Abstract: A single-rod pH measuring arrangement comprised of a pH-sensitive glass electrode and a reference electrode electrically communicating with the solution to be measured via a salt bridge. A plastic containing member partially surrounds the glass electrode in a manner providing an aperture through which the pH-sensitive part of the glass electrode projects. The edge of the plastic member lies adjacent to the surface of the glass electrode whereby the space between the two constitutes the salt bridge, with the latter being particularly insensitive to reference electrode problems such as solid protein layer deposition due to the blood coagulation system which leads to reference electrode potential instability.