Container containing a sensor and a storage solution, said sensor comprising a sensing area of metallic or a semi-conducting material covered with molecules having a MW>100 Dalton, said molecules being bound to the material, at least the sensing area being submerged in a storage solution, said storage solution having a composition that comprises at least 80% by volume of one or more of the compounds in the group consisting of water, ethanol, triethylene glycol and isopropanol, with the provisos that:
- a) if ethanol is present, the ethanol is present in a concentration of no more than 93% by volume of the storage solution;
- and
- b) if water is present, the water is present in a concentration of less than 80% by volume of the storage solution.