Polarographic study of simazine in micellar and emulsified media

Ultraviolet Absorption Spectra and Dissociation Constants of Diamino-1,3,5-triazines

This paper presents ultraviolet absorption spectra of two diamino-1,3,5-triazines, namely 1,3,5-triazine-2,4-diamine (DT) and 6-chloro-1,3,5-triazine-2,4-diamine (ClDT). The spectra were fitted to the log-normal distribution. In the more energetic zone of the spectrum both compounds presented common bands, placed around 204-205 and 223-226 nm (depending on the pH of the medium). At higher wavelengths the spectra were different, with bands appearing in the range 235-267 nm. From variations of the maximum absorbances of the individual bands, the pKb values 3.5 ± 0.2 and 1.2 ± 0.1 were obtained for protonation of the ring nitrogen placed between the amine radicals of DT and ClDT, respectively, and 9.35 ± 0.2 and 11.5 ± 0.1 for dissociation of the amino groups of DT and ClDT, respectively.

Reductive deactivation of some s-triazine herbicides: Prometryne, desmetryne and terbutryne

The electrochemical behaviour (DC and DPpolarography) of the methylthio-bis(alkylamino) s-triazine herbicides prometryne, desmetryne and terbutryne on mercury electrodes has been studied in the acidity range 2.25MH2SO4 to pH 6.5. Two two-electron irreversible reduction processes were found, complicated with adsorption. At pH values higher than the protonation pKof the triazine ring (ca. 4), this protonation reaction preceded the reduction processes. Reduction mechanisms are proposed for pH < pK and pH > pK. The products obtained in the electroreduction of dilute solutions of the above herbicides show a lower toxicological effect than that of the original compounds (lower aromatic character and cleavage of the ?SCH3 group). Thus electrochemical deactivation at pH ??3.5 and at potentials around ?1.10 V (vs. the Ag/AgCl/KClsat electrode) can be a valid method to deactivate these molecules. Finally, the reductive route can be an alternative environmental degradative process in waters under strong reductive conditions, with pH values equal or lower than 3.5 pH-units, and rich in carbonaceous materials on clays. In these ambients oxidative photolytic detoxification of herbicides cannot occur.