Described herein is a device for detecting the concentration of a given component in a solution, preferably the concentration of urea in solution with water, comprising: a means (2) for emitting radiation, at least one means (4) for receiving radiation, which is prearranged for determining at least one characteristic of the aforesaid radiation, and a light guide (6), which is prearranged for optically connecting the aforesaid emitting means to the aforesaid receiving means, wherein the aforesaid light guide (6) has at least one surface that is to come into contact with the aforesaid solution so as to determine an interface of separation between the aforesaid propagation medium and the aforesaid solution. The device further comprises control means (100) configured for obtaining a value indicating the concentration of the aforesaid compound in the aforesaid solution as a function of the signal coming from the aforesaid receiving means.
