Silver Nanoparticles-Based Nano-drop Spectrophotometric Determination of Cationic Surfactants Coupled with Hydrophobic Interaction; An Application to Pharmaceuticals and Environmental Samples

The proposed work describes the nanodrop spectrophotometric determination of cationic surfactants using citrate-modified silver nanoparticles based on the aggregation of silver nanoparticles induced by cationic surfactants due to the hydrophobic effect. The visible color change in the solution of silver nanoparticle includes a red shift with the quenching of the absorption spectra. The maximum absorbance was measured at wavelength, λmax 400 nm. The concentrations of cationic surfactants were determined using a nanodrop spectrophotometer with limits of detection of 15.0, 8.0, 6.0, 5.8, and 13.0 μM for dodecyl trimethyl ammonium bromide, myristil trimethyl ammonium bromide, cetrimonium trimethyl ammonium bromide, cetyl pyridinium chloride and benzalkonium chloride, respectively. The proposed method was successfully applied for the determination of cetyl pyridinium chloride in commercial mouthwasher, gum astringent and nasal spray pharmaceuticals and environmental samples.