The detection of small concentrations of heavy metals' cations in industrial residual waters, rivers and water deposits in general, is a very important and current problem. Its complexity not only lies in the device's capacity to recognize and quantify the presence of a certain cation, but to make it selectively, since these are generally in the presence of many others, which should not interfere in the determination.

This work is aimed at studying, developing and constructing potentiometric sensor prototypes for the control of cations of heavy metals: mercury (II), lead (II) and cadmium (II). There were used ionophores derived from thiourea for their construction, which is completely original. There were used quaternary ammonium salt to determine nitrate (which is important for agricultural products).

This work is characterized by its high scientific rigor and it embraces the realization of chemical - physical and characterization studies, the theoretical calculation of recognizer molecules' properties and the modelling of their interaction with cations using the theory of Density Functions, the synthesis of 46 new ionospheric compounds and the establishment of a thesis to explain each compound's selectivity in the sensor regarding the different cations. This has given rise to the publication of five new sensors: two of Pb (II), one of Cd (II) and two of Hg (II). So far, Hg (II) best sensor that has been reported.

The results appear in 21 articles (13 published, 7 approved and 1 in arbitration) in prestigious magazines. The most outstanding was published in the Journal of Quantum Chemistry, which received the prize to the best Scientific Article of IMRE in 2000. 50 presentations have also taken place in scientific events in Cuba, Mexico, Spain and Poland. It has given rise to 5 Master's degrees and 8 Diplomas defended, and to eight developing doctorates. The work and their authors also received the following university prizes in 2000: Best result in the Management of New Materials, Most Outstanding Research Group and More Outstanding Professor in the Scientific Work (Leonel Pérez Marín).