A combination of vortex-assisted liquid–liquid microextraction with fluorescence detection: An innovative approach for a green and highly sensitive determination of sodium dodecyl sulfate in water samples and pharmaceuticals

Abstract

A new green, highly sensitive, and selective method based on a combination of vortex-assisted liquid–liquid microextraction with fluorescence detection (VALLME-FLD) was developed for the determination of sodium dodecyl sulfate (SDS). The method is based on the reaction of SDS with the fluorophore 3,3′-diethyloxadicarbocyanine iodide (DODC) at pH 3, followed by VALLME of the formed ion associate (IA) into a microvolume of the organic phase (n-amyl acetate). Fluorescence measurements were made at 668 nm, with excitation at 635 nm. During the optimization, the influence of various chemical and physical factors on the relative fluorescence intensity was studied. The linearity of the calibration curve was observed in two concentration ranges of SDS, from 0.30 to 3.0 µg L-1, R2 = 0.9980 (microextraction into 70 µL n-amyl acetate), and 3.0 to 14.0 µg L-1, R2 = 0.9960 (microextraction into 500 µL n-amyl acetate). The limits of detection (LOD) were 0.10 µg L-1 and 0.90 µg L-1, respectively. The accuracy and precision of the proposed method were verified during two consecutive days with a relative standard derivation of 2.2–4.9 % and recovery of 93.3–106.7 %. The system showed high selectivity towards SDS in the presence of at least 200-times higher concentrations of NO3–; 500-times higher concentrations of F-, Br-, HPO42-, and Fe2+, and 1000-times higher concentrations of CO32–, SO42-, Cl-, Mg2+, and Ca2+. The method was developed and applied to the determination of SDS/anionic surfactants in real water samples and pharmaceutical tablets.