Method of preparing a fluid absorbent quantitative test device

• US 4,846,182 A
• Filed: 11/14/1983
• Issued: 07/11/1989
• Est. Priority Date: 01/11/1982
• Status: Expired due to Term

• Current Assignee: ALZA Corporation (Johnson & Johnson)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Norenberg, Marye S., Fogt, Eric J., Untereker, Darrel F., Coury, Arthur J.
• Primary Examiner(s): TUNG, TA HSUNG
• Application Number:
  US06/551,055
• Time in Patent Office: 2,066 Days
• Field of Search: 423/305, 423/595, 502/208, 502/317, 422/56, 422/58, 436/79, 436/125, 436/164, 436/165, 128/632, 128/636, 128/760
• US Class Current: 600/362
• CPC Class Codes: A61B 5/4266 sweat secretion
• CPC Class Codes: G01N 33/526 the element being adapted for a specific analyte
• CPC Class Codes: G01N 33/84 involving inorganic compounds or pH
• CPC Class Codes: Y10T 436/193333 In aqueous solution

Abstract

Preparation of an absorbent quantitative test device in the form of a flat patch. When placed on the skin of a subject, the device collects a fixed volume of sweat. It is particularly intended to be used in screen testing for cystic fibrosis by measuring the chloride level in sweat and providing a visual indication when the level is in excess of a predetermined concentration. A fill tab indicator undergoes a color change when the fixed volume of sweat has been collected signifying completion of the test. The device includes two concentric circular reaction areas of chemically treated absorbent paper or the like. The sweat sample is introduced into the device at the center of the first or inner circular reaction area which contains a chemical composition capable of reacting with all chloride in the sweat sample below a predetermined concentration value to screen out that amount of chloride. A second or outer ring-shaped reaction area contains a chemical composition which indicates a color change for any chloride reaching it in excess of the predetermined concentration value. The color change in the outer ring-shaped portion thereby provides a quantitative indication of the pressure of a concentration of chloride in the subject'"'"'s sweat in excess of the predetermined concentration level.

Claims

1. A method of preparing a quantitative testing device designed to provide a visual indication of a quantity of a substance in excess of a predetermined amount in a given volume of a test fluid, particularly wherein the test is for determining amounts of sodium chloride in human sweat in excess of a predetermined amount, comprising the steps:

forming a first reaction area comprised of an absorbent medium of predetermined absorbency;

impregnating the first reaction area absorbent medium with a predetermined quantity of silver phosphate for reaction with sodium chloride in the sweat;

forming a second reaction area of an absorbent medium;

impregnating the second reaction area absorbent medium with a quantity of silver chromate or dichromate for reaction with sodium chloride in the sweat which reaches the second area thereby providing a visual indication of the presence of sodium chloride in the second area, and

passing the sweat test fluid through the first reaction area and then into the second reaction area.

2. The method of claim 1 wherein the silver phosphate and silver chromate or dichromate are respectively formed and precipitated in situ in the absorbent media.

3. The method of claim 2 wherein the respective formation and precipitation is with sodium phosphate/silver nitrate and potassium chromate/silver nitrate.

4. The method of claim 2 wherein the in situ silver phosphate is formed by:

wetting the absorbent medium with silver nitrate solution;

drying the medium, and

reacting the silver nitrate in the medium with sodium phosphate solution.

5. The method of claim 2 wherein the in situ silver chromate or dichromate is formed by:

wetting the absorbent medium with silver nitrate solution;

drying the medium, and

reacting the silver nitrate in the medium with a quantity of potassium chromate or dichromate solution slightly in excess of the silver nitrate.

6. The method of claim 3 wherein silver dichromate is formed in situ by use of potassium dichromate.

7. A method of preparing a quantitative testing device designed to provide a visual indication of a quantity of sodium chloride in human sweat in excess of a predetermined amount in a given volume of sweat, the method comprising the steps:

forming a first reaction area comprised of an absorbent medium of predetermined absorbency;

impregnating the first reaction area absorbent medium with a predetermined quantity of first reactant selected to react with the substance in the fluid and wherein the first reactant comprises silver phosphate;

forming a second reaction area of an absorbent medium;

impregnating the second reaction area absorbent medium with a second reactant selected to react with the substance and provide a visual indication of the reaction and wherein the second reactant comprises silver chromate;

arranging the first and second reaction areas such that the test fluid must be passed through the first reaction area in order to reach the second reaction area, and

wherein a third reaction area is included for receiving fluid which passes through the second reaction area and the second reaction area is of a predetermined absorbency; and

further

wherein the third area contains silver nitrate and the second reaction area contains an amount of potassium chromate which is carried by any excess fluid to the third reaction area for reaction with the silver nitrate therein.