Speciation of organoarsenicals in aqueous solutions by Raman spectrometry and quantum chemical calculations

Knowledge about the existence and stability of different species of organoarsenicals in solution is of the most significant interest for fields so different as chemical, environmental, biological, toxicological and forensic. This work provides a comparative evaluation of the Raman spectra of four organoarsenicals (o-arsanilic acid, parsanilic acid, roxarsone and cacodylic acid) in aqueous solutions under acidic, neutral and alkaline conditions. Speciation of some of these organoarsenicals is possible by Raman spectrometry at different selected pHs. Further, we examine the proficiency of computational chemistry to obtain the theoretical Raman spectra of the four organoarsenicals compounds. To this end, we employ a computational protocol that includes explicit water molecules and conformational sampling, finding that the calculated organoarsenicals spectra agree reasonably well with those experimentally obtained in an aqueous solution in the whole pH range covered. Finally, we highlight the effectiveness of quantum chemical calculations to identify organoarsenicals in an aqueous solution.

Automated summary

This study provides a comparative evaluation of the Raman spectra of four organoarsenicals in aqueous solutions under different pH conditions. It also examines the proficiency of computational chemistry in obtaining theoretical Raman spectra for these compounds. The results show that Raman spectrometry and computational chemistry can effectively identify the species and spectral features of organoarsenicals under different pH conditions.