CLINICAL ANALYSES METHODS AND SYSTEMS

Abstract: Mixing technique particularly useful as part of the process for the clinical analyses of liquid biological samples. The sample is placed in a cuvette (24) along with a reagent (44) and a diluent (52). The top (opening) (117) of the cuvette (24) is squeezed (reduced in size) and an air jet (J) is directed against the liquid surface formed in the cuvette (24) adjacent the junction of the liquid surface with the wall of the cuvette (24) to create a vortex to produce thorough mixing of the contents of the cuvette (24) and substantially prevent any splashing of the liquid contents.

Description: CLINICAfr ANALYSIS ϋLEϊHΩΩS U £I≤I£M≤ pACKgROϋWP Ω£ Xfifi INVENTION i. Ei≤lΔ QΣ. tn≤ Invention This invention relates generally to the mixing of materials and to the analysis of the results of such mixing. In particular, the invention relates to improved etnods, apparatus and systems for mixing materials and the analysis of the results of such improved mixing. The present invention is particularly useful in automated chemistry analyzers for determining the presence and levels of one or more selected constituents in relatively small biological liquid samples. ii. escri TPion ς∑ fcώ≤ griar his. Numerous automated clinical analyzers are known and widely used in hospital clinical laboratories. An example of sucn an analyzer is the multi-channel type analyzer. A multi-cnannel analyzer is one in which a series of different tests are performed simultaneously by the analyzer, and in paral lel with one another. Such an analyzer can be best visual ized as a series of batcn analyzers operating in parallel wherein each channel performs a singl e analysis test. Tne multi-channel type analyzer general ly utilizes a liquid reagent to react with the particular constituent being tested in tne sample and a pnoto-optical system to read the optical absorbence of the sample wnich corresponds to the level of the constituent in the sample. Although this type of automated analyzer has received wide acceptance in the clinical laboratory certain drawbacks are associated with its use. For exampl e, altnougn tne multi-channel type analyzer is reliable due to its simplicity, cost effective for large number of samples and nas a relatively nign test throughput rate, it is l imited in the sense that it can only be effectively util ized to perform a singl e constituent analysis at a time on a relatively large number of sampl es. In addition, sucn analyzers are not capabl e of performing emergency "stat" tests due to their rel atively long and complex set up time and their inherent inahil ity to economical ly analyze a singl e test sample. A further significant disadvantage found is that altnougn tney can simultaneously perform tests for multiple constituents on the same sample, generally all of tnese tests must be performed for every sample wne her desired or not. This results in a waste of botn sample material and the reagents used in the unnecessary tests. Furthermore, due to the fact that multiple discrete and dedicated channels are utilized in such an instrument, there is significant duplication of numerous components which adds to the complexity and expense of tne overall instrument. An automated single track clinical analyzer which avoids tne above-described drawbacks is described in commonly owned U.S. Patent Application Serial No. 284,840, filed July 20, 1981 entitled, "Automated Analysis Instrument System". By using a unique photo- optical system, described in commonly owned U.S. Patent Application Serial No. 284,841, filed July 20, 1982 entitled, "Multichannel Spectropnotometer", greater flexibility of analysis at each analysis station is acnieved. Tnis is because the pnoto-optical system employs fiber optic bundles or similar light guides to transmit variable wavelengths of light to each analysis station from a single light source. Tne single track analyzer utilizes a disposable cuvette belt formed from thin plastic film and defining a series of discrete reaction compartments (cuvettes) which are transported in line ahead through the instrument. Such a cuvette belt is described in commonly owned U.S. Patent Application Serial No. 284,842, filed July 20, 1981 entitled, "Cuvette System For Automated Chemical Analyzers". This belt provides nandling flexibility and avoids the cross-contamination associated with flow-through cuvettes as well as avoiding tne wasning required for reusable cuvettes. Tne earlier clinical analyzers discussed above employed liquid reagent, and mixing of the reagent with the diluent prior to addition of the biological sample. On ' method of achieving such mixing was by shooting a stream of tne liquid reagent into the cuvette so as to produce a vortex-type mixing process. A preferred feature of the analyzer disclosed in U.S. Patent Application Serial No. 284,840 is that it is adapted to utilize dry particulate reagents, preferably in tablet form, which are dispensed into tne cuvettes from a rotating carousel wnich can hold a large number of doses. A preferred embodiment of tablet dispenser is described in commonly owned U.S. Patent Application Serial No. 285,022, filed July 20, 1981 entitled, "Tablet Dispensing Device". In order to effect dissolution of tne dry particulate reagent within the diluent prior to addition of the biological sample, tne reagent and diluent are mixed by ultrasonic means. An improvement in the reliability and controllability of tne analysis of liquid samples, particularly liquid biological samples, is achieved by mixing tne contents of tne cuvette after addition of tne sample by directing an air jet at an acute angle against the surface of tne liquid in the cuvette. Particularly good mixing is obtained when the air jet is directed at tne liquid surface adjacent its junction with the wall o tne cuvette. Tne optimum point of contact of the air jet witn tne liquid surface is the meniscus formed at tne junction between the liquid surface and the wall of tne cuvette. Tne combination of directing the air jet against the liquid surface adjacent its junction with the wall of the cuvette and directing it at an acute angle to the surface producing a norizontal component has the beneficial effect of creating a vortex which produces a thorough mixing of the contents of the cuvette. Thus, a whirling or circular motion is induced in the contents tending to form a cavity of vacuum in the center and to draw the materials at the edge towards tne center tnus providing an effective mixing action. Particularly wnere the air jet hits the contents of the cuvette in tne meniscus region, the contents tend to De raised up the wall of the cuvette opposite where the air jet hits tne contents creating a particularly effective vortex producing very good mixing of the sample witn tne diluent and reagent. Thus, a particulate reagent will become totally suspended within the diluent and tne sample optimizing the reaction of the sample therewith. This improved mixing tecnnique is described in commonly owned U.S. Patent Application Serial No. 575,924, filed February 1, 1984 entitled, "Clinical Analysis Systems and Metnods", the disclosure of wnicn is hereby incorporated by reference in its entirety herein. 87/0 -6- ≤IMMΔfiX QΣ X&Z INVENTION In several of the prior clinical analyzers as described above, the reagent and diluent are mixed in the cuvette prior to the addition of the liquid biological sample, either by snooting the reagent into the diluent to form a vortex in tne case of a liquid reagent or by ultrasonic mixing in the case of the dry particulate reagent. The present invention seeks to improve over both of tnese tecnniques. It nas ύeen found in accordance with the present invention tnat improved reliability and controllability of the analysis of tne samples is achieved by providing an improved swirl path during mixing and at the same time minimizing splasning of the sample. It is tnerefore an object of tne present invention to provide an improved method, apparatus and system for mixing materials and for analyzing the results of such mixing which are substantially devoid of many disadvantages of the prior art and wnicn also represent a substantial improvement over the prior art. Anotner object of the present invention is to provide an improved swirl path during mixing. Still another object of the present invention is to minimize splash of the liquid while providing an improved swirl path. Thus splasning of the contents out of tne cuvette leading to intercuvette contamination can be avoided. Still another object of the present invention is to provide a system for mixing materials which will allow keeping the mixing pressure at very nigh levels to acnieve excellent mixing witnout causing any of tne problems associated with splashing. Tne foregoing objects and others are accomplisned in accordance with the present invention by providing an improved method, apparatus and system for mixing materials, particularly biological liquid samples, and for analyzing tne mixed materials wherein tne materials are placed in a cuvette and an air jet is used to agitate tne materials sufficiently to cause the materials to mix. It is a critical step in accordance with tne present invention that during tne air jet mixing process, tne top (opening) of the cuvette is squeezed to reconfigure it and reduce the size of the opening. In an automated system, tne cuvette is partially filled to a predetermined liquid level and then advanced into alignment stationarily beneath a fixed nozzle so that tne latter is aimed at tne junction of liquid surface and cuvette wall at which time the top (opening) portion of tne cuvette is squeezed or reduced in size. Tne angle of tne air jet nozzle should ideally be as far as possible from the vertical providing maximum norizontal components of the air j et upon the liquid. Tne angle is determined oy tne diameter or the cuvette, tne liquid level in the cuvette, wnich is itsel f controlled by tne requirement to avoid splashing of the contents out of the cuvette, and the position of the noz _z> le over the moutn of the cuvette. Wnile it is preferred, particularly in an automated process, tnat tne air jet nozzle direct air into the cuvette from outside the cuvette, it is within the spirit and scope of this invention to direct the air jet from inside the cuvette and aimed at the liquid surface from a position above the liquid surface. While requiring insertion and removal of the nozzle into and out of tne cuvette (eitner by lowering and raising the nozzle or by raising and lowering the cuvette) tnis does nave tne advantage tnat the nozzle can oe angled more closely to the horizontal without spilling of tne contents. Thus, tne nozzle may be inclined at an angle of between about 0 degrees to about 90 degrees to the horizontal, with the preferred angle of between about 8 and 15 degrees. Depending - upon tne neight of the nozzle above tne liquid surface, it may become contaminated by the liquid during agitation in wnich case tne nozzle snould be cleaned witn diluent between mixing operations. It will be noted tnat in tnis embodiment as well as in that described above, tne nozzle is arranged above the liquid surface and is therefore non-invasive of the liquid. Tne present invention permits thorough mixing of the reagent, diluent and sample which enhances reliability and controllability of the test(s) of the sample. The mixing process occurs in a very fast time frame. Intercuvette contamination is avoided by reducing the size opening of the top of the cuvette and controlling tne mixing action so that splashing of material out of tne cuvette is prevented. There is no physical contact between the nozzle and the contents of the cuvette, and by naving tne nozzle arranged outside the cuvette, contamination of the nozzle is avoided and there is no need to move any component into tne cuvette to effect the mixing, tnus maximizing througnput in an automated process. Wnil e the unique air j et mixing system of this invention nas particular appl ication to the mixing of biol ogical sampl es in cl inical analyzers as described above, it also has general application to the mixing of liquids with one or more other l iquids or solids. DESCRIP ION ££ &E Otner features and advantages of tne present invention will become apparent from tne following description taken in conjunction witn the accompanying drawings wherein: Figure 1 is a schematic pl an v iew of an automatic clinical analyzer that can incorporate the features of the present invention; Figure 2 is a partial perspective view of the automated clinical analyzer shown in Figure 1; Figure 3 is a perspective view of a cuvette belt for use in the clinical analyzer of Figure 1; Figure 4 is a schematic side el evation of a mixing apparatus; Figure 5 is a partial perspectiv e view showing tne relationship of a mixing apparatus and apparatus for reducing the opening of the top of a cuvette during mixing in accordance with the features of the present invention; Figure 6 is a top pl an view of a cuv ette prior to tne top opening tnereof being squeezed during the mixing process; Figure 7 is a top pl an view of the cuv ette shown in Figure 6 as the top opening is squeezed by the apparatus illustrated in Figure 5; Figure 8 is a top plan view of the cuvette snown in Figure 7 af ter it has passed through the apparatus snown in Figure 5; Figure 9 is a schematic side elevation view snowing tne mixing action produced when tne apparatus in accordance with the present invention is in use; and Figure 10 is a schematic side elevation view of a second embodiment of mixing apparatus suitable for use in tne clinical analyzer of Figure 1. DESCRIPTION QE PREFERRED Figures 1 and 2 illustrate, as one example, an automated clinical analyzer 10 generally described in the aforesaid U.S. Patent Application No. 575,924 that can incorporate the features of the present invention. More particularly, the analyzer is a Paramax Analytical System as manufactured by American Hospital Supply Corporation. Tne analyzer 10 is particularly adapted for the testing of constituents in biological fluids, sucn as blood samples. Tne analyzer comprises a series of processing stations past wnicn strips of disposable reaction cuvettes are indexed or advanced. The cuvettes 24 are supplied from a supply reel 20 as a continuous cuvette belt 22 and are indexed through the analyzer by tractor conveyor 30 wnich engages a row of index holes in the cuvette belt. Tne cuvettes are indexed in turn past the following stations: a belt cutter 28 for dividing the belt into sections; a tabletted reagent dispenser 40; a diluent and liquid reagent dispenser 50; an ultrasonic mixing horn 14; a sample dispenser 80 for dispensing Dioiogical samples delivered by a transfer carousel 64; an air j et mixing apparatus 15 including an apparatus for squeezing the top (opening) of the cuvette during tne air j et mixing process (shown and descr ibed nereinbelow) , according to the invention for mixing the sample witn the reagent and diluent in the cuvettes and substantially preventing splasning of the sample; eight photometric read stations 90 ; a f urther reagent dispenser 54 ; a further air j et mixing apparatus 15a for mixing the sample and the further reagent ; a cuvette sealer 26 and a cuvette col lection station 18. During their passage tnrougn the analyzer, the cuvettes are carried in a water bath 12 maintained at a constant temperature. The cuv ette bel t 22 is pref erably constructed and made in the manner more ful ly described in af o resaid U. S. Patent. Appl ication Serial No. 284,842. As snown in Figure 3, the belt 22 comprises two strips 111, 112 of transparent flexible plastic material which are moulded and sealed together to form a series of discrete, side-by-side parallel compartments (cuvettes) 24 separated by webs 115. Tne cuvettes are formed of a plastic material whicn is sufficiently flexibl e to enabl e the top to be squeezed so that the tops (openings) thereof are partially closed during the mixing process and then return to their normal top ( pening) position when the squeezing action is stopped. The compartments are closed at one end and have a top or opening or open moutn 117 at the other end so as to receive and retain fluid therein. For example, the cuvettes can be in the order of size so as to be capable of holding about 500 icroliters of fluid. The flat web material 115 between the vessels 24 includes a transport strip portion extending alongside the closed ends tnereof whicn is formed with indexing perforations or noles 26. These perforations are engaged by the tractor transport 30 of- the analyzer 10 for conveying the cuvettes therethrough and maintaining a precise alignment of the optical paths through tne cuvettes with the pnoto-optical examining system at the analysis stations 90. Tne transport 30 comprises a single continuous guide and support track extending througn the analyzer having a main tractor belt 32 which engages the indexing holes 26 in the cuvette belt 22 and advances the cuvettes through the instrument at a predetermined rate of advance. A short loading belt 34 threads the cuvette belt 22 into engagement with tne main tractor belt 32. The transport 30 advances or indexes the cuvettes tnrough the analyzer 10 in steps corresponding to the spacing between cuvettes (the pitch of the belt) with tne cuvettes being stopped and held stationary for a dwell period between each advance. Each step may suitably correspond to a time interval of 5 seconds witn a 4 second dwell time between each indexing advance of tne cuvettes. The reagent tablet dispenser carousel 42 comprises a circular array of tabletted reagent dispensers 40 and can be rotated to bring the correct solid reagent dispenser to solid reagent dispensing point "SRD" to drop a single reagent tablet 44 into a cuvette 24. As illustrated, tne carousel 42 accommodates thirty-two reagent tablet dispensers 40. It is rotated under microprocessor control to bring the correct tablet dispenser to the dispensing point for each cuvette. Tne dispensers 40 are detachable and can be loaded randomly. An automatic flagging system indicates when a dispenser is low in tablets. The diluent and/or liquid reagent dispenser 50 is located adjacent to carousel 42 for adding sufficient diluent 52 for reagent tablet 44 dissolution and/or for dispensing a liquid reagent into the reaction vessel (cuvette) 24 at point "LDD". Tne ultrasonic norn 14 acts on the cuvette contents for a sufficient length of time; for example, 45 seconds, to totally dissolve the reagent taolets. A sample loading and transfer carousel assembly 60 is lo cated downstream of the reagent and di l uent dispensers. Tnis carousel assembly comprises a loading carousel 62 into wnich patient samples 70 are randomly loaded. It also includes a transfer carousel 64 wnich accepts tne patient samples 70 from loading carousel 62, identifies the patient sample by means of a bar code reader 66 which reads a bar code label 72 placed on tne patient sample container and continuously feeds tne patient samples into the system. Finally, an unloading carousel 68 receives the patient samples 70 after testing and stores them in an organized manner in the event tnat they must later be located and retrieved. Tne loading carousel 62 permits continuous random loading of up to 96 patient samples. The transfer carousel 64 continuously feeds patient samples into the system for maximum tnrougnput. Standard collection tubes or microsample tubes may be accommodated thus allowing utilization of tne same containers in which the sample is collected; for example, in the case of blood samples, the "Vacutainer" tube which is commonly used to draw the serum specimen. Sample 80 for dispensing samples into the cuvettes 24 at point "SD" is located adjacent to transfer carousel 64. This sampler is designed to aspirate about 2 to 20 microliters of patient sample 70 from its container in tne transfer carousel and dispense it into a cuvette 24 during the four second dwell period while the cuvette is aligned with the sampler. Tne air jet mixing apparatus 15 (and 15a) directs an air jet, preferably at an acute angle, against the liquid surface in the cuvette adjacent its junction with the cuvette wall to create a vortex. The vortex produces a thorougn mixing of the sample with the reagent and diluent in accordance with the teachings of tne system as descrioed in the aforesaid U.S. Patent Application No. 575,924. In a preferred embodiment, the apparatus nas a fixed, inclined nozzle 150 and the cuvettes 24 are aligned in position beneath the nozzle and the air jet is switched on only during the dwell period when the cuvette is stationery. In order to ensure that the air jet correctly strikes the liquid surface, the liquid level is closely controlled. Eight photometric analysis stations 90 are located at points n SAl" through "SA8" along the cuvette track 30. The station "SAl" is arranged following the ultrasonic horn 14 for verifying proper reagent dispensing and dissolution. The second reagent dispenser 54 permits furtner reaction of the sample to be obtained following initial testing and is shown arranged between analysis stations "SA4" and B SA5 n . It could be located between any of tne analysis stations "SA2 n to "SA8 n . This capacity for optional reagent additions or triggered reaction capability gives added analytical versatility for multiple reagent test situations. The furtner air j et mixing apparatus 15a provides for tnorougn remixing of the cuvette contents fol lowing addition of further reagent at station 54. The cuvette sealer 16 seals the tops of the tested cuvettes for convenient clean disposal of completed samples at the cuvette disposal location where they are neatly collected into a lined disposal bin. The microprocessor control system of the clinical analyzer, which suitably has a 280 processing unit, controls all the operating units thereof in accordance with sample and test information inputted at a suitable operator interface keyboard. In accordance with the desired test results, quantities of a single sample may be dispensed into one or more cuvettes either alone or in combination with any one or more of the solid and liquid reagents and diluents, and examined at any one or more of the analysis stations 90. Test results are displayed on a screen and can be printed out. Turning now specifically to tne features of the present invention, tnere is shown in Figures 4 - 8 embodiments of a mixing apparatus together with an apparatus for reducing the top (opening) of the cuvette during the mixing process, according to the present invention, suitable for use on the above described automated clinical analyzer 10 at mixing station 15. Figure 4 snows an embodiment of mixing apparatus 15 comprising a nozzle 150 arranged above the path of the cuvettes 24 with wnich the cuvettes are in turn aligned so that the nozzle is directed preferably at an acute angle at tne junction between the surface of the liquid in the cuvette and the wall of the cuvette. The nozzle 150 is ixed in position. In order to insure that the air jet J produced thereby is properly coordinated with the liquid surface in the cuvette so that it strikes the surface at the junction tnereof with the cuvette wall, the quantities of reagent, diluent and sample are closely controlled so that the liquid in all the cuvettes is at a constant preset level. (One exception to this is where the sample is dispensed into a cuvette alone for sample blanking and mixing is not required.) Tne nozzle 150 is mounted on a frame 151 so that its orifice is just above the tops of the cuvettes witn sufficient clearance to avoid interference with the cuvettes as they are advanced. It may, for example, be about 0.7 mm above the tops of the cuvettes. While the nozzle is fixed in position during use, the frame 151 may incorporate means for adjusting the angle of the nozzle either manually or automatically during set-up or between runs. A valve 152 is provided for controlling the supply of air to the nozzle 150 from an air supply 153 to which it is connected by an air line 154. Operation of the valve 152 is by means of a controller 155 connected to the analyzer's microprocessor. As explained above, the cuvettes are indexed stepwise tnrough tne analyzer along track 30 and each cuvette is positioned stationarily in alignment beneath the orifice of the nozzle 150 during the dwell period between advancing steps. Activation of the air jet J is limited to this dwell period so that the cuvettes are stationary during mixing. A critical feature of tne present invention is illustrated in Figure 5 through 8. As snown in Figure 5> an air jet mixing apparatus, such as air jet mixing apparatus 15, includes a means to squeeze the top (opening) of the cuvette to reconfigure it during the application of the air jet mixer process. This is acpomplisned by guiding one edge of the cuvette by a fixed rail 170 and squeezing the other side of the cuvette towards it by a bracket 171 which acts as an obstacle in the path of the cuvette as it passes into and through the air jet mixing station. The net effect of this apparatus is that when the cuvette has been positioned at the air jet mixer for mixing the material therein, and is in a stationary position ready for mixing, the top (opening) portion of the cuvette is squeezed partially closed and neld in that position during tne mixing process. The squeezing or reconfiguring of the top (opening) or moutn of tne cuvette minimizes the opening to provide a better swirl path during the mixing process and also minimizes splash of the liquid contents. It has been found in accordance with the present invention that best results are achieved when the cuvette top (opening) is squeezed (closed up) to about 75 percent of tne original top (opening) size. Tne overall (before, during and after) effect on the top (opening) of a single cuvette 24A is best illustrated in Figures 6 through 8. The cuvette 24A illustrated in Figure 6 shows the top (opening) of a cuvette just prior to entering the air jet mixer station. In Figure 7 there is illustrated the top (opening) of cuvette 24A as it looks squeezed between fixed rail 170 and bracket 171 (See Figure 5) with the nozzle 150 of the air jet mixer in place ready for mixing. Figure 8 illustrates the cuvette 24A top (opening) after passing through the fixed rail and bracket squeezing apparatus. By directing the air jet J at an acute angle at the junction of tne liquid surface in the cuvette with the partially closed top (opening) portion with the cuvette wall, preferably so that the air jet hits the meniscus at tnis junction, a vortex is created which produces a thorougn mixing of the contents of tne cuvette. This mixing is such that even a reagent which is particularly immissible in tne diluent becomes totally suspended within the diluent and the reaction between tne reagent and the sample is more complete and rapidly ahieved. Figure 9 shows a representative pattern of such mixing within tne cuvette by the air jet J. However, the exact pattern of mixing taken by the material may be any suitable one. By ensuring that the air jet hits the liquid surface in the meniscus area, very good mixing within the material is achieved. During such mixing, it is seen that the materials climb the wall of the cuvette opposite the point where the air jet strikes tne liquid surface. This is depicted by the dotted swirling action behind the air jet at the right- hand side of the cuvette in Figure 9. By squeezing (closing) of the top (opening) of the cuvette as shown, all of the advantages of the present invention are achieved. The use of an air jet to mix tne contents of the cuvette in the manner described has been found to work surprisingly well considering the relatively small amount of fluid being mixed and the relatively small confines of the cuvette in which the mixing has to take place. Specific details of how the a r jet can be arranged with regard to the cuvette described nerein or other cuvette the various angles of the inclination of the jet, jet pressures, activation times, etc. are described in detail in the aforementioned U.S. patent application, Serial No. 575,924, all of wnich is incorporated by reference herein. In operation, the cuvettes 24 are advanced in turn into position beneath tne nozzle 150 in alignment therewith wnicn is closely controlled by the tractor belt 32, and tne top (opening) of each cuvette when in position for mixing is squeezed cl osed as shown by Figures 5 and 7. The microprocesso r, which has al ready cl osely controlled the quantities of materials dispensed into the cuvette to the preset l iquid l evel, then directs tne air jet at the meniscus at the junction between the liquid surface and the cuvette wall to create a vortex wnich produces a thorough mixing of the contents of the cuvette. At the end of the dwell period, the air j et s switched off , and the cuvette belt is advanced to bring the next cuvette into stationary position beneath the nozzle when the cuvette top (opening) squeezing step and mixing process is repeated. In the embodiment described above, the air j et nozzle 150 is non-invasive of the cuvette, thus maximizing throughput. However, in a modif ication as shown in Figure 10 , tne nozzl e is inserted into the cuv ette during the squeezing and mixing process as described above. This nas the effect of limiting throughput and may result in contamination of the nozzle which can be dealt with by flushing tne nozzle with diluent between mixing operations. However, it does produce a system in which the angl e of inclination of the nozzl e is not l imited by the geometry of the cuv ette so that it can be inclined more nearly to the horizontal thus desirably maximizing tne horizontal component of the air jet. In this embodiment, tne nozzle 150 has a dog¬ leg bend in it and is mounted on an elevator mechanism schematically represented at 160 by which it can be raised and l owered between a lowered, operativ e position as shown in solid outline and a raised, inoperative position as shown in dotted outline for cuvette indexing. With this arrangement the air jet angle can be reduced to as little as 8 degrees to the liquid surface (horizontal). An angle of between about 8 degrees and about 15 degrees to the horizontal is preferred. As in the previous embodiment, the air jet is directed at the junction between the liquid surface and tne cuvette wall. It should be understood that the above described embodiments of the invention are illustrative only, and tnat modifications thereof may occur to those skilled in the art. Accordingly, this invention is not to be regarded as limited to the embodiments disclosed nerein, but is to be limited only as defined by the appended claims.

Claims: CL M≤ 1. In a method of mixing materials, at least one of which is a liquid, in a cuvette wherein an air jet is used to agitate the materials sufficiently to cause the materials to mix, the improvement which comprises reducing the opening of the cuvette during the air jet mixing process. 2. A method in accordance with Claim 1 wherein the opening of the cuvette is reduced by squeezing the top of the cuvette opening to reconfigure it. 3. A method in accordance with Claim 2 wherein said opening of said cuvette is reduced up to about 75 percent of the original opening size. 4. A method in accordance with Claim 1 wherein said air jet is directed at an acute angle against the liquid surface in said cuvette adjacent its junction with the wall of said cuvette. 5. A method in accordance with Claim 4 including directing said air jet against the meniscus formed at the junction of the liquid surface and the wall of said cuvette. 6. A method in accordance with Claim 1 wherein said cuvette is maintained stationary during said mixing. 7. A method in accordance with Claim 1 including directing said air jet from a nozzle arranged outside said cuvette. 8. A method in accordance with Claim 1 including the step of inserting a nozzle into said cuvette to a position above the surface of said liquid and directing said air jet against the liquid surface from said nozzle. 9. A method in accordance with Claim 1 wherein said materials comprise a liquid and particulate material. 10. A method according to Claim 9 including directing said air jet against the meniscus formed at the junction of the liquid surface and the wall of said cuvette from a fixed nozzle arranged outside said cuvette wnile maintaining said cuvette stationary. 11. A method in accordance with Claim 1 wherein said materials comprise a biological sample and a reagent. 12. A method in accordance with Claim 1 wherein said materials comprise a biological sample, a reagent and a diluent. 13. A method in accordance with Cl aim 1 further comprising the step of analyzing the contents of said cuvette following said mixing step. 14. In a method of analyzing mater ial s including a biological sample and a liquid wherein the sample and liquid are dispensed into a cuvette and an air jet is used to produce a thorough mixing of al l materials to facilitate analyzing the contents of the cuv ette fol lowing the mixing, the improvement which comprises reducing the size of the opening of the cuvette during the air jet mixing process. 15. A method in accordance with Claim 14 herein said opening of said cuvette is reduced up to about 75 percent of the original opening size. 16. A method in accordance with Cl aim 14 wherein said materials include a diluent, reagent and l iquid biological sampl e which are mixed in said cuvette. 17. A method in accordance with Cl aim 16 in which said reagent is a dry particulate reagent. 18. A method in accordance with Claim 16 in which the contents following said mixing are analyzed a plurality of times at intervals. 19. A method in accordance with Cl aim 14 wjierein said air jet is directed at an acute angle against tne liquid surface in said cuvette adjacent its junction with the wall of said cuvette. 20. A method in accordance with Claim 14 wherein said analysis is by photometry. 21. A method in accordance with Claim 14 including advancing said cuvette beneath a fixed nozzle and maintaining said cuvette stationary while directing said air jet against said liquid surface from outside said cuvette. 22. A method according to Claim 14 including advancing said cuvette into alignment beneath a nozzle, lowering the nozzle into said cuvette closely above the liquid surface and maintaining said cuvette stationary while directing said air jet against said liquid surface from said nozzle. 23. Apparatus for mixing materials, at least one of which is a liquid, including means for dispensing said materials into a cuvette through its nozzle means opening for directing an air jet against the liquid surface so formed in the cuvette so as to agitate said materials sufficiently to cause mixing of said materials, means for reducing the size of the opening of the cuvette during the air jet mixing process, and means for advancing said cuvette from said dispensing means to align it with said nozzle means. 24. An apparatus acco rding to Cl aim 23 wherein said reducing means squeezes the top of said cuvette opening to reconfigure it. 25. An apparatus accor ding to Cl aim 23 wherein said reducing means is adapted to reduce said -cuvette opening up to about 75 percent of the original opening size. 26. An apparatus according to Cl aim 23 wherein said nozzle means is adapted to direct said air j et at an acute angle against said l iquid surface adjacent its junction with the wall of said cuvette. 27. Apparatus according to Claim 26 in which said cuvette is partially f illed by said dispensing means to a predetermined level and said cuvette is so aligned witn said nozzle that said air jet is directed against the meniscus formed at the junction of the liquid surface and a wall of the cuvette. 28. An apparatus accor ding to Cl aim 23 wherein said reducing means comprises two surfaces between which the portion of said cuvette with said opening passes. 29. Apparatus for mixing l iquid and particulate materials in a cuvette, comprising: means for dispensing at least one liquid and at least one particulate material into the cuvette through its opening to f orm a liquid surface in the cuvette bound by the wal l of the cuvette at a predetermined level in the cuvette; a fixed air j et nozzl e for directing an air j et against the liquid surface to produce a thorough mixing of sa id materials ; means for reducing the opening of the cuv ette during the air j et mixing process; and means for advancing the cuvette from the dispensing means into stationary position beneath said air jet nozzle in alignment with said nozzle. 30. Apparatus f or mixi ng l iquid and particular materials in a cuvette comprising: means for dispensing at least one liquid and at l east one particulate material into the cuvette through its opening to partial ly fill the cuvette and form a l iquid surface in the cuv ette bound by the wall of the cuvette; an air jet nozzle; means for advancing the cuvette from the di spensing means into s tati ona ry position beneath said air jet nozzle; means for lowering said air j et nozzle into the cuv ette to pos ition it a predetermined height above said liquid surface in the cuvette, said nozzle to direct an air j et against said liquid surface in the cuvette to produce a thorough mixing of said materials, and for raising said air j et nozzle out of said cuvette following said mixing; and means for reducing the opening of the cuv ette during the ai r j et mixing process. 31. A system for analyzing liquid biological samples comprising the following means and means f or advancing a cuvette between said means in order: (a) means for dispensing a reagent and a diluent into the cuv ette through its opening and for mixing the reagent and the diluent to dispense the reagent in tne diluent; (b) means for adding a liquid biological sample to the cuvette, the quantities of said reagent, diluent and sample dispensed being controlled so that together they partially fill the cuvette and define a liquid surface bound by the wall of the cuvette; (c) nozzle means for directing an air jet against the liquid surface so as to cause mixing of the contents of the cuvette to facilitate reactions of the sample; (d) means for reducing the opening of the cuvette during the air jet mixing process; and (e) means for analyzing the reaction of the reagent witn the sample following said mixing.

Inventors: MAZZA JOHN C, THOMPSON ROBERT R, MAZZA, JOHN, C., THOMPSON, ROBERT, R.
Applicants: BAXTER TRAVENOL LAB, BAXTER TRAVENOL LABORATORIES, INC.
Application year: 1987
Main classification: C12Q1
IPC codes: B01F13, C12M1, G01N33, G01N35