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

Abstract

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′(3″hexadecyl-2″benzothiazolinylidene)-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 2×10 −6 mol L −1 of SDS with a detection limit (LOD) of 8.3×10 −8 mol L −1. The relative standard deviation for the determination of 7×10 −7 mol L −1 SDS was 4.1%. Recoveries of 95.3–110.3% were found for the addition to 1.0×10 −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.