Air gap for controlling sample absorption and hematocrit dependence

• US 6,656,741 B1
• Filed: 03/03/1999
• Issued: 12/02/2003
• Est. Priority Date: 03/03/1999
• Status: Expired due to Term

• Current Assignee: Cilag Gmbh International (Johnson & Johnson)
• Original Assignee: Diabetes Diagnostics, Inc. (Johnson & Johnson)
• Inventors: Nelson, Eric M., Coe, Matthew A.
• Primary Examiner(s): ALEXANDER, LYLE
• Application Number:
  US09/261,707
• Time in Patent Office: 1,735 Days
• Field of Search: 422/56, 422/58, 422/61, 436/63, 436/177, 436/179, 436/180, 436/169, 436/164, 436/174
• US Class Current: 436/169
• CPC Class Codes: G01N 33/521 Single-layer analytical elements
• CPC Class Codes: Y10T 436/25375 Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]
• CPC Class Codes: Y10T 436/2575 Volumetric liquid transfer

Abstract

A method and apparatus for controlling the absorption of a liquid sample through an absorbent layer (2) and reducing the effect of hematocrit by applying the sample on one side of the layer (2a) and providing an air gap (4c) on the opposite side, so that absorption is controlled by preventing the release of air from the air gap.

Claims

1. A method for controlling the absorption of a liquid sample through an absorbent layer, comprising the steps of;

(a) providing an air gap defined by an absorbent layer, at least one side wall and a translucent window;

wherein the air gap is a closed chamber containing ambient air pressure, and

wherein the absorbent layer is permeable to gas when dry, but is relatively less permeable to gas when at least partially saturated with liquid;

(b) applying a liquid sample to the absorbent layer on the side opposite to the air gap such that the air pressure of the air gap is increased, thereby controlling liquid sample absorption by the absorbent layer.

2. The method of claim 1, wherein the sample is a human body fluid.

3. The method of claim 2, wherein the fluid is a blood sample.

4. An apparatus comprising an absorbent layer, at least one side wall and a translucent window, wherein the layer, at least one side wall and translucent window define an air gap, and wherein the air gap is a closed chamber containing ambient air pressure;

and wherein the absorbent layer is permeable to gas when dry, but is relatively less permeable to gas when at least partially saturated with liquid; and

wherein the absorbent layer, at least one sidewall, translucent window and air gap are adapted such that application of a liquid sample to the absorbent layer increases the air pressure of the air gap, thereby controlling liquid sample absorption by the absorbent layer.

5. The apparatus of claim 4, wherein the window is non-fogging.

6. The apparatus of claim 4, wherein the absorbent layer contains a reagent that indicates the presence of an analyte.

7. The apparatus of claim 4, further comprising a second layer in contact with the absorbent layer.