-*ι ,

This application is a contmuation-in-part application of U.S. Patent Application Serial Number

⁵ 07/425,346, filed October 13, 1989, which is a continuation

⁶ application of No. 07/253,383, filed October 3, 1988, a

7 continuation application No. 07/042,795, filed April 27, 8 1987.

⁹ BACKGROUND OF THE INVENTION ⁰ 1. Field of the Invention 1 This invention relates to a disposable cuvette for 2 holding a test sample or specimen, reagent, and diluent 3 while performing a test in an automated machine, primarily 4 for medical diagnostic purposes. The disposable cuvette can 5 be prepackaged with a dry reagent to which a diluent is ⁶ added during a test or with a liquid reagent thereby ⁷ eliminating the need for the addition of a diluent in an 8 automated test machine. 9 0 2. Description of the Prior Art 1 Cuvettes utilized for manual or automated medical 2 testing are well known. In general, a procedure is 3 established to measure the emergent wavelength of radiant 4 energy absorbed by a sample under analysis. In a manual 5 test, typically a technician loads a cuvette with a sample, 6 reagent and diluent necessary to accomplish the test, each 7 ingredient being precisely measured. The contents are mixed 8 and the emergent radiation is observed optically or 9 ocularly. Because the kind and precise quantity of reagent 0 and diluent employed are critical to a successful test 1 result, technician time and expertise to prepare and use 2 cuvettes are significant factors to be considered with 3 regard to cost, human error, and emergency diagnosis. 4 Preparation time has also become a significant factor with 5 the introduction of automated medical diagnostic machines. 6 Such machines and their corresponding cuvettes have 7 attempted to reduce preparation time by prepackaging various 8 reagents and/or diluents in a container that itself

ultimately houses a test performed therein. U.S. Patent 3,504,376 issued March 30, 1970 to Bednar et al. shows such a system. A significant factor in the use of automated test equipment is that the reagent and the diluent must be mixed prior to the addition of the sample so that the emergent radiation from the reagent-diluent mixture can provide a baseline measurement that is compared to the emergent radiation from the mixture that includes the sample. This factor precludes mixing the sample at the same time the diluent is added to the reagent. In the present invention, the sample or specimen is manually loaded in a separate chamber in the cuvette where it remains until after the reagent and diluent have been mixed and the baseline measurement of the reagent-diluent taken. The use of automated diagnostic test equipment still requires that all ingredients necessary for a specific test be precisel measured regardless of whether the cuvette is preloaded at the factory or loaded at the test site.

The use of multiple, separated compartments in testing vessels with automated machines is shown in U.S. Patent 3,504,376 issued to Bednar et al on March 31, 1970 (cited above) ; U.S. Patent 4,458,020 issued to Bohn et al. on July 3, 1984; and U.S. Patent 4,473,530 issued to Villa.- Real on September 25, 1984. Each vessel shown is a complex in physical structure and requires complex interaction with the test equipment for operation.

Disposal of test containers having the residual samples and reagents therein poses a significant environmental waste problem. Washing and reusing a cuvette is not a good practice because the test results could be affected by a poorly washed cuvette. With the present invention, the cuvette remains sealed after the test and is not reusable.

As the use of prepackaged cuvettes increases in volume, reducing the cost of the manufacture and ^" factor loading of the cuvette also becomes important.

1

² SUMMARY OF THE INVENTION

³ A disposable cuvette for performing

⁴ predetermined medical diagnostic test of a specimen o

⁵ sample in an automated machine comprising a hollow bod

⁶ shaped to form a container (having an open top) for use as

⁷ single reagent chamber. A cover is sealably attached ove

⁸ the open top of said body, said cover having both a

9 aperture for introducing a diluent into the container bod 10 and a specimen receiving chamber with a frangible floor 11 Attached to the cover is a hinged cap that includes a post 12 sized and positioned to pierce the floor of the specime η **>

--- chamber whenever the cap is closed over the cover.

¹⁴ precisely measured quantity of a reagent is loaded into th

¹⁵ container at the factory.

¹⁶ The specimen receiving chamber is integrall

1 1 formed wi •thi •n the cover and includes a frangible botto

18 floor that can be broken open by action of the cap post. Th

19 top of the specimen chamber may be covered by a thin hot 20 stamped film having a central annular opening for receivin 21 the end of a pipette for introduction of the specimen int 22 the specimen chamber.

•*)-*>

The diluent dispensing aperture in the cover m

24 include depressible flaps closely adjacent to each other b 25 separated by an "X" shaped space. The flaps act as a closu 26 for the body reaction chamber, but are easily opened by 27 diluent dispensing device. 28 The cover is joined and sonic welded or otherwi 29 bonded about the upper rim of the container body itself. 30 The cuvette is used for testing a sample 31 specimen as follows. Initially when the cuvette i 32 manufactured and prepared for market, a reagent o 33 predetermined kind and precisely measured quantity for 34 particular test is placed in the container body. The cov 35 is welded to the container body, but the cap, hinged to t 36 cover, is not closed. A bar coded label identifying t 37 particular diagnostic test to be performed in the cuvette 38 affixed to the outside wall of the cuvette body. The cuvet

* is then shipped with the cap in the open position to the site where the test is to be performed. A removable adhesive-backed film may be used to cover the top surface of the cover to prevent contamination prior to use. Once at the test site, after the adhesive-backed film is removed from the cover surface, the cuvette is readied for the automated test by the introduction of the specimen into the specimen receiving chamber in the cuvette cover. This loading is done manually by a technician inserting the end tip of a pipette containing the specimen into the annular opening in the top of the specimen receiving chamber in the cuvette cover.

The cuvette (now loaded with reagent and sample in a separate chamber) is placed into a circular cuvette holder (carousel) within the automated test machine. The cuvette while in place in the carousel is moved through a series of operations in the machine as follows: 1. The carousel moves the cuvette to the ba code reading station. This identifies the test to be performed.

2. Diluent addition is performed at the secon station. An automated dispensing arm pivots into position into the diluent receiving aperture of the cuvette. As diluent fills the reaction chamber, air is vented through the .005 inch diameter holes until diluent reaches the holes and the resulting surface tensions stops the fluid flow.

3. A vibrating action is now started to thoroughly mix the diluent and dry reagent to produce a working unit dose reagent.

4. The machine then measures the emergen radiation from the working reagent to obtain a baselin measurement, i.e. reagent absorptivity only.

5. The machine then moves the cuvette cap to closed position over the cuvette cover forcing the post t break through the specimen chamber floor causing the patien sample (urine, serum, plasma) to flow into the chambe containing the reagent and diluent. The cuvette at thi

1

² point is entirely sealed by the cap.

³ 6. A vibrating action is now started to mix th specimen and reagent.

⁵ 7. There is an incubation followed by a shor

⁶ vibration, then the radiant energy absorption test i

7 performed. The difference in absorptivity of the test minu

8 the baseline reading permits calculation of a result base

9 upon a standard value for that test lot which is supplied b

10 the bar code label to the instrument.

¹¹ 8. The cuvette can now be removed from th

--'- machine and safely discarded because the reacted specime p- ³ cannot escape from the cuvette once the cap is closed. Thi

¹⁴ feature reduces or limits the release of chemicals an

15 reacted patient samples in the hands of medical offic

16 personnel. The cuvette is not reusable. 17 In an alternate embodiment the invention may b 18 used wherein a liquid reagent is introduced into the cuvett 19 at the factory. With this embodiment and the replacement o 20 the dry reagent, the addition of a liquid diluent during th

²¹ machine test is eliminated. In order to prevent leakage o ² the liquid reagent, an additional gasket/plug is provided o

23 the top cover. This is essentially a planar sheet of 24 liquid impervious material and includes on one side a plu 25 sized to fit firmly into the aperture in the cover that wa 26 previously used for the diluent addition. Also the cover ha 27 been modified to eliminate the vents that were required whe 28 adding liquid diluent which is used with the dry reagent. 29 It is an object of this invention to provide a 30 improved cuvette that reduces the time required to prepare 31 cuvette for a specimen or sample test in an automate 32 machine. 33 It is another object of the invention to provide 34 cuvette that reduces the potential for human error b 35 including a premeasured reagent and a reagent-diluen 36 chamber of a predetermined volume when filled for 37 particular diagnostic, medical test that requires a precis 38 reagent/specimen/diluent quantity ratio.

And yet another object of this invention is to provide a disposable, non-reusable cuvette that can be used to safely dispose of the specimen and the reagent after the test is completed. Another object of the invention is to provide a cuvette that is non-complex in manufacture, that is readily pre-loaded with a reagent at the factory, that is easily manipulated by a technician during loading of the diluent and sample, and that is suitable for use in automated diagnostic testing machines. But yet still another object of this invention is to provide a disposable cuvette that can be used with a preloaded liquid reagent at the factory, that does not require the addition of a diluent during the test in an automatic diagnostic testing machine. In accordance with these and other objects which will be apparent hereinafter, the present invention will be described with particular reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of the present invention with the cap in the open position.

Figure 2 is a side elevational view of the invention in cross section, with the cap in the open position.

Figure 3 is a side elevational view of the present invention, in cross section, with the cap in the closed position.

Figure 4 is a top plan view of the invention with the cap in the open position.

Figure 5 is a side elevational view of the invention with the cap in the closed position. Figure 6 is an end elevational view of the invention looking at the end farther from the cap hinge. Figure 7 is an enlarged side elevational view of the invention, in cross section, with the cap in the ope position.

Figure 8 is a top perspective view of an alternat embodiment of the invention that includes (as show exploded) a gasket plug panel that is affixed to the top o the cover. Figure 9 shows a bottom perspective view of th alternate embodiment of the invention. Figure 10 shows yet another embodiment of th invention that is used with a prepackaged dry reagent only. Figure 11 shows a side elevational cross sectiona view of the alternate embodiment construction of the cuvett body and the specimen receiving chamber. Figure 12 shows a bottom perspective view of th cover used in the alternate embodiment of the invention. PREFERRED EMBODIMENT OF THE INVENTION

Referring now to the drawings, and in particula

Figure 1, the invention is shown generally at 10 comprise of transparent body 12 and a cover 20. The cuvette body 12 is a vessel or hollo container that includes end walls 14 connected to side wall 18 and bottom wall 16 forming a hollow rectangular box wit an open top. The body 12 may be molded as one piece from clear acrylic material, which is impervious to moisture o atmosphere. The body material is selected to be sufficientl transparent to permit radiant energy absorption testing of specimen or sample contained within the body which serves a a reaction chamber as will be further discussed. By way o example but not limitation, the dimensions of the cuvett body 12, stated in inches, may be .545 in length, .312 i width, and .545 in height. Of course the dimensions may var widely without departing from the scope of the invention. I is important that the volume of the reaction chamber be suc that the reaction chamber vaan filled acts to provide th exact volume for diluent added to the cuvette for predetermined test.

The cuvette 10 also includes a cover 20 that i sonic welded or otherwise bonded to body 12. The cover 2 provides several elements that are important for th

1

² different operational testing stages in the automated

³ machine.

⁴ As shown in Figures 2, 3, and 4, these elements

⁵ include the sample or specimen receiving chamber formed b

⁶ the cover barrier wall 22 having a vertical passage 22a sealed at its lower end by a frangible, thin floor 36 an

R . . . partially covered at its upper end by a thin film 24 havin a circular opening near its center for receiving the end of in ^u a pi.pette. The cover passage 22a in conj.uncti.on wi.th the

¹¹ bottom floor 36 form the receiving chamber for serum o

¹² sample that is introduced by pipette through the opening i

¹³ thin film 24.

Another important element of cover 20 is a second

15 vertical passage 26a that is partially covered by flaps 26 16 at its upper end. The flaps 26 are flexible and may be 17 opened downwardly by a pipette or other conduit shape 18 injector to permit the introduction of a diluent into the 19 reaction chamber formed by body 12. 20 The cover 20 also has four .005 inch diameter ven 21 holes 44 that are very important in the operation of th 22 cuvette. The vent hole diameter is sized appropriately s that air is vented to the outside as the diluent flows into

24 the reaction chamber. When the chamber is full, the surface 25 tension created by the .005 inch diameter holes prevents an

26 overflow of diluent through the vent holes 44. 27 The cover 20 includes a cap 28 attached by hinges 28 30. Protruding from one side of cap. 28 and substantially 29 perpendicular thereto is a lancet-like post 34 having 30 "cross" shaped cross section relative to its longitudinal 31 axis. The post 34 is sized in length and positioned relativ 32 to hinges 30 such that when cap 28 is closed over cover 20, 33 post 34 will be moved into passage 22a (serum receivin 34 chamber) piercing an opening in floor 36. The floor 36 i 35 connected to the chamber side walls 22a such that it canno 36 be detached by the action of post 34. (If detached, floor 36 37 might interfere with light passage through the cuvette.) 38 Also attached to cap 28 is a latch 32.

After the serum or sample has been manually adde to the receiving chamber 22a, the cuvette is now ready to b loaded into an automated testing machine. Note that the ca 28 is in the open position when the cuvette is placed in th test machine. Once in the machine, the cuvette bar cod label is read and the test parameters are automatically set Next the diluent is automatically dispensed into the cuvett and a vibrating mixing action takes place. After the reagen and diluent are fully mixed, a baseline radiant energ absorption reading is taken. After this initial measurement an interposer with roller bearing mechanism (not shown) i the machine closes the cap 28, and the cuvette, now sealed is vibrated. As the cap 28 is closed, the post 34 break through the sample chamber floor 36, allowing the sample t be mixed with the reagent-diluent mixture, aided by th vibration. With the cap in the closed position, the cuvett is completely sealed such that its contents cannot escape The cap 28 is fastened by the engagement of latch 32 with flange on bar 40. The machine can now complete the test o the sample.

The cover 20 may be made from high impact styren and sonic welded to the upper rim of body 12. Hinges 30 an cap 28 may be formed with the cover 20, with hinges 30 bein "living" hinges.

Figures 5 and 6 show the cuvette 10 after the ca 28 is closed. The cuvette, in accordance with the inventio described herein, is designed for use in an automate testing machine. The cap 28 includes parallel ridges 28 that project above the upper surface of cap 28 to act as ca stiffeners and a bearing contact surface for mechanicall closing the cap.

Figure 7 shows the cover 20 and the serum o sample receiving chamber 22a and molded bottom floor 36 wit a thinner flash section 36a (formed in an "X" shape) t provide break lines when the post 34 applies pressure as th cap 28. is closed. .

The top of the serum chamber 22a is partiall

1

² covered by hot stamped film 24. Film 24 has a small opening

³ burned in the center to act as access for the end tip of a

4 pipette containing serum or sample and also to wipe the 5 pipette tip dry as it is removed from the chamber 22a. 6 The top surfaces of the diluent access area (flaps 7 26 and adjacent area) are made parallel to the underside

⁸ surface of the cap 28 that abuts the diluent access

9 perimeter in order to provide a parallel seat for the 10 machine actuated, diluent dispenser tip and achieve a good

¹¹ seal when the cap 28 is closed.

¹² Figures 1 and 7 show vent holes 44 that aid in the • filling of the reagent chamber with diluent by allowing air that would otherwise be trapped in the reaction chamber to ¹ escape. Note that the diameter of each vent hole is sized so

16 that diluent will not escape through the vent holes because

17 of the surface tension of the diluent over the vent opening.

However, the vent holes are sealed from the ambient air when 19 the cap is closed. After the test has been completed, the

20 cuvette can be safely discarded because the contents are p*|

- ^{~ ~} - sealed from the ambient surroundings. pp

The cuvette and the specific test to be performed

23 therein (dependent upon the kind and quantity of reagent it 24 contains) is identified by labels 46 adhesively attached to 25 each side 38 of the cover. One label on one side would have 26 a machine readable bar code while the other side label would 27 display a letter or number code that is easily identified by 28 the test operator. pq

-- Referring now to Figure 8 an alternate embodiment

³ of the invention is shown which is used with a liquid

31 reagent. The liquid reagent is prepackaged in the cuvette at 32 the factory. By using a liquid reagent, it is not necessary 33 to provide the liquid diluent required with a dry reagent in 34 the automated test device when performing a test. Therefore, 35 in general, the cuvette 110 is modified (1) by eliminatin 36 the vent holes which are required when using a dry reagent 37 that requires diluent and (2) by adding an additional 38 sealing panel 144 which will be described in greater detail

below. The cuvette 110 is comprised of a hollow body 11 (providing a rectangular parallelepiped interior chamber that includes side walls 118 uniformly molded as a singl unit with end walls 114 and a bottom wall 116 (Figure 9 forming a hollow receptacle for receiving a liquid reagent prepackaged at the factory. The side walls 118 include a optically clear window 118a on opposite side walls 118 t permit the optical or ocular testing for the liquid reagen alone and when subsequently mixed with the specimen. On locating key 156 is centered on each side to locate th cuvette with respect to the automated testing machine.

The cover 120 is ultrasonically or otherwis bonded to the body 112 and includes a circular aperture 12 and a flat top wall 122 that includes a specimen chambe formed by side walls 122a and bottom trap doors 136 whic are sealed together initially but are frangibly openable b action of post 134 when the cap 128 is closed in th automated test machine. A purge reservoir 124 for purgin the diluent dispenser tip in the automated equipment i provided to wash out residual reagent and prevent carry ove into the next or following cuvette which may contain different reagent. The cover 120 includes a pair of arche side members 138 which function and interact with th automated machine as a roll down surface.

A sealing panel 144 is employed solely with cuvette using a liquid reagent, eliminating the need for diluent. The upper surface of top wall 122 also include grooves 154 longitudinally disposed along each edge whic receive glands 152 in the gasket/plug sealing panel 144 t firmly seal panel 144 over the cover surface 122. The pane 144 also includes an aperture 150 which permits access t the specimen chamber defined by walls 122a so that th specimen can be added to the specimen chamber.

The cap 128 includes a modified post 134 havin inclined surfaces 134b terminating in knife-like edge en tip 134a which acts as a plunger for piercing the specime chamber trap doors 136 at the centerline of the doors t

ensure proper separation to effect direct hinge action of the doors 136 to release the specimen into the cuvette body 112 containing the liquid reagent.

Referring now to Figure 9 the cuvette 110 is shown from a bottom perspective view disclosing the bottom wall 116 having an optically clear window 116a which permits fluorescent polarization and nephlometric type tests.

The cap 128 is unitarily connected by a hinge 130 which also acts to seal the end of the cuvette when the cap 128 is closed over the cover 120.

The cap 128 includes a pair of parallel ridges 160 which interact with the automated machine and rollers for closing the cap 128 and resulting in a secure latching of the cap.

A pair of snaps 132 which are integrally formed with the cap 128 are engaged into slot edges 140a at the opposite end of cover 120 to firmly attach the cap to the cover when the cap is closed resulting in a leak-proof seal.

Referring back to Figure 8, in the manufacture of the liquid reagent model, the plug/gasket sealing panel 144 is firmly attached at the factory to the top of cuvette cover 120 after the liquid reagent has been inserted into the cuvette body 112 chamber. With the panel 144 attached, the liquid reagent is sealed tightly within the cuvette by action of the panel 144 which includes plug 148 received into aperture 126 and the fact that the specimen trap doors 136 in the specimen chamber 122a are also sealed.

To perform a test using the liquid reagent model, the specimen is added to the specimen chamber 122a at the testing site, which may be a doctor's office, laboratory or the like. The cuvette 110 then is inserted into the automatic testing machine in the cuvette's cap open position as shown in Figure 8. The automated machine can first test the liquid reagent alone in its present state (before the specimen is mixed) while the cuvette 110 is located at a test station in the automatic testing machine. After a first measurement of the liquid reagent is obtained, optically or

ocularly, then the testing machine closes the cap 128, causing the post 134 to fracture and open the two incline trap doors 136 causing the specimen to be received into th interior chamber of cuvette body 112 containing the liqui reagent. The cuvette is then boosted for mixing, causing rocking action on its radius corners adjacent the botto floor 116, greatly increasing the mix action. A secon measurement is then obtained optically or ocularly of th liquid reagent-specimen mixture and the results calculate by the testing machine.

A raised sealing bead 142a (Figure 8) is dispose about the surface of cap surface 142. The bead is a raise portion such that when cap 128 is closed firmly agains panel 144 (made of a silicone rubber) , the bead 142a will b impressed into the silicone rubber of panel 144, forming a tight liquid impervious and air impervious seal about th cover top surface 122 including the purge chamber 124.

Referring now to Figure 10, a modified cuvett 110a for use wittr a prepackaged dry reagent (powdered o capsule) is shown which is inserted in the cuvette body 112. Note that in this embodiment the plug/gasket panel 144 (Figure 8) is not used. The aperture 126 acts to receive diluent dispensing probe in the automated machine (no shown) for dispensing diluent into the cuvette body 112 tha houses the dry reagent. The diluent is added at the tes site while performing the test in the automated machine. Th purge reservoir 124 collects diluent purged from the diluen dispensing tip (not shown) after the dispensing tip has bee withdrawn from aperture 126 during the testing process. I this alternate embodiment three vent slots 162, 164 and 16 are provided which collectively allow for air to escape fro the cuvette body 112 while the diluent is being added.

A thin frangible film 168 of hydrophobic metrice polypropylene is used to cover the vent holes 162, 164 an 166 and diluent aperture 126, specimen chamber 122a and th purge reservoir 124. The film 168 is gas permeable whic allows air to vent through the vent slots during diluen

dispensing while also allowing easy fracture for insertio of the specimen into the specimen chamber 122a. The film 16 provides another benefit in that the sealing beads 142a i cap 128 will also engage the thin film when the cap 128 i closed and locked over cover 120 again ensuring that th cuvette is sealed after the test is completed. The film i attached to the cover surface by a suitable glue. In this embodiment the cuvette 110a function similarly to the original cuvette 10 discussed in Figures through 7 with regard to the powdered and capsule reagent in term of operation and the automated machine.

Figures 9 and 11 show another improvement in th alternate embodiment of the invention that functions with carousel in the automated test machine which carries eac cuvette through the automated test machine. As shown i Figures 9 and 11, the side end wall 114 includes, on eac end, a lateral, concave channel 114a which acts to receiv snap legs -which are in the automated test machine (no shown) to firmly hold the cuvette in position relative t the carousel and the machine. Also the lower corners 114 formed by the side walls 114 and the bottom wall 116 hav equal predetermined radii of curvatures. At a particula stage in the automated test machine, the curved corners 114 engage surfaces having comparable curvatures on the sna legs to produce a rocking motion whenever the carousel i moved backward and forward to induce vigorous mixing withi the cuvette after the specimen has been introduced to th reaction chamber and the cap is closed. Thus the curved en portions 114b while engaging a similar surface of curvatur on the snap legs will permit a rocking motion back and fort for improved mixing action. The bottom wall surface 116 i substantially flat to permit a roller or wheel in th automated test machine to raise the cuvette, disengaging th snap legs from the snap leg detent 114a at the mixing stag in the machine. Thus the cuvette is configured on it outside and bottom walls to allow the snap legs in th automated testing machine to accomplish the dual purposes o

allowing for rocking the c vette for mixing while in th other stages to secure the cuvette in position in th carousel.

Figures 11 and 12 show the specimen receivin chamber defined by walls 122a and bottom trap doors 13 which are sealed together along a frangible center line 136 forming the bottom of the specimen chamber 122a

The bottom trap doors 136 are inclined to reduc possible trapping of bubbles when diluent or liquid reagen are dispensed through aperture 126. In their initial stat the hinged doors 136 are joined together and to the wall

122a of the specimen chamber so that the compartment i sealed from the body 112 chamber. The post 134 size an shape is configured to more

easily fracture and open the trap doors 136 in the specime chamber when the cap 128 is closed tightly over the cover o the cuvette. In the cross section as shown, the linea weakened portions 136a and 136b between the walls 122a an the doors 136 form an "H" shape. The trap doors 136 remai sealed until forced open by the post 134 which causes th centerline 136a and the wall edges 136b to frangibly detac forcing the doors to open mu: like a pair of trap doors Note that the bottom floor is inclined relative to th horizontal which aids in dispensing the specimen into th reagent containing chamber 112. Note also from Figures 8 an 10 that the post 134 end tip includes a pair of incline surfaces 134b terminating in the edge 134a which meets th centerline 136a of the trap doors 136 when the cap is close aiding the doors 136 to spread open from the cente position. This allows the specimen to be completely receive into the mixing chamber 112a where it mixes with either th dry reagent and diluent mixture or with a liquid reagent.

Figures 11 and 12 also show hinge 130 tha connects the cap 128 (partially shown) unitarily to th cover 120.

The present invention provides a disposable, non

reuseable cuvette that allows a technician in a doctor's office or laboratory to perform a variety of medical diagnostic tests quickly, safely, accurately and inexpensively by significantly reducing the technician loading activities required and the structural complexity of the cuvette and its interaction with the testing machine.

The i.nstant i.nventi.on has been shown and described herein m what it is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.