Multistation Photometric Analyzer

Abstract

A multistation, single-channel photometric solution analyzer having a rotor adapted to carry a plurality of removable cuvettes in the form of rigid, hollow, elongated bodies exteriorly engaged by a flange seating against an axially extending surface of the rotor. The cuvettes may be affixed to a flexible belt to facilitate transport, installation, and removal of cuvettes as a group.

Description

BACKGROUND OF THE INVENTION

This invention was made in the course of, or under, a contract 10 with the United States Atomic Energy Commission.

My invention relates generally to multistation, single-channel photometric solution analyzers, and more particularly to improvements in rotor assemblies used therein, and to means facilitating the transport, installation, and removal of removable cuvettes as a group.

Copending Pat. applications Ser. No. 784,739, Ser. No. 827,185, U.S. Pat. No. 3,547,547, of common assignee, described photometric solution analyzers wherein a rotor assembly is formed with a plurality of sample-receiving cavities, or cuvettes, disposed in a circular array about the axis of the assembly. Each cuvette is provided with axially aligned transparent windows. Rotation of the assembly successively interposes the cuvettes between a light source and circuitry adapted to measure the phototransmittance of the various samples in the cuvettes and thus determine chemical species concentrations in the samples.

The analyzers described in the above-referenced patent applications permit a substantial reduction in the time required for the analysis of large numbers of samples. Those analyzers are, however, subject to certain disadvantages. For example, the sample-analysis cavities, or cuvettes, must be cleaned very carefully between runs to avoid cross-contamination of samples, corrosion of the cuvettes themselves, and darkening of the cuvette windows resulting from exposure to dyes, film-forming liquids, and the like. Also, such analyzers are not well adapted for certain analytical procedures --as, for example, where it is desired to remove the samples rapidly from the cuvettes, transport the samples to a heating zone or incubation zone, and then rapidly reload the samples in a photometric analyzer for reanalysis.

It is, therefore, a general object of this invention to provide a photometric analyzer wherein successive samples are analyzed with little or no cross-contamination of the samples, contamination of the rotor, or run-to-run deterioration of the light-transmitting properties of the analyzer rotor.

It is another object of this invention to provide a modified photometric analyzer rotor adapted for use with removable cuvettes.

It is still another object to provide an arrangement whereby a multiplicity of removable cuvettes can be transported as a group, installed in the above-mentioned modified rotor as a group, and removed from the modified rotor as a group.

Other objects of the invention will be apparent from examination of the following description and the appended drawings.

SUMMARY OF THE INVENTION

In accordance with my invention, the photometric analyzer rotor is formed with a coaxial annulus formed with a circular array of recesses extending radially outward from the inner peripheral surface thereof for the reception of removable cuvettes. The typical cuvette is a hollow, rigid, elongated body exteriorly engaged by a flange and having a closed, light-transmitting end portion. Mounting of a cuvette in one of the recesses brings said end portion into registry with axially aligned light-transmitting means carried by the rotor. Rotation of the rotor successively interposes the cuvettes and their respective light-transmitting means between a light source and a photodetector whose output is fed to circuitry for measuring the light absorbency of said end portions of the cuvettes.

To facilitate handling as a group, the cuvettes may be affixed to the face of a flexible belt, the center-to-center spacing of the affixed cuvettes corresponding to that of the recesses in the rotor annulus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram, partly in section, of a photometric solution analyzer designed in accordance with this invention.

FIG. 2 is a series of four sectional views of a removable, double-function cuvette designed for use in a system of the kind shown in FIG. 1. The views illustrate the positions assumed by liquids in the cuvette during four successive stages of a normal operation of the system.

FIG. 3 is a perspective view, partly in section, of a belt-and-cuvette assembly designed for use in the system shown in FIG. 1.

FIG. 4 is a perspective view, partly in section, of an alternative form of the assembly shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, one form of this invention includes a rotor 1, which is in the form of a flat-bottomed bowl having an axis of rotation. The bowl is formed with an axially extending sidewall 2, or annulus, coaxial therewith. As shown, the base of the bowl is supportably mounted to a rotatable shaft 3 which in turn is connected to any suitable drive means (not shown) for rotation of the rotor about said axis.

The inner peripheral surface 4 of the annulus 2 is bored and counterbored to form a recess which extends radially outward toward the outer peripheral surface 6 of the annulus. The recess is proportioned to receive an end of a cuvette 8. The cuvette is formed with an exterior, annular, medial flange 19 which seats snugly in the counterbore when the cuvette is in normal operating position, as shown.

The cuvette 8 is a hollow and rigid body composed of transparent or translucent material, such as glass or plastic (e.g., nylon, Teflon, polyethylene, polypropylene). The cuvette preferably is formed by standard molding techniques. For example, the cuvette shown in FIG. 1 can conveniently be fabricated by combining two molded and similar cup-shaped members, each having an exterior flange coplanar with its open end. These members can be cemented together, flange-to-flange, to form the cuvette 8. When the cuvette is in operating position, a closed, light-transmitting end portion 7 thereof is in registry with axially aligned light-transmitting means 10 carried by the annulus. The means 10 may comprise axially aligned through-going openings (as shown in FIG. 1), transparent windows, light-transmitting fibers, or the like.

Still referring to FIG. 1, the internal medial portion of cuvette 8 is provided with a transversely extending barrier 11. The barrier is ramp-shaped in cross section, the bass of the ramp being affixed to the cuvette.

The cuvette 8 is positioned in the annulus with its barrier-containing portion lowermost. Thus, the barrier extends both upwardly from the floor of the cuvette and part way toward the opposite wall, presenting a sloping surface to any liquid in the uninserted chamber 9 of the cuvette and an essentially vertical face to any liquid in the inserted chamber thereof. At a selected speed of the rotor, centrifugal force will cause liquid to flow radially outward from chamber 9, over the barrier, but the barrier prevents flow in the opposite direction whether the rotor is rotating or at rest.

As shown, the normally uppermost surface of cuvette chamber 9 is provided with a port 12 at a point radially inward from the barrier 11. As will be described, this port is provided for the introduction of samples and reagents.

For simplicity, the rotor 1 has been described in terms of a single cuvette mounted in a single recess in the annulus 2. The rotor will, however, normally be provided with many recesses of the kind described, each for the reception of a cuvette 8. Rotation of the rotor interposes each of the cuvettes in turn between a photometric light source and a photodetector, both of which are positioned to align with the light-transmitting means 10 associated with each cuvette. The light source, the photodetector, and the output circuitry associated therewith for measuring the light-absorbency of each cuvette are described in detail in aforementioned application Ser. No. 784,739 and will not be described here as they do not constitute a part of this invention.

In a typical operation of the system of FIG. 1, the rotor 1 is loaded with cuvettes 8, which are oriented as shown. With the rotor at rest, a liquid sample is introduced to the chambers 9 through the ports 12. The rotor then is rotated to a predetermined speed transferring the samples to the end portions 7. One or more reagents then are admitted to the chambers 9 through ports 12, and the rotor operated at a speed transferring them into the end portions 7, where they blend with the sample, providing an analytical mixture whose absorbance is then determined.

Referring to FIG. 2, the sequence of operations just described is illustrated in terms of a cuvette which is functionally similar to that described. In FIG. 2, the sample is designated as 13 and the reagent as 14. The path of the light beam is indicated by an arrow. It will be noted that in the embodiment shown in FIG. 2 the cuvette chambers and the barrier are formed as an integral unit. It will also be noted that in cuvettes of the kind shown in FIGS. 1 and 2, the chamber 9 serves the function of the so-called transfer disc described in the above-referenced patent applications.

It will be understood that my invention is not limited to the use of any one type of cuvette, such as the two-chamber type shown in FIGS. 1 and 2. As indicated in FIG. 3, for example, the cuvettes may be single chambers 15 having flat upper and lower faces joined to an arcuate side wall and having an open end coplanar with an external rectangular flange. As shown, a lower edge 16 of the flange extends inwardly and upwardly in the shape of a ramp to serve as the above-mentioned barrier. Alternatively, as indicated in FIG. 4, the barrier may be in the form of an external tape 20 closing all but a small upper portion of the mouth of a single-chambered cuvette.

Again, cuvettes of the type illustrated in FIGS. 1 and 2 may be provided with a succession of barriers 11 and, if desired, with a series of corresponding ports 12 for the introduction of liquids.

The above-described combination of removable cuvettes and an analyzer rotor adapted for using the same obviates to a large extent the contamination, corrosion, and window-darkening problems sometimes encountered with rotors whose cuvettes are cavities molded, machined, or otherwise formed in the rotor body. Preferably, the removable cuvettes are formed of an inexpensive material permitting discard of the cuvettes after several uses or even a single use.

To facilitate the transport, insertion, and removal of a multiplicity of removable cuvettes, I have devised a special belt-and-cuvette assembly, three forms of which are shown in FIGS. 2, 3, and 4, respectively. In each of these arrangements, cuvettes are affixed to a face of a flexible belt 17, each cuvette having a closed, light-transmitting end portion 7 extending away from said face. As shown in FIGS. 3 and 4, the cuvettes are mounted in spaced relationship, their center-to-center spacing on the belt corresponding to the spacing of the cuvette-receiving recesses (5, FIG. 1) in the annulus (2, FIG. 1). The cuvettes may be removably attached to the belt or, if desired, permanently secured thereto. In either case, the belt can be used (a) to transport, simultaneously, a large number of properly oriented and spaced cuvettes, (b) to guide the mounted cuvettes as a group into their respective recesses in the rotor, and (c) to remove the installed cuvettes as a group. Preferably, the belt is not disengaged from the cuvettes following insertion of the latter but is installed or removed along with the cuvettes. Consequently, in some embodiments the cuvettes and the belts are molded as a continuous unit. If desired, the belt assembly is composed of an inexpensive plastic permitting discard of the assembly after a few uses or even a single use. As indicated in FIGS. 3 and 4 the belt may be perforated to provide ports for the introduction of liquids to the affixed cuvettes.

Referring again to FIG. 2, the belt 17 is illustrated as mounted between the confronting flanges of the mating halves of the cuvette 8. The belt may, for example, be friction-fitted in slots formed at the interface of the flanges or may be cemented to the flanges. In the embodiment shown in FIG. 2 the flange nearer the end portion 6 seats against the inner peripheral face of the annulus 2 when the cuvette is mounted in the rotor. In the arrangement of FIG. 3, the external flange of the cuvette is secured to the belt 17 and seats against the inner surface of the annulus. In the arrangement of FIG. 4, the cuvette is formed with an integral end flange. The body of the cuvette is passed through a hole in the belt 17, with the flange seating against the belt. The belt seats against the inner surface of the annulus 2 when the cuvette is installed in the rotor. The cuvette is exteriorly engaged by the belt, and the belt may be described as a flange which seats against the annulus. In still another embodiment (not shown) the cuvette is not formed with an integral flange; instead, the mouth of the cuvette is positioned flush against the belt and bonded thereto. Thus, the belt serves each cuvette as a flange which seats against the annulus 2.

If desired the cuvette may be designed with its body portion forming an angle of less than 90.degree. with its flange. This permits the cuvette to be mounted with its end portion 7 lower than its mouth, eliminating the need for a barrier to prevent outflow of liquid from the cuvette when at rest. If desired, removable cuvettes may be used in combination with transfer discs of the kind referred to above.

The foregoing description is offered for illustrative purposes only, and it is intended that this invention be limited only by the scope of the appended claims.

Claims

What I claim is:

1. In a photometric solution analyzer including a rotor assembly for periodically interposing at least one light-transmitting sample-analysis cuvette between a light source and means for measuring the light transmitted through the cuvette so interposed, the improvement wherein

a. said rotor comprises an annulus rotatable about an axis and having an inner and an outer peripheral surface, said annulus having at least one recess communicating with said inner surface and extending radially toward said outer surface, said annulus carrying light-transmitting means adjacent said recess for passing light through said annulus and said recess, and

b. said cuvette comprises a hollow, elongated, rigid body having a closed end portion of light-transmitting material insertable in said recess for registry with said light-transmitting means, and flange means affixed to said cuvette at a location remote from said closed end portion for seating against said inner surface of said annulus to maintain said end portion in registry with said light-transmitting means.

2. The combination of claim 1 wherein said light-transmitting means comprises a pair of aligned apertures disposed on either side of said recess and extending from said recess to the exterior of said annulus.

3. The combination of claim 1 wherein said flange means is integral with said cuvette.

4. The combination of claim 1 wherein said cuvette is exteriorly affixed to a flexible flat member extending in a plane substantially normal to the major axis of said cuvette.

5. The combination of claim 1 wherein said cuvette is composed of glass.

6. The combination of claim 1 wherein said cuvette is composed of a plastic.

7. The combination of claim 1 wherein said cuvette contains a solid barrier which is sealably joined to the inner surface thereof and which divides the interior of the cuvette into adjoining chambers which communicate through an open region above said barrier, said barrier presenting a substantially flat and upright surface to said closed end portion and a sloping surface to the opposite end of said cuvette.

8. In combination with a photometric solution analyzer comprising an annulus rotatable about an axis and formed with circumferentially spaced recesses extending radially outward from an inner peripheral surface thereof, with each of said recesses adapted to receive a closed, light-transmitting end portion of a cuvette readily insertable in and removable from said annulus, means for effecting the insertion and removal of said cuvettes from said recesses comprising belt means disposable within said annulus in a contiguous relation with the inner surface thereof and having a plurality of cuvettes affixed to a face thereof at spaced-apart locations along the length thereof, each affixed cuvette having a closed, light-transmitting end portion extending away from said face, the center-to-center spacing of said affixed cuvettes corresponding to that of said recesses.

9. The combination of claim 8 wherein said belt means and said cuvettes are of unitary construction.

10. The combination of claim 8 wherein said belt means is adapted to seat against the inner peripheral surface of said annulus when said affixed cuvettes are mounted in said recesses.