Analysis of Linear Alkylbenzene Sulfonate in Laundry Wastewater by HPLC–UV and UV–Vis Spectrophotometry

Abstract

AbstractA lack of natural water resources and an increase in the demand for fresh potable water has shifted focus to the possible reuse of recycled laundry wastewater water that is considered to be relatively clean. Organic components such as linear alkylbenzene sulfonates (LAS) are the major and most abundant contributing anionic surfactant constituents found in laundry detergents. The development and reliability of treatment methods targeted at purification of laundry wastewater necessitates a fast and accurate method for quantification of LAS. This paper focuses on a comparative study for the quantification of LAS based on traditional liquid–liquid extraction (LLE) and HPLC–UV methods. In the case of LLE, the anionic surfactant LAS complexes via ion association to a methylene blue (MB) cationic dye resulting in the formation of an anionic surfactant–methylene blue (AS–MB) complex. The AS–MB complex extracted with chloroform absorbs at a λ max of 653 nm. Optimized conditions for quantification of a single eluted LAS peak using HPLC–UV were obtained by isocratic elution on a C18 column with a 95 % acetonitrile and 5 % 0.7 M acetic acid mobile phase. Both methods displayed percentage recoveries >90 % and statistically showed reproducibility and precision in the quantitation of LAS. HPLC–UV prevailed over UV–Vis as the method of choice for LAS determinations given the ease of sample preparation and applicability to a wider range of samples. Typical levels of LAS in laundry samples assessed in this study ranged between 116 and 454 mg L−1.