current is also constant.  
      In the event that the light output from CR 1  fluctuates, the circuit&#39;s negative feedback will correct the error. For example, if CR 1  outputs too much light, CR 2 &#39;s current will increase. This increase in current will flow through R 4  and will drive Q 2 &#39;s base voltage down, causing the CR 1 &#39;s current to decrease. Similarly, too little light from CR 1  causes U 2  to output a higher voltage, yielding more current through CR 1  and more light output.  
      The response time of the circuit is limited by the combination of C 5  and R 4 . C 5  functions as an integrator to prevent any instantaneous fluctuation of the output, in effect averaging the error signal. R 4  and C 5  filter off any high frequency noise that would be superimposed on the light output of CR 1 .  
      Because the current flowing through the reference resistors R 5  and R 8  is on the order of 10 nA, board leakage currents caused by flux and oils can have a detrimental effect. To prevent leakage currents from disturbing the circuit the summing junction of the op-amp should be given special consideration. A teflon solder post C is provided to tie R 5 , CR 2 &#39;s anode, Us&#39;s summing input (pin  2 ), and C 5  together. Another teflon post D is provided to join R 5  and R 8 . Also, C 5  should be a high insulation resistance (&gt;30000 Megohm) capacitor to minimize shunt leakage through the feedback path around U 2 . A third, non-insulated, solder post is used to provide a connection point for CR 2 &#39;s cathode. Finally, the entire assembly is cleaned very thoroughly and then hermetically sealed to prevent deposits from forming.  
      In experimental testing, the circuit has shown that a short interval is necessary to allow the circuit voltages and currents to stabilize. A one-minute interval should be allowed between energization and observation to ensure that the light output will be stable.  
      Test Requirements:  
      In addition to the short circuit and open circuit tests performed by the in circuit tester, the following additional tests must be performed:  
      A. Power Logic  
      With +12 V and +5V applied to J 1  pins  4  and  3  respectively, drive J 1  pin  1  to ground. Verify that no current flows through R 6  and that the voltage at U 3  pin  1  is at ground potential. Now apply +12V to J 1  pin  1 . Verify that the voltage at pin U 3  pin  1  is between 0.4 and 2.8 V.  
      B. EEPOT Logic  
      If the EEPOT&#39;S non-volatile memory has a limited number of write cycles, varying this pot should only be done once during testing.  
      Bring the CS\pin to TTL (OV).  
      Next apply pulses to the EEPOT&#39;S INC pin and verify that the wiper moves in the direction of the U/D\ pin. Vary the U/D level and verify EEPOT operation. Also, verify that the current flowing through R 6  changes with the value of the EEPOT setting. Timing information for the EEPOT&#39;S control lines in the preferred embodiment is shown in  FIG. 89 .  
      C. Control Loop  
      Because the summing junction carries such small currents, measurement at this point is to be avoided. During the calibration of the LED and PMT module, the optical operation of the module will be verified  
      Hydraulic and Pneumatic Controls  
      The hydraulic and pneumatic controls for the various subunits of the analyzer are shown in  FIGS. 90-93 . All of the valves described herein are electrically actuated via the CPU. Referring first to  FIGS. 90, 91 ,  93 A and  93 B, a pair of three way diverter valves V 2  and V 5  are connected to a main water line  886  by a pair of flexible tubes  882  and  888 , respectively. The main water line  886  is connected to the de-ionized water reservoir  30 . A peristaltic pump  880  is operatively engaged with the tube  882  for drawing water from the reservoir  30  to the valve V 2 . A peristaltic pump  881  is operatively engaged with the tube  888  for pumping water from the reservoir  30  to the diverter valve V 5 . The valve V 2  is connected to a three way diverter valve V 1  by a tube  891  and to a three way diverter valve V 3  by a tube  892 . The diverter valve V 5  is connected to a three way diverter valve V 4  by a tube  893  to a three way diverter valve V 6  by a tube  894 . The valve V 2  diverts water from the tube  882  to the valve V 1 , or the valve V 3 . The valve V 2  is normally closed to the valve V 1  and normally open to the valve V 3 . The valve V 5  diverts water from the tube  888  to the valve V 4  or to the valve V 6 . The valve V 5  is normally closed to the valve V 6  and normally open to the valve V 4 . The divert valve V 1  diverts water to the syringe  651  through a tube  890 , or through the tube  671  to the housing  666  of the wash station  18 , see  FIG. 75 . The valve V 3  diverts water to the syringe  654  through a tube  925 , or to the housing  684  of the wash station  17  through the tube  689 . The valve V 5  diverts water from the tube  888  to the valve V 4 , or to the valve V 6 . The valve V 4  diverts water to the syringe  652  through a tube  895  or to the housing  672  of the wash station  15  through the tube  677 . The valve V 6  diverts water to the syringe  653  through a tube  926 , or to the housing  678  of the wash station  16  through the tube  683 . The valve V 1  is normally closed to the tube  890  and normally open to the tube  671 . The valve V 3  is normally closed to the tube  925  and normally open to the tube  689 . The valve V 4  is normally closed to the tube  895  and normally open to the line  677 . The valve V 6  is normally closed to the tube  926  and normally open to the tube  683 . A check valve  84  and a filter  883  is located in the tube  882 . A check valve  902  and a filter  889  is located in the tube  888 .  
      The waste fluid reservoir  31  is maintained at a sub-atmospheric pressure by a vacuum pump  896  which is connected to the waste fluid reservoir by an air line  897 . A main air line  898  extends from the reservoir  31  and is connected to a manifold  899  by a tube  900 . A plurality of valves V 7 , V 8 , V 9 , V 10  and V 11  are connected to the manifold  898  by tubes  910 ,  911 ,  912 ,  913  and  908 , respectively. A vacuum gauge  905  is also connected to the manifold  898  by a tube  907 . The valve V 11  is a bleeder valve which is opened and closed by a switch  906  which is, in turn, controlled by the gauge  905 . When the pressure in the manifold  899  exceeds a predetermined set pressure, as detected by the gauge  905 , the switch  906  is closed to open the bleeder valve  411  to release air and lower the pressure in the manifold  899  to the set pressure. When the set pressure is reached, the gauge  905  opens the switch  906  to close the valve V 11 . The valves V 7 , V 8 , V 9  and V 10  are on/off valves which are operatively connected to the wash stations  18 ,  15 ,  16 , and  17 , respectively. The valve V 7  is connected to the bottom of the housing  666  of the wash station  18  by a tube  670 . The valve V 8  is connected to the bottom of the housing  684  of the wash station  17  by a tube  690 . The valve V 9  is connected to the bottom of the housing  672  of the wash station  15  by the tube  675 . The valve V 10  is connected to the bottom of the housing  678  of the wash station  16  by the tube  681 .  
      A wash-dispense pump  903  is connected to the main water line  886  and to the nozzle  699  by a tube  692 . The pump  903  is a displacement pump which is actuated by a motor  904 . The pump  903  extends at an angle to the drive shaft of the motor  904  and is connected to the drive shaft by a universal coupling. The motor  904  is energized to rotate its drive shaft one complete revolution which produces a displacement cycle for the valve  903 . The amount of displacement is determined by the angle of the valve relative to the drive shaft of the motor. When the motor  904  is actuated for a single displacement cycle, water is pumped from the reservoir  30  to the nozzle  699  of the fixture  695  for a wash cycle.  
      The main water line  886  is connected to a pair of on/off valves V 16  and V 18 . The valve V 16  is connected to a tube  909  which splits into the tubes  702  and  697 , which are connected to the fixtures  700  and  695 , respectively. The valve V 18  is connected to the tube  844 , which extends from the fixture  840  at the luminometer assembly. The main vacuum line  898  is connected to a manifold  901  and on/off valves V 12 , V 13 , V 14 , V 15  and V 17  are connected to the manifold  901  by tubes  914 ,  915 ,  916 ,  917  and  918 , respectively. The valve V 12  is connected to the tube  729  which leads to the probe  725 . The valve V 13  is connected to the tube  728  which leads to the probe  726 . The valve V 14  is connected to the tube  836  which leads to the aspirating probe  834 . The valve V 15  is connected to a tube  927  which splits into the previously described tubes  703  and  698  to the fixtures  700  and  695 , respectively. The valve  17  is connected to the tube  845  which extends to the fixture  840 . A low pressure switch  924  is connected to the manifold  901  by a tube  919 . When the pressure in the manifolds  901  and  899  falls below a predetermined minimum value, the switch  924  sends a signal to the CPU to stop the machine.  
      A pump  920  is connected to the acid reservoir  33  by a tube  921  and to the tube  707  which leads to the acid dispensing probe  706 . A pump  922  is connected to the base solution reservoir  34  by a tube  923  and to the tube  839  which extends to the base dispensing probe  838 . Energization of the pump  920  dispenses a predetermined volume of acid from the reservoir  33  through the nozzle  706 . Energization of the pump  922  dispenses a predetermined volume of base solution through the nozzle  838 . Referring particularly to  FIGS. 93A and 93B , a single cuvette  40  will be followed as it travels along the event conveyor and through the luminometer. A sample solution is obtained by positioning the sample aspirating and dispensing probe  407  above one of the openings  255  and  256  of the sample transport system  26 . The probe  407  is lowered into the sample container and the syringe  651  is actuated with the valve V 1  in the closed position with respect to the tube  890 . This enables a volume of sample solution to be aspirated by the probe  407 . The probe  407  is then positioned over the sample dispense point  44  and lowered into a cuvette which is positioned below the point  44 . The syringe  651  is then actuated to dispense the aspirated sample solution into the cuvette. Valves V 1  and V 2  are actuated to divert water to the syringe  651  for dispensing a small amount of water into the cuvette to insure that all of the sample is dispensed if the test protocol calls for the addition of a diluent or pretreatment solution, the housing  666  of the wash station  18  is filled with water from the tube  671 . The probe aspirates the diluent or pretreatment solution, moves to the wash station  18  and is dipped into the water filled housing  666 . The probe is then positioned over the selected test sample solution for lowering into the sample and aspirating a volume of sample. The probe is then moved to the sample dispense point  44  for dispensing the aspirated sample and diluent pretreatment solution into the cuvette. The cuvette then proceeds along the event conveyor toward the point  45 . The sample probe  407  is then moved above the wash station  18  as water from the peristaltic pump  880  is diverted from the valve V 2  to the valve V 1  which diverts the water to the tube  890  which passes through the syringe  651  to the tube  659  and is dispensed through the probe  407  for cleaning the inside of the probe and then diverted by the valve V 1  through the tube  671  into the housing  666  for washing the outside of the probe  407 . The washing solution which is introduced into the housing  666  by the probe  407  and the tube  671  is aspirated from the bottom of the housing through the tube  670  by opening of the valve V 7 . The initial dispensing of water through the probe  407  fills the housing  666  which effectively cleans the outside of the probe as well. This water is aspirated from the bottom of the housing and the water from the tube  671  provides a final cleaning to the outside of the probe. The water is also aspirated from the bottom of the housing. The aspirated fluid passes through the tube  910  into the manifold  899  and eventually to the wastewater reservoir  31  through the tubes  900  and  898 .  
      After the cuvette  40  has been filled with sample at the sample dispenser point  44  it travels along the event conveyor to one of the reagent dispense points  45 ,  46 , or  47 , depending on the protocol of the test. Each reagent aspirating and dispensing probe is capable of picking up or aspirating traces or labeled reagent from the outer ring and a solid phase reagent from the inner ring or only one of the reagents. Any combination is possible. For example, for a particular cuvette, a labeled reagent may be picked up by the reagent probe system R 1  while the solid phase reagent is picked up by the reagent probe system R 2  or R 3  when the cuvette is approximately positioned at either of these systems. On the other hand, the reagent probe system R 1  can pick up a solid phase reagent while the labeled reagent is added by either the reagent probe systems R 2  or R 3 . As a practical matter, the reagent probe systems R 1  and R 2  are used primarily for protocols which require the aspiration and dispensing of both reagent solutions by a single probe. Although the reagent probe system R 3  is capable of aspirating both reagents, less incubation time is available so that the system is used primarily for adding a reagent solution to a cuvette which contains a single reagent that had been added by the reagent probe system R 1  or R 2 .  
      If the test protocol calls for the aspiration of one or both reagents by the reagent probe system R 1 , each reagent solution is aspirated by the actuation of the syringe  652  with the valve B 4  closed with respect to the tubes  895 . The reagent or reagents are drawn into the coiled section of the tube  660  which lies in the heated fluid bath  648  by drawing air into the probe  535  when the probe is out of contact with the reagent solution. When the probe is positioned above the cuvette which contains the corresponding sample to be tested, the syringe is actuated to first displace the air which is in the tube  660  and thereafter to dispense the reagent solution into the cuvette. The probe  535  is then positioned over the wash station  15  and then lowered into the wash station. The valve V 4  is actuated to divert water to the tube  895 . The water flows through the probe  535  for flooding the housing  672  and, simultaneously, washing the inside and outside of the probe  535 . At the same time, the valve  89  is opened to aspirate the waste fluid from the bottom of the housing  672  through the tube  675  which eventually finds its way to the waste fluid reservoir  31 . The valve V 4  is then returned to its normal state to divert water through the tube  677  into the housing  672  for a final washing of the outside of the probe  535 . This valve V 5  is in its normally open state with respect to the valve V 4  for the washing cycle of the probe  535 . If the test protocol calls for aspirating and dispensing of reagent by the reagent probe system R 2 , reagent is aspirated by the probe  576  by actuating the syringe  653  while the tube  926  is closed with respect to the valve V 6 . The reagent is dispensed into the cuvette which is located at the dispense point  46  by the syringe  653  using the same procedures as for the reagent probe system R 1 . The valve V 5  is actuated to divert water to valve V 6  and valve V 6  is actuated to divert water through the tube  926  to the probe  576  when the probe is positioned within the housing  678  of the wash station  16 . When the valve V 6  is returned to its normally opened state to divert water through the tube  683  for a final outside wash of the probe. The valve V 10  is opened for aspirating all of the waste fluid from the housing  678  through the tube  681 .  
      If the test protocol calls for the introduction of a reagent by the reagent probe system R 3 , reagent is aspirated by the probe  653  by actuation of the syringe  654  with the valve V 3  in its normally closed position with respect to the tube  925 . After dispensing of the reagent into the cuvette by the probe  653  so the probe is positioned within the housing  684  of the wash station  17  for a wash cycle. With the valve V 2  in its normally open position with resect to valve V 3 , the valve V 3  is actuated to divert water through the tube  925  to the reagent probe  653  for the initial washing step as described for the reagent probe systems R 1  and R 2 . Thereafter, the valve V 3  is returned to its normal state so that it is open with respect to the tube  689  for the final washing step. All of the waste fluid is aspirated from the bottom of the housing  684  by opening of the valve V 8 .  
      The cuvette continues to be advanced along the event conveyor uni it is positioned beneath the bore  696  of the fire  695 . After the probe  725  has been lowered, the probe  725  is lowered into the bore  696  so that it extends all the way to the bottom wall of the cuvette whereupon the valve V 12  is open for aspirating all of the liquid within the cuvette. The paramagnetic particles are drawn against the back wall of the cuvette by the magnets  740  and remain in the cuvette during aspiration of the liquid. The liquid includes unreacted labeled reagent and unreacted test sample. The pump  903  is actuated to dispense the deionized water from the main line  986  through the nozzle  699  against the front wall of the cuvette. If the test protocol calls for a second wash cycle, the deionized water from the first wash cycle is aspirated through the probe  725  by again opening the valve V 12 . The pump  903  is actuated for a second time to introduce de-ionized water from the main water line  886  through the nozzle  6599  for a second wash cycle. The liquid from the second wash cycle or the first wash cycle if only one wash cycle is required, remains in the cuvette until the cuvette is located beneath the port  701  of the fixture  700 . When the probe  726  is lowered through the bore  701  to the bottom of the cuvette, the valve V 13  is opened to aspirate all of the wash liquid from the cuvette. At this point all of the paramagnetic particles are held against the back wall of the cuvette by the magnets  741 . When the cuvette arrives at a point beneath the acid dispense fixture  704 , the pump  920  is actuated to dispense a predetermined volume of acid from the acid reservoir  33  through the tube  707  and through the nozzle  706  against the back wall of the cuvette which dislodges all of the paramagnetic particles from the back wall and resuspends them into the acid solution.  
      After the addition of acid solution into the cuvette, the cuvette is advanced along the event conveyor to the luminometer conveyor  761 , whereupon the cuvette is raised to the luminometer  760 . The cuvette is advanced by the carousel  800  to the position  848  in line with the opening  807  which leads to the photomultiplier tube  808 ,  FIG. 86 . With the cuvette in this position, the pump  922  is actuated to dispense a predetermined volume of base solution from the base reservoir  34  through the nozzle  838 . This produces a detection reaction “flash” which is read by the photomultiplier tube  808  as described previously. When the cuvette arrives at position  848  in the luminometer beneath the bore  841 , the probe  834  is lowered into the bore  841  to the bottom of the cuvette. The valve V 14  is opened to aspirate the liquid in the cuvette through the probe  834  and through the tube  836  to the manifold  901 . The liquid is then drawn into the waste fluid reservoir  31 . The valve  18  is then opened to introduce water into the bore  841  while the valve V 17  is opened. Continued aspiration of water through the probe  834  cleanses the inside of the probe while aspiration of water through the tube  845  helps to cleanse the outside of the probe. When the cuvette is advanced to the opening  811  it falls through the opening into the waste receptacle  35 .  
      All of the valves and pumps are controlled by the central processing unit in coordination with the operation of all of the machine subunits which are associated with the valves and pumps. All of the valves and other electrical components on the right side of the machine are connected to a connector  928  by a ribbon cable ( FIG. 92 ). The connector  928  is operatively connected to the CPU. All of the valves and electrical components on the left side of the machine are connected to a connector  879  by a ribbon cable ( FIGS. 90 and 91 ). The connector  879  is operatively connected to the CPU.  
      Software Capabilities  
      The software system for the analyzer is capable of multitasking operation. At any time, the operator may access test results by sample or by test, pending results by sample or by test, results history, calibration status, QC statistics, operating status, maintenance schedule, or service history.  
      Test Definitions are custom programmable, including selection of reporting units, number of decimal places in reported results, number of replicates, normal range, precision allowances, calibration interval, and automatic repeat with or without sample dilution.  
      Control Definitions are also programmable, including identity of control, selection of tests per control, and upper and lower limits per test, which will trigger flagging of out of range results. A plurality of specific test profiles may be defined and accessed. When a profile is requested, all assays selected in that profile are automatically performed.  
      Description of Flow Diagrams  
       FIGS. 94A and 95B  constitute a single flow diagram and are connected by the common symbol “PAGE  2 ”. The diagram of  FIGS. 94A and 94B  is a time line which illustrates the coordinated movements of the elements which advance the cuvettes from the supply hopper to the detection point in the luminometer at the beginning of a test run. The diagram also depicts the coordinated “home” or upper positioning of the probes and temperature checks. The designation “track” refers to the event conveyor and the “cuvette loader” refers to the mechanism for advancing the cuvettes along the preheater section to the event conveyor.  
       FIGS. 95A, 95B  and  95 C constitute a single flow diagram.  FIGS. 95A and 95B  are connected by their common symbol “PAGE”.  FIGS. 95B and 95C  are connected by their common symbol “PAGE  3 ” AND “PAGE  2 A”. The diagram of  FIGS. 95A, 95B  and  95 C is a time line which illustrated the coordinated movements of the mechanisms which advance the cuvettes and the coordinated movements and functioning of the probes along the event conveyor or “track.  
       FIGS. 96A, 96B  and  96 C constitute a single flow diagram.  FIGS. 96A and 96B  are connected by their common symbol “PAGE  2 ”.  FIGS. 96B and 96C  are connected by their common symbol “PAGE  3 ”. The diagram of  FIGS. 96A, 96B , and  96 C is a time line diagram which depicts the coordinated movements of the elements which advance the cuvettes and the coordination of the movements of the cuvettes with the dispensing of sample and reagent into the cuvettes.  
       FIG. 97  is a time line which depicts the coordination of the movements of the sample probe and the aspirating, dispensing and washing of the sample probe.  
       FIG. 98  is a time line diagram which depicts the coordinated movements of the inner ring of the sample transport system and the sample probe when a sample container or “cup” is added to the inner ring during a run of tests.  
       FIG. 99  is a time line diagram which depicts the movements of the probe transport system R 1  in coordinating the functions of the probe for the R 1  probe transport system.  
       FIG. 100  is a time line diagram which depicts the movements of the probe transport system R 2  in coordination with the functions of the probe for the R 2  probe transport system.  
       FIG. 101  is a time line diagram which depicts the movements of the probe transport system R 3  in coordination with the functions of the probe for the R 3  probe transport system.  
       FIG. 102  is a time line diagram which depicts the movements of the luminometer carousel and elevator in coordination with the functions of the luminometer.  
      Each subunit of the analyzer has its own routine which is determined by software and microprocessor hardware. Each subunit routine is integrated by the CPU with interfacing hardware and software programs. The coordinated movements and functions of all the analyzer subunits are determined by software programming which functions through the electronic hardware, reversible stepper motors, valves, pumps and sensors.  
     UTILITY OF THE INVENTION  
      A clinical laboratory instrument which is used to automate heterogeneous immunoassay testing. The microprocessor-based instrument fully automates each step of the assay.  
      It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.  
     EXAMPLES  
      The invention is further represented by the following examples which demonstrate the operation of the analyzer. The examples are intended to illustrate the application of the analyzer for performing assays and not to limit the invention. It is to be understood that additional assays, including diagnostic and analytical, of various formats may be implemented for use on the automated analyzer.  
     Example 1  
     Free Thyroxine (FT4)  
      A free thyroxine (FT4) assay has been developed for the above described automated analyzer. The FT4 assay is a competitive binding assay in which FT4 in a test sample competes with labeled T4 (tracer reagent) for a limited amount of T4 antiserum covalently coupled to the solid phase. In the preferred format of this assay acridinium ester is the label and paramagnetic particles serve as the solid phase. A test sample (25 uL.) acridinium eter labeled T4 (100 uL.) and anti-T4 paramagnetic particles (450 uL.) are dispensed by the analyzer into a cuvette and incubated for 7.5 minutes at 37° C. After incubation, magnetic separation and washes are performed as described prior to detection of the chemiluminescent signal. The amount of FT4 present in the test sample is determined by the level of the signed detected and is converted to a dose by a two-point data reduction algorithm.  
      The test assay has a sensitivity of 0.107 ng/dL. (minimum detectable dose defined as the 95% confidence limit at 0 ng/dL.) with a range of 0-13 ng/dL. The precision of the assay based on nine test runs over three days is provided in Table 1. The correlation of the automated test assay with a manual test assay (Magic® Lite Free T4, Ciba Corning Diagnostics, Corp.) provided a slope of 1.109, an intercept of 0.308 and correlation coefficient of 0.989 (N=131).  
      The specificity of the assay, i.e. % cross-reactivity, for various compounds is shown in Table 2.  
               TABLE 1                          PRECISION       Based on 9 runs, 3 days                         Mean FT4               concentration,   Within   Total       ng/dL   run % CV   % CV               0.62   4.5   5.1       0.79   3.5   3.6       1.05   3.5   7.9       1.15   4.4   5.7       1.39   3.5   4.4       1.71   2.5   5.8       6.42   4.7   5.9       8.98   8.0   9.1                  
 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                   
               
               
                 SPECIFICITY 
               
            
           
           
               
               
               
            
               
                   
                   
                 % Cross- 
               
               
                   
                 Compound 
                 Reactivity 
               
               
                   
                   
               
               
                   
                 L-triiodothyronine 
                    3.9% 
               
               
                   
                 D-thyroxine 
                   &gt;64% 
               
               
                   
                 D-triiodothyronine 
                    3.6% 
               
               
                   
                 Diiodotyrosine 
                 &lt;0.002% 
               
               
                   
                 Monoiodotyrosine 
                 &lt;0.002% 
               
               
                   
                 3,5-diiodo-L-thyronine 
                 &lt;0.002% 
               
               
                   
                 Reverse triiodothyronine 
                    3.1% 
               
               
                   
                   
               
            
           
         
       
     
     Example 2  
     Human Chorionic Gonadotropin (hCG)  
      A human chorionic gonadotropin (hCG) assay has been developed for the above described automated analyzer. The hCG assay is a sandwich assay which utilizes an, antibody-coated capture solid phase and a labeled antibody as a tracer reagent. In the preferred format of this assay acridinium ester is the label on a monoclonal antibody and polyclonal antibody coated paramagnetic particles serve as the capture solid phase. A test sample (50 uL.) and tracer reagent (100 uL.) are dispensed into a cuvette by the analyzer and incubated for 5.0 minutes at 37° C. The capture solid phase reagent (450 uL.) is then added to the cuvette followed by an additional incubation of 2.5 minutes. After the second incubation, magnetic separation and washes are performed as described above prior to detection of the chemiluminescent signal.  
      All data presented was generated based on a two-point calibration off a full standard master curve, consisting of ten standards. The standards, ranging from zero to 1000 mIU/mL., are calibrated against the WHO 1st 75/537 reference material.  
      The test assay has a sensitivity of less than 1 mIU/mL. (minimum dectable dose defined as the 95% confidence limit at 0 mIU/mL.) with a range of 01,000 mIU/mL. No hook effect seen at 400,000 mIU/mL. The precision of the assay based on five test runs over five weeks is provided in Table 3. The specificity of the assay without cross reactant and with cross reactant is provided in Table 4. Interfering substances added to test samples according to NCCLS protocols were assayed with results provided in Table 5. The correlation of the automated test assay with a manual test assay with a manual test assay (Magic® Lite hCG, Ciba Corning Diagnostics, Corp.) provided a slope of 1.08, an intercept of 1.03 and a correlation coefficient of 0.98 (N=172)  
               TABLE 3                          PRECISION       Based on 5 weeks stored 2-point calibration, 5 runs                             hCG   % CV of Dose                                     Control,   Within   Between           Study   mIU/mL   Run   Run   Total                                         1   13.9   3.7   3.0   4.8           124.8   3.4   3.2   4.7           329.1   2.7   6.9   7.4       2   13.9   4.9   9.9   11.0           129.1   3.2   6.3   7.1           331.7   4.2   7.5   8.6                  
 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                   
               
               
                 SPECIFICITY 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 hCG result 
                 hCG result 
                   
               
               
                   
                 Cross 
                 no cross 
                 with cross 
               
               
                   
                 reactant 
                 reactant, 
                 reactant, 
                 P value 
               
               
                   
                 (level tested) 
                 mIU/mL 
                 mIU/mL 
                 (95% C.I) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 TSH 
                 10.9 
                 11.1 
                 0.84 
               
               
                   
                 (2,000 uIU/mL) 
                 207.0 
                 214.9 
                 0.26 
               
               
                   
                   
                 472.0 
                 460.9 
                 0.50 
               
               
                   
                   
                 832.8 
                 812.0 
                 0.68 
               
               
                   
                 FSH 
                 13.1 
                 13.4 
                 0.35 
               
               
                   
                 (200 mIU/mL) 
                 123.4 
                 120.8 
                 0.42 
               
               
                   
                   
                 431.5 
                 427.6 
                 0.16 
               
               
                   
                   
                 849.1 
                 910.0 
                 0.40 
               
               
                   
                 LH 
                 4.5 
                 4.5 
                 0.85 
               
               
                   
                 (200 mIU/mL) 
                 207.4 
                 205.5 
                 0.65 
               
               
                   
                   
                 459.1 
                 480.2 
                 0.10 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                   
               
               
                 INTERFERING SUBSTANCES 
               
               
                 Patient samples were spiked with NCCLS recommended 
               
               
                 levels of various interfering substances. If P value &gt; 0.05, 
               
               
                 the difference in hCG dose is not statistically significant. 
               
            
           
           
               
               
               
               
               
            
               
                   
                 hCG 
                 hCG 
                 Spiked 
                   
               
               
                 Substance 
                 Control, 
                 Spiked, 
                 vs. 
                 P-Value 
               
               
                 (mg/dL) 
                 mIU/mL 
                 mIU/mL 
                 Control 
                 (95% C.I.) 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Conjugated 
                 11.8 
                 12.0 
                 101% 
                 0.54 
               
               
                 Bilirubin 
                 214.3 
                 218.2 
                 102 
                 0.25 
               
               
                 (20) 
                 471.2 
                 481.4 
                 102 
                 0.29 
               
               
                 Unconjug. 
                 2.7 
                 2.9 
                 106 
                 0.34 
               
               
                 Bilirubin 
                 46.7 
                 45.9 
                  98 
                 0.32 
               
               
                 (20) 
                 90.2 
                 93.1 
                 103 
                 0.04 
               
               
                   
                 179.3 
                 185.4 
                 103 
                 0.03 
               
               
                   
                 889.8 
                 875.5 
                 98 
                 0.78 
               
               
                 Lipid 
                 2.9 
                 3.1 
                 107 
                 0.54 
               
               
                 (1,000) 
                 22.0 
                 23.1 
                 105 
                 0.12 
               
               
                   
                 48.3 
                 50.5 
                 105 
                 0.04 
               
               
                   
                 94.3 
                 98.7 
                 105 
                 0.00 
               
               
                   
                 191.7 
                 189.8 
                  99 
                 0.57 
               
               
                   
                 871.1 
                 934.4 
                 107 
                 0.31 
               
               
                 Hemolysate 
                 2.4 
                 3.1 
                 126 
                 0.05 
               
               
                 (500) 
                 48.0 
                 48.4 
                 100 
                 0.72 
               
               
                   
                 92.3 
                 94.2 
                 102 
                 0.21 
               
               
                   
                 182.5 
                 197.7 
                 108 
                 0.05 
               
               
                   
                 1,029.6 
                 1,046.3 
                 102 
                 0.63 
               
               
                   
               
            
           
         
       
     
     Example 3  
     Digoxin  
      A digoxin assay has been developed for the above described automated analyzer. The digoxin assay architecture is a hapten solid phase with a labeled antibody (tracer reagent). In the preferred format of this assay, the tracer reagent is an acridinium ester labeled monoclonal anti-digoxin antibody; and the solid phase is paramagnetic particles to which digoxin-apoferritin has been immobilized. A test sample (150 uL.) and tracer reagent (50 uL.) are dispensed into a cuvette by the analyzer and incubated for 2.5 minutes at 37° C. The solid phase reagent (250 uL.) is then added to the cuvette followed by an additional incubation of 5.0 minutes. After the second incubation magnetic separation and washes are performed as described above prior to detection of the chemiluminescent signal.  
      All data presented was generated based upon a two-point recalibration off an original master curve. The master curve was generated using eight standards with valves ranging from zero to 6 ng/mL digoxin.  
      The test assay has a sensitivity of less than 0.1 ng/mL (minimum detectable dose defined as the 95% confidence limit at 0 ng/mL.) with a range of 0-5 ng/mL. The precision of the assay for patient samples and patient pools is provided in Table 6. The specificity of the assay is provided in Table 7. Interfering substances added to test samples according to NCCLS protocols were assayed with results provided in Table 8. The correlation of the automated test assay with a manual test assay (Magic Digoxin, Ciba Corning Diagnostics, Corp.) provided a slope of 1.00, an intercept of 008 and a correlation coefficient of 0.97 (N 130).  
               TABLE 6                       PRECISION                  A. Patient samples run in replicates of two.       13 patient samples were studied in each group.                             Mean digoxin   Within run           concentration   % CV                       0.52 ng/mL   6.5           0.81   4.7           1.05   4.7           1.22   4.9           1.37   5.6           1.49   5.2           1.86   4.2           2.68   2.3                             B. Patient pools and control run in replicates of 12 over 5 runs.                         Digoxin concentration   Within run % CV   Total % CV                                     Controls:   0.79 ng/mL   7.0   7.9           1.73   5.8   5.8           2.81   4.8   5.0       Patient Pools:   0.62 ng/mL   6.7   8.0           0.97   3.7   4.7           1.15   5.1   5.5           1.64   4.1   4.3           2.05   4.3   4.6           4.18   4.3   5.1                  
 
     
       
         
           
               
             
               
                 TABLE 7 
               
               
                   
               
               
                   
               
               
                 SPECIFICITY 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Compound 
                 % Cross-Reactivity 
               
               
                   
                   
               
               
                   
                 Digitoxin 
                  0.6% 
               
               
                   
                 β-Methyldigoxin 
                 109.4%  
               
               
                   
                 Deslanoside 
                 94.6% 
               
               
                   
                 Digoxigenin 
                 16.7% 
               
               
                   
                 Lanatoside C 
                 87.1% 
               
               
                   
                 Ouabain 
                  7.3% 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Compound 
                 Level Tested 
                 Effect on Dose 
               
               
                   
                   
               
               
                   
                 Cortisone 
                 20 ug/mL  
                 N.S. 
               
               
                   
                 Estradiol 
                 1 ug/mL 
                 N.S. 
               
               
                   
                 Progesterone 
                 1 ug/mL 
                 N.S. 
               
               
                   
                 Testosterone 
                 1 ug/mL 
                 N.S. 
               
               
                   
                 Prednisone 
                 20 ug/mL  
                 N.S. 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 8 
               
             
            
               
                   
               
               
                   
               
               
                 INTERFERING SUBSTANCES 
               
               
                 Patient samples were spiked with NCCLS recommended 
               
               
                 levels of various interfering substances. If P value &gt; 0.05, 
               
               
                 the difference in digoxin dose is not statistically significant. 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 Digoxin 
                 Digoxin 
                 Spiked 
                 P-Value 
               
               
                   
                 Substance 
                 Control, 
                 Spiked, 
                 vs. 
                 (95% 
               
               
                   
                 (mg/dL) 
                 ng/mL 
                 ng/mL 
                 Control 
                 C.I.) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Conjugated 
                 0.003 
                 0.008 
                 — 
                 0.36 
               
               
                   
                 Bilirubin 
                 0.54 
                 0.57 
                 106% 
                 0.20 
               
               
                   
                 (20) 
                 2.23 
                 2.21 
                  99% 
                 0.44 
               
               
                   
                 Unconjug. 
                 0.004 
                 0.000 
                 — 
                 0.30 
               
               
                   
                 Bilirubin 
                 0.56 
                 0.59 
                 105% 
                 0.06 
               
               
                   
                 (20) 
                 2.25 
                 2.22 
                  99% 
                 0.66 
               
               
                   
                 Lipid 
                 0.010 
                 0.012 
                 — 
                 0.89 
               
               
                   
                 (1,000) 
                 0.52 
                 0.58 
                 112% 
                 0.03 
               
               
                   
                   
                 2.06 
                 2.04 
                  99% 
                 0.69 
               
               
                   
                 Hemolysate 
                 0.0 
                 0.0 
                 — 
                 1.00 
               
               
                   
                 (500) 
                 0.52 
                 0.53 
                 102% 
                 0.75 
               
               
                   
                   
                 2.09 
                 2.10 
                 101% 
                 0.90 
               
               
                   
                   
               
            
           
         
       
     
     Example 4  
     Prostate Specific Antigen (PSA)  
      A prostate specific antigen (PSA) assay has been developed for the above described automated analyzer. The PSA assay utilizes an anti-PSA antibody solid phase and a labeled anti-PSA antibody as a tracer reagent. In the preferred format of this assay acridinium ester is the label on an affinity purified anti-PSA antibody and the solid phase is paramagnetic particles which is coated with anti-PSA monoclonal antibody. A test sample (100 uL.), tracer reagent (50 uL.) and solid phase reagent (250 uL.) are disposed into a cuvette by the analyze and incubated for 7.5 minutes at 37° C. After the incubation, magnetic separation and washes are performed as descried above prior to detection of the chemiluminescent signal.  
      All data presented was generated based on a two-point calibration off a standard curve consisting of eight points.  
      The test assay has a sensitivity of 0.2 ng/mL. (minimum detectable dose defined as the 95% confidence limit at 0 ng/mL.) with a dynamic range of 0200 ng/mL. and a high dose hook capacity out to 40,000 ng/mL. The precision of the assay based on five separate runs on three instruments over a five day period for commercial controls and patient pools is provided in Table 9. Interfringing substances, including endogenous compounds and cheno therapeutic agents, added to test samples according to NCCLS protocols were assayed with results provided in Tables 10 and 11. The correlation of the automated test assay with a manual test assay (Tandem R-R PSA, Hybritech) provided a slope of 1.01, an intercept of 3.65 and a correlation coefficient of 0.97 (N=73).  
               TABLE 9                          PRECISION       A. Analysis is based on 5 separate run on 3 instruments over a five day       period. Each run contained 12-14 repetitions.       Two point calibration was used throughout                                 PSA   % CV               Concentration,   Within   % CV           ng/mL   Run   Total                                                 Commercial                       Controls           (N = 70)           A   2.76   8.7   11.15           B   7.71   6.74   7.36           C   17.37   5.94   6.91           Patient           Pools           (N = 60)           1   15.79   4.49   6.46           2   25.91   5.73   7.64           3   48.78   5.54   8.65           4   93.66   5.81   8.07                      
 
     
       
         
           
               
             
               
                 TABLE 10 
               
             
            
               
                   
               
               
                   
               
               
                 INTERFERING SUBSTANCES 
               
               
                 (ENDOGENOUS COMPOUNDS) 
               
               
                 Patient samples at various PSA levels were spiked with maximal levels 
               
               
                 of endogenous interferents according to NCCLS protocols. 
               
            
           
           
               
               
               
               
               
            
               
                   
                 PSA 
                 PSA 
                 Spiked 
                   
               
               
                 Substance 
                 Control, 
                 Spiked, 
                 vs. 
               
               
                 (mg/dL) 
                 ng/mL 
                 ng/mL 
                 Control 
                 Mean +/− SD 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Hemoglobin 
                 7.08 
                 7.32 
                 103% 
                  99 +/− 4% 
               
               
                 (500) 
                 28.06 
                 27.86 
                 99% 
               
               
                   
                 51.06 
                 48.99 
                 96% 
               
               
                 Triglycerides 
                 7.08 
                 7.29 
                 103% 
                 102 +/− 5% 
               
               
                 (3000) 
                 28.06 
                 29.78 
                 106% 
               
               
                   
                 51.06 
                 49.18 
                 96% 
               
               
                 Unconjug. 
                 7.0 
                 7.6 
                 109% 
                 103 +/− 6% 
               
               
                 Bilirubin 
                 28.06 
                 28.45 
                 101% 
               
               
                 (20) 
                 57.54 
                 56.08 
                 98% 
               
               
                 Conjug. 
                 7.08 
                 7.57 
                 107% 
                 101 +/− 9% 
               
               
                 Bilirubin 
                 28.06 
                 29.44 
                 105% 
               
               
                 (20) 
                 51.06 
                 46.57 
                 91% 
               
               
                 Total Protein 
                 7.08 
                 6.51 
                 92% 
                  90 +/− 2% 
               
               
                 (12 gm/dL) 
                 28.06 
                 25.38 
                 90% 
               
               
                   
                 57.54 
                 50.98 
                 89% 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 11 
               
             
            
               
                   
               
               
                   
               
               
                 INTERFERING SUBSTANCES 
               
               
                 (CHEMOTHERAPEUTIC AGENTS) 
               
               
                 Patient samples at various PSA levels were spiked with drugs commonly 
               
               
                 used in the treatment of cancer of the prostate (N = 5). 
               
            
           
           
               
               
               
               
               
            
               
                   
                 PSA 
                 PSA 
                 Spiked 
                   
               
               
                 Substance 
                 Control, 
                 Spiked, 
                 vs. 
               
               
                 (ug/mL) 
                 ng/mL 
                 ng/mL 
                 Control 
                 Mean +/− SD 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Cyclophosphamide 
                 7.55 
                 7.17 
                 95% 
                  98 +/− 3% 
               
               
                 (330) 
                 28.06 
                 27.52 
                 97% 
               
               
                   
                 49.34 
                 49.8 
                 101% 
               
               
                 Doxorubicin 
                 7.55 
                 7.32 
                 97% 
                 100 +/− 3% 
               
               
                 (10) 
                 28.06 
                 28.22 
                 101% 
               
               
                   
                 49.34 
                 50.11 
                 102% 
               
               
                 Megestrol 
                 7.08 
                 7.47 
                 106% 
                 101 +/− 5% 
               
               
                 Acetate 
                 28.06 
                 28.42 
                 101% 
               
               
                 (79) 
                 51.06 
                 49.7 
                 97% 
               
               
                 Diethyl- 
                 7.08 
                 7.52 
                 106% 
                 101 +/− 5% 
               
               
                 Stilbesterol 
                 28.06 
                 28.10 
                 100% 
               
               
                 (2.5) 
                 57.54 
                 55.57 
                 97% 
               
               
                 Methotrexate 
                 7.08 
                 7.16 
                 101% 
                 101 +/− 3% 
               
               
                 (13.2) 
                 28.06 
                 28.98 
                 103% 
               
               
                   
                 51.06 
                 49.79 
                 98% 
               
               
                   
               
               
                   Prostatic acid phosphatase (PAP), &gt;95% pure, showed less than 0.01% cross reactivity