The invention relates to a method for automatically determining the inorganically and/or organically bound carbon contained in an aqueous cleaning solution, comprising the following program-controlled steps: a) drawing a sample from the cleaning solution with a predetermined volume, b) optionally, liberating the sample from solids and/or homogenising the sample, c) optionally, diluting the sample with water according to a ratio which is predetermined or determined as a result of a preliminary determination, d) determining the inorganically and/or organically bound carbon using techniques known per se, e) transferring the result of the determination to a remote location and issuing it, and/or saving the result on a data support and/or using it as a basis for further calculations. The invention also provides a program-controlled or externally initiated automatic method for checking the measuring device. Measures for protecting the bath can be introduced in a program-controlled manner or by external initiation.