A metal complex derivative from a coumarin bearing a porphyrin unit was spectroscopically characterized and its sensing ability towards the alkaloids caffeine , nicotine and cotinine was evaluated in these studies. This probe shows to be sensitive to the alkaloids studied, where a detectable amount of 2.5 ± 0.3 μM of cotinine was determined in dam water from the Vigia Dam located in the Montoito village region, Alentejo district, Portugal. The interaction of with cotinine was also verified by MALDI-TOF-MS, where it was found with peaks at 877.2 and 1053.3 m/z corresponding to the species [H](+) and [CotinineH](+), respectively.