Sensor element for the determination of the oxygen content of a sample, and process for making the same

Claim 2

A sensor element for determining the 0 2 content of a sample, comprising an indicator fluorescing with the amount of O2 acting upon it, which may be brought into contact with the sample at least partially and which will give off fluorescent light upon excitation, - the indicator substance being incorporated in a polymer carrier in at least approximately homogenous distribution -, wherein a cured silicone polymer is used as carrier material, to which the said indicator substance is added in solubilized form.

Claim 3

A sensor element according to claim 1, wherein an additional layer of polymer of low transparency is applied on the side of the polymer carrier facing the sample, e. g. a silicone coating containing particles of ferrous oxide.

Claim 4

A sensor element according to claim 1, wherein a thin mesh screen of metal or plastic is incorporated during polymerisation on the side of the polymer carrier facing the sample.

Claim 5

A sensor element according to any of claims 1-3, wherein polycyclic, homocyclic or heterocyclic aromatic molecules - preferably polycyclic aromatic hydrocarbons with a fluorescent decay time of To greater than 5 ns - are used as indicator substances.

Claim 6

A sensor element according to any of claims 1-4, wherein the polymer carrier containing the indicator substance is additionally provided with pigments, e. g. particles of ferrous oxide.

Claim 7

A sensor element according to claim 5, wherein the said pigment particles will be accumulated on the side of the polymer carrier facing the sample due to the influence of external fields of force, such as gravitational, electric or magnetic fields, during the curing process.

Claim 8

A sensor element according to any of claims 1-6, wherein for the purpose of immobilization the indicator substance is supplied in chemically modified form, preferably alkylated with longer hydrocarbon chains, branched or unbranched (from C 3 to C 2 ), such that indicator mobility in the polymer material is reduced.

Claim 10

A method according to claim 8, wherein the following steps are taken : First of all, the indicator substance and tertiary butyl chloride are dissolved in a solvent, e. g. CS 2 , or rather, the indicator substance is dissolved in an excess of tertiary butyl chloride without addition of another solvent. This solution is then reacted, with the use of aluminium chloride as a catalyst, and subsequently washed and dried. The excessive solvent is removed by rotary evaporation, and the solubilized indicator substance remaining as an oily residue is incorporated into the polymer mixture prepared. Finally. the polymer mixture filled with the solubilized indicator substance is moulded (e. g. into membranes) and cured.