Chemistry: analytical and immunological testing – Optical result – Including reagent preparation
Reexamination Certificate
1996-09-13
2001-02-27
Alexander, Lyle A. (Department: 1743)
Chemistry: analytical and immunological testing
Optical result
Including reagent preparation
C422S051000
Reexamination Certificate
active
06194219
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an analysis element for analyzing a specific component in a liquid sample, particularly, whole blood, and a method for preparing the analysis element.
BACKGROUND OF THE INVENTION
Analysis elements for analyzing a specific component in a liquid sample are known. For example, JP-A-2-150751 (corresponding to JP-B-7-21455) discloses an analysis element comprising a support having a through-hole, a porous film to which a reagent liquid containing light-reflecting insoluble particles has been applied and dried to form a reagent layer, the porous film being fixed on the support to cover the through-hole, and a sample holding layer fixed on the support to cover the reagent layer (the terms “JP-A” and “JP-B” as used herein mean an “unexamined published Japanese patent application” and an “examined Japanese patent publication”, respectively). In JP-A-2-150751, titanium oxide is used as light-reflecting insoluble particles which, when whole blood is applied to the element and observed from the support side, hide red blood cells from view and also cut off light.
Titanium dioxide particles are white particles which reflect light with little absorption and are hardly dissolved in all kinds of solvents. They have a broad particle size distribution from fine (0.001 &mgr;m) to coarse (1 mm or even greater). The smaller the particle size, the more liable to aggregation. Titanium dioxide particles are usually used in paints, ointments, cosmetics, and the like for making use of their opaqueness.
Since titanium dioxide particles are insoluble in a solvent and also liable to aggregate, they easily form lumps and precipitate in liquid, failing to provide a liquid system having a uniform concentration distribution throughout the liquid.
Therefore, in the preparation of an analysis element for analyzing a specific component in a liquid sample, a titanium dioxide dispersion (reagent liquid) undergoes aggregation and precipitation and cannot be applied to a substrate (porous film) uniformly. Such a disadvantage may be eliminated by adding a polymer or a thickener to make the reagent liquid viscous or by stirring the liquid. However, a liquid having a viscosity enough to prevent titanium dioxide particles from precipitating would have insufficient fluidity for easy application to a substrate and also deteriorate analysis precision of the analysis element. The stirring of a reagent liquid is accompanied by air entrapment. Once air bubbles are formed, they remain in the coating layer even after drying or burst to leave craters after drying.
The aggregation of titanium dioxide particles also proceed while the coating layer is being dried, making the surface of the coating layer non-uniform. When the titanium dioxide-containing layer serves as an optical reflecting layer, such non-uniformity of the surface causes non-uniform light reflection and seriously reduces the performance of the reagent layer. It has therefore been demanded to develop a technique for dispersing insoluble particles, such as titanium dioxide particles, in liquid uniformly without involving such an operation as might impair coating precision, i.e., stirring, and increasing the viscosity of the liquid more than necessary.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for preparing a reagent liquid having stably dispersed therein insoluble particles.
Another object of the invention is to provide an analysis element comprising a reagent layer having uniformly dispersed therein insoluble particles and having a uniform thickness and an even surface.
As a result of extensive study, the inventors of the present invention have found that aggregation or precipitation of insoluble particles in liquid can be inhibited or retarded in the presence of boric acid.
That is, these and other objects of the present invention have been attained by an analysis element for analyzing a specific component in a liquid sample, which comprises a reagent comprising insoluble particles and boric acid.
Furthermore, these and other objects of the present invention have been attained by a method for preparing a reagent liquid for use in the preparation of an analysis element for analyzing a specific component in a liquid sample, which comprises adding insoluble particles and boric acid to the reagent liquid.
REFERENCES:
patent: 4868106 (1989-09-01), Ito et al.
patent: 4871679 (1989-10-01), Tanaka et al.
patent: 4966784 (1990-10-01), Tanaka et al.
patent: 5008078 (1991-04-01), Yaginuma et al.
patent: 5286624 (1994-02-01), Terashima et al.
patent: 0371513 (1990-06-01), None
patent: 0481436 (1992-04-01), None
patent: 2004062 (1979-03-01), None
patent: 2007360 (1979-05-01), None
Higuchi Yoshihiko
Sakamoto Hisashi
Takahashi Yoshinori
Yamaguchi Takehiro
Alexander Lyle A.
Kyoto Dai-ichi Kagaku Co. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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