Abstract:
The invention simplifies the apparatus for the analysis of organic and inorganic compounds in solutions and atmospheres, or particulates in atmospheres. The apparatus supports molecular fluorescence and absorption analyses of trace environmental contaminants. The design of the apparatus allows for deployment within the confmes of a monitoring well or other locations of limited access. The primary advantages are the easy replacement and configuration of excitation sources and detectors to configure a sample chamber for a particular analysis while using mininal volumes of sample or reagent. Miminizing the volume of reagent used is a very important consideration in automated field analyses. The invention uses light emitting diodes (LEDs) and photodetectors coupled to fiber optics to reduce the complexity and cost of the optics and electronics of the measurement components. The invention allows for the automation of sampling, sample preparation and analysis of environmental contaminants in natural waters and particulates in atmospheres, i.e. bacteria spores. The composition of the walls of the sample chamber determines the type of sample, natural water or atmosphere, that can be analyzed by the apparatus.

Description:
BACKGROUND OF INVENTION  
         [0001]    The typical ultraviolet-visible (UV-Vis) molecular absorption spectroscopic method requires the reaction of an analyte with a colorimetric reagent. The resulting solution is transferred into a cuvette and the cuvette placed into a spectrophotometer for the analysis of the analyte in the solution. The cuvette may be characterized as a removable sample reservoir of the spectrophotometer. This methodology is difficult to automate, restricts the path length, and the optical system and electronics are large and expensive. The instrumentation is not optimized for long-term use in the field.  
           [0002]    A removable sample reservoir with detectors and sources embedded in the the walls of a cell containing the removable sample reservoir was disclosed in U.S. Pat. No. 5,107,133 by Klainer. The disclosure does simplify the optics and electronics over the typical UV-Vis methods, however, the method has a removable reservoir. The invention is not optimized for the automation of the sampling, sample preparation and analysis.  
           [0003]    A chemical reservoir sensor for molecular absorption and florescence was disclosed in U.S. Pat. No. 5,116,756 by Klainer et al. The invention sought to eliminate the need for fiber optics and used excitation sources and detectors embedded in the walls of the chemical reservoir, The chemical sensing reagent was contained within the body of the chemical reservoir and the analyte introduced into the reagent. The analyte was introduced into the chemical reservoir using a variety of techniques including permeable membranes embedded in the walls of the sample reservoir.  
           [0004]    The invention presented in this disclosure uses fittings containing the excitation source or detector or both. Fiber optics are used to transmit light from the excitation source into the interior of the sample cell. Fiber optics are used to transmit light from the interior of the sample chamber to the detector. The sample reservoir is not removal and the sensing reagent does not reside in the sample reservoir.  
           [0005]    There are several commercially-available fiber optic fittings for connecting fiber optics to sample curvettes for spectroscopic analysis. However, the terminal end of the fiber optic is conducted to an excitation source or a detector, or grating spectrometer, using a second fiber optic fitting. This invention does not transmit light through the optical fitting. The optical fittings described in this invention has the excitation source or detector located within the fittings. The fittings transmit electrical signals, not optical signals, to external instrument components, i.e. amplifers, etc. The second major difference is the terminal end of the fiber optic fitting in this disclosure is actually placed into the solution being analyzed. The commercially-available fiber optic fittings usually terminate at the outer wall of a cuvette. Several advantages to this design include the mininaturization of the entire system, the path length may be adjusted and the problems associated with bending fiberoptics in areas of limited space are eliminated.  
         SUMMARY OF INVENTION  
         [0006]    This invention automates sampling, sample preparation and analysis using small volumes of reagents. The invention is composed of a sample chamber allowing for the introduction and removal of samples and reagents. The UV-Vis excitation sources and detectors are located inside fittings with fiber optics for transmitting and receiving light from within the sample chamber. The fittings can be connected to the walls or end plates of the sample chamber. The orientation of the fittings determine the type of analyses to be performed. The analyses capable of being performed by this invention include molecular absorption and fluorescence. This allows the sample chamber to double as the analytical cell.  
           [0007]    The ability to perform both sample preparation and analysis in the same sample chamber/analytical cell allows for the automation of the sampling, sample preparation and measurement process with mininal volumes. The selection of the material used for the fabrication of the wall of the sample chamber determines the type of sample that can be analyzed. Impermeable materials used in the fabrication of the walls of the sample chamber are suitable for the analysis of natural waters. Permeable materials used in the fabrication of the walls of the sample chamber are suitable for the analysis of particulates (i.e. bacteria spores) in atmospheres. An example of a permeable material would be an expanded fluorocarbon membrane (i.e. Gortex). This material is capable filtering atmospheres and capturing particulates on the interior wall of the sample chamber. After the capture of a sufficient concentration of particulates, a calorimetric or other reagent can be introduced into the sample chamber causing a reaction with the particulates. The resulting solution is then analyzed. One of the major properties of expanded fluorocarbon membranes is the ability of the membrane to be impermeable to solutions while passing vapors and air. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]    [0008]FIG. 1 is an illustration of the sample chamber/analytical cell with mounting ports for optical fittings.  
         [0009]    [0009]FIG. 2 is an illustration of an optical fitting with excitation source or detector.  
         [0010]    [0010]FIG. 3 is an illustration of a reflecting fitting.  
         [0011]    [0011]FIG. 4 is an illustration of optical fitting incorporating both the excitation source and detector.  
         [0012]    [0012]FIG. 5 is an illustration of sample chamber and optical fitting configuration for molecular absorbance measurements.  
         [0013]    [0013]FIG. 6 is an illustration of sample chamber and optical fitting configuration for molecular florescence measurements.  
         [0014]    [0014]FIG. 7 is an illustration of sample chamber with a optical fitting incorporating both excitation source and detector and an optical fitting containing a reflecting surface for molecular absorbance measurements.  
         [0015]    [0015]FIG. 8 is an illustration of an optrode incorporating the excitation source, detection and reflecting surface in one assembly. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    The primary components of the invention are the sample chamber and various fiber optic fittings. The sample chamber serves as both the reaction and analytical cell. The material used in the construction of the sample chamber wall determines the type of sample that can be analyzed. The fiber optic fittings have several types of designs for supporting molecular florescence and absorption of molecules in atmospheres, solutions and airborne particulates. The placement of the fiber optic fittings on the end plates or walls of the sample chamber determine the type of analysis to be performed.  
         [0017]    [0017]FIG. 1 illustrates the sample chamber  1  with several possible locations for the analytical ports  2 ,  3 ,  4 . The actual number and locations of the analytical ports  2 ,  3   4  are determined by the type of sample to be analyzed and the type of analyses to be performed. One or more inlet/outlet ports  5  are used for introducing samples and reagents into the interior of the sample chamber  1  for analysis and/or removing the analyzed samples from the sample chamber. All the analytical ports  2 ,  3 ,  4  are fitted with threaded holes or other means for connecting a fiber optic fitting  6  of FIG. 2. The analytical port  2  located at the top of the sample chamber  1  may be used in conjunction with an analytical port  3  located on the side of the sample chamber  1 . Alternatively, The analytical port  2  located at the top of the sample chamber  1  may be used in conjunction with an analytical port  4  located on the bottom of the sample chamber  1 . There are several embodiments only requiring the use of one analytical port.  
         [0018]    The total volume of the sample chamber may be from 0.1 to 100 mL. The sample and reagent are introduced into the sample chamber  1  using one or more solution inlet/outlet ports  5 . The volume of aqueous samples and reagents introduced in the sample chamber  1  is controlled by water level sensors or other methods of liquid volume control. The solution within the sample chamber may be agitated to aid in the completion of the reaction. After the completion of the reaction, the resulting solution is analyzed within the sample chamber  1 . The sample chamber  1  couples as the analytical cell. This coupling of the sample chamber with the analytical cell allows for the use of small volumes of samples and reagents and can be easily automated.  
         [0019]    The walls of the sample chamber  1  may be fabricated from permeable or impermeable materials. A sample chamber  1  with walls fabricated from impermeable materials may be used for the analysis of natural waters and other aqueous and non-aqueous solutions. A sample chamber  1  with walls fabricated from permeable materials such as expanded fluorocarbon membrane is used for the analysis of particulates in air or other atmospheres. The particulates are collected on the interior wall of the sample chamber  1  by the introduction of particulates suspended in air or other atmosphere through the inlet/outlet port  5  and the air allowed to pass through the permeable wall trapping the particulates. After a sufficient concentration of particulates are collected on the interior wall of the sample chamber  1 , the air flow is terminated and a reagent, extraction fluid or other solution is introduced into the interior of the sample chamber  1  using the inlet/outlet port  5 . There can be more than one solution inlet/outlet port  5  for introducing solutions into the interior of the sample chamber  1 . The resulting solution of the particulate-reagent interaction is determined using molecular absorption, molecular fluorescence or other chemical/biological analytical methodologies.  
         [0020]    [0020]FIG. 2 illustrates the basic fiber optic fitting  6 . The basic fiber optic fitting is composed of screw threads  7  or other means of attaching the fiber optic component  6  to the sample chamber  1  with a seal. The fiber optic  8  is sealed into the body of the fiber optic fitting using a seal  7 . The seal  9  may be an epoxy or other sealant, heat shrink fluorocarbon polymer or other material forming a seal between the fiber optic  8  into the fiber optic fitting  6 . The fiber optic  8  is terminated in the excitation source/detector cavity  10 . The excitation source/detector cavity  10  contains the excitation source or detector  12  and back plate  13  which is used to mount the excitation source/detector  12  into the fiber optic fitting  6 . An optional optical filter  11  may be located between the excitation source or detector  12  and the fiber optic  8 . An electrical cable  14  is used to connect the excitation source or detector  12  to the appropriate electronic components for signal manipulation.  
         [0021]    The preferred excitation source  12  for the optical fittings are light emitting diodes (LEDs). The preferred detector  12  are solid state photodetectors. A preliminary design of this invention was tested for the determination of Cr(VI) using phenycarbazide employing a molecular absorbance technique. The two fiber optic fittings orientated along the same axis had a 4-cm path length.  
         [0022]    The excitation source fitting used a green LED (540 nm) and the detector fitting used a Hammatsu photodetector. The analysis had a limit of detection of 5 parts per billion using a total volume of 5 ml of solution and reagent.  
         [0023]    The fiber optic  8  is designed to pass beyond the end of the body of the iber optic fitting  6 . The fiber optic  8  may have the cladding removed to prevent a reaction of the cladding with the reagent used to perform the analysis. The composition of the fiber optic fitting  6  is selected to prevent a reaction with the reagent being used in the analysis. The path length is determined by the separation of the terminal ends of the fiber optics  8  not the dimensions of the sample cell  1 .  
         [0024]    The fiber optic fittings  6  are attached to the sample chamber  1  to create the various analytical methods, molecular florescence or absorption, of the solution contained in the sample chamber  1 .  
         [0025]    [0025]FIG. 3 illustrates a blank fitting  15  which is used to plug the analytical ports which are either not in use or can be used to aid in the analysis. The blank fitting  15  is attached to the sample chamber  1  of FIG. 1 with the use of threads  16  or other means of attachment to the sample chamber  1 . A mirror or other means of reflecting light  17  may be mounted on the blank body  15  which may be used to perform molecular absorbance measurements.  
         [0026]    [0026]FIG. 4 illustrates a dual fiber optic fitting  18 . The detector  19  and excitation source  20  are mounted in the same fiber optic fitting  18 . The detector cavity  21  can be fitted with an optional optical filter  22  which is placed closest to the terminal end of the detector fiber optic  23 . The detector  19  is located between the detector end plate  25  and the optical filter  22 . In some applications the optical filter  22  may not be required. The excitation source cavity  29  is fitted with an optional optical filter  30  which is placed closest to the terminal end of the source fiber optic  24 . The excitation source  20  is located between the source end plate  26  and the optical filter  30 . In some applications the optical filter  30  may not be required. The excitation source fiber optic  24  and the detector fiber optic  23  are passed through a seal  31  which allows the sufficient barrier between the dual fiber optic fitting  18  and the fiber optics  23 ,  24  to prevent leakage. The threads  32  or other method of attachment are used to attach the dual fiber optic body  18  to the sample chamber. The terminal ends of the excitation source fiber optic  24  and the detector fiber optic  23  are introduced directly into the sample being analyzed.  
         [0027]    [0027]FIG. 5 illustrates the use of an excitation source fitting  33  aligned along the same axis as an detector fitting  34 . The fittings  33 ,  34  are located on the opposite ends of a sample chamber  35 . The light from the excitation source fitting  33  is transmitted through the excitation source fiber optic  36  to the interior of the sample chamber  35 . The light, after passing through the solution is collected by the detector fiber optic  37  of the detector fitting  34 . The alignment of the optical fittings allow for molecular absorbance measurements.  
         [0028]    [0028]FIG. 6 illustrates the use of an excatiation source fitting  38  aligned along a different axis than the detector fitting  39 . The fittings  38 ,  39  are located at the top and side of the sample chamber  40 . The light from the excitation source fitting  38  is transmitted through the excitation source fiber optic  41  to the interior of the sample chamber  40 . The fluorescent light is collected by the detector fiber optic  42  of the detector fitting  39 . The alignment of the optical fittings allow for molecular florescence measurements.  
         [0029]    [0029]FIG. 7 illustrates the use of a dual optical fiber system with the excitation source and detector located in the same fitting  43 . Molecular absorbance measurements are performed by fitting the opposite analytical port with a blank fiber optic fitting  47  fitted with a reflecting surface  48 . The light emitted from the excitation source fiber optic  44  is reflected from the reflecting surface  48  on the blank fiber optic body  47  and collected by the detector fiber optic  45  which is used to measure absorbance of the species of interest in the sample. Molecular fluorescence measurements are performed by replacing the reflecting surface  48  of the blank fiber optic body  47  with a surface which does not reflect the excitation source light back into the detector fiber optic  45 . The wavelength of the light from the excitation source fiber optic  44  is used to excite the molecule of interest in the media. Upon fluorescence, the light from the excited molecules is collected through the detector fiber optic  45 .  
         [0030]    [0030]FIG. 8 illustates an optrode for use in either a sample chamber  1  of FIG. 1 or for use as a replacement for a spectrophotometer for performing colorimetric analysis in the laboratory. The detector  49  and excitation source  50  are both mounted in the same optrode body  62 . The detector cavity  51  is fitted with an optional optical filter  52  which is placed closest to the terminal end of the detector fiber optic  53 . The detector  49  is located between the detector end plate  55  and the optical filter  52 . In some applications the optical filter  52  may not be required. The excitation source cavity  59  is fitted with an optional optical filter  60  which is placed closest to the terminal end of the source fiber optic  54 . The excitation source  50  is located between the source end plate  56  and the optical filter  60 . In some applications the optical filter  60  may not be required. The excitation source fiber optic  54  and the detector fiber optic  53  are passed through a seal  61  which allows the sufficient barrier between the optrode body  62  and the fiber optics  53 ,  54  to prevent leakage. The terminal ends of the excitation source fiber optic  54  and the detector fiber optic  53  are introduced directly into the sample being analyzed. A reflecting surface  64  is suspended below the terminal ends of the excitation source fiber optic  54  and the detector fiber optic  53 . The reflecting surface  64  is typically located 0.5 to 3 cm below the terminal ends of the fiber optics  53 ,  54 . The reflecting surface  64  is used to reflect the light from the terminal end of the excitation source fiber optic  54  into the terminal end of the detector fiber optic  54 .  
         [0031]    The typical source used for the the excitation source  50  are LEDs. The typical detector  49  is solid-state photodetector. This optrode may be used independently of a sample chamber and can be used a substitute for a spectrophotometer in the colorimetric analysis of several analytes such as cobalt, chromoum (VI) and nickel.