A method and apparatus are disclosed for testing and inspecting containers coated by means of a plasma treatment, e.g. plastic bottles, which are coated for instance with amorphous silicon oxide or carbon compounds. The containers are tested by a measuring device trace-gas-analytically, e.g. mass-spectrometrically, for undesired foreign substances, such as acetaldehyde and/or antimony, escaping from the container material after a plasma coating treatment.