Cuvette holder for coagulation assay test

A cuvette holder is provided to allow a flow cell optical analyzer to be adapted for coagulation analysis. The flow cell analyzer has a light source and a photo detector defining a first and a second end of an optical path, a vacuum source for drawing a liquid sample through a flow cell positioned in the optical path so that light from the light source passes through the sample, and means for analyzing data collected at the photo detector. The coagulation analyzer has a light source and a photo detector defining the respective ends of an optical path, a cuvette containing a liquid sample positioned in the optical path for passage of light from the light source through the liquid sample, a means for agitating the liquid sample and a means for analyzing data collected at the photo detector. The adaptation is achieved by removing the flow cell and replacing the flow cell with a cuvette holder comprising an opening for receiving and holding the cuvette in the light path and communicating the vacuum source to the cuvette holder, the means for agitating provided by a magnetic stirring bar in the cuvette, the stirring bar being magnetically coupled to a rotor rotatably mounted in a rotor housing below the cuvette and having a permanent magnet mounted on a top surface thereof, wherein the rotor is rotated in the rotor housing by an air pressure differential in the rotor housing created by the communication of the vacuum source to the cuvette holder.

The present invention relates to a holder for containing a cuvette, 
particularly a cuvette used in a chemical analysis requiring agitation of 
the test material in the cuvette. More particularly, the invention relates 
to a cuvette holder having an impeller with a magnetic rod mounted 
thereupon built into the cuvette holder, so that when the impeller is 
caused to turn by an air pressure differential across the impeller, the 
moving magnetic rod causes rotation of a magnetic stirring bar contained 
within the cuvette. Even more particularly, the present invention allows 
an optical analysis apparatus having a vacuum source to be provided with a 
magnetic stirring source for the sample. 
BACKGROUND OF THE ART 
In conducting certain testing on bodily fluids such as blood, it is 
necessary to analyze the time that it takes the specimen to coagulate 
under certain specified conditions. In such a testing apparatus, it is 
common practice to use disposable sample containers, typically called 
cuvettes. When the specimen is placed in the cuvette, it is necessary to 
also place a small magnetic stirring rod in the cuvette to provide 
agitation to the specimen necessary to cause the coagulation. Because of 
the small size of the cuvettes and because of a need to not contaminate 
the side surfaces of the cuvette with fingerprints and the like when a 
photo-optical technique is being used for analyzing the coagulation 
progress, it is desirable to provide a cuvette holder which retains the 
cuvette in fixed spatial relationship to an optical path through the 
holder provided by apertures in the holder sides. It is also desirable to 
provide a cuvette holder having an impeller with a magnetic bar mounted on 
the impeller, so that the magnetic field induced by rotation of the 
impeller can cause a magnetic stirring rod contained within the cuvette to 
rotate in a complementary fashion. 
A clinical calorimeter is an instrument which employs color filters, a 
light source, a sample holder, typically either a holder for 
interchangeable cuvettes or a flow cell, and a photo detector. In an 
aspirating system, a controlled vacuum source is used to draw the sample 
under test into a flow cell aligned with the light path defined by the 
light source and the photo detector. Measurements of the absorbance or 
transmission of the light by the sample are made and used to determine 
quantitatively such analytes as glucose, cholesterol, enzymes, etc. The 
temperature of the samples is carefully controlled. Because the clinical 
calorimeter aspirates the sample from the cuvette, the clinical 
calorimeter is not provided with means to agitate the sample. 
A coagulation meter as is generally known in the prior art has a light 
source, a photo detector, a timer and a stirring means to determine the 
level of clotting agents in a serum sample. The reaction cuvette used is a 
vial containing a stir bar, which is magnetically coupled with a rotating 
magnetic source located in the coagulation meter. By knowing the time 
necessary for a clot to form on the stir bar and the temperature at which 
the test is conducted, the level of clotting agents present in a serum 
sample may be determined. 
It is a desirable yet unachieved goal of the prior art to provide a cuvette 
holder which allows a clinical calorimeter to perform the function of the 
coagulation meter without sacrificing the advantages of the existing 
features. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a device for 
holding a cuvette in a light path provided by an analytical instrument. 
The cuvette would contain a magnetic stirring bar to agitate the contents 
of the cuvette while in the light path. The device comprises an upper 
portion and a lower portion. The upper portion has an opening for 
receiving and holding the cuvette. The lower portion is affixed to the 
upper portion and comprises a rotor housing and a rotor, the rotor 
rotatably mounted in the rotor housing and having a permanent magnet 
mounted on a top surface thereof, such that the rotation of the rotor in 
the rotor housing induces a magnetic field which causes co-rotation of the 
stirring bar.

DETAILED DESCRIPTION OF THE INVENTION 
FIGS. 1 through 4 show the top portion 10 of the present invention cuvette 
holder in front, side, top and assembled side views, and FIG. 5 shows the 
entire cuvette holder, including the bottom portion 11. The top portion 10 
of the present invention comprises a generally rectangular solid body 12 
having a cylindrical bore 14 formed therethrough. The body 12 is 
preferably formed from a metallic material, particularly a metal which may 
have an anodized finish placed thereupon. As best seen in FIG. 3, the 
cylindrical bore 14 is generally centered and passes from a top surface 16 
of the rectangular solid body 12 to a bottom surface 18. Intersecting the 
cylindrical bore 14 and directed normally thereto, preferentially at a 
diameter of the cylindrical bore, is a smaller aperture 20 which serves as 
an optical viewing port for a light beam provided by the test apparatus 
used. This smaller aperture 20 is seen in FIGS. 2-4, but not shown in FIG. 
1, as it passes from the front to the back surface of the rectangular 
solid body 12. In addition to the cylindrical bore 14 through the 
rectangular solid body 12, the top surface 16 is provided with two 
additional bores 22 and 24, which are generally located in adjacent 
corners of the top surface 16. Bore 14 may be moved off center slightly, 
as is shown in FIG. 3, to accommodate holes 22 and 24. The first of these, 
bore 22, passes entirely through the rectangular solid body 12 parallel to 
the cylindrical bore 14. The second bore 24 extends only a partial 
distance through the rectangular solid body 12 from the top surface 16. 
This second bore 24 is sized and adapted for receiving and securing a 
handle member 26 used to place the device into the test apparatus and to 
remove it therefrom. Although a particular shape of the handle member is 
shown in FIGS. 1-4, this particular shape of handle is shown for 
illustrative purposes only and other variations are certainly available. 
The first bore 22 is sized and adapted to frictionally receive and retain 
a short length of tubing 28, preferably metallic tubing. The tubing should 
be sized with an outside diameter suitable for frictional engagement with 
a tube supplying vacuum to the analyzer with which this device will be 
used. 
In addition to the cylindrical bore 14 and the first bore 22, the bottom 
surface 18 of the rectangular solid body 12 is provided with two threaded 
bores 30, 32 for receiving screws, as will be described below. These bores 
30, 32 will typically be placed in the corners of the rectangular solid 
body 12 other than the corner in which the first bore 22 is made. 
Cylindrical bore 14 is sized so that it will receive a cuvette, usually a 
disposable cuvette, of the type in which the fluid being analyzed is 
contained. When placed in the bore 14, a closed end of the cuvette will be 
towards bottom surface 18 and an open end of the cuvette will be towards 
top surface 16, with fluid contained within the cuvette effectively in an 
optical path provided by bore 20 and such that a magnetic stirring bar 
placed in the cuvette is below, that is, towards surface 18, the optical 
path. 
Further assembly of the cuvette holder device is revealed by reference to 
FIG. 5, which shows the entire device in an exploded right side view, 
including the bottom portion 11. In completing assembly of the cuvette 
holder, a rotor housing 34 and a housing cover 36 are attached to the 
bottom surface 18 of the rectangular solid body 12. Both the housing cover 
36 and the rotor housing 34 are provided with corner-positioned apertures 
which may be aligned with the two screw-receiving bores 30, 32 in the 
bottom surface 18. Of these, apertures 60 and 62 in housing 34 receive 
screws 38 and 40 when the screws are passed through them and into bores 
30, 32, respectively. Similarly, apertures 61, 63 in the housing cover 36 
correspond to apertures 60, 62. In this manner, housing cover 36 and rotor 
housing 34 may be removably secured to the bottom surface 18. When this is 
done, the cover 36 and housing 34 define a chamber for containing a rotor, 
as will be described below. 
Further details of the housing cover 36 are seen in FIG. 6, which shows the 
housing cover in top plan view instead of the side view in which it is 
shown in FIG. 5. As indicated in the drawing, the preference is to provide 
a transparent housing cover, usually from a polymeric material, so that 
the interior of the rotor chamber may be observed through the bore 14 in 
the rectangular solid body 12. Likewise, FIGS. 7 and 9 show further 
details of the rotor housing 34. 
In addition to the apertures 61, 63 for receiving screws 38, 40, housing 
cover 36 has a third comer-positioned aperture 43, which is aligned with 
bore 22 so that bore 22 is in communication with the rotor housing 34 when 
the rotor housing and housing cover attached to rectangular solid body 12. 
When this communication is established, bore 48 in the rotor housing 
effectively becomes an extension of bore 22. Acting with bore 56, it 
communicates the chamber in the rotor housing with tube 28. 
The rotor housing 34 is generally hollow due to a large bore 46 and has a 
centrally positioned internally-threaded aperture 44, which is concentric 
with large bore 46. It also has a small conduit comprising co-linear bores 
56, 58 made through a side wall of the housing 34 and communicating bore 
48 with the exterior of the rotor housing 34. A further bore 64, 
positioned normal to bore 58 and originating from the bottom surface of 
the rotor housing also intersects bore 58. Rotor housing 34, like the 
housing cover 36, has a footprint essentially identical to that of the 
rectangular solid 12. A cone set screw 42 placed in the central aperture 
44 provides a pivot point upon which a rotor 50 with peripheral impeller 
members may be seated for rotation thereupon. 
As is seen in FIG. 8, the rotor 50 is typically comprised of a lightweight 
non-metallic material, preferably a polymeric material. The rotor 50 has a 
slot 51 on a top surface thereof and an axial aperture 54 therethrough. 
When a rectangular bar 52 of a magnetic material sized for being received 
in slot 51 is placed in the slot and retained therein, the rectangular bar 
effectively closes off the aperture 54, providing a seat for cone set 
screw 42. The retention of magnetic bar 52 in slot 51 may be through 
frictional fit, adhesive, or a variety of known means. The periphery of 
the rotor 50 is provided with a plurality of vanes 57 or the like to act 
as impellers. If an air pressure difference is induced across the inside 
of the rotor housing 34, air will flow from either the side wall bores 58, 
64 to the first bore 22 or in the opposite direction, but in either case 
the air flow will cause movement of the vanes 57 and rotation of the rotor 
50. When the rotor 50 is positioned immediately below and coaxial to the 
central aperture 14 in the rectangular solid 12, and a cuvette containing 
a magnetic stirring bar is positioned in the bottom of the central 
aperture, the magnetic field induced by the rotation of the magnet 52 
mounted on the top of the rotor 50 will cause rotation of the stirring bar 
in the cuvette. This will effect agitation of the sample in the cuvette. 
In order to achieve this objective, rotor 50 must be sized in diameter and 
thickness such that it does not impinge on the surfaces of the rotor 
housing in any way which would impede free rotation. 
When the cuvette holder of the present invention is used in a 
non-conventional apparatus for conducting the coagulation assay test, such 
as a calorimetric apparatus, the apparatus will typically be provided with 
an aspirator line and a vacuum pump. By attaching the aspirator feature to 
the tubing 28 protruding from aperture 22, the vacuum pump feature of the 
apparatus can be used to draw a vacuum on the rotor housing 34, thereby 
inducing a flow of air into the rotor housing 34 through the side wall 
aperture 56 and 58. This flow of air, caused by the pressure differential 
caused by the vacuum pump, will cause the rotor 50 to turn. The use of the 
cuvette holder of the present invention permits a colorimeter apparatus to 
be adapted to conduct photo-optical detection of coagulation and also 
allows easy and reliable insertion and removal of test cuvettes from the 
test cell and instrument. 
Although the specific application taught by this disclosure describes the 
use of this device for rotating a magnetic stirring bar in a cuvette used 
in a coagulation test, it will be recognized that a variety of chemical 
tests involve analysis of light passing through a cuvette containing a 
fluid which requires agitation as would be provided by a magnetic stirring 
bar. The present invention should find application in these devices.