An apparatus and a method for the determination and regulation of the concentration of at least one dissolved substance in a fluid circuit, in which the fluid circuit includes at least two partial circuits separated by a filter in a semi-permeable manner, includes a detection unit for determining a concentration difference of at least one first dissolved substance, a determination unit for determining the influence of at least one second dissolved substance which is not identical to the at least one first dissolved substance, and a regulation unit for regulating the concentration of the at least one dissolved substance in the fluid circuit.本発明は、流体回路における少なくとも1つの溶質の濃度を定量及び制御する装置及び方法に関し、流体回路は、少なくとも2つの部分回路を備え、各部分回路はフィルターによって半透過的に分離されている。
