A device for colorimetric assay of at least one component in a liquid sample, which device comprises a support having a through hole with an area of from 3 to 80 mm.sup.2, a transparent porous film which is provided on the support to cover the hole, a reagent layer provided on a surface of the porous...http://www.google.es/patents/US5227310?utm_source=gb-gplus-sharePatente US5227310 - Device and method for assay of liquid sample
