Capillary electrophoresis detection - Patent Review 5312535

Claims

We claim:

1. A capillary electrophoresis system comprising a capillary tube having a bore, an inner surface defining the bore, an outer surface, and a wall thickness of the tube defined between the surfaces, the bore having a width and being for transporting fluid, an input window in an outer surface portion of the tube and an output window in an outer surface portion of the tube, the input window and output window being spaced apart, at least one of the input window or output window defining a window width, and wherein the window width is not substantially greater than the bore width.

2. A system as claimed in claim 1 wherein the width of both the windows are not greater than the bore width.

3. A system as claimed in claim 1 wherein the width of at least one of the windows is equal to the bore width.

4. A system as claimed in claim 3 wherein the width of both the windows is equal to the bore width.

5. A capillary electrophoresis system comprising a capillary tube having a bore, the bore having a center, an inner surface defining the bore with a selected diameter, an outer surface, a wall thickness of the tube being defined between the surfaces, the bore being for transporting fluid past a detection path, an input window on an outer surface portion of the bore, the input window having opposite interfaces with the surface thereby defining the input window width, and an output window on an opposite outer surface portion of the tube, the output window having opposite interfaces with the surface thereby defining the output window width, and wherein the input and output window widths are additionally defined by a pair of intersecting straight lines directed from each respective opposite interface of an input window radially through the center of the bore to each respective opposite interface of the output window, and wherein the intersecting lines define a LaGrange Invariant for the detection path.

6. A capillary electrophoresis system comprising a capillary tube having a bore, an inner surface defining the bore with a selected diameter, an outer surface, a wall thickness of the tube being defined between the surfaces, the bore being for transporting fluid past a detection path, an input window on an outer surface portion of the tube and an output window on an opposite outer surface portion of the tube, wherein the input window and the output window define respective widths, the detection path being defined between the input window through the bore and to the output window, and wherein there is a LaGrange Invariant for the detection path and wherein the input and output windows have a width such that the LaGrange Invariant is substantially consistent through the detection path.

7. A system as claimed in claim 6 wherein the LaGrange Invariant is determined by the substantially maximum angle for receiving a signal in the bore relative to the substantially least signal through the tube wall.

8. A system as claimed in claim 7 wherein the LaGrange Invariant is selected to be the substantially highest value for the detection path.

9. A capillary electrophoresis system comprising a capillary tube having a bore, the bore having a center, an inner surface defining the bore with a selected diameter, an outer surface, a wall thickness of the tube being defined between the surfaces, the bore being for transporting fluid past a detection path, an input window on an outer surface portion of the tube, the input window having opposite interfaces with the outer surface of the tube thereby defining the input window width, and an output window on an opposite outer surface portion of the bore, the output window having opposite interfaces with the outer surface of the tube thereby defining the output window width, an axis through the center of the bore and a position midway between the interfaces of the input window and midway between the interfaces of the output window, and wherein the input and output window widths are established by H=Yn.sub.1 u.sub.0 wherein Y is substantially half the window widths and substantially half the diameter of the bore, n.sub.1 is the refractive index of the tube, u.sub.0 is the angle between the axis and the line from an interface of the windows through the center, and H is an optical constant for the system.

10. A system as claimed in claim 1 including an fiber optic input for directing input light to the input window, the fiber optic input having a Numerical Aperture and wherein the fiber optic input includes a core having an end face spaced a distance from the input window whereby light is transmitted from the fiber optic input end face, the end face having an interface and wherein lines of light from the interface are directed at a converging angle substantially equal to a half angle for the Numerical Aperture, and wherein the converging lines of light are directed towards the input window at a location defining a width substantially equal to the window width.

11. A system as claimed in claim 10 wherein the lines of light at the half angle for a Numerical Aperture of the fiber are directed towards a center of the bore.

12. A system as claimed in claim 10 including a fiber optic output for receiving light from the output window.

13. A system as claimed in claim 1 including an fiber optic output for receiving light from the output window, and the fiber optic output having a Numerical Aperture, and wherein the fiber optic output includes a core having an output end face spaced a distance from the output window, the end face having an interface with a cladding and wherein output lines of light from the output window define a diverging angle related to the Numerical Aperture, the diverging angle of light from the interface of the output window impacting the output fiber, such lines defining a width at the end face at least substantially no wider than the width of the end face of the fiber optic output.

14. A system as claimed in claim 13 wherein the diverging lines of light emanate from a center of the bore.

15. A system as claimed in claim 1 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

16. A system as claimed in claim 5 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

17. A system as claimed in claim 6 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

18. A system as claimed in claim 9 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

19. A system as claimed in claim 10 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

20. A system as claimed in claim 13 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

21. A system as claimed in claim 1 including multiple input windows spaced from each other and multiple output windows, the windows being spaced from each other.

22. A system as claimed in claim 1 wherein the input window is located opposite the output window.

23. A system as claimed in claim 21 wherein respective input windows are related to opposite output windows.

24. A system as claimed in claim 1 wherein the windows have a rectangular cross-section.

25. A capillary electrophoresis system comprising a capillary tube having a bore, an inner surface defining the bore diameter, an outer surface, a wall thickness of the tube being defined between the surfaces, the bore being for transporting fluid past a detection path, an input window on an outer surface portion of the tube and an output window on an opposite outer surface portion of the tube, at least one of the input window and output window defining a width, the width being substantially equal to the bore diameter, means for generating a signal, and wherein the signal directed along the detection path between the input and output windows essentially does not pass through the wall without additionally passing through the bore.

26. A system as claimed in claim 25 including a fiber optic input having a core and cladding for directing input light to the input window, and wherein the fiber optic input includes an end face for the core, the end face being spaced a distance from the input window whereby light related to a Numerical Aperture of the fiber optic input from an interface of the core and cladding defines a substantially straight line adjacent an edge of the input window width and to the center of the bore.

27. A system as claimed in claim 25 including a fiber optic output including a core and cladding for receiving output light from the output window, and wherein the fiber optic output includes an end face for the core, the end face being spaced a distance from the output window whereby output light related to a Numerical Aperture of the fiber optic output directed along a substantially straight line from the center of the bore adjacent an edge of the output window width is directed to a position at least within the interface of the core and cladding.

28. A system as claimed in claim 26 including a fiber optic output including a core and cladding for receiving output light from the output window, and wherein the fiber optic output includes an end face for the core, the end face being spaced a distance from the output window whereby the light from the center of the bore directed adjacent an edge of the output window width is directed to a position at least within the interface of the core and cladding.

29. A capillary electrophoresis optical system comprising a capillary tube having a bore with a center, an inner surface defining the bore with a selected diameter, an outer surface, and a wall thickness of the tube defined between the surfaces, the bore being for transporting fluid past an optical path, an optical input window in an outer surface of the tube and an optical output window in an opposite outer surface portion of the tube, at least one of the input window or output window defining an aperture width, and wherein the window width is not substantially greater than the bore diameter.

30. A system as claimed in claim 29 wherein the width of both the windows are not greater than the bore diameter.

31. A system as claimed in claim 29 wherein the width of at least one of the windows is equal to the bore diameter.

32. A system as claimed in claim 31 wherein the width of both the windows is equal to the bore diameter.

33. A capillary electrophoresis optical system comprising a capillary tube having a bore, the bore having a center, an inner surface defining the bore with a selected diameter, an outer surface, a wall thickness of the tube being defined between the surface, the bore being for transporting fluid past an optical path, an optical input window on an outer surface portion of the bore, the input window having opposite interfaces with the surface thereby defining the input window width, and an optical output window on an opposite outer surface portion of the tube, the output window having opposite interfaces with the surface thereby defining the output window width, and wherein the input and output window widths are defined by a pair of intersecting straight lines directed from each respective opposite interface of an input window radially through the center of the bore to each respective opposite interface of the output window and the window widths are substantially equal to the bore diameter.

34. A capillary electrophoresis optical system comprising a capillary tube having a bore, an inner surface defining the bore with a selected diameter, an outer surface, a wall thickness of the tube being defined between the surfaces, the bore being for transporting fluid past an optical path, an optical input window on an outer surface portion of the tube and an optical output window on an opposite outer surface portion of the tube, wherein the input window and the output window define respective widths, the optical path being defined between the input window and output window and wherein there is a LaGrange Invariant for the optical path and wherein the LaGrange Invariant is substantially consistent through the optical path.

35. A system as claimed in claim 34 wherein the LaGrange Invariant is determined by the substantially maximum angle for receiving light in the bore relative to the substantially least light through the tube wall.

36. A system as claimed in claim 35 wherein the LaGrange Invariant is selected to be substantially the highest value for the optical path.

37. A capillary electrophoresis optical system comprising a capillary tube having a bore, the bore having a center, an inner surface defining the bore with a selected diameter, an outer surface, a wall thickness of the tube being defined between the surfaces, the bore being for transporting fluid past an optical path, an optical input window on an outer surface portion of the tube, the input window having opposite interfaces with the outer surface of the tube thereby defining the input window width, and an optical output window on an opposite outer surface portion of the bore, the output window having opposite interfaces with the outer surface of the tube thereby defining the output window width, an optical axis through the center of the bore and a position midway between the interfaces of input window and midway between the interfaces of the output window, and wherein the input and output window widths are established by H=Yn.sub.1 u.sub.0 wherein Y is substantially half the window widths and substantially half the diameter of the bore, n.sub.1 is the refractive index of the tube, u.sub.0 is the angle between the optical axis and the line from an interface of the windows through the center, and H is an optical constant for the system.

38. A system as claimed in claim 29 including a fiber optic input for directing input light to the input window, the fiber optic input having a Numerical Aperture, and wherein the fiber optic input includes a core having an end face spaced a distance from the input window whereby light is transmitted from the fiber optic input end face, the end face having an interface with a cladding and wherein lines of light from the interface are directed at a converging angle substantially equal to a half angle for the Numerical Aperture, and wherein such converging lines of light are directed towards the input window to impact the input window at a location defining a width substantially equal to the window width.

39. A system as claimed in claim 38 wherein the lines of light at the half angle for a Numerical Aperture of the fiber are directed towards the center of the bore.

40. A system as claimed in claim 29 including a fiber optic output for receiving light from the output window.

41. A system as claimed in claim 29 including a fiber optic output for receiving light from the output window, and the fiber optic output having a Numerical Aperture, and wherein the fiber optic output includes a core having an output end face spaced a distance from the output window, the end face having an interface with a cladding and wherein output lines of light from the output window define an angular diverging angle related to the Numerical Aperture, the diverging angle being such that when lines of light from the interface of the output window impact the output fiber, such lines define a width at least substantially no wider than the width of the end face of the fiber optic output.

42. A system as claimed in claim 41 wherein the diverging lines of light emanate from the center of the bore.

43. A system as claimed in claim 29 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

44. A system as claimed in claim 33 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

45. A system as claimed in claim 34 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

46. A system as claimed in claim 37 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

47. A system as claimed in claim 38 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

48. A system as claimed in claim 41 wherein the capillary tube includes a coating and the windows are formed by selective removal of the coating.

49. A system as claimed in claim 29 including multiple input windows spaced from each other and multiple output windows, the windows spaced from each other.

50. A system as claimed in claim 29 wherein the input window is located radially opposite the output window.

51. A system as claimed in claim 49 wherein respective input windows are related to radially opposite output windows.

52. A system as claimed in claim 29 wherein the windows have a rectangular cross-section.

53. A capillary electrophoresis optical system comprising a capillary tube having a bore with a center, an inner surface defining the bore with a selected diameter, an outer surface, a wall thickness of the tube being defined between the surfaces, the bore being for transporting fluid past an optical path, an optical input to the tube and an optical output to the tube, and wherein the bore diameter defines a LaGrange Invariant, and wherein the optical path between the input and output conforms to the LaGrange Invariant.

54. A system as claimed in claim 53 including a fiber optic input for directing input light to the optical input, and wherein the fiber optic input defines a Numerical Aperture and wherein the Numerical Aperture is related to the LaGrange Invariant of the tube.

55. A system as claimed in claim 53 including an fiber optic output for receiving output light from the optical output, and wherein the fiber optic output defines a Numerical Aperture, and wherein the Numerical Aperture is related to the LaGrange Invariant of the tube.

56. A system as claimed in claim 54 including a fiber optic output for receiving output light from the output window, and defines a Numerical Aperture, and wherein the Numerical Aperture is matched in relation to the LaGrange Invariant of the tube.

57. A capillary electrophoresis optical system comprising a capillary tube having a bore with a center, an inner surface defining the bore with a selected diameter, an outer surface, and a wall thickness of the tube defined between the surfaces, the bore being for transporting fluid past an optical path, a fiber optic input for directing input light to the capillary, and wherein the fiber optic input includes a core having an end face spaced a distance from the input window whereby light is transmitted from the fiber optic input end face, the end face having an interface with a cladding and wherein light from the interface is directed at a converging angle related to a Numerical Aperture of the fiber input, a fiber optic output for receiving light from the capillary, and wherein the fiber optic output includes a core having an output end face spaced a distance from the capillary, the fiber optic output including a core having an interface with a cladding and wherein light is directed towards the interface, and wherein the light direction from the interface define a LaGrange Invariant for the optical path.

58. A system as claimed in claim 57 wherein the LaGrange Invariant is defined by a Numerical Aperture of the fiber optic input and fiber optic output.

RELATED APPLICATION

This invention relates to Application Ser. No. 07/847,783, filed Mar. 5, 1992 and entitled "Fiber Optic Flow Cell for Detection of Electrophoresis Separation with a Capillary Column and Method of Making Same." The contents thereof are incorporated by reference herein.

BACKGROUND

Accurately detecting light in a capillary electrophoresis system is an increasingly vital procedure for the analysis of chemicals, cells and biological matter.

This invention relates to a capillary electrophoresis system, particularly where light through a capillary tube is optically detected. More specifically, the invention relates to the precise detection of light output from such a capillary electrophoresis system. Additionally, the invention is concerned with optimizing light energy input to and output from a capillary electrophoresis tube so that, overall, there is obtained a highly sensitive capillary electrophoresis system.

Electrophoresis is an analytical technique whereby small volumes of mixed sample solution are separated by differences in electric charges and molecular sizes of individual sample components. Capillary electrophoresis requires the transportation of small, often minute, quantities of sample solution through a capillary tube under pressure or electrical differential. As the sample travels though the capillary tube, a separation of components of the sample is effected due to the differential.

A light source and a light detector are placed outside the capillary tube which is mounted in a support. As the sample, so separated, migrates through the capillary tube, light is passed along an optical path across the sample. By detecting the light output, information about the nature, for instance, the chemical make-up, of the sample can be obtained.

The capillary electrophoresis tube is a microbore tube and is used as the support and means for transporting liquid containing the sample. Typically, the dimension of the capillary bore diameter ranges from 5 to 500 microns. The shape usually employed for the capillary tube is cylindrical and the wall thicknesses of the tube ranges from 25 to 200 microns.

The nature of the walls of the capillary tube provide different refraction indices and generally cause inaccuracies in the light which is received by the detector. To provide accurate results, however, it is important to avoid optical problems such as distortions to the light caused by perturbations and wall effects of the tube.

The small sizes encountered in the capillary dimensions pose severe problems for accurate optical detection. These include problems arising from the short pathlength through the sample.

Detection of the separated components requires a measurable property of the component. Absorbance, for instance, is measured as the relative decrease in the intensity of the light at a selected wavelength passing through the sample due to the relative concentration of the sample being measured, its specific absorbtivity, and pathlength.

Absorbance is expressed by the Beer-Lambert-Bourgier Law:

A=kcl

where

A=Absorbance

k=molar extinction coefficient

c=concentration of the absorbing sample

l=pathlength through sample

When the pathlength becomes smaller, as is encountered with the minute capillary dimensions typically used, the magnitude of the Absorbance decreases.

With the circular cross section of the bore of the capillary tube, the pathlength also varies sinusoidally as light passes transversely through the capillary bore. The pathlength at the poles is zero, and is a maximum length at the equator.

Another problem occurs when light from the light source passes through the solid wall material of the capillary tube without passing through the sample solution in the bore of the tube. This light, termed stray light, contributes to the light energy arriving at the detector without having been attenuated by the absorbing sample.

Additional problems arise in the optical system for detection of solution volumes at the tiny dimensions used for capillaries. To assure reproducible reliable determinations of detected light, the capillary tube must be positioned in the optical system rigidly and accurately. It is difficult and costly to achieve the mechanical tolerances required to meet these conditions where the bore of the tube is movable relative to the window for light that enters the bore.

There is a need to provide a system which can provide accurate data and information within modern detail standards and yet have relaxed precision mechanical tolerances and requirements.

The prior art has used optical systems and optical devices such as lenses and slits in the optical path to improve the optical system. These devices themselves create optical distortions and changes, such as dispersion, to the light. Further inaccuracies are thus created in the detected light.

There is a need to provide a system with a minimum number of optical elements and devices between the signal input and the detected signal.

Light for the optical system is obtained and received through fiber optical input and output. The fiber optic has a core and cladding which have different refractive indices, and the light is propagated in the fiber core. An Angle of Acceptance of the fiber is the half-angle of an Acceptance cone of the fiber. This is the angle about the central axis of the fiber. It is also the angle at the interface of the core and cladding, namely, the Angle of Acceptance is defined by the difference in the refractive index of the core and cladding. Light entering a fiber at angles greater than the acceptance angle leak away and are not propagated to the output end of the fiber optic. Similarly, light normally does not exit a fiber at an angle greater than the Angle of Acceptance.

A Numerical Aperture of the fiber is related to the Angle of Acceptance through the fiber, and is a measure of light-gathering power of the fiber optic. The Numerical Aperture is the sine of the Angle of Acceptance for the fiber.

Prior art systems have not been able to optimize the optical system and the relationship of light generation and propagation in a fiber optic and the detection characteristics in capillary electrophoresis systems.

There is a need for an improved capillary electrophoresis detection system having less distortion of light, and which is easily configured with the fiber optics of the optical system. Also, there is a need for a system which optimizes the use of the light energy from a fiber optic as measured by the Numerical Aperture into the capillary electrophoresis tube. Further, there is in turn, the need for the output from the capillary electrophoresis tube to be related to a receiving fiber optic so as to maximize the receipt of the light from the tube as measured by the Numerical Aperture of the receiving fiber optic.

SUMMARY

The present invention provides an optical system for capillary electrophoresis which markedly improves the characteristics of capillary electrophoresis detection and of the optical system. The invention significantly minimizes multiple problems encountered with prior art systems.

The invented system provides a capillary electrophoresis system comprising a capillary tube having a bore that transports sample fluid past a detection path, namely an optical path. An inner surface of the bore defines a selected diameter. A wall thickness is defined between the inner surface and an outer surface. The optical path is defined so that light between an optical input window and an optical output window to the tube does not pass through the wall without additionally passing through the bore.

The input window is provided preferably on an outer surface portion of the tube and the output window is provided preferably on an opposite outer surface portion of the tube. The tube is opaque to light passage through the bore at one or more selected wavelengths except at the windows, which are discretely shaped and located relative to the capillary tube bore.

At least one of the input window or output window defines an aperture width and the aperture width is substantially no greater than the bore diameter. "Opposite" is considered as positions diametrically opposed to each other.

With this configuration, substantially only the critical and optimized light passes into the tube through the bore and out of the tube. The sample passing in the bore can be detected with substantially improved accuracy and detail.

Preferably, both apertures have a width substantially no greater than the bore diameter and preferably are configured to be of a substantially equal width as the bore diameter. The width of both apertures is preferably equal to the bore diameter.

The aperture width is preferably defined by respective straight lines directed adjacently from respective interfaces between an input window and the outer surface of the bore to the respective opposite interfaces between an output window and the outer surface of the bore. Each respective line passes radially through a central longitudinal axis of the bore, and each respective straight line adjacent respectively opposite interfaces defining the width of the input window and output window.

A LaGrange Invariant is an optical Invariant which is related to the aperture of light in the optical path, is a constant for the optical path, and is defined by the maximum aperture in the optical path.

In one form of the invention, the width of the windows also defines an optical aperture width which is established in terms of a LaGrange Invariant. In another form of the invention, the diameter of the bore and at least one, and preferably both, windows define the optical aperture width in terms of the LaGrange Invariant.

The Invariant for the input and output apertures are retained at a relatively high value, preferably as high as possible. The higher the Invariant, the greater the amount of light energy passing through the bore. The Invariant is consistent through at least the optical path between the input window and output window. The value of the LaGrange Invariant is determined by substantially the diameter of the capillary bore. Since the diameter is preferably equal to the window width, the LaGrange Invariant is also defined by the window width.

In the present invention, the Invariant is also defined by the angle between the line from a window interface to the bore center to either side of a transverse axis along the optical path through the bore center. It is the substantially maximum angle for receiving light in the bore relative to the least light through the tube wall. By having the window width, namely, the aperture width so defined, substantially only the critical light passes through the capillary bore and then reaches the output window. Light which would otherwise render the detection inaccurate is masked out of the capillary electrophoresis system between input and output.

The LaGrange Invariant defines the location and width of the windows, and also the ratio of the fiber end diameter and the window width. As such, the LaGrange Invariant defines the extremities of the optical system and the optical envelop or optical caustic.

In a preferred form of the invention, there is provided a fiber optic input for directing an input signal, namely light, to the input window and a fiber optic input for receiving light from the output window. The light from the fiber input falls within both a diverging cone and a converging cone of light, the conical half angle being the Angle of Acceptance of the fiber. Similarly, light into the output fiber is received in a converging cone and a diverging cone, also defined by its respective Angle of Acceptance. Thus, the angles of the respective converging and diverging cones are established by the Angles of Acceptance of the fibers. The converging input cone from the fiber input and the diverging cone for the fiber output are matched with the optical path of the capillary tube.

The fiber input includes an end which is spaced a selected distance from the input window whereby the width of the converging cone containing the light rays from the fiber input end face defines a converging angle cone which substantially matches or mates with the width of the input window.

The spacing of the end of the input fiber is also such that the cross-sectional area of the converging cone at the end of the input fiber is established by the LaGrange Invariant of the capillary electrophoresis tube.

The output light from the capillary falls within an angle substantially equal to the Angle of Acceptance of the fiber optic output. The spacing of the receiving end face of the fiber output from the output window is such that the diverging cone of light exiting from the tube defines a width so that it constitutes at least a substantially equal cross-section of the receiving end face of the core of the fiber output. This relationship of a diverging output cone is set up in matching relation to the La Grange Invariant of the capillary tube.

The apex of the converging cone from the fiber input is directed inwardly into the tube and is located preferably at or towards the center of the bore. The apex of the diverging cone to the fiber output is also located preferably at or towards the center of the bore.

The tube outer surface normally includes a confromal coating of a polymer which is opaque to light energy at the ultraviolet wavelength. The input and output windows are formed by selectively removing at least this coating by a laser. Ideally, the windows should be located as close to the bore as possible to minimize interference with the light. To this end, a portion of the wall can in some cases also be removed to locate the inside of the window closer to the bore.

Preferably, the capillary tube is rigidly mounted in a holder with the tube secured and held by flashing elements from the molding process for fabricating the holder. Thereafter, laser energy is precisely applied to cut the windows in sequence. The input window and output window are selectively formed in turn. This effectively creates a masking to the ultraviolet wavelengths constituted by the coating while permitting the ultraviolet wavelengths to enter and leave the tubing through the windows.

By the present invention, there is provided an optical path which includes an input fiber, the capillary tube and an output fiber without the need for additional optical elements, such as lenses or slits, to focus or manipulate a light beam through the capillary tube. By having light pass from input fiber through air and directly into the glass constituting the capillary tube, distortion is minimized and detection accuracy is notably enhanced. By having the windows integrally formed in the tube wall, and the capillary tube rigidly fixed in the holder, the ease of optical and mechanical alignment of the electrophoresis system is markedly simplified.

This system provides for substantially more light to pass through the sample in the bore of the capillary tube and to the output window without passing through unnecessary parts of the tube and being available to provide for distortion of the required detected results of the sample.

By using the critical angle relationship as defined by the window and fiber characteristics, light containing information, namely light modulated by only the sample in the bore, passes to the output fiber. This permits for obtaining relevant sensitive detected information of the requisite sample. Also, the light output is obtained without distortion or aberrations caused by the optical elements.

The net result is a highly significantly improved optical system for capillary electrophoresis, with a substantial improvement in the efficiency of light transmission from the input through the tube and to the output.

The invention has application to wavelengths extending at least in the electromagnetic spectrum, and particularly from the infrared through visible to the ultraviolet wavelengths.

The invention is further described with reference to the accompanying drawings.

DRAWINGS

FIG. 1 is a system layout illustrating a cross-sectional end view of a capillary tube with representative light rays passing through the bore of the capillary tube, and diamet