Chemistry: analytical and immunological testing – Oxygen containing – Carbonyl – ether – aldehyde or ketone containing
Reexamination Certificate
2000-05-30
2002-08-20
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Oxygen containing
Carbonyl, ether, aldehyde or ketone containing
C436S130000, C436S169000, C422S051000, C422S051000, C422S051000
Reexamination Certificate
active
06436716
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a composition, method, and device for determining the concentration of an aldehyde in a sample. More particularly, the present invention relates to a method and device for assaying an aqueous sample for an aldehyde concentration over the range of 0% to greater than 4%, by weight, by using an improved indicator reagent composition. Contrary to prior compositions, the present indicator reagent compositions have the advantage of quantitatively measuring a high range of aldehyde concentration in a sample without requiring multistep titration procedures. The invention is particularly effective for determining the concentration of a monoaldehyde, such as formaldehyde, or a dialdehyde, such as glutaraldehyde.
BACKGROUND OF THE INVENTION
Aldehydes have been used for many years in the medical sciences for various purposes. It is well known, for example, that formaldehyde and glutaraldehyde are useful for fixing and preserving tissue specimens. In recent years, the role of aldehydes in the medical community has expanded to that of a germicide useful for disinfecting or sterilizing medical instruments.
The use of formaldehyde and glutaraldehyde in disinfecting and sterilizing hemodialyzers is particularly common. Due to the proliferating reuse of hemodialyzers, the need for safe, accurate, and efficient methods of testing for disinfectant levels in the eluant of a hemodialyzer has increased dramatically.
The effectiveness of the germicidal solution depends on the concentration of the aldehyde. Currently, 2% glutaraldehyde and 4% formaldehyde, by weight, are used as germicidal solutions. These germicidal solutions are commercially available or can be manually prepared. The monitoring of the aldehyde levels in the solution is particularly important in assuring the effectiveness of the disinfectant. Unfortunately, the procedures presently available generally either require a multistep titration, lack accurate quantification, or involve complicated sample preparation, which hampers the convenience and efficiency of the assay.
For instance, several colormetric procedures are available for the detection of trace amounts of formaldehyde. The test kits for these colormetric assays, however, are only available in an ampule format. The procedures commonly employ Schiff's reagent or Edgriwe's reagent as the indicator. Schiff's reagent, which is prepared from rosaniline and bisulfite in concentrated hydrochloric acid, and Edgriwe's reagent, which consists of chromotropic acid in strong sulfuric acid, both require strong acid. However, strong acids generally are avoided in a dry reagent strip test because the corrosive nature of the acids degrades the carrier, typically cellulose, for the indicator reagent composition.
In addition, in some cases, the colormetric procedures require heat for the reaction to occur, which also is inconsistent with a convenient, quantitative dry reagent strip test. Moreover, the detection ranges of current colormetric procedures are extremely sensitive, i.e., detect formaldehyde concentrations in the range of parts per million (ppm), and are not suitable for the measurement of higher aldehyde concentrations in the weight percent (%) ranges.
For the determination of percent levels of formaldehyde, the sodium sulfite and sodium bisulfite methods have been used. In these methods, the reaction of a sodium sulfite or sodium bisulfite reagent with formaldehyde generates an equal molar amount of sodium hydroxide. The amount of formaldehyde is estimated from the amount of acid required to titrate the generated sodium hydroxide. For a more thorough description of the sodium sulfite and sodium bisulfite methods, see J. F. Walker, “Quantitative Analysis of Formaldehyde,” in
Formaldehyde
, 3
rd ed.,
Reinhold Publishing Corporation, New York, N.Y., pp. 486-488 (1964). Though accurate, each method requires multiple steps leading up to the titration. In addition, the production of caustic sodium hydroxide makes it difficult to provide a quantitative dry reagent strip assay.
Organic nitrogen compounds, such as amines, amides, ureides, amino acids, and proteins having a hydrogen bonded to the nitrogen, also react with formaldehyde to provide a useful assay for formaldehyde content. For example, formaldehyde reacts with lower amino acids, such as alanine, asparagine, and glycine in an aqueous solution. The aqueous solutions of these lower amino acids have a slightly acidic or neutral pH. In the presence of formaldehyde, however, the amino acids react as strong acids. The concentration of formaldehyde can be determined by end point titration of the amino acid-formaldehyde solution with an alkaline solution. Further description of the reaction of formaldehyde with organic nitrogen containing compounds, and more particularly amino acids, can be found in J. F. Walker, “Reaction with Amines, Amides and Nitriles,” in
Formaldehyde
, 3
rd ed
., Reinhold Publishing Corporation, New York, N.Y., pp. 359-414, in particular pp. 395-398 (1964).
The reaction of another aldehyde, glutaraldehyde, with a mixture of sodium sulfite and an amine compound, for example glycine, is the subject of various U.S. patents. U.S. Pat. Nos. 4,521,376 and 4,463,980 describe a test system for glutaraldehyde consisting of a mixture having a defined ratio of sodium sulfite and an amine compound, in particular the amino acid glycine. The sodium sulfite and the amino acid react with glutaraldehyde to form a yellow-colored complex.
In practice, the commercial product utilizing the principles described in U.S. Pat. Nos. 4,521,376 and 4,463,980 involves a three-step reaction. First, glutaraldehyde is reacted with sodium sulfite to form a sulfite addition product and sodium hydroxide. Second, sodium hydroxide reacts with glycine to form sodium glycinate. Third, sodium glycinate reacts with another molecule of glutaraldehyde to form a yellow-colored addition product. The test strips based on this chemical sequence are “semi-quantitative” chemical indicators for use in determining whether the concentration of glutaraldehyde is above or below an established minimum concentration for a solution. The test strips are commercially available as the CIDEX® family of solutions test strips (Johnson & Johnson Medical, Inc., Arlington, Tex., U.S.A.).
More precisely, the “semi-quantitative” test strip is a qualitative threshold test to determine whether the concentration of glutaraldehyde in a given sample meets a designated threshold. The test serves to indicate, either positively or negatively, whether the disinfectant solution contains a required minimum effective level of glutaraldehyde. A sample that contains the threshold level changes the color of the strip to yellow, indicating that the sample passes the assay. If the sample does not contain the threshold level of glutaraldehyde, the strip does not change to a yellow color, indicating that the sample fails the assay. The test does not provide a continuous quantitative assay of glutaraldehyde levels in the solution.
Likewise, other commercially available test strips also are qualitative, rather than quantitative, indicators of whether the aldehyde concentration in the disinfecting solution is above a threshold level. For example, a commercially available test strip for formaldehyde allows for assay of formaldehyde levels between 2.5% and 4.0% in the disinfecting solution. The qualitative commercial test strips contain the hydrochloride salt of glycine, which releases hydrochloric acid as a product of the reaction with formaldehyde. The release of hydrochloric acid in solution causes a color change in a pH indicator. These marketed strips are available under the trade name SERIM™ Formaldehyde Test Strips (Serim Research Corporation, Elkhart, Ind., U.S.A.). Moreover, the test strips do not provide a quantitative measurement of formaldehyde levels in the solution.
Reagent test strips also have been employed in testing steam sterilized products. The detection of formaldehyde vapor in dry or mixed steam is describ
Cross LaToya
Integrated Biomedical Technology Inc.
Warden Jill
LandOfFree
Aldehyde test strip does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aldehyde test strip, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aldehyde test strip will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2921353