To provide at least one measuring instrument or sensor for measuring a chemical or physical parameter of a liquid to detect gas bubbles, for example, air bubbles in a measuring cell filled with the liquid, preferably a sample solution, a quality inspection liquid or a calibration liquid.

A dielectric constant of the liquid or an amount induced therefrom is measured at the first pressure p1 in the measuring cell, the first measured value S1 is detected thereby, a dielectric constant of the liquid or an amount depending thereon is measured at least at the second pressure p2 after changing the pressure in the measuring cell, the second measured value S2 is detected thereby, and the presence of the gas bubbles in the liquid is estimated based on comparison of the two measured values S1, S2.