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Test strip including integral specimen flow retarding structure

  • US 5,755,231 A
  • Filed: 05/17/1995
  • Issued: 05/26/1998
  • Est. Priority Date: 05/17/1995
  • Status: Expired due to Fees
First Claim
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1. A test strip, comprising:

  • a first layer comprising a first porous substrate having a first-layer chemical system impregnated therein, the first-layer chemical system comprising an indicator reagent, wherein the indicator reagent comprises a mixture selected from the group consisting of (1) a mixture of 4-aminoantipyrine and N-ethyl-N-sulfohydroxypropyl-m-toluidine, sodium salt, (2) a mixture of 4-aminoantipyrine and N-ethyl-N-2 Sulfo ethyl m-Toluidine, and (3) a mixture of 3-Methyl-2-benzothiazolinone hydrazone hydrochloride hydrate and N-ethyl-N-sulfohydroxypropyl-m-toluidine, sodium salt; and

    a flow-retarding layer comprising a differential flow-retarding material having a percolation rate for blood plasma faster than a percolation rate for red blood cells, the flow-retarding layer overlying the first layer and permitting from about 10 percent to about 90 percent by volume of the red cells to pass therethrough in a period of 45 seconds.

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