The invention relates to an a sensor system (100) for quantitatively detecting at least one compound in a fluid mixture, said fluid mixture comprising the compound to be detected, wherein the sensor system (100) comprises a sorbent material (102) being capable of sorbing the at least one compound to be detected, wherein the sorbent material (102) undergoes a temperature change when sorbing the at least one compound; at least a first temperature sensor (104) for measuring the temperature of the sorbent material (102); and a control unit (110) being adapted for quantitatively determining the at least one compound to be detected based on the temperature change of the sorbent material (102). Such a sensor system (100) provides an improved measurement especially in the field of oxygen concentrators. The invention further relates to an oxygen concentrator (10) for generating oxygen enriched gas as well as to a method of quantitatively detecting at least one compound in a fluid mixture.