Chemistry: analytical and immunological testing – Including titration or ph determination
Reexamination Certificate
1995-05-01
2002-10-22
Huff, Sheela (Department: 1642)
Chemistry: analytical and immunological testing
Including titration or ph determination
C435S007900, C435S007720, C436S166000, C436S063000, C436S504000, C422S082050
Reexamination Certificate
active
06468805
ABSTRACT:
This invention relates to a single reagent for use in determining pH in urine, or other fluids, being screened for drugs of abuse. This invention is particularly useful in automated analyzers used in screening for drugs of abuse.
As the use of illicit drugs in the workplace, public transportation, professional and amateur athletics and the like has grown, public concern for the health and safety of individuals, as well as concern for the negative impact of such drug use on productivity of industry, and its inherent economic impact, and the general well being and health of the community at large has grown as well. Such concern has led to the use of analysis of urine as a way to detect and deter drug use. Such testing for drugs of abuse in industry, as for prospective and current employees, military personnel, transportation employees, professional and amateur athletes, as well as people under supervision of the criminal justice system, has become a relative common occurrence.
Because of the intrusive nature of such testing commonly performed by examining a urine sample, the testing procedure must withstand vigorous scrutiny. Since a positive test result of screening for drugs of abuse may have serious impact on the life of a person being tested, the incentive for the drug user to alter the test specimen is high. The users of drugs of abuse have developed a number of ways to adulterate the collected specimen, thus attempting to produce a false negative result in the drug screening test being conducted.
A user of drugs of abuse may attempt to affect the test results, thus producing a false negative test result, or upon occasion, a false positive result, as by: 1) dilution—efforts to reduce the drug concentration in the urine sample; b) substitution for liquids such as clean (that is, drug-free) urine, soda, tea, apple juice for the drug-containing sample; or c) adulteration—addition to the urine specimen of foreign material in an attempt to invalidate the test.
Illicit drug users have learned to falsify urine screening tests by in vitro adulteration of urine sample by the addition of several readily available agents, including household products, among others, NaCl, soap, such as hand or dish soap, bleach, vinegar, Drano, NaHCO
3
, Visine, Gold Seal Tea (available in natural food stores), or (H
2
O
2
).
Additionally, users of drugs of abuse may eliminate some drugs more rapidly from their bodies by altering their urinary pH. Abusers of phencyclidine or amphetamines may be treated with NH
4
Cl to hasten detoxification, thus increasing the rate at which substances (phencyclidine or amphetamines) are eliminated from their bodies. This treatment with NH
4
Cl also results in lowering the pH of the user's urine.
While the use of some in vitro adulterants can be eliminated by the direct observation of the test subject during the collection process, such direct observation is often deemed unacceptable. In vivo adulterants represent an additional burden to the screening processor because they are consumed by the drug user several hours or days prior to screening of the sample, and can be detected only by laboratory means.
Such adulteration can affect all three commonly used methods for drugs of abuse, namely: florescent polarization immunoassay (FPIA), radioimmunoassay (RIA), and enzyme immunoassay (EMIT or EIA). Consequently, clinical chemistry literature recommends that testing for drugs of abuse in urine samples include testing for adulterants to identify urine samples which have been adulterated. See Mikkelsen and Ash, “Adulterants Causing False Negatives In Illicit Drug Testing”,
Clin. Chem
. 34/11, 2333-2336 (1988); and Warner, “Interference of Common Household Chemicals In Immunoassay Methods For Drugs Of Abuse”,
Clin. Chem
., 35/4, 648-651 (1989).
Accordingly, a need exists for providing an easy and convenient manner by which to make a determination of the presence of adulterants in urine samples which are being tested for drugs of abuse. A further need exists for a convenient manner by which such determinations may be made in conjunction with an automatic analyzing process for drugs of abuse.
SUMMARY OF THE INVENTION
The present invention relates to a single reagent to detect simultaneously multiple levels of pH in urine or other fluids. This reagent is designed to be used on automated analyzers used for drugs of abuse testing.
The purpose of the reagent is to facilitate the conducting of pH testing simultaneously while conducting drug tests on the same automatic analyzer. Specifically, if the pH of the urine, or other sample fluid being tested, is out of the normal range, that is, greater than 9.0 or less than 4.5, such variation from the normal range will cause false negative readings, or in some cases false positive readings when tested by three of the above-noted most common drug-screening methods; namely, EIA (enzyme immunoassay), FPIA (fluorescent polarization immunoassay), and RIA (radio-immunoassay.)
Use of the reagent of this invention permits the technician conducting the test to halt the testing process, or assay, as soon as the out-of-range pH determination is made. The ability to terminate the screening process by ascertaining that the pH is out of range, and therefore presumably adulterated, would result in reduced technician's efforts and time, providing an economic savings to the testing laboratory. Furthermore, the early interruption and cessation of the automated screening process may facilitate earlier obtention of a substitute specimen from the person being tested, providing more accurate determinations to the agency which had determined the original necessity for the test.
The use of the instant reagent permits the determination of pH of the testing sample to be done by the automated substance abuse testing program, rather than the relatively cumbersome methods of pH test (litmus) paper, which must be dipped in the urine, or by pH metering.
The instant reagent comprises an aqueous solution of two different pH indicators that effect a color change, specifically one indicator for basic, or high pH, and one for acidic, or low pH, wherein further, the solution contains a surfactant and is adjusted to a predetermined pH point.
DETAILED DESCRIPTION OF THE INVENTION
The pH reagent of the instant invention comprises an aqueous solution of a basic indicator which effects a color change, an acidic indicator which effects a color change, a surfactant and NaOH or HCl solution to adjust to a pH of 6.0.
Suitable basic indicators for use in the instant invention comprise bromcresol green, bromphenol blue, tetrabromphenol blue or brom-chlorphenol blue.
Suitable acidic indicators comprise thymol blue, bromothymol blue, metacresol purple or phenolphthalein.
The preferred surfactant is a brij 35 solution of polyoxyethylene 23 lauryl ether, 30% by weight in the total solution volume.
Upon completion of the preparation of the reagent, the reagent solution is adjusted to pH 6.0, using NaOH or HCl, as appropriate. At pH of 6.0, the solution is green in color.
REFERENCES:
patent: 3122420 (1964-02-01), Rebar et al.
patent: 3146070 (1964-08-01), Collins
patent: 4769215 (1988-09-01), Ehrenkranz
patent: 4806487 (1989-02-01), Akers et al.
patent: 4822743 (1989-04-01), Wegrzyn
patent: 4960585 (1990-10-01), Tehrani
patent: 5049358 (1991-09-01), Lau
patent: 5069878 (1991-12-01), Ehrenkranz
patent: 5077222 (1991-12-01), Lau
patent: 5096813 (1992-03-01), Krumhar et al.
patent: 5464775 (1995-11-01), Smith
patent: 58007946 (1974-02-01), None
patent: 58007946 (1983-02-01), None
CRC Handbook of Chemistry and Physics 63rdedition 1982-1983.*
Weast; 1982-83; CRC Handbook of Chemistry and Physics pp. D-157 to D-158.
Ames; Dec. 1992; Package Insert for Ames Reagent Strips.
Chimera Research and Chemical Inc.
Huff Sheela
Larson Herbert W.
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