Resonance Rayleigh Scattering Spectrometric Determination of Anionic Surfactants Based on the Reaction with Thionin

In a B-R buffer medium of pH 2.36, an appropriate amount of anionic surfactant (SDBS, SDS or SLS) sample solution was reacted with 1.0 mL of 1.0×10-4mol·L-1 thionin solution in a total volume of 10 mL, to form an ion association complex, of which the intensity of resonance Rayleigh scattering (IRRS) was measured at the wavelength of 655 nm. Values of ΔIRRS (difference between values of IRRS of sample and blank) was found to keep linear relationships with values of mass concentration of 3 anionic surfactants in the ranges of 0.05-3.0 mg·L-1 for SDBS, 0.5-3.0 mg·L-1 for SDS and 1.0-5.0 mg·L-1 for SLS, with limits of detection (3S/N) of 0.017, 0.166 and 0.571 mg·L-1 respectively. The proposed method was applied to the determination of SDBS in samples of 2 CRM′s and 2 samples of environmental water; results obtained by this method were found to check quite well with certified values and the results found by photometry with methylene blue.