Abstract: The proposed multipurpose ion-selective sensor is designed to be operational in any spatial position in harsh environment and incorporates a housing tube (1) where a number of elements are fixed and electrically connected to a measurement transmitter; these members include: a detachable indicator electrode (3) which employs a solid indicator system (33) with a solid membrane contacting the analysed liquid; a detachable reference electrode (4) with a hollow body (20) accommodates a potential-forming semi-element (21), a connecting member (22) and electrolyte (29) filled with a solid dispersed material forming a spatial structure (30) in the electrolyte (29), whereby the structure is rigidly linked with internal surface (31) of the reference electrode (4) body (20), the potential-forming semi-element (21) and with the connecting member (22).