Trace level detection of the azo base of organic dye by surface-enhanced Raman spectroscopy

Water pollution with synthetic pigments is becoming an emerging problem due to the potential damage to aquatic sources and its consequences for flora, fauna, and human health. Currently, techniques to detect the presence of these pollutant pigments in water reach concentrations of mu g/L and require pretreatment to detect them. In this work, we present a quick and easy methodology to determine the presence of the basic unit used in textile pigments, 4-(pyridin-4-yldiazenyl)phenyl-amine (4-PDPA), in a synthetic seawater matrix and a real one from the coast of the city of Valparaiso, Chile, using Surface Enhanced Raman Spectroscopy (SERS). Colloidal gold was used as the active surface, spectra corresponding to the pigment profile were recorded without pretreatment of the matrix used, and the pigment was detected at concentrations 0.00198 mu g/L up to two orders of magnitude lower than current methods (0.0198 mu g/L).