LUMINESCENCE TEST APPARATUS AND INJECTOR ASSEMBLY THEREFOR

Abstract: Luminescence test apparatus comprising photometer means (17) and associated readout, an injection assembly (21) and a shutter-incorporating holder for receiving a cuvette (29) or other receptacle containing the sample to be tested. The injection assembly includes a barrel housing (71), a cap (65), a supply tube, an injector (77) and a surrounding protecting guide (83). A rotatable shutter mechanism is incorporated as a part of the holder and employs coaxial hollow shutter elements (33, 37) designed to block all passage of light except when ports (41, 57, 59) in the elements are aligned. After the sample-carrying cuvette (29) is placed axially within the hollow shutter elements, the injection assembly (21) is lowered into place. The cap (65) fits about the top of the movable shutter element, and the protecting guide (83) axially aligns the upper end of the cuvette and retracts upward so the injector (77) projects thereinto. The injector (77) directs liquid against the sidewall of the cuvette (29) at a location just above the level of the sample to initiate swirling and rapid, thorough mixing, and as a result, reproducible test results are achieved.

Description: LUMINESCENCE TEST APPARATUS AND INJECTOR ASSEMBLY THEREFOR The present invention relates to test apparatus generally; however it is more particularly illustrated with respect to test apparatus designed for clinical or biological analysis based on luminescence. Luminescence is generally referred to as the light emitted by the glow worm, the firefly and certain varieties of fish and other marine life, including bacteria and plankton. It also includes light which is emitted from synthesized organic chemicals, such as lu inol, and it is more specifically referred to as biolu inescence or chemiluminescence, depending upon the source of the reacting materials. In both cases, the light is derived from a chemical, rather than a thermal reaction, without the necessity, as in the case of fluorescence, for excitation from an external source. Light which is emitted is measured in units called photons by an instrument, called a photometer. BACKGROUND OF THE INVENTION Bioluminescent reactions generally involve the use of an enzyme derived from firefly lanterns, termed "luciferase", as a catalyst, and the reaction is an indication of the measure of adenosine triphosphate (ATP) which is a fundamental component of the energy cycle or of nicotinamide adene dinucleotide (NADH) , a substance which is vital to cell metabolism. ATP and NADH are present only in living cells, and therefore, they are accepted indicators of the presence or absence of life in a certain biological sample being tested. In medicine, the detection or measurement of ATP can provide a basis for the microbiologist to rapidly verify the presence of bacteria in urine, blood, or some other body fluid. Since ATP is only present in living cells, detection of ATP may enable Blood Banks to assess the viability of the blood in their inventories. The clinical chemist may use determinations of the amount of ATP in cells to detect disfunction of the cells, or may use the determination of the amount consumed in a reaction to derive other information, e.g., the serum level of drugs. Because NADH is a participant in several enzymatic reactions, the estimation of NADH by bioluminescenee measurement allows measurement of at least a dozen enzyme systems. For industrial and environmental uses, ATP determinations can provide information about relevant biological activity, e.g., the activity of degrading agents in sewage treatment, as well as other information about water quality. Chemiluminescence can be used in immunoassays, which are medical diagnostic procedures based upon the science of immunology dealing with the interaction of antigens and antibodies. In chemiluminescence immunoassays, for example, the light-producing chemical may be attached, through a chemical process, to a specific antibody or antigen and thereby serve as a label to be read when the antigen-antibody complex is ultimately formed. Test apparatus, such as that disclosed in U.S. Patent No. 3,871,767, has certain limitations and some disadvantages, and more sophisticated and reliable test apparatus is desired. SUMMARY OF THE PRESENT INVENTION Luminescence test apparatus is provided which couples a holder with a photometer and its associated read-out, which bolder is designed to accommodate a cuvette of standard design. The cuvette is manually loaded into the holder which incorporates a shutter mechanism that is designed to block passage of all light from reaching the photometer other than that created chemically in the cuvette during the time when it is open. A movable hollow cylindrical shutter element rotates about a central axis in cooperation with a fixed shutter element. Once the cuvette carrying the sample to be OMH WΠΌ tested is placed in the holder, the injection assembly is lowered into place to create a light-tight environment in the central region where the cuvette resides. The injector for delivering the chemical reactants to the sample solution in the cuvette to be tested is protected by a surrounding, retractable guide. As the assembly is lowered into place, a cap fits downward over a rounded upper edge of the rotatable shutter element and assures alignment of the injector with the holder. The inwardly converging bottom surface of the guide engages the top of the cuvette, and the guide retracts upward against the pressure of a downwardly-biasing spring as the cap is seated in place ' on the holder. A detent enters a groove in the undersurface of the cap and locks the injection assembly to the holder when the cap is rotated to the ready or TEST position opening the shutter. In the ready position, the lower discharge end of the injector . extends into the upper end of the cuvette, and the discharge outlet is aligned to direct liquid against the sidewall of the cuvette just above the surface level of the sample to initiate swirling and rapid, thorough mixing of the chemical reactants which are injected via a supply system connected to the upper end of the injector. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a front perspective view of luminescence test apparatus embodying various features of the invention; FIGURE 2 is an enlarged sectional view taken along the central axis of the injection assembly and the holder, looking at the FIG. 1 apparatus from the front with the shutter closed, and diagrammatically illustrating certain other components of the apparatus; FIGURE 3 is an exploded perspective view of the shutter mechanism plus certain other components of the test apparatus shown in FIG. 1; FIGURE 4 is an enlarged fragmentary plan view showing the assembled components of FIG. 3; FIGURE 5 is an enlarged sectional view taken generally along the line 5-5 of FIG. 4; FIGURE 6 is an enlarged fragmentary view showing the initial mating of the cap with the top of the holder and the detent, as the injection assembly is lowered into place; and FIGURE 7 is an enlarged sectional view similar to FIG. 2 showing the cap after rotation to the TEST position and the shutter open, with the cuvette in place and liquid being discharged; and FIGURE 8 is an enlarged fragmentary- sectional view taken generally along the line 8-8 of FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Luminescence test apparatus is provided which includes a chassis 11 which surrounds the mechanical and electronic working components and which on its front face includes both a digital read-out 13 and a graphical read-out 15 which display the results of measurement of the luminescence reaching the photometer 17 through a double convex lens arrangement 18 which are both located within the chassis. An opening in the rear left-hand portion of the upper panel of the chassis 11 provides clearance for the holder 19 which is disposed therebelow and extends upward just above the level of the upper panel. The injection assembly 21 is disposed atop the holder 19 and may be manually removed and simply set to one side, or it may be -mounted by a suitable bracket on a vertical rod to allow it to be slid upward and downward and swung to one side to permit installation and removal of a sample-carrying cuvette 29. A dispenser 23 of standard design, preferably a motor-driven dispenser, is mated with a bottle of commercially available reagent, i.e., the enzyme Luciferase plus its substrate Luciferin. The dispenser 23 is ajustably set to dispense a precise amount of liguid in a desired short interval of time each time it is actuated. A manually operated dispenser may alternatively be used if it meets these specifications. The dispenser 23 supplies the liquid through flexible tubing 27, which may be light-shielding Teflon tubing, that leads to the top of the injector assembly 21. Generally, a round-bottomed tube of glass or plastic can be used as a receptacle or cuvette 29 to hold the liguid sample to be tested. It may be either transparent or translucent. The elongated test tube 29 is of sufficient length to extend upward so that its upper end is easily accessible above the bottom of a well 31 that is provided at the upper end of a rotatable shutter element 33. The holder 19, which incorporates the shutter mechanism, is supported within a base or block 35 which is in turn attached to the top panel of the chassis 11 by screws or the like extending through the holes 36 therein. A fixed shutter 37 is mounted in the block 35 by screws extending up through its circular base 38 and includes an upstanding tubular portion 39 of circular cross-section, which defines the central axis of the shutter mechanism with which the injector assembly is coaxial when it is installed thereupon. A short upstanding ring 40 is received in a complementary groove in the undersurface of the base 35 and blocks passage of light thereinto. A port or opening 41 of generally rectangular shape is provided about midway between the top and bottom of the tubular section 39. The port 41 is cut to have dimensions intermediate the ports in the rotatable shutter 33 as explained hereinafter. The fixed shutter 37 is installed in the block 35 so that the port 41 faces the screen of a side-window photo ultiplier tube which serves as the photometer 17 and which is located to the right thereof as one looks at it from the front of the chassis 11, as depicted in FIG. 2. The interior region of the tubular fixed OMP shutter terminates in a flat bottom surface 45 which includes a tapped hole 47 located on the centerline constituting the central axis. The rotatable shutter 33 is hollow having an elongated cavity 48 along its centerline extending downward from an enlarged region 49 at its upper end wherein the well 31 is formed. The lower portion of the cavity 48 is formed by a lower hollow cylindrical section 51 which has an outer diameter just less than the inner diameter * of the tubular sidewall 39 of the fixed shutter within which it rotates. The bottom of the rotatable shutter 33 has a central hole 52 through which a shoulder screw 53 or the like extends to enter the tapped hole 47 of the fixed shutter 37 to complete the subassembly of the two shutter elements. Plastic bearing rings 54a and b (FIG. 7) surround the stem of the shoulder screw 53 above and below the bottom wall of the rotatable shutter element 33 and serve as thrust bearings. The upper ring 54a may be a relatively rigid material, such as nylon, while the lower ring 54b is formed from Teflon or the like which undergoes cold flow when the screw 53 is tightened to seat the shoulder upon the bottom wall 45. A liner 55 having an inner diameter just larger than the standard cuvette 29 lines the cavity 48 to collect any liquid which could inadvertently reach it. The liner 55 is preferably formed from translucent but cloudy polypropylene to provide a light-diffusing effect. An outer tubular skirt 56 is a part of the movable shutter and is spaced from the hollow cylindrical section 51 a distance just greater than the thickness of the fixed shutter tubular portion 39. The outer skirt 56 not only assures the relative rotational compatibility of the fixed and movable shutter elements, but substantially increases the light- ightness of the overall subassembly without the necessity of achieving very close tolerances in manufacturing. Aligned rectangular ports 57,59 are respectively formed in the outer skirt 56 and in the inner hollow cylindrical section 51 of the rotatable shutter. These ports are of different horizontal and vertical dimensions, as discussed hereinafter, with the interior port 59 being narrower than the port 57 in the outer skirt. A short tubular collar 61 is preferably seated in a groove in the upper surface of the block 35, within which collar a lower intermediate portion of the enlarged region 49 of the rotatable shutter is rotatably received. A notch 62, approximately semicircular in cross section, is cut in the undersurface and sidewall of the enlarged region - just above the intermediate portion, as best seen in FIG. 4. To effect rotation of the shutter 33, a radially disposed pin 63 is mounted extending radially outward from enlarged upper region 49 which defines the well 31. To further improve light-tightness, and - upstanding ring portion 64 of the base 35 may be provided which is received in a complementary recess in the undersurface of the rotatable shutter element (FIG. 7). The injection assembly 21 terminates in a lower cap 65 which is sized to fit downward over the rounded upper end of the rotatable shutter 33. A groove 67 is cut in the interior wall of the depending flange portion of the cap, and the cap is mounted by screws 69 extending upward through the cap into tapped holes in a main barrel 71 of the injector. The barrel 71 has a central passageway 73 which is located on the central axis defined by the fixed shutter, and the central passageway narrows at a neck region 75 near the upper end thereof. A long metallic injector needle 77 extends downward from a bushing 79 installed in the neck 75. The length of the needle 77 is such that it extends out the bottom of the passageway 73, and the lower discharge end portion 81 of the needle, which is otherwise straight, is bent at an angle of between about 3° and about 10°, preferably about 5°, for about the last one-quarter inch, so that the discharge outlet at the bottom of the needle 77 will be directed at a specific location along the sidewall of the cuvette 29, as discussed in more detail hereinafter. The relatively fragile lower needle tip is protected by an injector guide 83, which has an enlarged lower portion and a main cylindrical body that allows it to freely slide up and down in the barrel passageway 73. An interior central channel 85 through the guide 83 is larger in diameter than the needle 77, and the lower portion of the channel 85 receives a length 87 of polytetrafluoroethylene (Teflon) tubing so as to assure a good sliding fit with the needle. The central channel 85 of the injector guide 83 is enlarged further near its lower end where it surrounds the discharge tip 81 of the needle just above the point where it terminates in a frusto-conical bottom surface 89. The inwardly converging disposition of this bottom surface 89 serves a centering function with the top of the cuvette 29, as described hereinafter. The guide 83 is adapted to slide between an extended and a retracted position and is- biased to the downward extended position by a compression spring 91 which is located in the upper end of the barrel passageway 73 where it seats about the lower portion of the needle bushing 79 and bears against the upper end of the guide. A split-ring clip 93 or the like is snapped into a groove in the outer wall of the guide 83, and the clip travels in an enlarged region in the upper section of the cap 65 that terminates in a ledge 95. When the clip 93 abuts the ledge 95, the guide 83 is in its fully extended position. The opaque Teflon tubing 27 from the dispenser 23 passes downward through a strain relief 97 that protrudes upward from an upper end cap 98 for the barrel, which strain relief is held therewithin by a suitable ferrule 99. The Teflon tubing is connected to the short upper end of the needle 77 that extends upward from the needle bushing 79, using suitable ferrules 101 that are compressed in place by a compression nut 103 which is screwed downward into the internally threaded upper end of the barrel passageway 73 from the intermediate position shown in FIG. 2. With the tubing 27 attached to the upper end of the needle, the barrel end cap 98, which has female threads at its lower end that mate with male threads on the upper end of the barrel 71, is screwed downward as indicated by the arrow in FIG. 2 into " position against a washer 105 made of neoprene or the like. The barrel 71, the barrel end cap 98, the Teflon tubing 27 and the strain relief 97, as well as the cap 65 and the shutter elements 33 and 37, are all made of opaque light-blocking material. Accordingly, the design is extremely light-tight so that any light which is emitted through the aligned shutter ports is assured to originate in the chemical luminescence-producing reaction taking place in the cuvette 29 and is not leakage into the apparatus through the injection assembly 21. With the rotatable shutter element 33 in the LOAD position, the cap 65 and the injection assembly are separable from the top of the shutter element 33 so that the well 31 at the upper end of the holder 19 is accessible, and in this LOAD position the rotatable shutter element 37 is positioned approximately 180° from the position wherein its ports are aligned with the port 41 in the fixed shutter. The cuvette 29 carrying the liquid sample to be tested is then lowered into the well 31 until it is in place within the liner 55 in rotatable shutter 33 with its lower end located just below the level of the bottom edges of the rectangular ports in the shutter elements. As the injection assembly 21 is lowered into place, the interior cylindrical wall 107 of the depending flange portion of the cap 65 centers on the curved upper end of the rotatable shutter 33 to insure that the injection assembly 21 is aligned on the main centerline, and the frusto-conical surface 89 of the injector guide contacts the upper end of the cuvette 29 to achieve a dual function. At the same time, as illustrated in FIG. 6, the upper surface of the groove 67 in the cap 65 engages the top surface of the head of a locking detent 109 that is mounted in a hole 111 in the top surface of the block 35. The hole 111 is aligned at an angle of between about 10° and about 30°, preferably about 15°, from the vertical and is generally radial to the main centerline of the holder. A compression spring 113 biases the detent upward and toward the rotatable shutter element where it is seated in the notch 62 therein in the LOAD position. Further downward movement of the cap 65 causes the head of the detent 109 to move downward out of the notch 62; however, the angular alignment of the hole 111 effects an outward movement of the head within the groove 67 of the cap causing the bottom edge 114 of the cap that partially defines the groove to become engaged in locking arrangement in the recess 115 cut in the detent 109 that defines the head section thereof. As the downward movement of the injector assembly is completed, the needle-protecting guide 83 completes its upward movement into its retracted position while, at the same time, the inwardly converging surface 89 assures that the upper end of the cuvette is in a precisely centered alignment with respect to the needle and within the cavity 48 provided in the interior of the rotatable shutter, as illustrated in FIG. 7. At the same time, the pin 63 is received in a corresponding radial recess 117 cut in the undersurface of the cap 65. Rotation of the cap 65 about 180° via a radially extending handle 119 turns the shutter mechanism to the fully open position, termed the TEST position, and the apparatus is ready to assay a sample. The cap 65 stops precisely at the desired LOAD and TEST positions because a depending pin- 121 (FIG. 2) hits one or the other of two abutments 123 press fit into a circular groove 125 in the top surface of the block 35 just interior of the collar 61. A synthetic rubber O-ring 126 serves as a bearing between the rotatable shutter element 33 and the base 35. As shown in FIGURE 7, in the final position, the discharge tip 81 of the needle is well below the upper end of the cuvette 29 so that it is ready for delivery of the chemical reagents. Because the notch 62 in the rotatable shutter is now displaced 180° from the detent 109 (see FIG. 4) , the cap 65 is locked to the holder 19, and potentially damaging ambient light cannot reach the sensitive electrode of the photometer 17. Activation of the dispenser 23 causes a fixed quantity of liquid to flow through the Teflon tubing 27 down the needle 77 and to be discharged as a narrow stream from the port at the lower end of the needle in a given time interval, e.g., about one second. Because the end portion 81 of the needle is aligned at a small angle from the central axis, between about 3° and 10° and preferably at about 5°, the narrow stream of liquid being discharged downwardly and just slightly radially outwardly from the needle port impinges against the sidewall of the cuvette at a location just above the surface of the liquid sample contained therein. The orientation is preferably such that the narrow stream impinges against a region of the sidewall that will be at or just below the final surface level in the cuvette after all of the reagent is dispensed. This precision is made possible and is reproducible even with the broad tolerances in the dimensions of glass or plastic tubes because of the precise centering achieved by the inwardly converging bottom surface 89 of the retractable guide 83. This creates a swirling action about a horizontal axis in the sample as depicted in FIG. 7 and assures rapid, thorough mixing is achieved without the creation of froth that could slow down the time of the reaction and harm the reproducibility of the test. The ultimate liquid level is slightly above the top of the shutter port 59. Effective reproducible measurement of luminescence is dependent upon achieving prompt, thorough and consistent mixing because the rapidity of the reaction is such that measurement of peak luminescence may often occur a few seconds, e.g. 2 or 3, following the mixing of the reagents with the sample and sometimes within hundreds of milliseconds. The apparatus is provided with circuitry that monitors the photomultiplier tube reading 20 times a second and automatically updates and continues to display the peak reading sensed until a set number of seconds, e.g. 2, expire without a further increase in the light reaching the photometer, at which time the read-out values are locked in. Subsequently, rotation of the handle 119 counterclockwise about 180° closes the shutter mechanism and realigns the detent 109 and the notch 62 so the cap 65 can be removed and a new sample substituted for the next test. Reproducibility of results in apparatus of this type within about 3% is obtained for a reaction that will peak in about 2 seconds and is due in large part to the design of the injector 21. For example, the apparatus may employ cuvettes 29 in the form of 6 x 50 mm. clear glass tubes that are accommodated in a liner 55 disposed within a fixed shutter element 37 having an interior diameter of about one-half inch. The port 59 in the interior hollow cylindrical portion of the rotatable "shutter 33 may be about 0.35 inch across, the port 41 in the fixed shutter may be about 0.45 inch wide, and the horizontal dimension of the port 57 in the outer skirt may be about 0.63 inch. The discharge port of the needle 77 may be located about 5mm. into the cuvette 29, and the inner diameter of the needle should be between about 0.01 and 0.04 inch. The size is dependent upon the amount of liquid to be injected and the size of the cuvette 29, and an 0.016 I.D. needle is used to inject about 100 in a 6 x 50mm tube. Its orientation for the discharge of about 100 of reagent into a dilute sample of about 75 is sufficiently precise to assure the desired reproducibility of peak luminescence achievement and measurement even when the peak occurs less than 5 seconds following the start of pumping by the dispenser 23. The size of the cuvette 29 - ' - ' is preferably chosen so that the final depth of the liquid is between about one and about one and one-half times the diameter of the cuvette to assure prompt thorough mixing occurs. The shutter arrangement accomplishes the effective blocking of ambient light when it is in the closed positon without the use of pressure-bearing seals which are inherently subject to wear and surface imperfections and without the need to hold close manufacturing tolerences. The baffling effect is such that ambient light photons entering the cavity 48 from the top when the cap 65 is removed must travel out through the port 59, then forward through the thin tubular passageway between the shutter elements 33, 37, out the port 41, and then back through the thin tubular passageway interior of the skirt 56 to the rearward-facing port 57. Any photons able to travel through this maze can be attenuated by a light-absorbing pad 128 optionally mounted in the block 35 opposite the port 57 of the closed shutter (FIG. 2) . The shapes of both the outer surface of the rotatable shutter 33, particularly in its enlarged upper portion 49, and of the corresponding regions at the top of the block 35 are employed to minimize the entry of ambient light through this region, and additional rings 64 can be provided if felt necessary for a particular test apparatus. This ring 64, the upstanding collar 61 and an inwardly extending flange 130 are effective in shutting out the entry of ambient light. Although the apparatus has been described with regard to the best mode of construction presently contemplated by the inventors, it should be understood that various changes and modifications as would be obvious to one having the ordinary skill in the art may 0 be made without departing from the scope of the invention which is defined solely by the appended claims. For example, although the injection assembly has been described in conjunction with an overall test apparatus that measures the light emitted from a 5 luminescence reaction, it may also be advantageously employed in other test apparatus where the prompt initiation of a time-critical reaction is necessary to achieve reproducibility of measurement. For example, it can advantageously be used in enzymatic assays, such as - 1 those for LDP wherein knowledge of a precise storting point is important, as well as in kinetic assays, such as those where the glucose content of a substrate is being measured. Similarly, the shutter mechanism has application in other chemical reaction measurement 5 apparutus wherein control of light-transmission is important. Likewise the detent mechanism for securing a removable cap to a rotatable element is expected to have broader application to other test apparatus. Particular features of the invention are emphasized in the claims " which follow.

Claims: CLAIMS; 1. In a luminescence test apparatus wherein a controlled light-emitting chemical reaction is carried out within a light-transmitting receptacle and wherein photometer means is provided for monitoring the amount of light emitted, the combination of an injection assembly for delivering a metered amount of liguid to said receptacle and a shutter mechanism for allowing emitted light from said receptacle to reach the photometer means when in the open position, said shutter mechanism including a fixed shutter element and a rotatable shutter element, said fixed shutter element having a wall portion which is curved in the horizontal plane having a radius of curvature about a central axis of said shutter mechanism and having a first port through which light can pass, said port being located between said central axis and the photometer means, said rotatable shutter element being mounted for rotation about said central axis and including a hollow cylindrical portion of a size sufficient to receive a receptacle therewithin which has a radius of curvature matched to said fixed shutter element and has a second port formed therein, and means for rotating said rotatable element between a closed position and an open position wherein said first and second ports are aligned, said injection assembly comprising an injector having a discharge outlet, and supply means communicating with said injector for supplying liquid, cap means for engaging the upper end of said rotatable shutter having a depending flange which fits downward therearound in the installed position, guide means located along said central axis in surrounding relationship to said injector, said guide means being axially displaceable relative to said injector between an extended position where it extends below the discharge outlet of said injector and a retracted position, said guide means having an inwardly converging bottom surface being adapted for engaging the upper end of a receptacle disposed within said rotatable shutter when in said extended position, and means biasing said guide means to said extended position, said guide means when in said retracted position permitting said injector discharge outlet to project into the interior of an underlying receptable, said inwardly converging bottom surface serving to center the upper end of the receptacle relative to said center axis. 2. The invention of Claim 1 wherein said injector includes an elongated needle located along said central axis, the bottom tip portion of said needle being bent at a small angle from said central axis so that said discharge tip portion of said needle is directed toward a sidewall of the receptacle at a location just above the surface level of a standard liquid sample in the receptacle. 3. The invention of Claim 2 wherein said fixed, shutter element includes an upstanding tubular section which constitutes said wall portion and wherein said rotatable shutter element hollow cylindrical portion fits inside said tubular section. 4. The invention of Claim 3 wherein said rotatable shutter element has a depending outer skirt which surrounds said fixed shutter element and which contains a third port that is aligned with said second port. 5. The invention of Claim 3 wherein said inwardly converging surface of said guide means is a frusto-conical surface. 6. -The invention of Claim 4 wherein said first port is larger than said second port said third port is larger than said first port. 7. The invention of Claim 1 wherein said shutter mechanism is disposed in a surrounding base having a hole in its upper surface that is at an angle of about 10° to 30° to the vertical and generally radial s to said central axis, wherein a detent is slidably disposed in said hole and biased upward by underlying spring means, and wherein said rotatable shutter element has a notch in its outer surface which receives the upper end of said detent when said shutter is in the closed position and prevents rotation thereof until said detent is depressed. 8. The invention of Claim 7 wherein said rotatable shutter element and said cap include interengaging means that mate with said cap in said installed position so that rotation of said cap effects rotation of said shutter element. 9. The invention of Claim 8 wherein said detent has a recess below its upper end that forms an upper head, wherein said cap depending flange has a groove formed in the interior surface thereof which is proportioned to receive said head, the upper surface of which groove engages said head and depresses same when said cap is moved downward into the installed position. 10. In test apparatus wherein a time-sensitive chemical reaction is carried out, an injection assembly for delivering a metered amount of liquid to an underlying receptacle, said injection assembly comprising an injector having a discharge outlet, supply means communicating with said injector for supplying liquid, guide means located in surrounding relationship to said injector, said guide means being displaceable relative to said injector between a lower extended position where it extends below the discharge outlet of said injector and an upper retracted position, said -guide means having an inwardly converging bottom surface being adapted for engaging the upper end of an underlying receptacle when in said extended position, and means biasing said guide means to said extended position, said guide means when in said retracted position permitting said injector discharge outlet to project downward into the interior of an underlying receptacle, said inwardly converging bottom surface serving to precisely position the upper end of the receptacle relative to said injector. 11. The invention of Claim 10 wherein said injector includes an elongated needle having an inner diameter between about 0.010 in. and about 0.040 in., which needle has a straight main portion and a bottom tip portion that is bent at a small angle from said straight portion so that said discharge tip portion of said needle is directed toward a sidewall of the receptacle at a location just above the surface level of a standard liquid sample in the receptacle. 12. In test apparatus wherein a chemical reaction is carried out within a light-transmitting receptacle and wherein means is provided for monitoring such reaction, a shutter mechanism for allowing light flow therethrough when in the open position, said shutter mechanism including a fixed shutter element and a movable shutter element that is rotatable about an axis, said fixed shutter element having a wall portion which is curved in a plane perpendicular to said axis and which has a first port through which light can pass, said movable shutter element including a hollow cylindrical portion of a size sufficient to receive a receptacle therewithin which has a radius of curvature matched to said fixed shutter element and has a second port formed therein, and means mounting said movable element for rotation about said axis between a closed position wherein said ports are about 180° out of alignment and an open position wherein said first and second ports are aligned. 13. The invention of Claim 12 wherein said fixed shutter element includes a tubular section which constitutes said wall portion, wherein said rotatable shutter element hollow cylindrical portion fits inside said tubular section, wherein said rotatable shutter element has a depending outer skirt which surrounds said fixed shutter element and which contains a third port that is aligned with said second port, wherein cap means is provided for engaging the upper end of said rotatable shutter, which has a depending flange that fits downward therearound in the installed position, and wherein interengaging means is provided in said cap means and said movable shutter element so that rotation of said cap means effects rotation of said movable shutter element. 14. Test apparatus which includes a removable cap that is proportioned for installation upon a protruding portion of a rotatable element that is - ■ mounted for rotation in a surrounding base, wherein the improvement comprises said cap being of generally circular cross section and having a depending flange which fits downward around said protruding portion in the installed position, said surrounding base haying a hole in its upper surface that is at an angle of about 10° to 30° to the vertical and generally radial to the axis of said rotatable element, a detent slidably disposed in said hole and biased upward by underlying spring means, and said rotatable element having a notch in its outer surface which receives the upper end of said detent when said rotatable element is in one specific position and prevents rotation thereof until said detent is depressed. 15. The invention of Claim 14 wherein said rotatable element and said cap include interengaging means that mate with said cap in said installed position so that rotation of said cap effects rotation of said element, wherein said detent has a recess below its upper end that forms an upper head, and wherein said cap depending flange has a groove formed in the interior surface thereof which is proportioned to receive said head, the upper surface of which groove engages said head and depresses same when said cap is moved into the installed position. 16. A method of performing an assay using a luminescence reaction, which method comprises disposing a generally round bottom receptacle containing a liquid sample to be assayed into a cavity within test - apparatus, capping said cavity to preclude the entry of ambient light thereinto, opening shutter mechanism so that there is a path therethrough to light-monitoring means, injecting a metered amount of liquid chemical reactant into said receptacle in predetermined amount of time in a manner to create swirling mixing therein about a horizontal axis and measuring the peak light emitted from the luminescence reaction. 17. The method of Claim 16 wherein said chemical reactant is injected as a narrow stream that contacts the sidewall of said receptacle at a location just above the surface level of said sample. 18. The method of Claim 17 wherein said narrow stream is defined by an elongated needle between about 0.01 and about 0.04 -inch in inner diameter and wherein said injecting is accomplished in a time of not more than about one second. 19. The method of Claim 18 wherein the relationship between the receptacle and the amount of chemical reactant injected is such that the depth of the sample plus chemical reactant is not greater than about one and one-half times the diameter of said receptacle.

Inventors: NIELSEN WYN YOLAND, NIELSEN, WYN, YOLAND
Applicants: DIAGNOSTIC SCIENCES INC, DIAGNOSTIC SCIENCES, INC.
Application year: 1983
Main classification: G01N21
IPC codes: G01N21