Optics: measuring and testing – Standard
Reexamination Certificate
1999-09-24
2002-02-19
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Standard
Reexamination Certificate
active
06348965
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to fluorescence and absorption spectroscopy using solid state standard coatings on optical glass or quartz. More specifically it relates to the calibration of fluorescence or absorbance reading microplate readers or spectrometers using a solid state device invention which is shaped to fit into square or bullet shaped microplate holders or spectrometer chambers and are read on appropriate fluorescence or absorption readers.
BACKGROUND OF THE INVENTION
Standards which validate true capacity and integrity of various measuring devices are well known in the art. Whether standards used are solid, gas or liquid samples, they are quite common among all testing machines. The purpose of standards is to make sure that testing equipment is reading accurately, so that the measurements obtained on unknown quantities can be accepted as true and reliable. For this reason all testing machines have some standard that uniformly performs calibrations to assure readings which are consistent with the samples used and the unknowns tested. Traditionally this has required many samples of the materials at various compositions used as controls.
Spectroscopy is used to identify various unknown substances by reading spectroscopic patterns. Usually samples are tested over a wide range of wavelengths, from the Ultra Violet to Visible to Infra-Red bands of the spectrum. Testing relies on the consistent absorption or fluorescence by various compounds at specific wavelengths of light which produce a consistent pattern identifying the substance. Sometimes making an accurate identification of a substance is difficult because it is entirely dependent on absorption values of the substance. With fluorescent spectroscopy the user can examine the absorption or excitation of the compound as well as its emission of energy in the form of light as it returns to the ground state. For these substances, there are now two readings, which make it possible to identify unknowns with greater precision than ever before. To produce more accurate readings, solid state standards in microplates of any number can be made that standardize testing so that readings can be relied upon quickly and uniformly. The compounds absorb light during excitation and emit light of longer wavelength during emission. Furthermore, fluorescence spectroscopy is much more sensitive than U.V., visible or infra-red spectroscopy. This is because fluorescence is the excitation of the compound to a glow. This fluorescent glow can also be amplified to extremes by increasing voltage to the photomultiplier tube.
A review of the patent literature shows that the use of solid state standards with coatings in the calibration of microplate readers is a novel idea and not covered in the patent literature. For example, U.S. Pat. No. 4,661,711 uses an internal standard consisting of a fiberoptic bundle which fluoresces to calibrate a detector after splitting a light beam. The standard presented herein is an external optical glass moiety shaped to fit within a microplate holder or spectrometer chamber which is read in the corresponding instrument. The coated insert when read, gives a non changing reading provided that the photomultiplier (detector), voltage to the photomultiplier tube, lamp light output, monochomator if present and internal electronics do not change over time.
U.S. Pat. No. 5,414,258 entitled “Apparatus and method for calibration of fluorescence”, describes an apparatus for reading the non visible fluorescence intensity of bar code shaped fluorescent targets which can be adjusted in the apparatus by changing the distance between the target and the detector or by changing the area of the target exposed to the detector. The solid state standards of the present invention can be used in absorption spectroscopy as well as fluorescence spectroscopy, and are shaped to fit microplate wells not as bar codes. The distance to the photomultiplier tubes is constant when reading these solid state standards in microplate readers although voltages applied to the photomultiplier tube (gain), will decrease or increase the relative magnitude of the fluorescence detected.
U.S. Pat. No. 3,854,050 entitled “High precision fluorometer for measuring enzymatic substrates in tissue” uses a fluorescent glass in combination with attenuating filters in a custom cuvette standard. The present invention however describes a microplate reader which uses absorbance or fluorescence standards on coated glass or quartz contoured to fit in a microplate or spectrometer; in contrast to the macro-cuvette holding apparatus described in the '050 patent which employs a rectangular cuvette shaped reference. Instead of using attenuating filters to delimit the fluorescent emission of a specific reference standard, the invention disclosed herein uses industrial coatings which absorb in the Ultra Violet, Visible or Infra-Red electromagnetic ranges and are stable over time.
U.S. Pat. No. 5,503,910, entitled “Organic electroluminescence device”, describes an organic electroluminescence device consisting of a transparent anode (negatively charged electrode) which is coated with two layers of organic. When an electric field is applied, the first organic layer emits light at 380-480 nm, the second layer emits light at 480-580 nm and an organic in the first and second layer emits light at 580-620 nm. Overall the effect of this device is the emission of high energy white light. Alternatively in the present invention the reference standards emit monochromatic light when exposed to light delivered through an excitation or absorbance filter and are not dependant upon an electric field to emit light. More tellingly the samples or standards are coated with fluorescent or absorptive substances rather than an anode.
U.S. Pat. No. 4,868,126 entitled “Method of calibrating a fluorescent microscope using fluorescent calibration microbeads simulating stained cells” uses a hydrophilic microbead which covalently binds to a fluorescent molecule and can be visualized under a fluorescence microscope. The beads are microscopic (ranging from 1-20 microns) and therefore scatter light, which may be a limiting factor in a quantitative measurement device such as a microplate reader. Another problem with the microbeads-fluorescent molecule covalent bond is their lack of stability in solution. The coatings in the present invention are baked at 250 degrees Centigrade for several days by spectral coating experts resulting in a stable microwell insert.
U.S. Pat. No. 5,689,110 entitled “Calibration method and apparatus for optical scanner”, uses a beam splitter in a fluorescence spectrometer to compare two internal solid state standards, a calibration ruby and a gold standard. Neither of these standards are among the coatings which are utilized by the invention disclosed herein and moreover the standards are external to the measurement device. Furthermore a ratio method similar to the one described by the '110 patent could not be used in a microplate reader.
U.S. Pat. No. 4,925,629 discloses a diagnostic device for preparing a standard calibration curve which employs a set of liquid standard tubes of diluted liquids which serve as a reservoir of connecting tubes. A micropipetting device then simultaneously draws up solution from eight tubes for serial transfer to other tubes. In contrast to the use of liquid as a standard, the present invention uses microplate pellets independently placed within the microplate and may be coated with known fluorescent or calorimetric substances. Another difference between the present invention and that of the '169 patent is that due to evaporation, standards in a liquid state will decrease in volume and become more concentrated over time producing erroneous readings. The standards described herein are permanently fashioned to have a fixed pathlength. The microplate pellets disclosed herein are independently absorbing or fluorescent pieces so that they may be read and reread without further dilutional manipulation or transfer between pla
Hood Andrew
Palladino Henry
Stafira Michael P.
Ward & Olivo
LandOfFree
Solid state fluorescence and absorption spectroscopy does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solid state fluorescence and absorption spectroscopy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solid state fluorescence and absorption spectroscopy will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2976345