Multilayer ion test means

Claim 1

A test means for determining the presence of an ion in an aqueous test sample, the test means comprising: (a) a reagent layer chosen from a group consisting of (i) a substantially nonpolar, nonporous carrier matrix incorporated with an ionophore capable of forming a complex with a specific ion to be determined and a neutral reporter substance having a dissociable proton, which proton is capable of dissociating upon interaction of the reporter with the complex of the ionophore and the cation to produce a detectable response; and (ii) a hydrophilic carrier matrix incorporated with finely divided globules of a hydrophobic vehicle, the globules containing an ionophore capable of forming a complex with a specific ion to be determined and a neutral reporter substance having a dissociable proton which proton is capable of dissociating upon interaction of the reporter with the complex of the ionophore and the cation to produce a detectable response; and (b) a reflecting layer disposed on top of the reagent layer and in laminar relationship thereto, the reflecting layer including one or more materials which act as a background in order to facilitate the determination of a detectable response in the reagent layer; and optionally, (c) an opacifying layer in laminar relationship to the reflecting layer and disposed on top of the reflecting layer, the opacifying layer containing particles for imparting an opaque appearance to the layer.