Ionic reservoir at electrode surface

An ion selective electrode comprising an electrode and a membrane comprising a closely packed array of amphiphilic molecules and a plurality of ionophores selected from the group consisting of valinomycin, crown ether analogues and ion selective ion channels, the membrane is connected to the electrode by means of a linker molecule(s) in a manner such that a hydrophilic space is provided between the membrane and the electrode, the space allows the flux of ions through the ionophores, the linker molecule comprising within the same molecule a hydrophobic region which constitutes at least a proportion of the amphiphilic molecules making up the membrane or is attached to or is embedded in the membrane, an attachment region attached to the electrode and a hydrophilic region intermediate said hydrophobic and attachment regions and spanning said space between the membrane and the electrode, wherein the hydrophobic region is selected from the group consisting of dioleyl glutamate, di(X) glutamate where X is an alkyl chain between 12-20 carbon atoms in length, selected from the group consisting of glycerol didodecanoate, glycerol ditetradecanoate, glycerol dihexadecanoate, glycerol dioctadecanoate, glyceroldioleate, archaebacterial lipid, synthetic membranes spanning archaebacterial lipid mimics and membrane compatible ion channels;

• the attachment region is selected from the group consisting of thiol, disulphide, sulphide, thione, xanthate, phosphine, isonitrile and silyl groups, and the hydrophilic region of the linker molecule being selected from the group consisting of an oligo/ethylene oxide group consisting of 4 to 20 ethylene oxide units or 1-4 sub-units of tetraethylene glycol attached to succinic acid, or 1 to 4 succinic acid/1 to 4 diesterified, 1,2,3,4,-butanetetraol subunits.

A method of producing an electrode membrane combination comprising:

• (1) forming a solution containing linker molecules comprising attachment regions, hydrophilic regions and hydrophobic regions which either self-assemble to form a membrane monolayer including a plurality of ionophores or which are attached to or which are embedded in a membrane monolayer composed of self-assembling amphiphilic molecules and a plurality of ionophores;
• (2) contacting the electrode with the solution, the composition of the electrode and the attachment regions being selected such that the attachment regions chemisorb to the electrode;
• (3) rinsing the coated electrode;
• and
• (4) soaking the coated electrode in trifluoroethanol or similar solution for about one week or treating said coated electrode at 60.degree. C. for one hour in a solution selected from the group consisting of trifluoroethanol, trifluoroethanol/ethanol, and dimethyl sulfoxide.