Abstract:
A compact microflowcell apparatus having a disposable flowcell unit that can be fabricated with uniform optical characteristics and an associated support fixture adapted to be placed in the sample compartment of a standard fluorimeter or spectrophotometer to accommodate different light path configurations in such instruments.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims the benefit of priority of Provisional Patent Application Ser. No. 60/656,803 filed Feb. 25, 2005 for Leanna M. Levine, the entire content of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to a compact microflowcell apparatus for use in spectrographic and fluorimetric measuring equipment.  
       BACKGROUND OF THE INVENTION  
       [0003]     A flowcell is generally defined as a device carrying a solution stream that is placed in a path between a light source and light detection system to measure the optical characteristics of the solution stream.  
         [0004]     Flowcells are commonly used in devices such as a spectrophotometer, colorimeter, or fluorimeter to measure the light transmissivity, absorbance, and reflectivity characteristics of fluids, solutions, or gases; either in stasis or in dynamic flow.  
         [0005]     In practice, the flowcell is fixedly mounted in a suitable holder that is placed in a sample compartment of an analyzer apparatus, such as a fluorimeter, and light is directed to the flowcell carrying the sample fluid or solution being analyzed. The excitation light is transmitted through the sample and/or reflected by the sample in a manner to yield a light output that is representative of a particular characteristic of the fluid or solution.  
         [0006]     Prior art flowcells typically comprise transparent bodies adapted to contain a sample volume and are fabricated from quartz or UV transparent plastics. Such flowcells require a relatively large sample volume, on the order of 100 microliters or greater and are fragile and difficult to clean. In addition, the fabrication process generally results in non-uniform optical characteristics producing variations in transmitted or reflected light from unit to unit.  
         [0007]     Fluorometers and similar analyzing apparatus often have multiple optical ports configured to direct the excitation and emission light pathways for a sample being analyzed. Such light pathways may be L-shaped, T-shaped, or straight-through paths or a combination of light paths to permit simultaneous measurements of different sample characteristics. In order to accommodate specific optical port configurations, the flowcell holder needs to be designed for the light pathways of the apparatus being used.  
         [0008]     The present invention is directed to an improved flowcell and support fixture that has important advantages and benefits over prior art flowcells and holders of the type described above.  
         [0009]     The flowcell of the invention has a layered assembly construction to provide a disposable flowcell unit that can be fabricated with uniform optical characteristics. The associated support fixture of the invention is easily adaptable to accommodate different light path configurations in analyzing instruments and can be placed in the sample compartment of a standard fluorimeter, or spectrophotometer.  
         [0010]     The flowcell is designed for easy insertion and replacement in the support fixture. In addition, the fluid inlet and outlet ports are located at the top end of the flowcell body. As such, in an installation where it may be difficult to make connections to a prior art type of flowcell, a flowcell of the present invention can be readily accessed so that its connections and mounting are easily reached.  
         [0011]     In addition, the flowcell assembly provides for a reduced sample volume and improved optical characteristics. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0012]      FIG. 1  is an exploded view of a flowcell of the invention;  
         [0013]      FIG. 2  is an assembly view of a flowcell of the invention;  
         [0014]      FIG. 3  is an exploded view of a support fixture of the invention;  
         [0015]      FIG. 4  is a diagrammatic view of an embodiment of the support fixture of  FIG. 3 ; and  
         [0016]      FIG. 5  is a diagrammatic view of an embodiment of a support fixture of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     The apparatus of the invention comprises a disposable microflowcell and support fixture to enable real-time monitoring of chemical and biological samples. The invention is adapted to fit into a conventional cuvette holder found in spectrophotometer or fluorimeter type instruments.  
         [0018]     A typical sample to be analyzed by such instruments requires that the cuvette or sample holder contain a minimum sample volume of at least 70 microliters. The microflowcell of the invention, however, can contain chemical or biological samples having sample volumes from about 0.1 to about 30.0 microliters.  
         [0019]     The design of the microflowcell allows real-time monitoring of changes in an analyte in the sample stream and permits the same sample volume to be monitored under a variety of sample concentrations. The apparatus of the invention can fit into a standard 1 cm×1 cm cuvette holder.  
         [0020]     With reference to  FIG. 1 , a flowcell    10    of the invention comprises a laminated layer assembly having a central layer portion  23 , a top film portion  19  and a bottom film portion  20 .  
         [0021]     The central layer portion of the flowcell comprises a middle segment  14 , a top surface segment  22  and a bottom surface segment  21 . The middle segment has an aperture  15  defining the contour of a sample receiving well  13 . The central layer can be made of black, non-reflective material of various thicknesses to achieve a desired sample well volume.  
         [0022]     An outlet port  12  connected to a fluid exit channel  17  is formed on the top surface segment and an inlet port  11  connected to a fluid entrance channel  16  is formed on the bottom surface segment. The channels can be formed using an injection molding or embossing process, or by laminating a thin adhesive layer containing the channels onto the middle segment.  
         [0023]     As shown in  FIG. 1 , the inlet and outlet ports are located in close proximity to each other at a top end of the layer assembly.  
         [0024]     The optical window of the flowcell is formed by bonding a thin film (approximately 0.002 inches thick) transparent material  19  on the top surface segment of the central layer and bonding a thin film transparent material  20  on the bottom surface segment of the central layer to cover the aperture  15 .  
         [0025]     The flowcell assembly is between 0.070 and 0.020 inches thick with a contained volume that varies from 30 microliters to less than 100 nanoliters, depending on the contour of the optical window and the thickness of the central layer.  
         [0026]     The optical window is preferably elliptical in shape to optimize the surface area exposed to the excitation light beam of a fluorimeter and the fluorescence light emitted to a detector. The window also has a wide exit channel  18  necking into a thin (approximately 1 mm) channel  17  to allow air bubbles to be trapped away from the light path. In addition, the surface of the flowcell can be treated to reduce air bubble formation by activating the surface using a corona, plasma or flame treatment to create reactive species at the surface that will selectively interact with various gaseous elements that may be present in a reduced atmosphere chamber.  
         [0027]     The microflowcell can be used to monitor fluorescence of a sample in the UV and visible light regions by employing selected plastic films to form the optical window. The films can also have surface coatings to optimize optical properties for a particular application. In addition, a porous membrane can be placed in the inlet or outlet pathways to retain materials having relatively large surface areas, such as microbeads, so that reagents can be concentrated on the surface of the material to increase the detection sensitivity. The microbeads can be used in or out of the optical pathways.  
         [0028]     Flowcell windows of the invention can also be fabricated from polarized material with one face of the window having vertical polarization and the opposite window face having horizontal polarization. By using a fluorimeter with two light detection pathways set 180 degrees from each other, and the excitation light pathway set at 90° to both, the fluorescence polarization of a sample in the optical window can be monitored in real time. Alternatively, the 180° dual pathway light detection mode can be used to monitor the emission of two different wavelengths of light from the sample. In this application, the surfaces of the optical window are treated or coated to make them opaque to wavelengths detected on opposite window faces.  
         [0029]     Another alternative flowcell design can have optical window faces that are UV transparent and non-birefringent. In this application, the flowcell is optimized for depth with the smallest optical window that allows the excitation light source and focusing optics to fill the face of the window with collimated light.  
         [0030]     The support fixture of the invention is adapted to hold the microflowcell at a specified angle to the excitation and emission light pathways in analyzer apparatus.  
         [0031]     With reference to  FIG. 2 , another embodiment of a flowcell    30    of the invention is shown, comprising a laminated assembly having a top surface segment  32 , a bottom surface segment  34 , a top film  36  and a bottom film  38 .  
         [0032]     An outlet port  46  connected to a fluid exit channel  48  is formed on the bottom surface segment and an inlet port  40  connected to a fluid entrance channel  42  and a sample receiving well through-hole aperture  44  is formed on the top surface segment. The inlet and outlet ports are located in close proximity to each other at a top end of the laminated assembly.  
         [0033]     The optical window of the flowcell is formed by bonding a thin (approximately 0.002 inches thick) transparent top layer cover film on the top surface segment and bonding a thin transparent bottom layer cover film on the bottom surface segment to cover the sample receiving well through-hole aperture.  
         [0034]     The top and bottom surface segments can be made of black, non-reflective material, such as Delrin, of various thicknesses to achieve a desired sample receiving well volume.  
         [0035]     The optical window is preferably elliptical in shape to maximize the surface area exposed to the excitation light beam of a fluorimeter and the fluorescence light emitted to a detector.  
         [0036]     With reference to  FIG. 3 , an exploded view of a support fixture of the invention is shown comprising a first side portion  50  having a first optical window  51 , a through-hole  52  and a corresponding longitudinal slot  53  adapted to receive the flowcell of the invention.  
         [0037]     A second side portion  54  of the support fixture has a second optical window  55 , a through-hole  56  and a mating longitudinal slot  57  adapted to receive the flowcell.  
         [0038]     The fixture is fabricated using a non-reflecting and non-emitting material such as black Delrin, for example, with a flowcell slot along a diagonal of the fixture, adapted to permit the flowcell to slide into place and be positioned in the light pathways of the optical windows.  
         [0039]     With reference to  FIG. 4 , one embodiment of the support fixture    60    for use in a standard 90° fluorimeter is shown where a microflowcell  62  is held at a 45° angle between the excitation light  68  and the emission light  70  pathways.  
         [0040]     The fixture contains a first optical window  69  and through-hole  71  to allow excitation light to impinge on a first side  62  of the flowcell and a second optical window  64  and through-hole  72  placed at 90° to the excitation light pathway to collect emitted light  70  from a second side  63  of the flowcell. Inserts  65  and  67  are provided in the fixture to hold a focusing lens for the excitation light source and a collimating lens to optimize detection of the emitted light.  
         [0041]     With reference to  FIG. 5 , another embodiment of the fixture is shown where the excitation and emission light pathways are located on the same side of the flowcell.  
         [0042]     The fixture contains a first optical window  84  and through-hole  92  to allow excitation light  88  to impinge on the surface of the flowcell  89  and a second optical window  86  and through-hole  94  placed at 90° to the excitation light source to collect emitted light  90  from the same surface of the flowcell. In this embodiment, the fixture is fabricated with a slot  82  along the diagonal that allows the flowcell  89  to slide into place and be held at a 45° angle to the excitation and emission light pathways. Inserts  85  and  87  are provided in the fixture to hold light focusing and collimating lenses.  
         [0043]     Although the various features of novelty that characterize the invention have been described in terms of certain preferred embodiments, other embodiments will become apparent to those of ordinary skill in the art, in view of the disclosure herein. Accordingly, the present invention is not limited by the recitation of the preferred embodiments, but is instead intended to be defined solely by reference to the appended claims.