SENSOR FOR DETERMINING THE CONCENTRATION OF AN ACIDIC OR BASIC COMPOUND AND USE OF A WATER-SOLUBLE PROTECTIVE LAYER HAVING PH BUFFERING PROPERTIES FOR PROTECTING THE SAME

The present invention relates to a sensor for determining the concentration of an acidic or basic compound dissolved in water, wherein the determination is based on an ingress of gas or vapor of said compound, causing a change in pH value, within an inner buffer separated from a sample side by a membrane that is permeable to gases and impermeable to ions, characterized in that a layer is provided between the membrane and the sample side, wherein the layer substantially covers the membrane, wherein the layer is water-soluble and has pH buffering properties. The present invention further relates to the use of a water-soluble layer having pH buffering properties for protecting a sensor for determining the concentration of an acidic or basic compound from ingress of an acidic or basic gas during non-use of the sensor.