Trace determination of linear alkylbenzene sulfonates using ionic liquid based ultrasound-assisted dispersive liquid-liquid microextraction and response surface methodology

A new method was developed for determination of linear alkylbenzene sulfonates (LASs) in environmental water samples using ionic liquid based ultrasound-assisted dispersive liquid-liquid microextraction (IL-USA-DLLME) coupled with spectrophotometry detection. Different operational conditions affecting extraction efficiency of LASs including pH, volume of extraction solvent, methylene blue (MB) concentration, salt concentration and sonication time were studied via central composite design (CCD) optimization method. The statistical parameters of the model were F = 39.01 and R-2 = 0.9254. The optimal conditions were 8.3 for sample pH, 72 mu L for extraction solvent, 49.2 mu g mL(-1) for MB concentration, 17.2% (w/v) for sodium chloride concentration and 30 s for sonication time. Under the optimal conditions, a calibration curve was obtained with linear dynamic range between 0.8 and 100 ng mL(-1) and detection limit of 0.37 ng mL(-1). The relative standard deviation (RSD %, n = 5) for the extraction and determination of 40.0 ng mL(-1) of linear alkylbenzene sulfonates in the aqueous samples was obtained as 2.0%. The proposed method was successfully applied to determine concentrations of LASs in different non-spiked aqueous samples and satisfactory results were obtained.