An important parameter for the calculating of rate constants or for process enhancement, both for sciences and engineering, is the knowledge of gas concentrations of gas-liquid systems. We introduce the method SelPULCON for the determination of gas concentrations in liquids for NMR active substances (e.g., hydrogen) by means of NMR spectroscopy. This method is based on the "principle of reciprocity" and correlates the absolute signal intensity of the sample with that of an external reference. As a selective excitation is applied, this method is independent of whether the solvent is deuterated or not. In this way one can measure the gas concentration in almost all solutions and utilize all of the advantages of the NMR spectroscopy (e.g., for in situ or OPERANDO investigations). To demonstrate this method, we determined the hydrogen saturation concentrations in eight organic solvents at 25 degrees C and 0.101 MPa total pressure, for example, in dichloromethane (c = 1.51 mmol.dm(-3), b = 1.15 mmol.kg(-1)) and in 2,2,2-trifluoroethanol (c = 3.28 mmol.dm(-3), b = 2.39 mmol.kg(-1)).