3811840 is referenced by 83 patents and cites 10 patents.

Test device for detecting low concentrations of substances in test fluids comprising an absorbent wick having a substantially flat surface portion enclosed in a fluid impervious sheath having an aperture of predetermined limited area formed therein, the aperture being contiguous to and exposing a predetermined limited area of the flat surface portion of the wick, which portion is incorporated with a reagent specifically reactable with the substance being detected. In use the device is immersed into the test fluid so that the aperture is submerged and the device, allowed to remain therein while the test fluid contacts the reagent area adjacent to the aperture and migrates into the remainder of the wick. The reagent is immobilized with respect to the liquid. The sheath adjacent to the wick is opaque.

Test device for detecting low concentrations of substances in fluids
Application Number
Publication Number
Application Date
April 1, 1969
Publication Date
May 21, 1974
Rupe Chauncey Orvis
Rosenfield Richard Gordon
Bauer Robert
Miles Laboratories
G01n 33/16
G01n 33/00
G01n 31/14
G01N 33/52
G01N 31/22
C12Q 01/54
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