The invention relates to a modular absorption measuring system (1) for fluid media comprising a detection module (2) and a sample module (3), which comprises a sample chamber (14). The detection module (2) comprises a detection system (5), which also comprises an electromagnetic radiation source (8) and a quantum detector (9). The radiation source (8) is designed for supplying light in the direction of the sample chamber (14) and the quantum detector (9) is designed for receiving light from the sample chamber (14). The electromagnetic radiation source (8) is designed as an electroluminescence component and the detection module (2) and the sample module (3) are also designed to be arranged on top of one another.