A coumarin-based molecular probe can be used for the sensing of peptides and aminoglycoside antibiotics. The probe reacts with the primary amine group(s) of the analytes to give a mixture of covalent adducts with distinct colors. Each analyte gives rise to a characteristic UV–vis spectrum. A pattern-based analysis of the spectra allows identifying structurally related analytes. Furthermore, it is possible to obtain information about the quantity and the purity of the analytes.