Apparatus and method for analyzing particles suspended in a liquid

• US 5,351,118 A
• Filed: 06/10/1991
• Issued: 09/27/1994
• Est. Priority Date: 05/04/1990
• Status: Expired due to Fees

• Current Assignee: Biometic APS
• Original Assignee: Biometic APS
• Inventors: Spinell, Max
• Primary Examiner(s): McGraw, Vincent P.
• Assistant Examiner(s): KEESEE, LACHARLES
• Application Number:
  US07/688,545
• Time in Patent Office: 1,205 Days
• Field of Search: 356/335, 356/336, 356/337, 356/338, 356/72, 356/73, 356/39, 356/244, 356/246, 250/283, 422/62.1, 422/81, 422/103, 436/810, 436/805, 436/806, 324/71.4
• US Class Current: 356/72
• CPC Class Codes: G01N 1/38 Diluting, dispersing or mixing samples
• CPC Class Codes: G01N 15/10 Investigating individual particles
• CPC Class Codes: G01N 15/1404 Handling flow, e.g. hydrodynamic focusing
• CPC Class Codes: G01N 15/1409 Handling samples, e.g. injecting samples
• CPC Class Codes: G01N 2015/1019 Associating Coulter-counter and optical flow cytometer [OFC]
• CPC Class Codes: G01N 2015/135 Electrodes
• CPC Class Codes: G01N 2015/1418 Eliminating clogging of debris
• CPC Class Codes: G01N 21/64 Fluorescence; Phosphorescence
• CPC Class Codes: Y10S 436/805 Optical property
• CPC Class Codes: Y10S 436/806 Electrical property or magnetic property

Abstract

An apparatus and a method for analyzing particles suspended in a liquid are described, which particles are of a type or are prepared so as to emit radiation characteristic of the particles when exposed to radiation. Particular fluorescence-photometrical flow cytometry is described in connection with biological cell populations.

The apparatus comprises an elongated flow area in the shape of a channel provided in a cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface. The first and the second body members are adapted to be moved relative to one another between a first position, in which the planar facial surfaces are in fluid-tight contact with one another, and a second position, in which the planar facial surfaces are spaced apart. At least one of the planar facial surfaces of one of the body members is provided with an elongated groove. In the first position, the first and second body members together define the cuvette in which the elongated flow area is defined by the elongated groove constituting a capillary passage. An inlet for feeding the liquid to the elongated flow area is provided in one of the body members and an outlet for discharging the liquid from the elongated flow area is provided in the very same or in the other body member. At least one of the body members is transparent to light to which the particles are exposed and further transparent to the radiation emitted by the particles. Two electrodes are further described for carrying out an election of particles suspended in the liquid by means of a measurement of the electrical conductivity of the fluid, which particles are of a specific size for subsequent registration of fluorescence when exposed to radiation.

Claims

1. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette,

means for feeding said fluid medium to said elongated flow area,

means for discharging said fluid medium from said elongated flow area,

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction,

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation,

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface,

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart,

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position,

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area,

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette, and

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles.

2. A method of analyzing particles suspended in a fluid medium by means of an apparatus according to claim 1, comprising the following steps:

feeding said fluid medium in which said particles are suspended into said elongated flow area through said means for feeding said fluid medium to said elongated flow area,

guiding said fluid medium in said first direction through said elongated flow area of said cuvette,

exposing said fluid medium in which said particles are suspended to said radiation in a second direction defining an angle relative to said first direction,

picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation by means of said means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation,

discharging said fluid from said elongated flow area by means of said means for discharging said fluid medium from said elongated flow area, and

in case a blocking of said elongated flow area or of said means for feeding said fluid medium to said elongated flow area occurs, moving said first and second body members to said second position so as to expel said fluid medium from said elongated flow area and further from said means for feeding said fluid medium to said elongated flow area, and thus eliminate said blocking.

3. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette, said elongated flow area constituting a capillary passage;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative t one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated grove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette; and

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles.

4. An apparatus according to claim 3, said capillary passage having the shape of a geometrical section of a rectilinear cylinder having a circular cross section of a radius of curvature of approximately 50 μ

m.

5. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles; and

at least two electrodes for generating an electrical field through which said fluid medium is passed when guided through said elongated flow area.

6. An apparatus according to claim 5, said elongated flow area constituting a capillary passage.

7. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles;

at least two electrodes for generating an electrical field through which said fluid medium is passed when guided through said elongated flow area; and

said electrodes being embedded within said first or second body member providing exposed electrode surfaces at said elongated flow area.

8. An apparatus according to claim 7, said elongated flow area constituting a capillary passage.

9. An apparatus according to claim 7, said electrodes being arranged in succession relative to said first direction for generating said electrical field having lines of flux extending at a part of said elongated flow area substantially homogeneously and substantially parallel with said first direction.

10. An apparatus according to claim 7, said electrodes being spaced apart at said elongated flow area defining a minimum spacing of approximately 0.08 mm.

11. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles; and

said mean for exposing said fluid medium to said radiation being constituted by a light source.

12. An apparatus according to claim 11, said light source generating light which is focused at a specific area of said elongated flow area.

13. An apparatus according to claim 12, further comprising a focusing means constituted by an objective lens arranged in direct optical communication with said cuvette for focusing said light at said specific area.

14. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles;

at least two electrodes for generating an electrical field through which said fluid medium is passed when guided through said elongated flow area; and

said means for exposing said fluid medium to said radiation being constituted by a light source.

15. An apparatus according to claim 14, said electrodes being embedded within said first or second body member providing exposed electrode surfaces at said elongated flow area.

16. An apparatus according to claim 15, said electrodes being arranged in succession relative to said first direction for generating said electrical field having lines of flux extending a part of said elongated flow area substantially homogeneously and substantially parallel with said first direction.

17. An apparatus according to claim 14, said electrodes being spaced apart at said elongated flow area defining a minimum spacing of approximately 0.08 mm.

18. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles;

at least two electrodes for generating an electrical field through which said fluid medium is passed when guided through said elongated flow area;

said means for exposing said fluid medium to said radiation being constituted by a light source, said light source generating light which is focused at a specific area of said elongated flow area;

said electrodes and said specific area being arranged in succession relative to said first direction; and

said electrodes being arranged upstream relative to said specific area.

19. An apparatus according to claim 18, further comprising a light reflecting means for reflecting said radiation emitted by said particles, when exposed to said light from said light source, to said means for picking up said radiation.

20. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

p1 said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles;

at least two electrodes for generating an electrical field through which said fluid medium is passed when guided through said elongated flow area;

said means for exposing said fluid medium to said radiation being constituted by a light source, said light source generating light which is focused at a specific area of said elongated flow area, said electrodes and said specific area being arranged in succession relative to said first direction;

said electrodes being arranged upstream relative to said specific area;

said light source being constituted by a flash; and

a control means connected to said electrodes and to said flash for controlling the operation thereof in response to the detection of the particle passing through said electrical field so as to expose said particle to said light from said flash.

21. An apparatus according to claim 20, further comprising a light reflecting means for reflecting said radiation emitted by said particles, when exposed to said light from said light source, to said means for picking up said radiation.

22. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles;

at least two electrodes for generating an electrical field through which said fluid medium is passed when guided through said elongated flow area;

said electrodes being embedded within said first or second body member providing exposed electrode surfaces at said elongated flow area;

said electrodes and a specific area of said elongated flow area being arranged in succession relative to said first direction;

said electrodes being arranged upstreams relative to said specific area;

means for exposing said fluid medium to said radiation constituted by a light source being further constituted by a flash; and

a control means connected to said electrodes and to said flash for controlling the operation thereof in response to the detection of the particle passing through said electrical field so as to expose said particle to said light from said flash.

23. An apparatus according to claim 22, said light reflecting means being constituted by one of said exposed electrode surfaces.

24. An apparatus according to claim 23, said exposed electrode surface constituting said light reflecting means being arranged at said elongated groove.

25. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles;

an agitating means constituted by a wire and a wire rotating means, said wire being arranged extending through said means for feeding said fluid medium to said elongated flow area and at least partially into said elongated flow area, said wire being rotated relative to its rotational axis by means of said wire rotating means so as, to any substantial extent, to eliminate the risk of blocking said feeding means and said elongated flow area.

26. An apparatus according to claim 25, said wire having a circular cross section or alternatively a non-circular cross section, such as a polygonal cross section.

27. An apparatus according to claim 26, said wire being of a material which is compatible with said fluid medium and which does not swell to any substantial extent in water, such as nylon, polypropylene, polycarbonate, or Teflon™

.

28. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles; and

a means for feeding a diluent to said elongated flow area.

29. An apparatus according to claim 28, further comprising means for controlling the supply of said diluent to said elongated flow area.

30. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles;

at least two electrodes for generating an electrical field through which said fluid medium is passed when guided through said elongated flow area;

said means for exposing said fluid medium to said radiation being constituted by a light source, said light source generating light which is focused at a specific area of said elongated flow area;

said electrodes and said specific area being arranged in succession relative to said first direction;

said light source being constituted by a flash;

a control means connected to said electrodes and to said flash and controlling the operation thereof in response to the detection of the particle passing through said electrical field so as to expose said particles to said light from said flash;

a means for feeding a diluent to said elongated flow area;

means for controlling the supply of said diluent to said elongated flow area and;

said means for controlling the supply of diluent to said elongated flow area being connected to and being controlled by said control means.

31. An apparatus according to claim 30, said means for feeding said diluent to said elongated flow area being arranged upstream relative to said electrodes, and said control means controlling said means for controlling the supply of said diluent to said elongated flow area so as to provide a predetermined particle-flow rate through said elongated flow area.

32. An apparatus according to claim 30, said means for feeding said diluent to said elongated flow area being arranged upstream relative to said electrodes, and said control means controlling said means for controlling the supply of said diluent to said elongated flow area so as to present said particles to said exposure means individually and at a rate lower than a predetermined maximum rate, such as a rate of 100 particles per second.

33. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles; and

a flow control means for controlling the flow of said fluid medium through said elongated flow area.

34. An apparatus according to claim 33, said flow control means being constituted by a pump connected to said means for discharging said fluid medium from said elongated flow area and generating a substantially constant flow rate of said fluid medium through said elongated flow area.

35. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles; and

a spring-loading means actuating at least one of said body members by a spring force perpendicular to said facial surfaces of said body members.

36. An apparatus according to claim 35, said first and second body members being movable relative to one another by parallel displacing at least one of said two body members in a direction perpendicular to said planar facial surfaces of said body members.

37. An apparatus according to claim 35, further comprising a stop means receiving said spring-loaded body member when said body members are moved to said second position so as to maintain said spring-loaded body member in a well-defined position.

38. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles; and

a means for conducting a rinsing liquid to said planar facial surfaces of said body members when said body members are in said second position.

39. An apparatus according to claim 39, further comprising a rotatable rinsing brush, which is movable relative to said body members across said planar facial surfaces thereof when said body members are in said second position so as to mechanically clean said planar facial surfaces.

40. An apparatus for analyzing particles suspended in a fluid medium, said particles being capable of emitting radiation characteristic of said particles when exposed to radiation, and comprising:

a cuvette, in which an elongated flow area having the shape of a passage is provided for guiding said fluid medium in a first direction through said elongated flow area of said cuvette;

means for feeding said fluid medium to said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for discharging said fluid medium from said elongated flow area;

means for exposing said fluid medium to said radiation in a second direction defining an angle relative to said first direction;

means for picking up at least part of said radiation characteristic of said particles and emitted by said particles when exposed to radiation;

said cuvette comprising a first body member having a planar facial surface and a second body member having a planar facial surface;

said first and second body members being movable relative to one another between a first position, in which said planar facial surfaces are positioned closely adjoining one another, and a second position, in which said planar facial surfaces are positioned spaced apart;

at least said facial surface of said first body member being provided with an elongated groove defining together with said adjoining facial surface of said second body member said elongated flow area having the shape of said passage when said body members are in said first position;

said means for feeding said fluid medium to said elongated flow area comprising an inlet provided in one of said body members and extending from the exterior relative to said cuvette to an inlet aperture of said elongated flow area;

said means for discharging said fluid medium comprising an outlet provided in one of said body members and extending from an outlet aperture of said elongated flow area to the exterior relative to said cuvette;

at least one of said body members being transparent to said radiation to which said fluid medium is exposed and to said radiation emitted by said particles; and

said apparatus being adapted to carry out a flow-cytometrical analysis of fluorescent particles, in particular the size of the particles is within the range of approximately 8-15 μ

m.