Chemistry: analytical and immunological testing – Involving an insoluble carrier for immobilizing immunochemicals
Reexamination Certificate
2000-03-17
2002-10-08
Nguyen, Bao-Thuy L. (Department: 1641)
Chemistry: analytical and immunological testing
Involving an insoluble carrier for immobilizing immunochemicals
C436S020000, C436S514000, C436S525000, C436S810000, C436S816000, C436S901000, C435S007100, C435S007930, C435S970000, C435S973000, C435S975000, C422S051000, C422S051000, C422S051000, C422S051000, C422S068100, C422S105000
Reexamination Certificate
active
06461873
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invnetion
The present invention relates generally to the detection of certain chemical substances. More specifically, the invention is a device for detecting the presence and concentration of caffeine in a beverage.
2. Description of Related Art
Many beverages contain caffeine as an active ingredient, such as coffee, tea, hot chocolate, and soft drinks. For many people caffeine serves as a useful stimulant. However, others may have an allergic reaction to caffeine. In addition, too much caffeine may result in insomnia, restlessness, and gastrointestinal problems. Pregnant or nursing women may wish to avoid caffeine for fear of harmful affects on their child. Caffeine also a diuretic effect on many individuals. For these reasons, it is often desirable to restrict the daily intake of caffeine or eliminate caffeine containing beverages from the diet.
Many of the known methods for identifying caffeine in a beverage and detecting the concentration of caffeine in the beverage are only suitable for use in the laboratory. It would therefore be desirable for the consumer to have a device for measuring the caffeine content of a beverage quickly and easily for use in the home, in restaurants, and the like. Such a device would enable the consumer to shun a beverage having a high caffeine concentration, or to reduce the quantity ingested to a safer level. A few devices have been proposed which are designed to permit the consumer to detect either the presence or the concentration of caffeine in a beverage, fluid, or other product.
U.S. Pat. No. 5,610,072, issued on Mar. 11, 1997 to Scherl, et al., discloses a dipstick and a method for detecting caffeine in beverages. The dipstick is impregnated with a reagent that changes color when reacted with caffeine. The dipstick preferably includes a beverage dipping section, an adjacent temperature moderation section, and an adjacent reagent-impregnated section. The device uses either enzymes or antibodies which react to produce hydrogen peroxide in the presence of caffeine, which subsequently reacts with a chromogen such as potassium iodide. The resulting color changes is compared with a color chart to determine the concentration of caffeine.
U.S. Pat. No. 5,817,454, issued on Oct. 6, 1998 to Harris, et al., discloses a portable apparatus and a method for detecting the presence of caffeine and the like in a beverage. The apparatus comprises a first portion comprising phosphodiesterase enzyme, a second portion comprising cyclic AMP, and a means for indicating inhibition of degradation of the cyclic AMP by the phosphodiesterase due to the presence of caffeine or the like. The method comprises contacting a portion of the beverage with a phosphodiesterase enzyme and cyclic AMP, and further contacting the portion with the means for indicating the inhibition, typically a pH indicator paper. The method produces a qualitative indication of the presence of caffeine, but not a quantitative measure of its concentration.
U.S. Pat. No. 5,824,554 issued on Oct. 20, 1998 to McKay discloses a method and a device for the detection of allergenic substances in food products. The device comprises a dining mat formed of an absorbent material with small spots of reagents applied to isolated zones on the mat. In use, the food product is applied to a reagent and if the food product contains the allergenic substance, the reagent will change its appearance. One of the allergenic substances tested for is caffeine, which produces a color change when reacted with Mayer's, Wagner's, or Dragendorff's reagents. The test is qualitative, and does not provide a quantitative measure of the amount of caffeine in the beverage or food product.
There are several problems with the above devices, at least to the extent that they are relied upon for quantitative information of the amount of caffeine in the beverage. The devices tend to be expensive to the extent that they rely upon enzymes or antibodies. The measurement of concentration by comparison of a color change to a chart can prove to be quite subjective. In terms of providing a quantitative measure of caffeine concentration, the devices appear not to require a measured volume of test sample, and thus are prone to error. Further, the devices provide no means for selectively absorbing caffeine from the test sample.
The caffeine detector of the present invention uses a molecular imprint polymer (MIP) as a chromatographic medium. A “molecular imprint polymer” is a polymer which is prepared by polymerizing monomers around a template or “print” molecule, which is then removed from the polymer by extraction or other means so that the polymer will selectively absorb the template or print molecule upon re-exposure to the print molecule. U.S. Pat. No. 5,821,311, U.S. Pat. No. 5,872,198, and U.S. Pat. No. 5,959,050, issued Oct. 13, 1998, Feb. 16, 1999, and Sep. 28, 1999, respectively, to Mosbach, et al. describe certain MIP polymers, a polymerization process, and symmetrical beads produced by suspension polymerization from functional monomers for use as chromatographic media. U.S. Pat. No. 5,814,223 and U.S. Pat. No. 5,916,445, issued Sep. 29, 1998 and Jun. 29, 1999, respectively, to Hjertén, et al., disclose a gel type chromatographic media and method for preparing the media, the media being formed by a molecular imprint polymer prepared from a nonionizable polymerizable substance which is nonreactive to the imprinted molecule.
An article by Lai, et al., in the Canadian Journal of Chemistry, Vol. 76, pp. 265-273 (1998) teaches the preparation of an MIP in which the template molecule is caffeine for the detection of small quantities of caffeine using an optical phenomenon known as surface plasma resonance. The polymer was prepared from methacrylic acid and ethylene glycol dimethacrylate in the presence of caffeine, which was subsequently removed by Soxhlet extraction. A thin overlayer of the polymer was placed on a silver film and showed selective absorption of caffeine as opposed to xanthine and theophylline, a similar methyl xanthine. Applicant obtained a sample of the MIP prepared by Dr. Lai. Although this polymer may be adequate for use in surface plasmon resonance, it proved unable to absorb sufficient caffeine for use as a caffeine detector, apparently due to too much cross-linking.
Consequently, the prior art fails to teach a device or practice which enables an operator to simply, safely, and reliably detect the concentration of caffeine in the beverage. None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.
SUMMARY OF THE INVENTION
The caffeine detector uses a paper chromatographic technique to measure the concentration of caffeine in a beverage. The device includes a well or other receptacle for containing a predetermined test volume of the beverage. A paper strip is suspended so that one end of the strip dips into the well. The strip is divided into two zones, the first zone being coated with at least one molecular imprint polymer (MIP) which absorbs substances which may interfere with quantification of caffeine. The second zone is coated with an MIP which selectively absorbs caffeine and chromogenic reagents which provide calorimetric visualization of the migration of caffeine through the second zone. The second zone bears indicia calibrating the paper strip so that the concentration of caffeine in the beverage may be determined by the height or distance which the caffeine migrates up the paper strip.
Accordingly, it is a principal object of the invention to provide a simple, safe, and efficient device for detecting the presence or concentration of caffeine in a beverage.
It is another object of the invention to provide a simple, safe, and efficient device for detecting the presence or concentration of caffeine in the beverage which may be used by the ultimate beverage consumer on a per cup basis.
It is a further object of the invention to provide a device which utilizes a paper chromatographic m
Baugh Steven
Catania Daniel
Ignelzi Steven
Litman Richard C.
Nguyen Bao-Thuy L.
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