Fluorescence quenching method for the determination of sodium dodecyl sulphate with near-infrared hydrophobic dye in the presence of Triton X-100

A fluorophotometric method for the determination of anionic surfactant sodium dodecyl sulphate (SDS) was proposed. The method is based on the quenching effect of SDS on the fluorescence of near-infrared (NIR) hydrophobic dye, 2-[4'chloro-7'(3hexadecyl-2benzothiazolinylidene)-3',5'-(1''',3'''-propanediyl)-1',3',5'-heptatriene-1'-yl]-3-ethylbenzothiazolium iodide (dye I) in the presence of Triton X-100. The calibration graph is linear in the concentration range from 0 to 2 x 10(-6) mol L-1 of SDS with a detection limit (LOD) of 8.3 x 10(-8) mol L-1. The relative standard deviation for the determination of 7 x 10(-7) mol L-1 SDS was 4.1%. Recoveries of 95.3-110.3% were found for the addition to 1.0 x 10(-6) mol L-1 SDS in the analysis of environmental water samples. Preliminary research shows that the fluorescence quenching is due to the formation of dye aggregate facilitated by SDS. (C) 2004 Elsevier B.V. All rights reserved.