Method for determining the concentration of a substance in a liquid by measuring electrical current in a test strip

• US 6,525,549 B1
• Filed: 07/27/2000
• Issued: 02/25/2003
• Est. Priority Date: 08/04/1999
• Status: Expired due to Fees

• Current Assignee: LRE Technology Partner GmbH
• Original Assignee: LRE Technology Partner GmbH
• Inventors: Poellmann, Norbert
• Primary Examiner(s): KARLSEN, ERNEST F
• Application Number:
  US09/626,505
• Time in Patent Office: 943 Days
• Field of Search: 324/642, 324/644, 324/645, 324/646, 324/717, 702/19, 702/108, 204/406, 205/775
• US Class Current: 324/717
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875

Abstract

In a method for determining the concentration of a substance in a liquid, especially for blood sugar determination, the investigated liquid is applied to the test field of a test strip (14) to be measured by way of electrical current and the resulting oxidation current in the test field is captured and evaluated. The timewise course of the oxidation current strength is captured during a calculated interval beginning with the application of the liquid, a first extreme value (34) of the current strength is compared with at least one threshold value, and an indication is produced depending on the result of the comparison.

Claims

1. A method for the determination of the concentration of a substance in a liquid, in which the liquid to be investigated is applied to a chemical containing areal test field (18) of a test strip (14) processed by electrical current measurement and wherein an oxidation current strength effected in the test field (18) by reaction of the applied liquid with the test field chemical has a timewise course, said method comprising, providing a test strip (14) such as aforesaid, applying a quantity of a liquid to be investigated to the test field (18) of the test strip to produce a timewise course of oxidation current strength in the test field, capturing the timewise course of the oxidation current strength within a time interval calculated from the beginning of the fluid application, investigating the captured timewise course of the oxidation current strength to define a first extreme value (34) of the current strength, comparing said first extreme value (34) of the current strength with at least one threshold value, and providing an indication depending on the result of the comparison.

2. A method according to claim 1, further comprising sensing the current strength at the ends of sample periods, which periods are short in comparison to said time interval.

3. A method according to claim 1, further comprising, if in said comparing step the first extreme value (34) does not equal or exceed said threshold value, indicating a predetermined time frame within which a subsequent application of the investigated fluid onto the test field need take place.

4. A method according to claim 1, further comprising determining the time point at which the extreme value (34) of the current strength is reached and using that time point as a zero point for a timewise measurement of the reaction occurring in the test field.

5. A method according to claim 4, further comprising determining the time point at which the extreme value (34) of the oxidation current strength is reached by forming the first derivative with respect to time of the oxidation current strength/time curve.

6. A device for the electrical current determination of the concentration of a substance in a liquid, said device comprising a device housing (10) with a test strip support (12) for receiving a test strip (14) processable by way of electrical current measurement with a test field (18) and with electrodes (20) connected to the test field (18), a measurement and evaluation circuit (24) with measurement feelers (28) for contacting the electrodes (20) of the test strip (14) connected with the measurement and evaluation circuit, and an indicator device (22) responsive to the measurement and evaluation circuit (24), wherein the measurement and evaluation circuit (24) contains a computer and is structured to carry out the method according to claim 1.