Method and apparatus for chemical spot test analysis

• US 4,298,345 A
• Filed: 03/30/1979
• Issued: 11/03/1981
• Est. Priority Date: 11/21/1977
• Status: Expired due to Term

• Current Assignee: Banque Paribas The Equitable Tower, International Equipment Company, Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Damon Corporation (Thor Industries Incorporated)
• Inventors: Lim, Franklin, Sodickson, Lester A.
• Primary Examiner(s): Serwin, R. E.
• Application Number:
  US06/025,497
• Time in Patent Office: 949 Days
• Field of Search: 23/230 R, 422/56, 422/57, 422/58, 422/100
• US Class Current: 422/420
• CPC Class Codes: G01N 21/8483 Investigating reagent band test-element handling not specific to a test method G01N33/4875; analytical elements specific to chemical analysis of biological material G01N33/52; autometer with reagent band G01N35/04
• CPC Class Codes: G01N 33/528 Atypical element structures, e.g. gloves, rods, tampons, toilet paper

Abstract

Chemical analysis of a sample with reagents spotted on a fibrous or porous medium employs a medium pretreated both with reagents and with conditioning agent. The conditioning agent increases the degree to which the liquid reactants wet the medium. One form of pretreated medium has different reagents located predominantly within different selected zones.

Liquid is applied to the medium, typically as diluted sample, at a rate selected to enhance formation of repeatable spots. In one embodiment the liquid is applied by flowing it onto a wick element seated on the medium. The wick is disc-like and small relative to the spot which the reactants form on the medium. The disc can be pretreated to carry reagent, which the liquid transfers to the medium.

The analysis instrument receives a reaction medium between selectively recessed upper and lower surfaces aligned in opposition at the reaction spot being analyzed.

The analysis can, depending on the analytical reaction, the medium and the precision required, proceed while the reactants are wet or can measure a reaction product after the reactants are dry. A single point analysis can also be made.

Claims

1. A method for preparing a porous medium for use in chemical spot test analysis employing a measured parameter responsive to concentration of a reaction-produced material at a test site on the porous medium, said method including the improvement comprising the step of exposing at least said test site of said medium to a liquid preparation conditioning agent having a balance of hydrophobic and hydrophilic properties for retarding the spreading of liquid in the medium and for increasing the concentration of liquid the medium can hold, said exposure being sufficient, after drying, to diminish the absorption of liquid by the porous structure of said medium.

2. A method as defined in claim 1, comprising the further improvement comprising the step of introducing reaction-producing reagents to said test site together with said liquid preparation of conditioning agent.

3. A method as defined in claim 1, comprising the further improvement in which said conditioning agent includes a thickening element and a surfactant.

4. A method as defined in claim 1, comprising the further improvement in which said conditioning agent includes a thickening ingredient selected from the group consisting of a high molecular weight crystalline, ethylene oxide polymer, albumin, gum arabic, guar gum, and mannitol.

5. A method as defined in claim 1, comprising the further improvement in which said conditioning agent is a low molecular weight polyol surfactant of selected hydrophobic and hydrophilic characters.

6. A porous medium for use in measuring a selected product of chemical reactants at a test site on the medium with means for subjecting the site to oscillating electromagnetic energy and for sensing a selected parameter of energy which is responsive to the oscillating energy and to the presence of the selected reaction product, said medium having the improvement comprising a conditioning agent in at least the test site of the medium, said conditioning agent being present from exposure of the medium to a solution of said agent and subsequent drying, said agent having hydrophobic and hydrophilic properties selected for retarding the spread of liquid in the medium and for increasing the concentration of liquid the medium can hold.

7. A medium as defined in claim 6 in which said conditioning agent includes a thickening element and a surfactant.

8. A medium as defined in claim 6 in which said conditioning agent includes a thickening element selected from the group consisting of high molecular weight crystalline, ethylene oxide polymer, albumin, gum arabic, guar gum, and mannitol.

9. A medium as defined in claim 6 in which said conditioning agent is a low molecular weight polyol surfactant of selected hydrophilic and selected hydrophobic characters.

10. In a porous medium having a test site for bearing chemical reactants which produce a reaction product measurable upon being subjected to oscillating electromagnetic energy, a parameter of which is responsive to the presence of the selected reaction product and is sensed for measurement, said porous medium having a substantially uniform structure within and contiguously beyond the test site, the improvement comprising a wick overlying a fragmentary central portion of the test site for receiving liquid and for controlling the rate of delivery to the test site of such liquid.

11. In a porous medium according to claim 10, the further improvement wherein said wick is a disc-like member.

12. In a porous medium according to claim 10, the further improvement wherein said wick comprises a cylindrical disc-like element having a diameter substantially between one millimeter and three millimeters.

13. In a porous medium according to claim 10, the further improvement wherein said wick is a cylindrical disc-like member having a diameter substantially in the order of one to two millimeters.

14. In a porous medium according to claim 10, the further improvement comprising a chemical reagent carried on said wick for transfer therefrom to said porous medium upon the flowing of liquid through the wick.

15. Apparatus according to claim 10 further comprising a reagent carried on said wick element for transfer therefrom to said medium upon the flowing of liquid through the wick element.