Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Calorimeter
Patent
1982-10-14
1984-06-12
Turk, Arnold
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Calorimeter
422 57, 435 14, 435 27, 435805, G01N 2178
Patent
active
044540949
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an indicator for detecting at least one test substance in a test medium, comprising a carrier and a reaction system, consisting of at least a first reactant and a second reactant, applied separately on the carrier, said first reactant being intended to travel by diffusion to the second reactant through a path in the carrier, soaked by the test medium, while reacting with the test substance.
An indicator of this type is disclosed in U.S. patent application Ser. No. 806,687 now abandoned, in which there is disclosed e.g. an indicator for detecting of the enzyme catalase in milk. The reaction system employed consists partly of a first enzyme for generating hydrogen peroxide, namely glucose and the enzyme glucose oxidase, and partly of a color-generating system consisting of the enzyme peroxidase and o-tolidine, which latter is converted from a colorless state into a colored state, if it is allowed to react with hydrogen peroxide. In principle, the first, hydrogen peroxide-generating system is applied to a carrier in a distance to the color-generating system. When the test shall be performed, the carrier--preferably a paper strip--is soaked with the test medium, that is to say the milk. Hydrogen peroxide is evolved, which travels by diffusion in the direction towards the color-generating system. On its way the hydrogen peroxide has to travel by diffusion through a part of the carrier, which is soaked by test medium. If this contains the substance sought, catalase, the latter will react with the hydrogen peroxide to an extent, that is determined by its concentration, and no or a limited quantity of the hydrogen peroxide generated can travel by diffusion to the color-generating system to give rise to a color. The intensity of the color thus depends on the concentration of any remaining hydrogen peroxide and thus inversely on the concentration of catalase in the test medium.
This indicator may give good results, but these are dependent on a number of factors. The accuracy of the catalase determination thus demands an exact time schedule for the measuring procedure, good light and a color scale for comparison between the color developed and the color scale, provided with catalase concentration figures at different color tinges. The color tinge may show considerable variation depending on variations in the color of the milk itself, disturbing substances in the milk or the air, and the age of the indicator. The color tinges in the color system peroxidase-o-tolidine may also vary with different charges in commercial production.
The objective of the present invention is to provide an indicator which has none of the mentioned drawbacks. Such an indicator is characterized, according to the invention, in that the first reactant is applied within at least one limited locality, while the second reactant is applied within at least one locality in a varying distance from the locality of the first reactant.
By this design of the indicator the first reactant, e.g. hydrogen peroxide, will travel by diffusion along paths of different length through the carrier towards the second reactant, e.g. a color generating system like peroxidase-o-tolidine, and thereby be consumed to a greater or smaller extent, according to the provision of test substance of the type sought in the part of the carrier, which is situated between said localities, and which is soaked by the test medium. A longer path of diffusion gives on opportunity for a higher degree of reaction between the first reactant and the test substance which means that a correspondingly less amount of the first reactant can reach the second reactant to form e.g. a color. It is probably most convenient to use such reaction systems, which give rise directly to a visually detectable color change, even if other reaction systems could be considered, e.g. such systems, in which the color is only developed by spraying a developer on it.
Suitably the indicator is made of a plane material, like a paper sheet or the like as a carrier.
In one embodiment of th
REFERENCES:
patent: 3723064 (1973-03-01), Liotta
patent: 3798004 (1974-03-01), Zerachia et al.
patent: 3964871 (1976-06-01), Becton
patent: 4046513 (1977-09-01), Johnson
patent: 4181501 (1980-01-01), Keese et al.
Bjorling Karl T.
Gronberg Ann-Marie M. S.
Alfa-Laval AB
Turk Arnold
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